Module 6

Question 1

Distribution

Answer 1

Where individual organisms are found within an ecosystem. Is usually uneven throughout the ecosystem as they are generally found where abiotic factors favour them, so their survival rate is high due to having all the resources they need and low predation.

Question 2

Measuring distribution by systematic, non random sampling

Answer 2

• A line transect is where a line of surveyor’s tape if layed on the ground and samples are taken at regular intervals and describing organisms which touch the line or are are a certain distance away
• A belt transect provides more information and 2 parallel lines are marked and samples are taken in the area between these specific points.

Question 3

What is an advantage of systematic sampling?

Answer 3

Systematic sampling identifies different areas within the overall habitat to sample separately which allows scientists to study how the differing abiotic factors in different areas of the habitat affect the distribution of species. Can show how plant species changes you move inland from the sea.

Question 4

Abundance

Answer 4

The number of individuals of a species present in an area at any given time. This may fluctuate daily dur to immigration and births, and emigration and deaths.

Question 5

What is a population?

Why is abundance hard to measure and how can you make it more accurate?

Answer 5

• A population is a group of similar organisms living in a given are at a given time. They can rarely be counted accurately as not all can be caught and it can be time consuming to count all the members, or the counting process could damage the environment. We therefore estimate using sampling techniques.
• To increase accuracy, use as large a sample size as possible as there is a lower probability that chance will influence the result. Random sampling should be used to reduce bias.

Question 6

How do you measure plant abundance?

Answer 6

Quadrats are placed randomly in an area and the number of individuals contained in the quadrat are counted.

The number of individuals and area of sample are all the quadrat samples added together

Question 7

Why can you measure aniamls with quadrats?

What do you need to ensure when handling animals?

How do you measure abundance of animals?

Answer 7

• Animals move so can’t measure with quadrats
• Handle carefully and for as short time as possible

Capture-mark-release-recapture is used to estimate population size

1. Capture as many individuals as possible in a sample area
2. Mark or tag each individual in a way that doesn’t harm them- toxic paint or reverse camo. Can clip small part of fur or mark snails inside shells
3. Release the marked animals back into the sample area and allow time for them to redistribute themselves throughout the habitat
4. Recapture as many individuals as possible in the original sample area
5. Record the number of marked and unmarked individuals present in the sample (release all individuals back into their habitat.)
6. Use Lincoln index to estimate the population size

Question 8

What is the equation to estimate population size for capture-mark-release-recapture?

What does a greater number of marked individuals captured mean?

How can you compare species eveness?

How do you calculate biodiversity from this?

Answer 8

(SS)

smaller population.

compare the total number of each organisms present

use the Simpsons index of diversity (SS) where D is the chance that any 2 individuals picked at random will be from different species

Question 9

How is species frequency and species density calculated with quadrats?

Answer 9

Species frequency- calculate the percentage of quadrats that included each species

Species density- the number of individual organisms within a quadrat

Question 10

How do you identiy organisms?

Answer 10

identification key are used which can contain images to identify the organism into a particular species based on the presence of a number of identifiable characteristics

Question 11

Why is random sampling used?

How is it done with quadrats?

What is ACFOR?

How are aniamls measured by random sampling?

Answer 11

Reduces bias

1. Can place tape measures at right angles to each other along the 2 sides of the sample area and random numbers are generated using an app to give coordinates of where to put the quadrats
2. Count number of individuals in the girds. Often have to do % cover for plants as its hard to see the individual plants by estimating or by counting the number of squares the species is present in and converting to a %
3. Calculate mean then multiply by total area

• Sometimes species are too numerous to count and plants cant always be isolated to an abundance scale like ACFOR is used (abundant, common, frequent, occasional, rare). First you decide how many plants/ animals have to be present to be considered common…. This speeds up recordings.

Animals are harder as they can be small, and lots just appear at night. Instead of quadrats they use:

1. Beating trays- a large white sheet is placed on the ground or supported by struts and held below a tree. The tree is shaken to dislodge animals.
2. Pooter- scientists can use this to suck small animals into a gall or plastic tube. Can use it to collect animals from a beating tray.
3. Sweep net- large nets catch flying insects and insects that live in long grass
4. Pond net- stronger nets lift water from pond and rivers and the water drains through to leave vegetation and animals behind
5. Pitfall traps- cans or jars buried in the ground filled, with paper or cardboard to provide shelter, and covered with a lid or stone to keep out rain. Collects ground dwelling insects which are often nocturnal. Deep enough they cant crawl out
6. Kick sampling- study organisms in a river to disturb the substrate. Net downstream for set period of time captures organisms
7. Slow moving like muscles can be measured using quadrats
8. Tullgren funnel

Question 12

Why can non-random sampling be good?

What are the types of non random sampling?

Answer 12

Random sampling can take too long

Opportunistic sampling:

Walk around until you find an area convenient to sample. However, the area you chose may not be representative of the area. If you don’t have time to look anywhere else, often students pick places easy to reach, safe and don’t involve walking too far.

Stratified sampling:

In ecosystems there may be different habitats occupying different proportions of the total area. To get a fair representation of the biodiversity in the ecosystem, its bets to estimate the proportion of total area occupied by these habitats and then sample accordingly. If 10% if woodland, then 10% of samples should be taken from woodland.

Systematic sampling:

If there is an abrupt change from 1 habitat to another or a gradual change in conditions across the area random sampling won’t reflect the distribution. Transects. Line transect results are converted into a drawing which shows distribution. Shows change down a gradient, like a slope or changing abiotic feature. Belt transects can be continuous or is the distance is long then at regular intervals. Results are converted into a kite diagram. Is biased as you choose where to put the transect and this area may not be representative but is easier as don’t have to measure coordinates.

Question 13

Why are abiotic factors measured?

What is the advantage of being measured with sensors?

How are the measured?

Needed to draw conclusions about the organisms present and the conditions they need for survival so measured at every sampling point

Can be measured quickly and accurately with a range of sensors which are good because;

Rapid changes can be detected

Human error in taking readings is reduces

A high degree of precision can be achieved

Data can eb stored and tracked on a computer

Answer 13

• Needed to draw conclusions about the organisms present and the conditions they need for survival so measured at every sampling point

Can be measured quickly and accurately with a range of sensors which are good because:

• Rapid changes can be detected
• Human error in taking readings is reduces
• A high degree of precision can be achieved
• Data can eb stored and tracked on a computer

(SS)

Question 14

Describe this population growth curve

What is the population growth curve of organisms that reproduce asexually?

Answer 14

2- no constraints act to limit the population explosion

3- fluctuations due to fluctuations in limiting factors like predators

Organisms that reproduce asexually can produce a J shaped curve as they exploit the resources when they become available. They reach a peak and then crash often before carrying capacity is reached. They are often controlled more by abiotic factors

Question 15

Examples of limiting factors for population growth

Answer 15

EG. Competition for resources, build-up of toxic by-products of metabolism, disease

Abiotic- non-living like temp, pH, water availability, oxygen availability, humidity. Remain constant when population density changes.

Biotic- living like predators, disease, competition. Have greater affect when population density increases.

Question 16

Carrying caacity

Answer 16

the maximum population size an environment can support

Question 17

Envrionemtnal resistance

Answer 17

the combined effect of that prevent the further increase of a population

Question 18

Why can migration happen and what are the types?

Answer 18

Can happen when an area reaches its carrying capacity

Immigration- movement into an area increases population size

Emigration- individual organisms move away from a particular area and decrease population size

Question 19

What are density independent factors?

Answer 19

factors that have an effect on the whole population regardless of size. They can dramatically change the population size. EG- earthquake, fires, volcanic eruptions, storms. They can even remove whole populations of a species from a region.

Question 20

What type of factor is competition?

Interspecific competition

Intraspecific competition

Answer 20

biotic

competition between different species

competition between members of the same species

Question 21

Interspecific variation

example

Answer 21

Results in a reduction of the resource they are competing for for both populations. EG food, means less energy for growth and reproduction so smaller populations result.

If 1 is better adapted, then the less well adapted one is likely tot be outcompeted and f conditions remain the same then the less well adapted species will decline in number until it no longer exists in that habitat- competitive exclusion principle

EG. Grey squirrel native to N America was introduced to UK causing the native red squirrel to disappear in many areas as the grey can eat a wider range of food and is larger so can store more fat so has better chance of survival and ability to reproduce An increasing population of greys further reduces food supply for red

Question 22

Intraspecific variation

Answer 22

Greater availability of resources means larger population size can be supported. This creates fluctuations in number of organisms over time

(SS):

1- plentiful resource for all organisms to survive and reproduce causes population size to increase

2- due to increased population, the resources are limited so population decreases as not enough for all to survive

3- less competition due to smaller population so more survive and reproduce

Question 23

Niche

Answer 23

the role of a species in a habitat, including its trophic level, its interactions with the abiotic environment and interactions with other species eg as a predator, host or a symbiont, parasite or pollinator. Species with similar niches the competition will be more intense

Question 24

Competitive exclusion

Answer 24

when individuals of different species compete for the same resources, one species may succeed and the other be excluded from the niche and completely disappear

Question 25

Resource partitioning

Answer 25

different species competing for the same sort of resource or resources occupy slightly different niches so they avoid direct competition, like having different places to catch the same insects

Question 26

Character displacement

Answer 26

2 species that compete with each other show differences in characteristics (features) where they exist in the same ecosystem but do not show these differences where they do not coexist

Question 27

How have predators and prey adapted?

Answer 27

Predators have evolved to be highly efficient at capturing prey by sudden burst of speed, stealth, and fast reactions. Prey organisms have evolved to avoid capture through camouflage, mimicry, defence mechanisms like spines. They have to evolve together so don’t become extinct.

Question 28

Describe the predator prey graph

Answer 28

1. An increase in prey population due to few/no limiting factors provides more food for predators so more can survive and reproduce so predator population increases after lag due to reproduction
2. Increased predator population eats more prey so they decline as death rate is greater than birth rate
3. Reduced prey means can’t support larger predator population as intraspecific competition for food increases so predator population decreases as die/ less offspring
4. Reduced predator numbers means less prey killed so they survive and reproduce increasing the prey population and cycle restarts

Question 29

What are the issues with the predator prey graph?

Answer 29

• Often more complicated due to other factors like plant food for prey or other predators and seasonal changes in abiotic factors
• Also the decrease in number of prey is often due to intraspecific competition for food than predation
• Often not just one predator and prey so can feed on other prey if one decreases in numbers

Question 30

Why does sucession occur?

What are the types?

Answer 30

Succession occurs as a result of changes in the environment causing plant and animal species present to change

Primary succession- on an area of land that has been newly formed or exposed like bare rock. No soil or organic material present to begin with

Secondary succession- occurs on new areas of land where soil is present, but it contains no plant or animal species. Eg bare earth that remains after a forest fire

Question 31

When does primary succession occur?

Answer 31

• Volcanoes erupt depositing lava and when it cools and solidifies igneous rock is created
• Sand is blown by the wind or deposited by te sea to create new sand dunes
• Silt and mud are deposited at river estuaries
• Glaciers retreat depositing rubble and exposing rock

Question 32

What are the stages of succession called?

What happens at each stage?

Answer 32

These are known as seral stages or sere

At each stage key species are identified that change the abiotic factors like soil so its more suitable for the subsequent existence of other species. Different plant and animals species are better adapted to the current conditions and they outcompete to become the dominant species

Question 33

What are the main seral stages?

Answer 33

• Pioneer community
• Intermediate community (has seral stages within it)
• Climax community

diagram

Question 34

Pioneer community-

How do species arrive?

What adaptations do they have?

Answer 34

• Primary succession begins by the colonisation of an inhospitable environment by pioneer species. This is the 1st seral stage. The species arrive as spores or seeds carried by wind from nearby land masses or by animals droppings. They have adaptations:

1. Ability to produce large quantities of seeds or spores which are blown by wind and deposited on new land
2. Seeds that germinate rapidly
3. Ability to photosynthesise to produce own energy
4. Tolerance to extreme environments
5. Ability to fix nitrogen from atmosphere so adding to mineral content of soil

Question 35

Intermediate community

Answer 35

Over time weathering of bare rock produces particles that form the basis of soil. It cant support species but when pioneer species die they decompose and release organic products to the soil- humus . the soil can then support new species known as secondary colonisers as it has minerals including nitrates ad ability to retain some water. They arrive as spores or seeds. Animals can start to colonise if pioneer species provide a food source.

Tertiary colonisers arrive as environmental conditions improve. The plants have waxy cuticles for water loss and can survive in conditions without an abundance of water, but do need to get most their water and mineral salts from the soil

At each stage the rock continues to be eroded and the mass of organic matter increases. When organisms decompose, they contribute to a deeper, more nutrient rich soil which retains more water. The conditions are then more favourable for small flowering plants like grasses, shrubs then small tress.

Question 36

Climax community

How does biodiversity change over succession?

Answer 36

• Final seral stage when the community is in a stable state with little change over time. There are a few dominant species which are different depending on the climate
• Biodiversity tends to increase as succession takes place, but the climax is often not the most biodiverse, as this tends to be mid succession and then decreases due to dominant species outcompeting pioneer and other species, eliminating them

Question 37

Animal succession- primary and secondary consumers

Answer 37

Primary consumers like insects and worms are first to colonise an area as thy consume and shelter in the mosses and lichen. As they have to move from neighbouring areas, animals succession is slower than plant, especially if the new land is geographically isolated like a new volcanic island

Secondary consumers will arrive once suitable food source is established, and existing plant cover will provide then with suitable habitat. Eventually larger organisms like mammals and reptiles will colonise when biotic conditions are favourable

Question 38

What causes deflected succession?

What is the name of the final stage?

Give examples of causes:

Answer 38

Human activities can halt the natural flow of succession and prevent the ecosystem reaching climax community. The final stage is then known as a plagioclimax. Often due to agriculture:

• Grazing and trampling of vegetation by domesticated animals so lare areas remain grassland
• Removing existing vegetation like shrub lad to plant crops so crops become the final community
• Burning for forest clearance leads to increase in biodiversity as provides space and nutrient rich ash for other species to grow like shrubs

Question 39

Definition of conservation

What is conservation

Answer 39

The maintenance of biodiversity and sustainability of biological resources using different methods of in situ and ex situ management

• Management of habitats and species taking into account that both will change over time in response to environmental changes – dynamic
• Allowing managed use of wildlife and habitats by humans -sustainable development so resources can be used without running out
• Also involves reclamation so ecosystems are restored that have been damaged or destroyed eg from floods, a new building project, controlled burning.
• Natural environment

Question 40

Definition fo preservation

What is preservation

Answer 40

The protection of ecosystems, habitats and species for the future without allowing any use by humans

• Maintaining species and habitats as they are now so they will continue to exist in the future
• Protecting them from any use by humans
• Often used when preserving sensitive resources which can be damaged or destroyed by disturbances eg newly formed caves called virgin caves contain sensitive geological formations or unique systems and walking between them may cause irreparable damage
• No point having a resource that can’t be used?
• Objects and buildings or nature reserves and marine conservation zones

Question 41

Reasons to conserve biological resources: social, economic and ethical

Answer 41

Question 42

Sustainable resources definition

Sustainable management definition

Answer 42

a biological resource required as a food or raw material that is renewed by the activity of organisms so that there is always sufficient stocks to take from the environment

aims to provide for the needs of an increasing human population without harming ecosystems, both natural ad artificial, and their ability to provide materials and services for us

Question 43

Why are fish stocks and treaties needed to provide a sustainable resource?

How are the protected?

example

Answer 43

• Stocks around the world are severely depleted and some have collapsed entirely due to increasing demand for food with population growth
• The regulatory organisation has to determine the maximum sustainable yield (number or biomass of fish that can be caught without reducing the potential of the fish stock to regenerate itself each year

1. Setting up exclusion zones where fishing is banned (spawning grounds or nursery grounds where fish reproduce or young fish develop)
2. Limit number of boats that can fish a particular species or in a particular area
3. Ban fishing at certain times of year (during spawning)
4. Rules on type of fishing gear like regulating mesh size of nets and hook size so small fish aren’t taken and can and can survive long enough to breed
5. Quotas so can’t take over a certain number or mass of fish per year- common fisheries policy in EU
6. Inspection of catches at ports and fisheries protection vessels to police at sea
7. Restock sea with young fish
8. Fish farming prevents loos of wild species. Placed in rice fields at planting time and grow to edible size when rice is ready to harvest.

Ecosystem approach aims to understand the structure and dynamics of the whole ecosystem including the position of fishing populations within the food web and how they interact with other populations. Includes giving protection to seabed habitats that are at risk from trawling. Fat older female fish are the best spawners so should be conserved, whereas usually older fish are removed as they are easier to catch

EG. Gulf of Maine NW Atlantic closed to fishing in mid 90s and 5 yrs later all recovered except cod

Question 44

Why does timber need to be conserved?

What types of trees are there?

What are the methods of conservation?

Answer 44

• Heavy requirement for timber in world wars reduced forest in UK
• Tree crops can be fast growing coniferous trees like pine and fir grown for commercial processes like paper making and construction. Slower growing broad-leaved trees include oak, beech.

1. Clear felling involves cutting trees over a certain area, taking all the trees usually the same age. Very destructive to biodiversity as soil is exposed so erosion and nutrient loss occur. Followed by replanting rather than waiting for regrowth to ensure biodiversity and water cycle remain and is an economic method.
2. Selective felling minimises damage by cutting some mature trees, diseased trees and unwanted species. Leaves space for regeneration. Access for machinery required. Best trees have time to grow to maturity when have higher economic value.
3. Strip felling is clearance of small strips or patches leaving adjacent areas untouched. Areas are replanted and adjacent areas cut when have grown to harvestable size. Large areas not felled at same time so less disruption and chance that biodiversity will be affected and little soil erosion.
4. Coppicing manages broad leaved woodlands where stumps are left to regrow. Several stems grow from the stump which grow rapidly due to well-developed root systems. After 5 years they are cut down to stumps again. Can be repeated indefinitely. Small patches are cut at different times providing a variety of habitats and high biodiversity as trees never grow enough to block out the light so succession cant occur and more species can survive. Wood can’t be used in construction but can be used for paper industry, burnt in power stations for electricity and fencing. Pollarding is similar but trunk is cut higher up so deer don’t eat new shoots.
5. Plant trees optimal distance apart to reduce competition. Higher yield as more wood is produced per tree
6. Manage pests and pathogens to maximise yields

Question 45

Masai Mara national reserve in south Kenya

Farming

Ecotourism

Conservation

Research

How is a balance acheived between conservation and human needs?

Answer 45

• Savannah ecosystem divided by the mara river
• Fertile regions close to the river are combo of rich grassland and woodland and further from it are open plains with scattered shrubs and trees
• Home to wide range of large animals and famous for annual zebra and wildebeest migrations
• Region used to be dominated by acacia bush which was habitat for tsetse fly which carried sleeping sickness
• Government workers and indigenous communities cleared this tree and so did elephants, fire and cattle grazing

Farming - grazing

• Traditionally used by local tribes for livestock grazing. Practiced semi-nomadic farming where tribes frequently moved depending on climate variation and presence of tsetse flies, allowing vegetation to recover
• Grazing is now limited to areas on the edge of the reserve a local tribes are prevented from entering the park. Populations have grown in these marginal areas, larger herds graze the grassland areas and trees are removed for fuel. This increases risk of soil erosion

Farming- cultivation

• Level of cultivation has increased recently as grassland converted to cropland, so natural vegetation is removed and nutrients in soil are used up. Then fertilisers are relied on for crop growth

Ecotourism

• Main economic input as thousands of people visit each year. Supports conservation and is sustainable as reduces impact of tourists on natural environment. Benefits local people as well as visitors
• Can negatively impact environment like walking on hiking trails causing soil erosion and habitat changes

Conservation

• Conservation of endangered species like black rhino which is on ICUN critically endangered list. Trade is illegal but rhino horn is in demand for use in traditional medicine in SE Asia
• An active conservation programme established to balance needs of locals and those of wildlife. Included employment of reserve rangers, provision of communication equipment, vehicles and infrastructure. This helps deter poachers entering reserve, helping rhino populations increase

Research

• Mara predator project monitor lion populations to identify population trends and response to changes in land management, human settlements, livestock movements and tourism
• The Mara-Meru cheetah project aims to monitor cheetah population and evaluate impact of human activity
• Human land sue is incompatible with wildlife survival and increased wildlife density threatens pastoral and cultivation lifestyles. Balance must be maintained
• Elephants threaten cultivation by trampling, and others eat crops. Land may be fenced, but this negatively effects natural migration
• Legal hunting for excess animals to maintain population numbers and bring in money for conservation work. Number must be constantly monitored to maintain natural balance in ecosystem
• Livestock faces threats from migratory wildlife – during annual wildebeest migration they outcompete cattle for grass and diseases are introduced to domesticated animals and vice Vera
• Human population expanding requires new homes and land for agriculture, which decreases wildlife density

Question 46

Terai region of Nepal

How ecosystems can be managed to manage conflict between conservation and human needs:

• Sustainable forest management
• Species conservation
• Sustianable agriculture

Answer 46

• Rich agricultural area with a belt of well-watered flood plains
• High population density, so natural resources are at risk of being overused
• Lots of biodiversity with subtropical plants and thick forest
• Millions rely on it for livelihoods by tourism, wood products and fuel and national income
• Poverty and corruption have caused large areas to be cleared for agriculture or to sell timber
• This has exacerbated effects of monsoon flooding, causing severe disruption to communities downstream

Sustainable forest management

• Provide a livelihood for locals, conserve forests and provide nepali state with income for general development
• Supportive national legislation and development of local community forestry groups
• Local groups set harvesting rules, rates and prices for products, determine how surplus income is spent
• Small forestry businesses work together to gain forestry stewardship council certification, an international standard which rewards sustainable forestry
• Have improved soil and water management, increased retail price of forestry products so greater economic input, generated employment and income through forest protection and secured biodiversity of the forested areas and conservation of forested areas

Species conservation

• Home to Bengal tiger which is endangered and Indian elephant. These are protected by 14 reserves as they are at risk of poaching for ivory trade and traditional Asian medicine.
• Nepalese government and army patrol national parks to protect animals
• Tigers hard to conserve as are top predators and require a large are to hunt. To conserve them, you need to ensure there is a fully functioning ecosystem with enough land to provide enough prey
• Removal of top predators deceases biodiversity all at levels
• Conserving are areas can be hard when human populations rely n these areas for fuels and grazing livestock
• Even though large enough protected areas are uncommon, wildlife corridors connect protected areas so large animals can use them without threat

Promoting sustainable agriculture

• Promote production of fruit and veg in hills and mountain regions to avoid further intensification of the terai
• Improving irrigation to enhance crop production
• Multiple cropping on one bit of land each season
• Growth of nitrogen fixing crops like pulses and legumes to enhance soil fertility
• Growing crop varieties resistant to various soil, climatic and biotic challenges through genetic engineering
• Fertilisation to enhance crop yields like manure

Question 47

Peat bogs

Why is conservation needed and how is it being done?

Answer 47

• Wet spongy ground containing decomposing vegetation
• Carbon sink but when dried can be sued as fuel. Need to preserve for climate change
• Peat is important for farmers and gardeners, who mix it with soil to improve soil structure and increase acidity
• Retains moisture very well and prevents excess water killing roots when soil is wet
• Commercial peat extraction by gardeners is a major threat
• Forms when plant material can’t fully decay due to acidic and anaerobic conditions
• Wide range of insects supported
• Lack of predators and human disturbance makes ideal place for birds to nest and the nutritious vegetation provides food for many species. Large open ground provides ideal hunting ground for birds of prey.
• Areas of peat are rapidly diminishing due to afforestation, peat extraction and agricultural intensification including land drainage
• It is important they are conserved due to biodiversity and flood management and carbon storage
• Must restore water levels by blocking ditches which allow water to drain off
• Remove seedling trees for. Areas which remove water
• Using controlled grazing to maintain biodiversity as it ensures diverse wetland surface and provides a wide range of habitats for many are insect species
• Natural England and the wildlife trusts are doing conservation as lots of peat is in poor condition

Question 48

Galapagos islands, pacific ocean plants and animals

The effect of human activites on plants and animals and how they can be controlled

Answer 48

• Volcanic islands that have never been connected to mainland
• The original flora and fauna that reached the islands had to survive crossing hundreds of km of ocean
• Most land animals are reptiles, with only 1 mammal species, the Galapagos rice rat which arrived floating on rafts of vegetation. Also marine birds
• Many species are unique to the islands, as they adapted to the environment in isolation EG Galapagos giant tortoise, flightless cormorant which has reduced wings better for fishing underwater when flight not needed to escape predators. The marine iguana can swim unlike the land one, and are dark coloured so can bask in the sun to raise their body temperature before swimming
• There are 3 zones, each which support a particular plant species
• Coastal zone has salt tolerant plants like mangrove. The arid zone has drought tolerant species like cacti. The humid zone has dense cloud forest.
• Weren’t visited until 19th century by humans
• Whaling trade disrupted islands fragile ecosystem allowing domestic animals to roam loose like goats outcompeting giant tortoises, chopping forests for fires to render down whale fat and removing live tortoises to sustain the whalers on long voyages as the tortoises can survive long periods without food or water
• Disrupted habitats by urbanisation and tourism development and farming
• Green sea turtles caught in fish nets and overfishing
• Introduced species trampled eggs
• Introduced pathogens like bird flu
• Tourist boats cause pollution and eutrophication from agriculture, oil spills
• National park established in 1959:

1. Introduction of park rangers across the islands
2. Limiting human access to particular islands or specific parts of islands
3. Controlling migration to and from islands
4. Strict controls of movement of introduced animals like pigs

Question 49

Antarctica plants and animals

The effect of human activites on plants and animals and how they can be controlled

Answer 49

• Almost entirely covered in an ice sheet, holding 70% of worlds fresh water
• Only summer and winter (24 hr sunlight and darkness)
• Endothermic animals rely on thick blubber like whales, seals and penguins
• Emperor penguin is the only warm blooded penguin that remains in winter. Females lay an egg in mid winter and leave to spend winter at sea whereas male remain on land keeping the egg warm
• A few invertebrates live on the continent all year like the wingless midge
• Plants can only grow in the ice free regions. Lichens and moss grow in sand, soil, rock and on the weathered bones and feathers of dead animals. Algae can grown in sheltered areas. Phytoplankton makes use og high concentration of minerals in summer waters, which feed many animals.
• However global warming causing ice sheet to break up and ozone depletion are caused from human activity elsewhere. Species can then survive further. Loss of ice can loose phytoplankton and then reduced species, and reduce breeding ground for penguins
• Tourist are bringing alien animal and plant species
• Hunting of whales , seals and fishing has depleted species
• Soil contamination around scientific research stations
• Discharging of waste into sea like human sewage

1. Visits are only allowed for a few hours to selected areas
2. The Antarctic treaty protects unique nature of Antarctic continent and includes:
3. Scientific cooperation between nations
4. Protection of the Antarctic environment
5. Conservation of plants and animals, sustainable fishing
6. Designation and management of protected areas
7. Management of tourism

Question 50

Snowdonia national park, Wales, plants and animals

The effect of human activites on plants and animals and how they can be controlled

Answer 50

• Highest mountain range in England and wales and contains lakes, rivers and ancient woodland ad heath
• Rich diversity provides home for wide range of birds like coast and estuary birds like oystercatchers, forest birds like redstart and moorland and mountain birds like sparrow hawks.
• Over 40 species of land animals like badgers, voles, deer
• Plants species are diverse with arctic alpine plants at the top and woodland at the bottom
• Snowdonia national park conserves the biodiversity of the region
• The park is home to over 25,000 people, many of whom work on the land. This attracts lots fo visitors for climbing, walking, water sports
• Rhododendrons form large bushes or shrubs and were introduced as a horticultural plant. Now they prevent light reaching the ground so few plants can survive and killed local vegetation. They don’t support any other species as their eaves are poisonous. When they die the branches grow roots and establish new plants. The leaves decompose slowly so ruin soils
• Try to cut them down and burn them with herbicides sprayed on after. Stem injection involved drilling holes and applying herbicides

The park authority:

1. Conserves and enhances natural beauty, wildlife and cultural heritage of area
2. Promote opportunities for the understanding and enjoyment of the special qualities of the park
3. Enhance the economic and social wellbeing of communities in the park
4. To preserve the natural beauty of Snowdonia, the Dinorwig HEP station was built deep inside a mountain inside caverns, minimising impact on environment and meeting human demand for energy

Question 51

Lake district plants and animals

The effect of human activites on plants and animals and how they can be controlled

Answer 51

• England’s largest national park, with regions of moorland and fell, lakes dammed by glacial moraines at end of last ice age, and ancient woodland
• The varied landscapes provide habitats for a wide range of animals including water voles, bat, red deer and golden eagle, red squirrel is under threat as is vendace a fish only found here and that’s on ICUN endangered list
• Habitats ca exist above the central tree line in the fells which is rare in the UK, supporting arctic-alpine plant communities

1. Lake district national park authority conserves he region while enabling access for millions of visitors each year
2. Active management of countryside involves replanting native tree species

Question 52

International wildlife law and programmes

Answer 52

SSSI (sites of special scientific interest)

A conservation designation denoting a protected area, usually describing an area with rare species of flora or fauna or important geological features

HAPS (Hadley angling and preservation society)

A small club to control fishing in Jacks lake, Hadley woods, Hertfordshire. The lake is available to members and day tickets

UNCLS (united nations convention on the laws of the sea)

International agreement which defines the rights and responsibilities of nations with respect to their use of the worlds oceans, establishing guidelines for businesses, the environment and the management of marine natural resources

Question 53

What are the factors affecting the evolution of a species?

Answer 53

1. genetic bottleneck
2. genetic drift
3. founder effect
4. stabilising selection
5. directional selection
6. disruptive selection

Question 54

What is a genetic bottleneck?

Example

Answer 54

Sharp reduction in the size of a population which lasts for at least 1 generation. Due to limiting factors. They can be density dependent factors- dependent on population size and include predation, competition, parasitism and communicable disease. Density independent factors affect populations of all sizes in the same way including climate change, natural disasters, seasonal change, human activities like deforestation. A smaller population has less genetic diversity and cannot adapt to change so are more likely to become extinct than evolve. Can be positive as a beneficial mutation will have greater impact and lead to quicker development of new species.

EG. Cheetahs experienced initial bottleneck 10,000 years ago with others more recently. They share 99% of their alleles with members of the species instead of 80% so are having interbreeding a reduced fertility issues.

Question 55

What is genetic drift?

Answer 55

A change in allele frequency due to the random nature of mutation in a small population creates new alleles or by chance if an allele is passed. As it is in a small population there is a greater impact.

Question 56

What is the founder effect?

example

Answer 56

An extreme example of genetic drift where small populations can arise due to the establishment of new colonies by a few isolated individuals. The smaller populations have smaller gene pools than original population so less genetic variation. The frequency of alleles are much higher so have a bigger impact in natural selection.

EG. The Afrikaner population in S Africa descended from a few Dutch settlers and have a high frequency of Huntington’s disease as only 1 original settlers had that allele.

Question 57

What is stabilising selection?

Example

Answer 57

Survival of the fittest/ natural selection, where those with average phenotypes are selected for and extremities of the phenotype are selected against. The extremities reduce the survival chances and those with average phenotypes are more likely to survive and reproduce. This results in a reduction in the frequency of alleles at the extremities and an increase in frequency of average alleles, so a population remains stable for a particular character.

EG. There is a higher death in very small and very large babies, so birth weight remains fairly stable, as a new extreme phenotype has no selective advantage so wont be selected.

Question 58

What is directional selection?

Example

Answer 58

When there is a change in the environment and the most common phenotype is no longer has the competitive advantage. Organisms that are less common and have more extreme phenotypes are positively selected. The allele frequency than shifts towards the extreme phenotypes and evolution occurs as they survive and reproduce.

EG. Peppered moths the darker ones became advantageous as pale lichen died and soot covered trees.

Question 59

What is disruptive selection?

Example

Answer 59

The extremities are selected for and the norm selected against.

EG. Feather colour of male lazuli buntings in N America. Feather colour of young males can range bright blue to dull brown. There is competition for territory and female birds. Dull male birds are seen as non-threatening and bright ones too threatening. The intermediate colour is attacked by adult birds so fail to mate and establish territories.

Question 60

What is speciation?

What causes it?

Answer 60

Speciation is the formation of a new species through the process of evolution

1. Due to isolation so lack of interbreeding so now gene flow between the 2 groups
2. Alleles within the groups undergo random mutations and different environments mean different selection pressures
3. Accumulation of mutations eventually lead to large changes in phenotype so species can no longer interbreed as so different species

Question 61

What is allopatric speciation?

Example

Answer 61

When some members of a population are separated from the rest of the group by a physical barrier such as a river or the sea. The environments of the different groups are often so different so different selection pressures result in different adaptations. The founder effect often occurs, and genetic drift further enhances differences in the populations.

EG. Finches on Galapagos islands flew to and were stranded on different islands from the mainland. They have evolved due to different food sources on each island- phenotypic divergence. New species evolved.

Question 62

What is sympatric speciation?

Example

Answer 62

Occurs within populations that share the same habitat, less frequently than allopatric and more common in plants. When members of 2 different species interbreed and form fertile offspring a hybrid is formed and is a new species. It may no longer be able to interbed with members of either parent population which stops gene flow and isolates the hybrid organism. Also due to reproductive differences so that individuals in close proximity can’t interbreed with the rest of the population.

EG. blind mole rats are found in different types of soil in N Israel but they only interbreed with rats in the same soil type. The lack of gen flow is causing genetic differences and they could accumulate so that they are unable to interbreed and are separate species. As they are in the same habitat, gene flow sometimes still occurs.

Reproductive barriers can prevent the formation of a zygote and fertilisation. They can also reduce the viability of offspring after fertilisation.

Question 63

What are isolating mechanissm resulting in the evolution a new species?

Answer 63

Allopatric speciation

Sympatric speciation

Question 64

Wild type allele

Answer 64

Populations are usually polymorphic as they display more than 1 phenotype for most characteristics. The allele coding for the most common or normal characteristic is called the wild type allele, and other forms of that allele from mutations are called mutants.

Question 65

Artificial selection

Answer 65

• Instead of changes in the environment leading to survival of the fittest, farmers or breeders select desirable characteristics for breeding of plants and animals.
• Individuals with the desired characteristics are selected and interbred, and the best offspring are selected and bred. Interbreeding is repeated over many generations changing the frequency of alleles within the population and eventually speciation.

Question 66

Issues with artificial selection/ ethical considerations

Answer 66

1. The problem with limiting the gene pool is genetic diversity is decreased which reduces the chances of a population evolving and adapting to changes in the environment.
2. Genetic disorders often caused by recessive alleles have a greater chance of homozygous alleles and to get the disease. Organisms are less able to survive and reproduce.
3. When selecting desired features, damaging genes can be selected resulting in damaging diseases and conditions EG breathing problems in bulldogs for their shortened snout

Question 67

Examples of artificial selection

Answer 67

EG. Modern bread wheat originally from wild wheat and wild grass interbred to create hybrids. However the hybrids chromosomes were not compatible so wouldn’t pair up meaning meiosis isn’t possible. A chance chromosome mutation in the hybrid caused the chromosome number to double so the plants could now form fertile species. This is called polyploidy. Continues to mutate and further hybridisation occurs. Modern wheat formed by further artificial selection.

EG. Modern dogs. Selective breeding has given rise to a variety of dog breeds. They originally evolved from the ancestral grey wolf which was selected for its ability to be tamed and used for hunting. The selection for the ability to be tamed caused physical changes which were ideal for tasks. Terriers were selected for running into burrows after rabbits as they were fast and small .all dogs are the same species but may result in speciation.

EG. Milk yield in dairy cows. Milk yield is controlled by many genes and so is continuous variation. Also affected by environmental conditions, so farmers may also use music and human contact to improve yield. Selective breeding has been used to improve milk yield.

Question 68

Importance of maintaining genetic resources

Answer 68

Seed banks keep samples of seeds from both the wild type and domesticated varieties. They can increase genetic diversity by outbreeding- breeding unrelated or distantly related varieties. This reduced the occurrence of homozygous recessives and increases ability to adapt to environmental change

rare breed farms

Question 69

mutation

Answer 69

a random change in the amount of structure of DNA of an organism

Ultimate source of genetic variation creating new alleles and forming the basis of evolution

Changes nucleotide sequence, new allele, new protein

Question 70

Point/ gene mutation

Answer 70

affects the DNA at a specific locus on a chromosome eg. Sickle cell anaemia

Question 71

Chromosonal mutation

Answer 71

affect whole chromosomes, by changing the number of chromosomes in a nucleus or structure of individual chromosomes eg. Downs syndrome

Include:

• Deletion- section of chromosome breaks off and is lost in cell
• Duplication- sections get duplicated on a Chromosome
• Translocation- a section of 1 chromosome breaks off and joins another non homologous chromosome
• Inversion- section of chromosome breaks off, is reversed and then joins back onto chromosome

Question 72

What can happen to mutations associated with mitosis and meiosis?

Answer 72

• Mutation associated with mitosis is a somatic mutation and is not passes on and may contribute to ageing or cancer
• Mutations associated with meiosis are inherited so can be passes on to offspring

Question 73

What increases the incidence of mutations?

Answer 73

1. Mutagenic agents like x-rays, gamma rays, UV rays, alpha and beta particles, tar in cigarettes
2. Genetic engineering
3. Age

Question 74

What type of single base mutations can you get?

Answer 74

1. Point mutations: a base substitution occurs
2. Frameshift mutation

Question 75

Types of point mutations/ substitution

Answer 75

1. Silent mutation (where both triplet codes code for the same aa)
2. Missense mutation- where one aa code is replaced by a code for another aa changing the codon, aa, primary structure… 3d shape of protein
3. Nonsense mutation- where the code for an aa is replaced by a stop codon. Non functional

Or the mutation could occur in non coding DNA

Mutation may not have an effect even if it causes a change in aa sequence- recessive allele isn’t expressed, or one of many genes involved in expression of a characteristic can reduce the effect of a single mutation

Question 76

Frameshift mutation

Answer 76

• One or more nucleotides pairs are inserted or deleted from a length of DNA
• Results in an entirely different sequence of aa from the point of insertion or deletion by shifting the reading frame of sequence of bases
• If 3 nucleotides added/ deleted, reading frame wont shift but the protein formed may still be affected by new aa

Question 77

Diseases from mutations

Answer 77

Sickle cell anaemia

• A base substitution occurs so A replaced with a T
• Codon changes from CAT to CTT
• Non polar aa valine is incorporated instead of polar glutamate
• HbS crystallises and forms sticky fibres which distort RBC shape

Cystic fibrosis

• Deletion of a triplet of base pairs deleted an aa.
• Causes lung problems due to thickened mucus

Cancer

• Point mutation in protooncogenes changes them into oncogenes that cant be switched off leading to unregulated cell division and tumour formation

Huntington’s disease

• Expanded triple nucleotide repeat. The normal gene for Huntington protein contains CAG repeats but if the number of repeats exceeds a threshold number the protein is altered sufficiently to cause Huntington disease
• Increases decay of certain neurones in brain

Question 78

Beneficial mutations

Answer 78

• Mutation in a protein present on CSM of human cells means HIV cant bind and enter these cells so are immune to HIV infection
• Ability to digest lactose, the sugar in milk. Most mammals become lactose intolerant after they cease to suckle. Helps prevent disease like osteoporosis and prevented individuals starving In famines

Question 79

Neutral mutations

Answer 79

• Cat coat hair determined by 2 alleles, dominant for short and long for recessive allele
• Ability to taste a chemical called PTC caused by a mutated allele. PTC is bitter but not usually in our food. Brussels contain a similar compound and people who can taste don’t like them.

Question 80

Transcriptional control

Answer 80

1. chromatin remodelling
2. histone modification
3. lac operon

Question 81

How is waste avoided through genes?

Answer 81

Each cell contains all your genes but not all are expressed

Some are on all the time eg for respiration, some only when needed

Question 82

Chromatin remodelling

Answer 82

Heterochromatin: tightly wound DNA so chromosomes visible in cell division

Euchromatin: loosely wound DNA in interphase

Transcription of gene only possible in interphase as RNA polymerase cant access genes when tightly wound

This ensures protein synthesis doesn’t occur in cell division, so we synthesise the proteins necessary for cell division in time and prevents complex energy consuming protein synthesis happening when cell dividing

Question 83

Histone modification

Answer 83

DNA coils around histones as DNA is neg and they are pos. histones can be modified to increase of decrease degree of packaging. Making histones more pos causes DNA to coil less tight so certain genes can be transcribed by adding acetyl groups of phosphate groups (acetylation/phosphorylation).

Methyl groups (methylation) makes histones more hydrophobic so bind tighter together and DNA coils tighter preventing transcripti9on of genes.

Question 84

Operon

Answer 84

group of genes that are transcribed at the same time under control of same regulatory mechanism. Only found in prokaryotes

Question 85

What are the structural genes in the lac operon and what do they do?

Answer 85

​

• The bacterium E.coli can use either glucose or lactose
• As lactose is a disaccharide it must first be hydrolysed so glucose is preferred
• E.coli has genes that code for 2 enzymes involved in the digestion and absorption of lactose

1. B galactoside permease (lactose permease)- transports lactose into the cell
2. B galactosidase (lactase)- hydrolyses lactose to glucose and galactose

The genes are switched off if glucose is present and switched on if only lactose is present to save aa and energy

Question 86

What are the regions of the lac operon?

Answer 86

structural genes

operator region O- the gene switch

Promoter p- binding site for RNA polymerase needed for transcription of structural genes

Regulator gene 1- not part of operon, continually synthesises a repressor protein which binds to O in abscence of lactose. repressor protein wsitches on/of transcription of genes by blocking RNA polymerase binding to site P

Question 87

What hapens in the lac operon when glucose is present?

Answer 87

• The regulator gene (l) is expressed and the repressor protein is synthesised.
• The repressor protein binds to the Operator site
• The repressor protein blocks the Promoter site
• this stops RNA polymerase from binding to the promoter.
• The structural genes are not transcribed so the enzymes are not synthesised.

Question 88

What hapens in the lac operon when glucose is absent but lactose is present?

Answer 88

• Lactose (the inducer molecule) fits onto the repressor protein at another active site
• This causes the repressor protein to change its shape (a conformational change).
• Repressor dissociates from the operator site.
• RNA polymerase can now reach its promoter site and bind to the promoter
• The structural genes are transcribed, and the enzymes are synthesised.
• E. coli can then make use of the lactose.

Question 89

Role of CAP binding site and regulatory sites

Answer 89

• In addition to the structural genes, the lac operon contains a number of regulatory DNA sequences. These are regions of DNA to which particular regulatory proteins can bind, controlling transcription of the operon.
• CAP binding site is a positive regulatory site. The catabolite activator protein (CAP), when bound to cAMP binds to the CAP binding site promoting RNA polymerase binding to the promoter and hence transcription.

promoter is the RNA polymerase binding site

operator is a negative regulatory site bound by the lac repressor protein. The operator overlaps with the promoter, and when the lac repressor is bound, RNA polymerase cannot bind to the promoter and start transcription.

Question 90

Post transcriptional regulation of gene expression in eukaryotes/ RNA processing

Answer 90

• genes not only code for a polypeptide but also contain non coding regions known as introns.
• The coding regions are called exons.
• Before a protein can be synthesised the introns must be removed (spliced) from the primary mRNA before it leaves the nucleus
• The splicing is catalysed by Snurps – small nuclear ribonucleic proteins
• The exons are now spliced together to produce mature mRNA
• This ensures the correct primary structure of the polypeptide is produced

To produce different polypeptides from 1 gene, different introns spliced out

Question 91

Post translational regulation of gene expression in eukaryotes

Answer 91

• cAMP is sometimes needed to activate a protein once it has been synthesised before it can be functional
• EG. In muscle cells cAMP binds to an allosteric site on the enzyme glycogen phosphorylase to initiate glycogenolysis for energy. Inhibited by ATP so only when cells need energy will cAMP activate the process
• Can involve addition of non protein groups like carbohydrate chains, lipids or phosphates
• Involve modifying aa and formation of bonds like disulphide bridges
• Folding or shortening of proteins

Question 92

Morphogenesis

Answer 92

regulation of the pattern of anatomical development

Question 93

Homeobox genes

Answer 93

Contains a conserved stretch of DNA called the homeobox sequence (180 base pair sequence of DNA). Is a regulatory gene which is transcribed to form transcription factors. These bind to DNA to switch on and off genes that control body plan, causing them to be transcribed.

• Control how an organism’s body develops as it grows from a zygote into an organism- they are developmental regulatory genes
• They determine the body plan by specifying the identity of a particular body segment
• Genes in this group contain a conserved stretch of DNA called the homeobox and are nearly identical in all species across plants, animals and fungi – highly conserved implies they are fundamental to development
• This is 180 base pair sequence of DNA that has been found in many regulatory genes coding for the production of polypeptides about 60 aa long that act as transcription factors
• These factors bind to a particular region of DNA and cause it to be transcribed
• So a single homeobox gene can switch on a whole collection of other genes- by turning genes on and off in the correct order they ensure genes are expressed in the correct order so help give the basic pattern to the body
• Collinearity between the order of the homeobox genes and the expression pattern
• 8 homeobox genes regulate the identity of regions within the adult embryo
• The order of genes determines the body plan

Question 94

Hox genes

Answer 94

• Particular set of regulatory genes responsible for assigning the head to tail body (polarity) pattern in very early embryos
• They are a subset of homeobox genes
• Every hox gene is a homeobox gene, but not every homeobox gene is a hox gene
• Highly conserved
• Only present in animals
• The individual vertebrae and associated structures have all developed from segments in the embryo called somites
• The somites are directed by hox genes to develop in a particular way depending on their position in the sequence

Question 95

Homeosis

example

Answer 95

Homeosis is a mutation of a homeobox gene that causes transformation of 1 area of the body into another area. This can be so disastrous the organisms doesn’t usually survive

EG. The body plan of a typical insect is head-thorax-abdomen. Thorax is made from 3 segments and a pair of legs grows from each segment. A homeobox gene called Antp is usually turned on in the thorax causing legs to develop and turned off in the head

In some mutant flies the Antp gene is switched on in the head producing legs instead of antennae

• Fruit flies are investigated for genetic studies as small, easy to keep and short life cycle

Question 96

Hox clusters

Answer 96

• Hox genes are arranged in clusters
• Their order on the chromosome is the same as the order in which they appear along the body
• The more hox clusters the more complicated the body pattern

Question 97

1. Proto-oncogenes:
2. Tumour suppressor genes:

Answer 97

1. stimulate cell division
2. reduce cell division and can stimulate apoptosis

Question 98

What are cyclins

Answer 98

To move between different stages of the cell cycle, regulatory protein molecules (cylcins) activate enzymes with then activate or deactivate further key enzymes to cause the necessary changes

Question 99

Features of apoptosis

Answer 99

• Programmes cell death in multicellular organisms
• Different to necrosis because all the contents of the cell are contained and recycled
• Very quick process
• Highly regulated occurs after about 50 mitotic divisions
• Telomere- base pairs at end of chromosome get shorter as cell divides. When so short signals for apoptosis to occur

Question 100

Stages of apoptosis

Answer 100

1. Enzymes break down the cytoskeleton
2. Cytoplasm becomes dense with tightly packed organelles
3. Cell membrane changes and blebs form
4. Chromatin condenses and nuclear envelope breaks up
5. Cell breaks into vesicles
6. Vesicles removed by phagocytosis- cellular debris disposed of so doesn’t cause damage

Question 101

Why is apoptosis useful?

Answer 101

1. Metamorphis- when tadpoles change into frogs they loose their tail. The tail cells are removed by apoptosis
2. Embryo development- to separate fingers and toes, to remove ineffective T lymphocytes
3. Acts as a protective device for body as destroys and removes any cells that are genetically damaged and could give rise to cancer

Cells undergoing apoptosis can release chemical signals stimulating mitosis and cell proliferation leading to remodelling of tissues

Question 102

Problems with apoptosis

Answer 102

1. If there is not enough apoptosis then you can get tumour formation as they are immortal
2. No apoptosis between digits during embryo development leads to Syndactyly which can be fixed by surgery
3. Too much apoptosis leads to cell loss and degeneration (neurodegenerative diseases such as Parkinson’s or Alzheimer’s disease

Rate of dying should balance rate if cells produced by mitosis- cells are constantly being replaced and destroyed

Question 103

Control of mitosis and apoptosis by internal factors:

Answer 103

When cells experience stress these factors initiate apoptosis:

1. Irreparable genetic damage
2. RNA decay
3. Internal biochemical changes such as oxidation causing cellular injury

Question 104

Control of mitosis and apoptosis by external factors:

Answer 104

1. Cytokines (from immune system)
2. Hormones
3. Growth factors
4. Nitric oxide (makes the IMM more permeable to H+ so the proton gradient is lost)
5. Viruses and bacteria
6. Harmful pollutants
7. UV light

Question 105

Biotechnology

Answer 105

involves applying biological organisms or enzymes in the production of useful products or carrying out useful services.

Question 106

Advantages of using microorganisms

Answer 106

1. No ethical issues
2. Wide range of microorganisms can carry out many different chemical synthesis or degradations- produce useful proteins/ chemicals that can be harvested
3. Genetic engineering means we can artificially manipulate microorganisms to carry out synthesis reactions they normally wouldn’t (produce human insulin)
4. Have a short life cycle and rapid growth rate so if given right conditions of food, O2, temp, lots can be produced quickly.
5. Simple and cheap nutrient requirements. Genetic modification also means they can utilise materials which would have been wasted, making new raw materials for the syntheses, much cheaper than raw materials needed for other industrial processes
6. Most need low temperatures, O2 supply and food and removal of waste gases. They provide own catalysts in the form of enzymes so processes are cheaper than high temperatures and pressures and expensive catalyst used in non biological industrial processes

Question 107

Disadvantages of using microorganisms

Answer 107

1. If conditions aren’t ideal the microorganisms don’t grow properly so don’t work efficiently
2. Conditions ideal for microorganisms can be ideal for microorganisms causing disease or food to go off so the processes must be sterile
3. Some people make ethical issues with GM microorganisms must this is less common in microorganisms
4. Don’t produce unproductive cells and tissues like wood and bone

Question 108

What is a culture?

What is a medium?

What is a closed culture?

Answer 108

• Culture: a growth of microorganisms of one or more species
• Medium: could be a liquid such as nutrient broth or a solid surface such as nutrient agar gel
• In a closed culture environment, where conditions are fixed and contained, no new materials are added and no waste products or organisms are removed.

Question 109

Standard growth curve and pahses

Answer 109

Lag phase: adapting to new environment. Growing, synthesising specific enzymes, switching on genes. Taking in water. Cells active but not reproducing.

Log phase: rate of bacterial production is close to or at its theoretical maximum. Population doubles each generation. Plenty of space and nutrients.

Stationary phase: growth rate= 0. Number of cells by binary fission cancelled by number of cells dying. Nutrient levels decreasing, waste products build up.

Death phase: reproduction almost ceased and death rate increases. High levels of toxic by-products, nutrients used up

N=N₀x 2ⁿ is the formula for number of individual organisms

Question 110

What would happen if more nutrients were added in the lag and stationary phases?

Answer 110

• If more nutrients were added in the lag phase, nothing would happen, as there aren’t limiting nutrients, the cells need time for enzymes and genes.
• If nutrients were added in the stationary phase, another log phase may begin, but waste products may prevent this of lack of space.

Question 111

Indirect food making

Answer 111

The microorganisms have an action on other foods, not the product Eg. For bread it is flour

Question 112

Limiting factors preventing exponential growth:

Answer 112

• Nutrients
• O2 levels as demand increases from respiration
• Temperature for enzyme controlled reactions in microorganisms. Higher temp speeds up growth and reproduction, too high can denature and kill microorganisms
• Build up of waste can be toxic and inhibit further growth and kill the culture
• Ph as CO2 produced by bacteria respiring. Can affect enzyme activity and inhibit growth

Question 113

Baking

Answer 113

Microorganisms- yeast mixed with sugar and water to respire aerobically. CO2 produced makes bread rise

Steps in commercial process-

1. Active yeast mixture added to flour and other ingredients. Yeast enzyme break down starch in flour to maltose, and break disaccharides to monosaccharides. Mixed and left in warm environment to rise
2. Yeast respires aerobically producing co2, creating air bubbles.
3. Dough is knocked back to remove excess air, kneaded, shaped and left to rise again
4. Cooked in hot oven where the CO2 bubbles expand so bread rises. Yeast cells are killed

Question 114

Brewing

Answer 114

Microorganisms- yeast respires anaerobically to produce ethanol. Traditional yeasts ferment 20-80*C, but GM yeasts ferment lower so are cheaper. They clump together (flocculate) and sink at end of process leaving beer clear

Steps in commercial process-

1. Malting- barley germinates producing amylase to catalyse hydrolysis of starch to maltose which yeast can respire. Germination is stopped by heating the grain between 40-70*C to denature enzymes and stop hydrolysis
2. Milling- grains crushed to remove sugars
3. Mashing- hot water poured over grain to dissolve sugars and other soluble compounds to form wort.
4. Boiling- wort is boiled with hops for flavour and antiseptic. Boiling concentrates the wort which is then cooled
5. Fermentation- yeast added to ferment the wort to produce CO2 and ethanol. Temp maintained for optimum anaerobic respiration (fermentation). Yeast then inhibited by falling pH, build up of ethanol and lack of oxygen.
6. Maturation- beer is conditioned for 4-29 days and temps of 2-6*C in tanks
7. Finishing- beer is filtered, pasteurised then bottled or canned with addition of CO2
8. Alcohol content 4-9%

Question 115

Cheese making

Answer 115

Microorganisms- bacteria feed on lactose in milk, changing the texture and taste and inhibiting growth of bacteria which make milk go off

Steps in commercial process-

1. Milk is pasteurised (heated for 95*C for 20 seconds to kill of natural bacteria) and homogenised (fat droplets evenly distributed through milk)
2. Mixed with bacterial cultures and sometimes chymosin enzyme and kept until milk separates into solid curds and liquid whey
3. For cottage cheese, the curds are separated from the whey, packed and sold
4. Most cheese the curds are cut and cooked in whey then strained through draining moulds and cheesecloth. Whey used for animal feed
5. Curds put into steel or wooden drums and may be pressed. They are left to dry, mature and ripen before eating as the bacteria continue to act for weeks-years

Question 116

Yoghurt making

Answer 116

Microorganisms- bacteria (often lactobacillus bulgaricus which forms ethanol) and (streptococcus thermophilus forms lactic acid) produce extracellular polymers giving yoghurt its smooth thick texture

Steps in commercial process-

1. Skimmed milk powder is added to milk and the mixture is pasteurised, homogenised and cooled to 47*C
2. The milk is mixed with a 1:1 ratio of the 2 bacteria’s and incubated at 45*C for 4-5hrs
3. At the end of fermentation, the yoghurt may be put into cartons at a temperature of 10*C or mixed with previously sterilised fruit
4. Thick set yoghurts are mixed and ferment in the pot
5. Yoghurt has a 19 day shelf life if stored at 2-3*C

Question 117

Direct food making

Answer 117

• People eat fungi as mushrooms
• Due to potential protein shortages, single cell protein or SCP (quorn) uses microorganisms to directly produce the protein you eat
• Eg- Quorn is made of the fungus Fusarium venetatum, a single celled fungus grown in fermenter using glucose syrup as a food source. The microorganisms are combined with albumin (egg white) then compressed and formed to meat healthy substitutes
• Other attempts to make proteins from microorganism have not been successful including yeasts, algae and bacteria used to grow proteins that match animal proteins found in meat as well as plant proteins.

Question 118

Advantages of using microorganisms for direct food making

Answer 118

1. They can be grown on almost anything
2. reproduce fast and produce protein faster than plants and animals
3. low in fat
4. They can also be made to taste like anything.
5. Not reliant on weather, breeding cycles. Can be increased/ decreased on demand
6. Can use a wide variety of materials including human waste so cheap. Cheaper than growing crops and take up less space
7. No ethical issues
8. Microorganisms can be GM to produce the protein required

Question 119

Disadvantages of using microorganisms for direct food making

Answer 119

1. People don’t want to eat microorganisms grown on waste.
2. Some microorganism can also produce toxins if the conditions aren’t optimum
3. Microorganisms must be separated from nutrient broth and processed to make the food
4. Need sterile conditions carefully controlled makes it more expensive
5. People have concerns eating GM food
6. Protein has to be purified to ensure contains no toxins or contaminants
7. Needs additives as little natural flavour
8. Less energy, protein and iron than meat

Question 120

Define:

Cloning

Natural cloning

Answer 120

Cloning- a process that occurs naturally and artificially to produce a group of genetically identical organisms

Natural cloning- uses vegetative propagation (asexual reproduction) in which a new plant grows from part of the parent plant- the meristem. This is a region of undifferentiated cells (root and shoot tips – apical buds or

cambium). The new plants are clones of the parent

Question 121

Vegetative propagation:

Answer 121

1. Runners- lateral stem growth over soil surface and roots develop where touches the ground. Adventitious roots form at nodes and new plantlets grow. Runners wither and die once new plant is established. EG strawberry and spider plants
2. Tubers- swollen parts of underground stems (stolons) store food. Forms lateral buds which grow into new plants EG. potatoes
3. Rhizomes- horizontal underground stems which grow shoots at intervals EG ginger
4. Bulbs/ corms- short swollen stems with food from photosynthesis. Can be divided up and each grows into a new plant (usually the next season) EG garlic, daffodils, tulips

Question 122

Artificial cloning in plants:

Answer 122

Assists the natural process of vegetative reproduction

1. Can take cuttings- remove stem, root or leaf from parent plant and grow in controlled conditions until adventitious roots or shoots greow. Hormones ofte used to help roots growth
2. Division- works with plants that grow in clumps. Dig up clump, separate into smaller plants and replant further apart
3. Grafting- joining structure together from 2 or more plants. Commonly used for fruit trees. The scion has good fruit qualities and is attached to the root stock which has good roots which can grow in environment. You get the best features from each plant. Plastic bag can be ties around it to retain moisture- humidity prevents transpiration while xylem fuses as hard to take up water.

Question 123

Advantages and disadvantages of artificial cloning in plants

Answer 123

Advantages:

1. Quick and easy to grow as seeds are susceptible to disease, pests, frost
2. Uniform appearance and size (reliable quality, size helps harvesting and packaging)
3. Cheaper to produce
4. Can pass on good characteristics so well adapted to outcompete other plants

Disadvantages:

1. All plants at equal risk of disease/ pests- no resistant ones
2. Loss of genetic variation (species unable to adapt to environmental change like global temp)

Question 124

Micropropagation

Answer 124

• Makes huge numbers of genetically identical offspring from 1 parent plant using sterile tissue culture techniques
• Produces potatoes, sugar cane, bananas, strawberries, grapes, orchids
• Good if the plant doesn’t readily produce seeds, is rare, needs to be pathogen free, doesn’t respond to natural cloning

1. Tissue sample scraped from parent plant- explant. Sterilised in sterilising agent eg sodium dichloroisocyanurate
2. 2.Sterile culture medium of plant hormones stimulating mitosis. Cells proliferate forming a mass of undifferentiated cells called a callus
3. Callus divided into individual cells or clumps and transferred to a new medium- agar growth medium containing nutrients, auxins and gibberellins
4. Samples develop into tiny plantlets- genetically identical plants, and planted into compost

Question 125

Advantages and disadvantages of microprogatation

Answer 125

Advantages:

1. Large numbers from a single seed
2. Less space needed
3. Quick as don’t have to wait for seed production
4. International exchange as sterile so no quarantine
5. Less plant diseases by careful selection and sterile techniques
6. Overcomes seasonal restrictions
7. Selection of desirable traits
8. Can grow plants usually infertile/ hard to grow from seed
9. Can increase numbers of rare plants
10. Culturing meristem tissue produces disease free plants

Disadvantages:

1. Monoculture so susceptible to same diseases/ environmental change
2. Expensive, needs skilled staff
3. Explants and plantlets susceptible to infection

Question 126

natural clones in animals

Answer 126

Animals rarely reproduce asexually

Vertebrates:

• Identical twins are formed from the same sperm and egg, which has divided into 2 after fertilisation
• May look different due to position and nutrition in uterus
• They are clones of each other not their parents

Invertebrates:

• Starfish can regenerate entire animals from fragments of the original
• Flatworms and sponges fragment and form new identical animals as part of normal reproduction.
• They are all clones of original

Question 127

Artificial cloning in animals

Answer 127

Embryonic cells are totipotent so can differentiate into any type of adult cell found in the organism

The properties of these cells can be used to artificially clone animals

Question 128

Embryo twinning

Answer 128

1. A high value female is treated with hormones so she super ovulates, releasing more eggs than usual
2. Her eggs and the sperm of a high value male are collected and fused by IVF
3. Grow in vitro to 16-cell embryo, before too many divisions will no longer be totipotent
4. Split totipotent cells from developing embryo into several separate segments and implant into several surrogate mothers- single pregnancies less risky than twin
5. Embryos develop into foetus and are born normally. Each offspring is a clone- genetically identical

Used routinely in livestock since 1980’s

Question 129

Advantages and disadvantages of embryo twinning

Answer 129

Advantages:

1. Elite female doesn’t have to go theouhg risky pregnancy
2. No embryos are destroyed
3. Can freeze embryos and use 1 to see characteristics. If they are good can unfreeze and use all.
4. Max offspring with good characteristics

Disadvantages:

1. Involves meiosis and fertilisation so not possible to predict offspring exactly
2. Loss of genetic diversity
3. Increased susceptibility to disease/ pests

Question 130

Reproductive cloning

Answer 130

1. Uses the technique somatic cell nuclear transfer (SCNT)
2. Nucleus is removed from an egg to form an enucleated ovum.
3. Its fused with the nucleus from a differentiated adult cell from the same species
4. A needle can be used to remove and insert the nucleus or an electric current applied so they fuse
5. Once the egg has formed a small embryo, its implanted ‘culture’ in ties oviduct of animal.
6. The early embryo is then recovered and implanted into a surrogate mother

This clones an adult animal

Question 131

Advantages and disadvantages of reproductive cloning

Answer 131

Advantages:

1. Can mass produce animals with desired characteristics eg high milk yield
2. Can be used for pharmed animals- production of animals which have been genetically engineered to produce drugs in milk
3. Can be used to preserve rare breed or endangered animals (interspecific SCNT where embryo is implanted back into domesticated animal as rarely enough females of same species to receive embryos
4. Know what genes will be in offspring as no meiosis

Disadvantages:

1. Cloned offspring often have reduced longevity- abnormally large organs
2. Often unsuccessful
3. Risk like of clone and mother
4. Inefficient- many eggs to produce a single offspring
5. Religious and moral objections

Question 132

Therapeutic cloning

Answer 132

• Therapeutic cloning uses embryos from reproductive cloning to generate cells, tissues and organs to replace those lost by disease or accidents
• Not whole organisms
• Less likely to reject
• Does destroy and embryo as doesn’t produce another organism

Question 133

Types of metabolites produced by microorgaisms

Answer 133

Primary metabolites- compounds produced during normal growth of an organism

Secondary metabolites- made once growth slows/stops e.g. Penicillin production- bacteria provide competition as decompose nutrients which are limiting in stationary phase. Antibiotics kill competition.

The production of primary metabolites will be proportional to the abundance of microorganism

Question 134

Penicillin production

Answer 134

1. A fermenter is filled with nutrients and fungi (penicillium chrysogenum) and allowed to grow for a week
2. Temperature (25-27), pH (6.5) and nutrient levels are constantly monitored. Needs high O2 levels
3. As nutrients are depleted, penicillium is produced which is extracted and purified

• Paddle stirrers to keep oxygenated as may be thick so diffusion not good enough for all microorganisms to get food and o2
• Rich nutrient medium
• Temp maintained by cooling jacket
• Small fermenter as hard to maintain oxygen levels in large ones

Question 135

Insulin production

Answer 135

• People with type 1 diabetes and sometimes type 2 need regular injections to control blood sugar levels. Used to be extracted from pancreas of animals so supply depend on demand for meat. People were also allergic as it was often impure. Also ethical issues over animal products
• Genetically engineered bacteria were developed to make human insulin
• Bacteria grown in fermenter and downstream processing results in constant supply or pure human insulin

Question 136

Batch culture

Answer 136

Batch- microbes and all the nutrients required for the process are asses then allowed to grow for a fixed period of time before product is removed. No further nutrients are added. Secondary metabolites. Stopped before death phase

EG. Penicillin from fungus

• Contamination can lead to loss of large volumes of product
• Slower GR as nutrients decrease with time
• Less efficient, fermenter not used all the time
• Easy to set up and maintain
• Blockages less likely
• Fermenter can be cleaned and sterilised and used for a completely different process

Question 137

Continuous culture

Answer 137

Continuous- nutrients are added to the fermentation tank and products removed at regular intervals. Primary metabolites

EG insulin from GM E.coli

• Contamination results in loss of small amount of product
• Faster growth rate as nutrients added continuously
• More efficient as fermenter continually used
• Harder to set up and maintain- higher skill
• Blockages more likely
• Smaller vessels used as constantly adding product. Less space needed to obtain good yield

Question 138

Bioremediation

Answer 138

• Use of microorganism to remove toxic materials from soil or water like heavy metals and sewage
• Microorganism can also break down hydrocarbons in petroleum to CO2 and water
• Nutrients can be added to oil sills which encourages bacterial growth but too much can cause algae bloom
• As well as natural organism, GM bacteria are trying to be developed to break down contaminants they wouldn’t usually encounter EG bacteria have been engineered to remove mercury from water

Question 139

Why is aseptic technique needed?

Answer 139

Microorganisms need to be cultured in sterile conditions:

1. To avoid contamination by other microorganisms

• They could compete with the culture organisms for nutrients and space
• Reduce the product yield
• Spoil the product
• Produce toxic substances
• Destroy the culture organisms or their product

1. Prevents release of potentially harmful organisms into the environment
   * A mutation may occur making the strain pathogenic if not already

Question 140

Inoculating broth nutrient medium

Answer 140

1. Make a suspension of the bacteria to be grown
2. Mix a known volume with the sterile nutrient broth in the flask
3. Stopper the flask with cotton wool preventing air contamination
4. Incubate at suitable temperature, shaking regularly to aerate the broth providing O2 to bacteria growing

Question 141

Inoculating agar nutrient medium

Answer 141

1. Wire inoculating loop sterilised holding in a Bunsen flame until glows red hot. Not allowed to touch any surfaces as cools to avoid contamination
2. Dip sterile loop in bacterial suspension and remove lid of petri dish and make zig zag streak across surface of agar. Avoid loop digging into agar
3. Replace lid of petri dish, held down with tape but not sealed completely so O2 can get in, preventing growth of anaerobic bacteria.
4. Incubate at suitable temperature

Question 142

Aseptic technique

Answer 142

• Use disinfectant to sterilise working area
• Wear gloves and protective clothing and roll sleeves up to stope getting microbes on clothes stops them being transferred out the lab
• Keep doors and windows closed due to wind
• Sterile equipment (autoclave at high temps)
• Flame collecting loop (hold in Bunsen). Let it cool otherwise will kill microbes.
• Work near Bunsen flame to keep an updraft so less likely contamination from air
• Hold everything below flame so no air contamination
• Don’t put sterile equipment down
• Hold lid down so microbes from air don’t settle
• Flame neck of microbe bottle

Agar upside down so condensation doesn’t drip

Question 143

Why does growth of microorganisms need to me measured?

How is it measured?

Answer 143

• Is important as environmental health officers regularly inspect food premises and take samples for analysis, water boards check water supplies daily and many products are produced using bacteria grown in fermenters and their growth needs to be measured.

Direct count- remove sample, count under microscope and using counter chamber. May need to dilute sample if too many by serial dilution. Includes living and dead.

Viable count- sample diluted and plated. Colonies grow and counted. Each bacteria grows into a colony. Living only

Turbidimetry- sample put in colorimeter. Measures cloudiness (turbidity) of solution. Includes living and dead cells

• It’s not possible to count whole populations of microorganisms
• Instead the cells in a very small sample of culture are counted and the results multiplied up to give a population density in organisms per cm3 of culture
• Even then the population density is so high that cell counts are usually made in known dilutions of the culture- serial dilutions. You must multiply by the dilution factor
• Need enough colonies to count but need to be able to see individual colonies

Question 144

Advantages of isolated enzymes

Why are extracellular enzymes often used?

Answer 144

1. Less wasteful as whole microorganisms use up substrate growing and reproducing, producing biomass rather than product
2. More efficient as work at higher concentrations than is possible when part of whole microorganism. Can give enzymes ideal conditions for max product formation which may differ from conditions for growth of whole microorganism
3. More specific as no unwanted enzymes present, no wasteful side reactions
4. Pure product so no need to separate- expensive

• Secreted so easier to isolate and use
• Few extracellular enzymes used so easy to identify and isolate required one
• More robust than intracellular as conditions outside cells less tightly controlled than cytoplasm- temp, pH

Some intracellular still used as wider range of them

Question 145

How are enzymes immobilised?

Answer 145

1. Adsorption
2. Covalent bonding
3. entrapment

Attached to an inert support system over which the substrate passes and is converted to product. Enzymes are usually bound to membranes in cells

Question 146

Adsorption

Answer 146

• Enzymes are bound to a supporting surface (e.g. clay, porous carbon, glass beads, resins)
• Hydrophobic interactions and ionic links

Advantages

Enzymes stay exposed to substrates

Disadvantages

can distort active site- reducing activity

Bonding forces not always strong and can become detached and leak into the reaction mixture

Question 147

Covalent bonding

Answer 147

• Enzymes bonded onto a supporting surface such as clay using strong covalent bonds
• Mesh of cellulose, collagen

Advantages

Not likely to become detached as stronger

Enzymes accessible to substrate

Disadvantages

Expensive, can distort active site- reducing activity

Question 148

Entrapment

Answer 148

• Enzymes trapped in a matrix of polysaccharides, gelatin that does not allow free movement
• in a membrane, microcapsules

Advantages

Remains fully active site

Efficient, no contamination

Small effect on enzyme activity

Disadvanatges

Substrate must diffuse into the entrapment matrix

Product must diffuse out (i.e. slower action)

Expensive

Question 149

Making alginate beads

Answer 149

You will immobilise some enzymes and then use them to break down sucrose
The enzyme needed is called sucrase. Sucrase can be found in yeast cells

• Mix 20cm3 sodium alginate solution and 1cm3 yeast suspension together in the beaker.
• Use the teat pipette to add drops of the mixture into the calcium chloride solution. Small beads of alginate should form.
• Put the beads into the sieve and wash them under a running tap.
• Place the beads into the measuring cylinder.
• Test the sucrose solution with the reagent strip.
• Pour 25cm3 sucrose solution into the measuring cylinder and leave for 10 minutes.
• Test with the reagent strip every minute for 10 minutes and track the changes in terms of amount of glucose present

Question 150

Advantages and disadvantages of immobilised enzymes

Answer 150

Advanatges:

1. Products not contaminated with enzymes
2. Enzymes can be reused again and again so cheaper
3. Reaction is continuous so the process can be automated and therefore cheaper to run
4. Enzymes more stable at higher temp and pH which makes I cheaper as less controlled
5. More reliable as greater degree of control as stable microenvironment

Disadvantages:

1. Reduced efficiency- process of immobilising an enzyme may reduce its activity rate
2. Higher initial costs of materials as more expensive but don’t need to be replaced frequently
3. More expensive bioreactor
4. More technical issues as more complex so more things can go wrong

Question 151

Industrial uses of immobilised enzymes:

Glucose isomerase

Answer 151

• Converts glucose to fructose
• Glucose produced from cheap, starch rich plant material
• Produces high fructose corn syrup- much sweeter than sucrose
• Often used in diet foods
• Cheaper than sucrose
• No enzyme contamination

Question 152

Industrial uses of immobilised enzymes:

Penicillin acylase

Answer 152

• Used to make semi-synthetic penicillins e.g. amoxicillin and ampicillin from naturally produced penicillins
• Some penicillin resistant microorganisms are not resistant to these so can treat bacterial infections

Question 153

Industrial uses of immobilised enzymes:

Lactase

Answer 153

• Lactose -> glucose and galactose by hydrolysis
• Used to produce lactose free milk which provides calcium for strong bones and teeth- weak bones is osteoporosis

Question 154

Indistrial uses of immobilised enzymes:

Aminoacylase:

Answer 154

• Used to produce pure samples of L-amino acids by removing the acyl group from the nitrogen of an N-acyl-amino acid
• L-amino acids are the building blocks for the synthesis of a number of:
• Pharmaceutical compounds
• Agrochemical compounds
• Additives for food

Question 155

Industrial uses of immobilised enzymes:

Glucoamylase

Answer 155

• During the hydrolysis of starch, short polymers of glucose (dextrins) are formed by amylase
• Immobilised glucoamylase converts dextrins to glucose
• Can be immobilised on a variety of surfaces and used to digest sources of starch e.g. corn and cassava
• Used also to ferment starch pulp to alcohol to produce gasohol
• Also to make high fructose corn syrup

Question 156

Industrial uses of immobilised enzymes:

Nitrile hydratase:

Answer 156

• Converts nitriles to amides including acrylonitrile to acylamide- hydration
• Acrylamide can be polymerised to form polyacryamide (plastic used as a thickener)
• can be used to treat water – sticks small contaminants together so they can be precipitated and easily filtered
• Also used in paper making and gel for electrophoresis
• The process used to need extreme conditionms and expensive and unwanted by-products and poor yield, and needed catalyst. Immobilise enzymes means moderate conditions so cheaper, 99% yield and no byproducts