3.7- Chapter 19- Populations in Ecosystems

Question 1

What is ecology?

Answer 1

Study of inter-relationships between organisms and their environment- non-living factors (abiotic) and living factors (biotic).

Question 2

What are ecosystems?

Answer 2

dynamic systems made up of a community and non-living factors. e.g. a pond. Can be very large to very small. Contain a number of species.

Question 3

What is the carrying capacity?

Answer 3

• The maximum stable population size of a species an ecosystem can support.
• Varies as a result of limiting abiotic and biotic factors.
• Can be sustained over a relatively long period.

Question 4

What is a population?

Answer 4

A group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed.

Question 5

What is a community?

Answer 5

All the populations of different species living together and interacting at a particular place at the same time.

Question 6

What is a habitat?

Answer 6

• The place where an organism normally lives.
• Characterised by physical conditions and other types of organisms present.
• Within an ecosystem there are many habitats.

Question 7

What are microhabitats?

Answer 7

• Smaller units within habitats with their own microclimate.
• e.g. mud at the bottom of the stream- microhabitats for bloodworms.

Question 8

Describe the features of ecosystems?

Answer 8

• Ecosystems- interacting biotic and abiotic factors in a particular area- number of communities.
• Community of organisms with the non-living (abiotic) conditions in the area in which they live. E.g. a pond/ lake.
• Vary in size- small to large.

Question 9

What conditions are there in ecosystems?

Answer 9

• Both biotic and abiotic conditions:
• Biotic conditions- living features of an ecosystem e.g. the presence of predators or food.
• Abiotic conditions- non-living features of an ecosystem- e.g. temperature.

Question 10

What major process occur in ecosystems?

Answer 10

• The flow of energy through the system- energy is transferred.
• The recycling of elements within the system.
• There is little to no net loss or gain between natural ecosystems- most energy is transferred and elements are recycled.

Question 11

Describe habitats.

Answer 11

• Place where an organism lives within an ecosystem.
• Within each habitat, each species has its own niche.

Question 12

What is an ecological niche?

Answer 12

• Within a habitat a species occupies a niche governed by adaptation to both abiotic and biotic conditions- describes how the organism is adapted to its environment to survive reproduce, and maintain a viable population.
• A niche is the role of a species within its habitat- e.g. what it eats, what it does, where it lives.
• Niche includes:
• Biotic interactions- what it eats, what its eaten by, what the organism competes with.
• Abiotic interactions- temperature range it can live in, time of day its active.
• Some species may appear very similar but their behaviour may be different due to different levels of tolerance to environmental factors.
• Each species has it’s unique niche as no niche can be occupied by more than one species- some species appear similar but they have slight differences.

Question 13

What is the competitive exclusion principle?

Answer 13

• No two species can occupy the same niche as they will compete with each other- the competition means one will not be able to outcompete the other and will die out.
• Exclusion is based on adaptions- the better adapted species outcompetes the other.

Question 14

Describe adaptions and their relations to niche.

Answer 14

• Adaptions- features members of a species have to increase chances of survival and reproduction.
• Can be physiological (processes inside body), behavioural (way an organism acts) or anatomical (structural features). E.g. giraffes have long necks- help them reach vegetation.
• Organisms with better adaptions are more likely to survive, reproduce and pass on advantageous alleles determining adaptions. This increases the frequency of these alleles in the population- adaptions become more common- natural selection.
• Every species- adapted to use an ecosystem like no other species can- unique niche.
• Organisms- better adapted to abiotic conditions (water, temperature etc.) and biotic conditions (predation and competition) within an ecosystem and their niche, are the ones more likely to survive interspecific competition and outcompete the other species.

Question 15

Whaat is population?

Answer 15

All the organism of one species in a habitat- make up a community.

Question 16

What is population size?

Answer 16

Total number of organisms of one species in a habitat- dynamic- changes over time.

Question 17

How can population sizes and carrying capacity vary.

Answer 17

• Populations are dynamic and vary in size and composition over time.
• Population sizes and carrying capacity within ecosystems vary due to many different factors.
• Changes in these factors influence the rate of growth and size of the population.
• Populations within communities are affected by, and in turn affect abiotic and biotic factors.

Question 18

What are the factors that impact population sizes and carrying capacities within ecosystems and communities?

Answer 18

• Abiotic factors- physiochemical factors e.g. temperature, rainfall.
• Biotic factors- interactions between organisms- affected by other populations- interspecific and intraspecific competition, pathogens and predation.

Question 19

Why is a population often difficult to measure or define?

Answer 19

• The boundaries of a population are often difficult to define.
• Populations are dynamic and vary in size and composition over time.

Question 20

How can you plot graphs of population size?

Answer 20

• Where a population grows in size slowly- can plot a graph of population against time.
• Large population size difference- exponential e.g. in the growth of bacteria, can be mitigated with a log scale, making it easier to see patterns.

Question 21

Why does no population grow indefinitely?

Answer 21

• Factors limit growth- e.g. food, water etc.
• Accumulation of toxic wastes, disease and predators limit growth.
• The population stays within the carrying capacity of its ecosystem.

Question 22

How must you describe factors in relation to the the population size?

Answer 22

• Link the birth and death rates of individuals in a population.
• e.g. increase in food- doesn’t mean more individuals just bigger individuals- so have to show what it means e.g. more food= more likely to survive and reproduce so population increases.
• This means effects usually take longer to influence the population size- there is a time lag.

Question 23

Describe the overall growth rate of micro-organisms.

Answer 23

With enough food and space- population size of microorganisms grows at a steady rate.

Question 24

Describe how you investigate the growth of micro-organisms.

Answer 24

• Investigated by growing bacteria in liquid broth- broth culture.
• Light passed through sample of broth- scattered because bacteria present- reduces light passing through culture- spectrophotometer measures amount of light passing through- absorbance value- more bacteria present= less light passing through detected by the spectrophotometer- producing higher absorbance value. High absorbance value= high number of bacteria and vice versa.
• Absorbance- proportional to number of bacteria- convert the number to show population of bacteria.

Question 25

How do you plot the graph of bacteria growth?

Answer 25

• Plotted over time- produces an exponential graph- bacteria doubling at regular intervals.
• As numbers increase steeply over a short period of time- it’s hard to draw a scale- logarithm scales can be used to plot the graph instead- results in a straight line graph- need to be able to read log scale to read the graph.

Question 26

How does population size vary in a population growth curve of photosynthetic bacteria.

Answer 26

1. Initially when there are good conditions, the population increases rapidly because all the factors needed for growth are persent and there is no limiting factors.
2. Over time, more nutrients are consumed as the population becomes larger, the population becomes so large the bacteria prevent light reaching those at lower levels, other species may be introduced and compete for the same resources as the bacteria or predate on bacteria, and wintery conditions may bring lower light intensity, making conditions tought.
3. The growth of hte population slows and then stops.
4. The population size sometimes then decreases
5. The population then reaches a constant size until conditions change and factors improve to increase growth again.

Question 27

Name the main abiotic factors that can affect population growth.

Answer 27

• Temperature
• Light
• pH
• Water and humidity

Question 28

Describe the general impact of abiotic conditions on a species.

Answer 28

• When abiotic conditions are ideal for a species, organisms can grow more quickly and reproduce more successfully.
• When abiotic conditions aren’t ideal for a species, organisms can’t grow as fast or reproduce as successfully.
• When abiotic factors are below the optimum- fewer individuals are able to survive if adaptions are not suited to conditions.
• If no individuals have adaptions to survive- the population becomes extinct.

Question 29

How does temperature affect population size in general.

Answer 29

• Each species has a different optimum temperature where it survives best
• Further from optimum= few individuals are able to survive- adaptions further away from optimum- smaller population.

Question 30

How does temperature affect population size of cold-blooded animals.

Answer 30

• If fall below optimum- enzymes work more slowly- metablic rate reduced- smaller carrying capacity.
• Above optimum- enzymes work less efficiently and denature- carrying capacity and population size reduced

Question 31

How do changes in temperature affect warm-blooded animals?

Answer 31

• Warm blooded animals- birds and mammals- maintain constant body temperature regardless of external temperature.
• Extreme temperature changes from the optimum- mean more energy expended trying to maintain normal body temperature.
• Less energy for growth and reproduction.
• Carrying capacity and population size reduced.

Question 32

How does light impact population size?

Answer 32

• Light is the main source of energy for most ecosystems- basic necessity of life.
• Rate of photosynthesis increases as light intensity increases.
• Faster photosynthesis= faster plant growth and more seeds.
• Carrying capacity greater and carrying capacity of animals that feed on the plants greater.

Question 33

How does pH impact population size?

Answer 33

• Affects the action of enzymes.
• Enzymes- have optimum pH where work most effectively.
• Population of organisms larger where the right pH exists and smaller where pH is different from the optumum.

Question 34

How does water and humidity impact population size?

Answer 34

• Low water= small population- only species adapted to dry conditions
• Humidity- affects transpiration rates of plants and evaporation rates of water from animals.
• Dry condidtions- populations adapted to tolerate low humidity large than those with no adaptions.
• Carrying capacity of adapted populations greater.

Question 35

What biotic factors affect the population size and carrying capacity.

Answer 35

• Interspecific and Intraspecific competition
• Predation
• Pathogens

Question 36

What is competition?

Answer 36

• Two or more individuals share a resource that is in insufficient quantity to satisfy all their needs.
• Competition occurs within and between populations for means of survival.
• Leads to evolution of the species and adaptions.

Question 37

What are the two types of competition and describe them.

Answer 37

• Intraspecific competition- competition between members of the same species
• Interspecific competition- competition between members of different species.

Question 38

Describe intraspecific competition.

Answer 38

• Individuals of the same species compete for resources and mates to survive and reproduce.
• The availability of resources determines population size and competition- more= larger population and less competition and v.v.
• Can cause cyclical change in population size around the carrying capacity- population grows, shrinks, then grows again:
• The population increases when resources are plentiful.
• As the population increases, there’s more organisms competing for the same amount of space and food- resources become limiting.
• If population grows beyond carrying capacity- not enough resources for all the organisms- population declines.
• Smaller population- less competition for space and food- better for growth and reproduction- population grows again- cyclical.

Question 39

Draw a graph to represent the cyclical nature of intraspecific competition.

Answer 39

Answer on revision card.

Question 40

Describe interspecific competion.

Answer 40

• Different species compete with each other for the same resources.
• The resources available to both populations are reduced so both have less energy for growth and reproduction and both population sizes will be lowered.
• If one species has a competitive advantage- this population becomes larger than the other population- it out-competes it. The other population may become extinct.

Question 41

Describe the competitive exclusion principle.

Answer 41

• In interspecific competition, species usually has a competitive advantage- this population increases while the other population decreases.
• If conditions remain the same and the species occupy the same ecological niche (habitat, food etc.)- this will lead to the complete removal of one species.
• In competition for limited resources- the species that uses these resources most effectively will ultimately eliminate the other- it out-competes it.
• If species occupy different niches e.g. similar but eat different foods- competitive exclusion can’t happen.
• No two species can occupy the same niche for a long time without one species eliminating the other- it becomes extinct e.g. Grey squirrels and red squirrels.

Question 42

Describe the predator- prey relationship

Answer 42

Interspecific- their population sizes are interlinked- the population of one changing causes the population of the other to change.

Question 43

What is predation?

Answer 43

When one organism is consumed by another.

Question 44

What is a predator?

Answer 44

An animal that feeds on another animal.

Question 45

What is prey?

Answer 45

Animals that are fed on by other animals.

Question 46

Why is evolution important for predators and prey?

Answer 46

• Predators and prey evolve together- as predators have become more evolved and better adapted at catching prey, prey have evolved to become better at escaping predators.
• If predators and prey do not adapt one may become extinct, which may lead to the extinction of the other.

Question 47

Why are habitats important for predator- prey relationships?

Answer 47

• If prey and predator are brought together in a lab, they prey exterminates the predator- demonstrating habitats are important for survival of prey.
• In habitats, the area a population can travel is greater and the variety of environment is more diverse- more potential refuges- prey can escape predation because they are harder to find and catch and rarely become extinct.

Question 48

Why is it hard to study predator-prey relationships?

Answer 48

• Can’t be studied in a lab as doesn’t reflect what happens in the wild.
• Not possible to count all individuals in a population- population can only be estimated- no guarantee of accuracy- data must be treated with caution.
• It is hard to reflect predator-prey relationships with data- other factors, such as the preys food supply, disease and climatic factors may be affecting results. Predators eat a range of foods so the predator and prey aren’t directly linked

Question 49

How does the predator-prey relationship affect population size cyclically?

Answer 49

• Prey population increases- more food for predators- predator population grows.
• Predators eat prey, reducing prey population.
• With fewer prey, the predators have greater competition.
• The predator population is reduced as some are unable to obtain enough prey to survive and reproduce.
• With few predators left, fewer prey are eaten and more survive and reproduce so the prey population increases.
• With more prey for food, the predator population increases.

Question 50

Describe how the predator prey population changes graphically?

Answer 50

Predator and prey populations cyclically fluctuate

Question 51

How does the predator prey relationship influence evolution?

Answer 51

• Population crashes are important for evolution
• Fluctuations create selection pressues- individuals who escape predators,, catch prey, or withstand disease/ bad climate- more likely to survive and reproduce.
• The population becomes better adapted to conditions

Question 52

What measures are used surrounding populations?

Answer 52

Populations of organisms are investigated by looking at distribution and abundance of a species in a particular area.

Question 53

What is distribution?

Answer 53

Where a particular species is within the area you’re investigating.

Question 54

What is abundance.

Answer 54

Number of individuals within a species within a given area.

Question 55

How can abundance be measured?

Answer 55

• Frequency- the number of samples a species is recorded in (e.g. in a quadrat). Useful if species are hard to count. Quick and easy. Doesn’t provide detailed information on distribution and density.
• Percentage cover- estimate of area that a species covers- useful when a species is abundant. Data can be collected rapidly and individual plants don’t need to be counted but less useful when organisms overlap. Only works for non-motile or slow-moving species.
• Measurements depend on whether species are motile.

Question 56

Why is abundance and distribution hard to measure.

Answer 56

• It’s impossible to count every organism
• Counting organisms is time-consuming and can damage habitats.

Question 57

How can abundance and distribution be estimated?

Answer 57

• Small samples studied in detail.
• Samples should be representative of the wholoe habitat so conclusions are reliable.

Question 58

What factors must be considered when taking samples?

Answer 58

• Choose an area to sample- small area within area investigated.
• Random to avoid bias- e.g. using random number generator.
• Use appropriate techniques to measure the sample.
• Repeat taking as many samples as possible- reduces likelihood results due to chance.
• Number of individuals in the whole area can be estimated taking the mean of the data collected and multiplying it by the size of the whole area.

Question 59

What sampling techniques can be used to study habitats?

Answer 59

• Random sampling using frame/ point quadrats- abundance of slow moving or non-motile organisms.
• Systematic sampling along a belt transect- distribution- abundance of slow moving or non-motile organisms.
• Sampling motile organisms using mark-release-recapture.

Question 60

How can abundance of slow-moving or non-motile organisms be measured?

Answer 60

• Measured using random sampling involving quadrats.
• Quadrats are placed on the ground at random points within the area you’re investigating.

Question 61

How can abundance be measured (numerically)?

Answer 61

• Frequency- whether a species is encountered in a quadrat and how many it occurs in- then put over the total amount of quadrats e.g. 5/10 is 50%.
• Percentage cover- estimate of area in a quadrat that a plant species covers.

Question 62

Describe the different types of quadrats.

Answer 62

• Frame quadrat- square frame- divided into equally sized subdivisions. Placed in different locations in the area and the abundance of each species is recorded- sometimes individually or sometimes as percentage cover.
• A point quadrat- horizontal bar with two legs- holes at set interviews where pins dropped- what pin touches is recorded.

Question 63

What factors must be considered when using quadrats?

Answer 63

• Size of quadrat- depends on size of plant/ animals counted and distribution- larger= larger quadrats. If species not evently distributed- large number of small quadrats- more representative than small number of large quadrats.
• Number of quadrats- more= more reliable. Balance needs to be reached with time constraints. Greater number of species- greater number of quadrats for reliable results.
• Position of quadrats- must be random.

Question 64

Why is random sampling important?

Answer 64

Avoids bias which ensures the data is reliable.

Question 65

How do you obtain a random sample with quadrats?

Answer 65

• Random number generators-** divide area into a grid** with tape measures and use random number generators to select coordinates to sample from. Place quadrats at these coordinates.
• Running means- work out all of the mean of the data for each sample- once the mean no longer changes by a large amount- you should have a realistic estimate of the whole area.

Question 66

Describe how an estimate for abundance is achieved through quadrats.

Answer 66

• Divide area into a grid with tape measures and use random number generators to select coordinates to sample from.
• **Place quadrats at these coordinates. **
• Once a sample is selected, count the frequency/ percentage cover of the species in each quadrat and multiply the mean by the number of squares in the grid to find an estimate for the whole area.

Question 67

How can a reliable result be achieved from quadrats.

Answer 67

• To achieve a reliable result a large sample size is used with many quadrats selected at random- mean of all samples obtained.
• The larger the number of samples= more representative of the community.

Question 68

When is systematic sampling used?

Answer 68

Systematic sampling is used to measure distribution- achieved using transects which show how organisms are distributed over an area.

Question 69

What can systematic sampling show?

Answer 69

• Gradual changes in ecosystems.
• Lines of succession- shows the stages of succession across an area.
• Effects of abiotic factors on populations.

Question 70

How is systematic sampling achieved in habitats.

Answer 70

• Transects.
• Laying a tape measure straight across the ground.
• A quadrat is laid along the line at equal intervals adn the species within it is recorded.

Question 71

What are the two types of transect?

Answer 71

• Belt transects- quadrats are placed next to each other along the transect to work out species frequency and percentage cover along the transect.
• Interrupted belt transects- take measurements using a quadrat placed at regular intervals e.g. every two metres. Makes it easier to cover a large distance.

Question 72

Describe required practical 12- Investigation into the effect of a named environmental factor on the distribution of a given species.

Answer 72

Distribution changes depending on abiotic factors- e.g. shade-loving plants may be closer to trees than to in full sunlight. This can be investigated.

Question 73

Give an example method for investigation into the effect of a named environmental factor on the distribution of a given species.

Answer 73

• Marram grass and soil pH.
• Place a tape measure in a straight line from the shore to inland.
• Take a 1m² quadrat divided into 100 squares.
• Starting from the shore, place the quadrat near the tape measure.
• Count the squares containing marram grass and record the result as percentage cover. Take repeat quadrat samples next to your initial quadrat and take a mean.
• At each sample point measure pH using a pH probe and record results.
• Repeat every 10m along the transect.

Question 74

How do you process results when investigating into the effect of a named environmental factor on the distribution of a given species.

Answer 74

• Sketch a with two lines- distance from the shore should be on the x-axis. Then one line should be the variable and the other should be percentage cover.
• Think of explanations for the variable and also the percentage cover. Remember, that even if there is a correlation, it may not be a causation, as there could be many other factors affecting results- biotic and abiotic.

Question 75

What issues should be considered when completing fieldwork?

Answer 75

• Ethical issues- when carrying out fieldwork be careful to make the smallest impact on the environment as possible- e.g. avoid stepping on plants and too much trampling, minimise stress to animals.
• Safety issues- should plan ahead with a risk assessment- assess risk of uneven ground, stings, bites, and weather.

Question 76

Why can quadrats and transects not be used to measure the abundance of all organisms?

Answer 76

• Quadrats and transects are good to measure plants and non-moving or slow moving animals.
• Can’t measure motile organisms as move away when approached, are often hidden and are difficult to find and identify.

Question 77

What method is used to measure the abundance of motile organisms?

Answer 77

Mark-release-recapture

Question 78

How does mark release recapture work?

Answer 78

• Capture a sample of animals in a set amount of time using a set amount of people.
• Mark the animals- ensure marking in a harmless way so that it does not affect survival.
• Release the animals back into the community.
• Wait a set amount of time, e.g. a week for the organisms to randomly distribute before collecting a second sample from the same population in the same amount of time using a same amount of people.
• Count how many individuals are marked and unmarked and use the equation to estimate the population size.
• Population= number in first sample × number in second sample divided by number of marked in second sample/number recaptured- always mention the equation in these questions.

Question 79

What is the equation for mark-release-recapture?

Answer 79

Population= number in first sample × number in second sample divided by number of marked in second sample / number recaptured

Question 80

What assumptions are made in mark- release- recapture?

Answer 80

• The proportion of marked to unmarked individuals in the 2nd sample is the same as the proportion of marked to unmarked individuals in the population as a whole- the population size doesn’t change due to:
• Emigration or immigration.
• Births.
• Deaths.
• The marked individuals distribute themselves evenly amongst the rest of the population- if the conditions are unfavourable this will not happen.
• The method of marking doesn’t affect the individuals chance of survival e.g. it isn’t toxic or doesn’t make the individual less camouflaged.
• The mark isn’t rubbed off during investigation.

Question 81

How should motile organisms be captured?

Answer 81

• Nets and traps are used.
• These should be designed to avoid causing animals unnecessary stress, as it could reduce it’s chance of survive or influence it to avoid the trap, interfering with the accuracy of the estimate.

Question 82

What is succession?

Answer 82

• Ecosystems- dynamic- constantly change as populations fluctuate- changes can be slow or rapid.
• Succession- describes changes in an ecosystem over time.

Question 83

How does succession work?

Answer 83

• Has stages- at each stage in succession, certain species change the environment so that it becomes:
• Less suitable for the existing species- the new species may out-compete the existing one and take over.
• More suitable for other species with different adaptions- the species may be out-competed by the better adapted new species.
• This leads to a series of successional changes- biotic conditions alter the abiotic conditions which in turn alter the biotic conditions- this causes one community of organisms to be succeeded (replaced) by another.
• Changes that organisms produce in their abiotic environment during succession can result in a less hostile environment, making it easier for other species to survive, enabling new communities to form and changing biodiversity.

Question 84

What are hte different types of succession?

Answer 84

Primary and secondary.

Question 85

What is primary succession?

Answer 85

• Primary succession- occurs on newly formed/ exposed barren land where there are no organic materials or soil present. Has stages from colonisation by pioneer species to climax community.
• Barren land can result from many factors e.g. volcanoes erupting, sand piled into a dune, sea level falling.

Question 86

Describe pioneer species.

Answer 86

• • The first stage of primary succession is colonisation by a pioneer species (the first species to settle an area) of barren land:
• Settle their seeds and spores blown in by the wind e.g. marram grass, lichen.
• Have adapted features to make them suitable for colonisation of hostile abiotic conditions- limited water, few minerals and nutrients, high light intensity, exposure to wind and rain, fluctuating temperature.

Question 87

Give some example adaptions of pioneer species.

Answer 87

• Asexual reproduction- can rapidly multiply to build up a population.
• Production of large quantities of wind-dispersed seeds/ spores- easily reach isolated areas.
• Rapid germination of seeds- don’t require a period of dormancy.
• Ability to photosynthesis- light available but not other food.
• Ability to fix nitrogen from the atmosphere- as soil has few/ no nutrients.
• Tolerance to extreme conditions

Question 88

Describe primary sucession.

Answer 88

• The first stage of primary succession is colonisation by a pioneer species (the first species to settle an area) of barren land.
• Pioneer species change the abiotic conditions- die and microorganisms decompose dead organic material- forms a thin soil as able to e.g. fix nitrogen, soil helps to retain water. Makes conditions less hostile and more suitable to new species with different adaptions which can move in and grow.
• New organisms- die and decompose- add more organic material- make the soil deeper and richer in minerals e.g. nitrates.
• Nitrogen-fixing bacteria form in deeper soil- turn nitrogen from the atmosphere into ammonia- used by plants. Larger plants e.g. shrubs can grow- retains more water and contains more nutrients.
• New species- change the environment so it becomes less suitable for the previous species.
• At each stage, different plants and animals better adapted for the changing conditions, move in, out-compete plants and animals that are already there and become the dominant species. The dominant species- one which causes the most change to the abiotic environment- makes it more suitable for other species. During this time changes occur to biodiversity.
• Succession continues- ecosystem becomes more complex- new species move in alongside existing ones- biodiversity increases.
• Plants- create more habitats for animals- abiotic conditions become less hostile and biomass increases.
• Eventually these changes result in a climax community.

Question 89

Describe a climax community.

Answer 89

• Ecosystem supporting the largest and most complex community of plants and animals it can.
• Remains in a largely steady state.
• Same species present- stable community.
• Abiotic factors remain more or less constant.
• Populations are stable around the carrying capacity.
• Abiotic factors of the ecosystem, largely climate, determine the species of the climax community.

Question 90

What is the climax community for a set climate called?

Answer 90

The climatic climax.

Question 91

Describe the process ofsuccession of lichen.

Answer 91

• Lichens survive on bare rock with little moisture. They weather the rock producing sand/ soil. When the lichens die and decompose they release nutrients into the soil which support small plants. Therefore, the lichens change the abiotic environment by creating soil and nutrients for organisms that follow.
• Mosses and ferns follow. The continued erosion of the rock and increased amounts of organic matter from the death of plants makes they layer of soil thicker. The Organic material holds water making it easier for other plants to grow. These species change the abiotic environment, making it less hostile and more suitable for organisms to follow e.g. small flowering plants and grasses, then shrubs, then trees.
• These species provide sources of food for animals, leading to food chains that develop into complex food webs and communities of plants and animals.
• The climax community then forms- this is deciduous oak woodland in the UK. The climax community has a stable state over a long period of time with a balanced equilibrium io species, with few, if any, new species replacing those that are established. Many species flourish and there is more biodiversity.

Question 92

Describe how animals undergo succession.

Answer 92

• Animals undergo similar series of succession but their succession is determined by plant types available for food and habitats.
• In the lichen example:
• Dead lichens- provide food for small animals- e.g. mites.
• Mosses and grasses- provide foods and habitats for insects, millipedes and worms.
• These are followed by secondary consumers e.g. centipede- feed on these organisms.
• Development of flowing plants- helps to support communities of butterflies and moths.
• Development of trees- supports larger organisms e.g. reptiles, mammals and birds.

Question 93

Describe secondary succession.

Answer 93

• Occurs when land already sustaining life is altered e.g. land clearance for agriculture or a forest fire, however, the soil remains.
• Occurs during any stage after the pioneer stage.
• The established community of species is destroyed usually without too much disturbance to the soil.
• Process very similar to primary succession but because of existing soil layer- starts at a later stage- pioneer species are larger plants e.g. shrubs.
• The ecosystem returns to its climax community through succession but more rapidly as soil already exists with spores and seeds that are still alive.
• There is an influx of animals and plants through dispersal and migration from surrounding areas.
• Because the land has been altered some of the species become different.

Question 94

Describe the common features of succession.

Answer 94

• Pioneer species colonise the area and cause a change in the environment e.g. food for other species.
• Abiotic environment becomes less hostile and more suitable to other species- soil forms helping to retain water, nutrients are more plentiful, plants provide shelter from the wind. New species can then colonise the area.
• This leads to a greater number and variety of habitats and niches- overall increase in species diversity/richness.
• This results in increased biodiversity- different species occupy these habitats- evident in the early stages.
• Increased biodiversity leads to increasingly complex food-webs and increased biomass.
• Biodiversity peaks mid-succession- after decreases and the climax community is reached. Decrease due to new species out-competing pioneer and other species as succession continues- leads to their elimination from the community.

Question 95

How can humans influence succession?

Answer 95

• Humans can prevent succession, stopping a climax community from developing.
• When succession is stopped artificially the resulting climax community is called the plagioclimax e.g. mowing the lawn, grazing.
• This enables some species that may not survive in the climax community to survive and can be a form of conservation.

Question 96

What is conservation?

Answer 96

Protection and management of species and habitats (ecosystems) in a sustainable way- so that enough resources are taken to meet the needs of today without reducing the ability of those in the future to meet their own needs.

Question 97

What does conservation involve?

Answer 97

• Involves active intervention by humans to maintain ecosystems and biodiversity- involves management of existing resources and reclamation of damaged areas.
• Conservation- dynamic- methods need to be adapted to constant changes within ecosystem.

Question 98

What conflict is there with regards to conservation.

Answer 98

Conflict between human needs and conservation- management is needed to find a balance of human needs and conservation to maintain the sustainability of natural resources.

Question 99

What are the reasons for conservation.

Answer 99

• Sustainability- maintain our planet and support our life system.
• Ethical- respect for other species who also occupy the Earth.
• Economic- gene pools that create valuable substances, provides ecosystem services that enable productivity.
• Cultural and aesthetic- inspire writers, places of cultural/spiritual significance, areas of recreation.

Question 100

What is the most frequent method of conservation?

Answer 100

The management of succession.

Question 101

How does conservation thruogh the management of succession work?

Answer 101

• Many species that existed in earlier stages of succession are no longer present in the climax community due to habitats disappearing after being out-competed.
• To conserve these habitats- human activities manage succession by preventing the next stage- interrupt so that the ecosystem stays in its current stage of succession.
• This conserves species who would otherwise not survive in the climax community, ensuring increased biodiversity- makes it more likely species will survive if conditions change to become more harsh.
• E.g. moorlands conserved by grazing and burning heather- destroy young tree saplings so prevent succession to woodland.
• Heaths/ grasslands are the result of human activities converting oak woodland to grazing land- e.g. sheep eat saplings- prevent them from developing into trees.
• If the factor preventing succession is removed- the ecosystem develops into climax community e.g. farmland abandoned- shrubs take over then woodland.

Question 102

Give example methods of conservation.

Answer 102

• Managing succession.
• Seed banks.
• Captive breeding.
• Fishing quotas.
• Protected areas.
• Managing livestock.

Question 103

Describe how seed banks aid conservation and the benefits and drawbacks.

Answer 103

• Store of seeds from different plant species- if they become extinct or are lost from a particular habitat- seeds can be used to reintroduce species.
• Large numbers of species conserved in small space- seeds are small.
• Can be stored for long periods of time- as long as the area is cool and dry.
• Seeds need to be regularly tested to see if they’re viable- expensive and time-consuming.

Question 104

Describe how captive breeding aids conservation and the benefits and drawbacks.

Answer 104

• Breeding animals in controlled environments- usually species that are endangered or extinct in the wild- bred to increase their numbers.
• Can involve problems for animals as they do not breed easily outside their natural habitat or are not kept in their natural conditions.
• Animals can be reintroduced to the wild- increases numbers in the wild- conserve numbers and restore species after extinction.
• Reintroduction- cause problems e.g. carrying diseases, preventing evolution.

Question 105

Describe how fishing quotas aid conservation and the benefits and drawbacks.

Answer 105

• Limits to the amount of fish species fishermen are allowed to catch- conserve fish species to prevent the species reaching low levels of extinction.
• Can be unpopular with fishermen- limit income.
• Leads to discards- ships catching more fish than they are allowed to then throwing back fish so don’t exceed quota- wasteful.
• International cooperation- problem in areas with international fishing.

Question 106

Describe how protected areas aid conservation and the benefits and drawbacks.

Answer 106

• e.g. nature reserves- protect habitats and species by restricting urban and industrial development and farming.
• Habitats- managed to conserve them.
• Protected areas- may be used as tourist attractions to raise money- however can lead to conflict with conservation.

Question 107

Describe how livestock can be managed to aid conservation.

Answer 107

• Ensure livestock numbers remain small so their populations do not grow large enough to cause competition.
• Choose livestock that do not directly compete against the species.
• Keep livestock in enclosed/ separate areas to the habitat.
• Choose to grow crops so there is no competition.

Question 108

How do you assess data with regards to conservation.

Answer 108

• You may need to evaluate evidence and data concerning issues relating to the conservation of species and habitats and consider conflicting evidence.
• Describe the data- changes over time, using numerical values. Compare to controls.
• Draw conclusions- what the data suggests from the description.
• Evaluate the method- whether effects of other variables were factored into the control/ the study, the size of the sample (bigger= more accuracy), random sampling to remove bias and increases accuracy.
• If repeat studies have occurred and draw the same conclusion- enables it to be increasingly accepted.

Question 109

How do you assess conflicting data with regards to conservation.

Answer 109

• Describe the data- use statistics from the graph.
• Draw conclusions- state that they conflict with the previous study.
• Evaluate the method in comparison with the previous study- whether control variables were the same or other factors were at play, the sample size, statistical test.