B24 - Populations and sustainability

Question 1

What are limiting factors?

Answer 1

• environmental resource/constraint that limits the population growth (prevents the population from rising above a certain level)

Question 2

What is the population growth curve?

Answer 2

• phase 1: slow growth
  
  • small no. of individuals that are initially present reproduce
  • birth rate is greater than the death rate which causes an increase in population size
• phase 2: rapid growth
  
  • as no. of breeding populations increase, total population multiplies exponentially
  • there are no constraints limiting this
• phase 3: stable state
  
  • external constraints causes population size to fluctuate (overall size stays the same)
  • birth/death rates are equal
  • slight increases and decreases can be due to the fluctuations in limiting factors (e.g. predators)

Question 3

What do limiting factors do?

Answer 3

• they can prevent further growth of a population (and in some cases cause it to decline)

Question 4

What are abiotic limiting factors?

Answer 4

• temperature
• light
• pH
• availability of water/oxygen
• humidity

Question 5

What are biotic limiting factors?

Answer 5

• predators
• disease
• competition

Question 6

What is carrying capacity?

Answer 6

• it is the maximum population size that an environment can support

Question 7

What is migration?

Answer 7

• immigration:
  
  • movement of individual organisms into a particular area (increases population size)
• emigration:
  
  • movement of individual organisms away from a particular area (deceases population size)

Question 8

What are density dependent factors?

Answer 8

• factors that have an effect on the whole population regardless of its size
• can dramatically change population size
  
  • earthquakes
  • fires
  • volcanic eruptions
  • storms

Question 9

What are the types of competition?

Answer 9

• interspecific:
  
  • competition between different species
• intraspecific:
  
  • competition between members of the same species

Question 10

What is interspecific competition?

Answer 10

• where two or more different species of organism compete for the same resource
• this results in the reduction of the resource available for both populations
  
  • less food will lead to organisms with less energy (to grow/reproduce)
  • this results in smaller populations
• if one species of organism is better adapted, then the less adapted one will be outcompeted
  
  • the less well adapted species will the decline in number and eventually die out in the habitat with the better adapted species

Question 11

What is competitive exclusion principle?

Answer 11

• where two species are competing for limited resources, the one that uses them more effectively will eventually eliminate the other

Question 12

What is an example of interspecific competition?

Answer 12

• competition between red and grey squirrels for food and territory
  
  • grey squirrel was introduced in the UK and it’s pop. quickly increased
  • this caused the decrease in red squirrel pop. size
• since grey squirrel can eat a wider range of food than the red squirrel as it is larger
  
  • this increases its chance of survival and its ability to reproduce which then increases its pop.
  • a further increase will reduce the food supply available to the red squirrels which reduces their ability to survive and reproduce

Question 13

What is intraspecific competition?

Answer 13

• where members of the same species compete for the same resource
• the availability of the specific resource determines the population size
  
  • greater availability = larger population
  • results in fluctuations over time

Question 14

What is the intraspecific graph?

Answer 14

• stage 1:
  
  • when resource is plentiful, all organisms have enough of the resource to survive and reproduce
  • this results in an increased population size
• stage 2:
  
  • the increased pop. means that there are more individuals to share the food/space available
  • this limits the resources and will cause the population size to decrease
• stage 3:
  
  • less competition due to the smaller population size (less organisms competing for same resource)
  • more organisms survive and reproduce (pop. growth)

Question 15

What is predation?

Answer 15

• where an organism (predator) kills and eats another organism (prey)
  
  • type of interspecific competition
• they have evolved to become highly efficient at capturing prey (fast reactions, stealth)
  
  • ** prey have also evoked through camouflage, mimicry etc. **

Question 16

What is the predator-prey graph?

Answer 16

• same pattern in general (peaks and troughs mirror each other)
• stage 1:
  
  • increase in prey population provides more food for the predators
  • allows them to survive and reproduce (increases predator pop.)
• stage 2:
  
  • increased predator pop. eats more prey organisms (decline in prey pop.)
  • death rate of prey population is greater than its birth rate
• stage 3:
  
  • reduced prey population can no longer support the large predator population
  • intraspecific competition for food increases (decrease in predator pop.)
• stage 4:
  
  • reduced predator numbers results in less prey pop. being killed
  • so more prey organisms survive and reproduce (increasing prey pop.)

** other factors can also affect this (availability of food plants of the prey, presence of other predators) **

Question 17

What is conservation?

Answer 17

• the maintenance of biodiversity through human action or management so that natural resources can be used without running out
  
  • diversity between species, genetic diversity within species, habitats
  • maintain sustainable development
• reclamation = process of restoring ecosystems that have been damaged/destroyed

Question 18

What is preservation?

Answer 18

• protection of an area by restricting/banning human interference so that the ecosystem is kept in its original state
  
  • often used for ecological, archaeological, or paleontological resources (can easily be damaged by disturbances)
• ** objects and buildings are preserved, while the natural environment is conserved **

Question 19

Why is conservation important?

Answer 19

• economic:
  
  • provides resources for humans that are needed to survive (and provide income)
  • e.g. rainforest species can provide medicinal drugs, clothes, food
• social:
  
  • ecosystems can be used as a means of relaxation and exercise
  • e.g. bird watching, cycling
• ethical:
  
  • all organisms have the right to exist and play an important role in the ecosystem
  • we have the moral responsibility for future generations to conserve the wide variety of ecosystems

Question 20

Why is sustainability important?

Answer 20

• conserves natural resources for future generations
• it is a renewable resource that is being economically exploited in a way that it will not run out
• aims of sustainability:
  
  • preserve environment
  • ensures resources are available for future generations
  • allows humans in all societies to live comfortably
  • enables less economically developed countries to develop
  • creates a more even balance in the consumption of these resources between more EDCs and less EDCs
• ** prevents finite resources from being used to so quickly **

Question 21

What is small-scale timber production?

Answer 21

• to produce timber on a small scale, coppicing is used (tree trunk cut close to the ground)
  
  • new shoots form from the cut surface
  • those shoots are then cut and more are produced (useful for fencing)
• rotational coppicing also takes place and trees are only cut in a particular section until all have been coppiced
  
  • it then begins in another area allowing more time for the coppiced trees to grow
  • this maintains biodiversity as the trees never grow to block the sunlight (so succession cannot occur)
• alternative method = pollarding
  
  • trunk is cut higher up so that deer and other animals cannot eat the new shoots

Question 22

What is large-scale timber production?

Answer 22

• this is based around the technique of felling large areas of forest
• to ensure sustainable production, timber companies:
  
  • practise selective cutting (only largest trees)
  • replace trees by replanting instead of natural regeneration
  • plant trees an optimal distance apart to reduce competition
  • manage pests/pathogens
  • ensure that areas of forest remain for indigenous people
• disadvantage is that habitats are destroyed, soil metals reduced and bare soil is left to erode
  
  • trees are important for binding soil, and maintaining nutrient levels in the carbon/nitrogen cycles

Question 23

What is sustainable fishing?

Answer 23

• fish provide a valuable source of protein within human diet
• overfishing has led to the decrease in some species of fish (unable to regenerate)
• to overcome this, international agreements have been introduced
  
  • Common Fisheries Policy (EU)
  • fishing quotas provide limits on the no. of particular species of fish that are caught
  • aims to maintain a natural population of those species
• other techniques include:
  
  • nets with different mesh sizes (allows for immature fish to escape)
  • commercial/recreational fishing allowed at certain times of the year (protects breeding season of some species)
  • fish farming to maintain supply of protein and preventing loss of wild species

Question 24

What is Masai Mara’s ecosystem?

Answer 24

• MMNR is primary savannah ecosystem
• fertile regions close to the river are a combination of grass/woodland
• further from river = open plants with scattered shrubs and trees
• region was dominated by acacia bush which provided a habitat for the tsetse fly (carrier of sleeping sickness)
  
  • gov. workers then cleared major tracts of acacia and other animals have further reduced the presence of acacia/woody plants

Question 25

What is farming like in Masai Mara?

Answer 25

• grazing:
  
  • traditionally used for livestock grazing
  • Masai practiced traditional method of farming known as semi-nomadic farming
  • tribes frequently moved around which allowed vegetation time to recover from animal grazing
  • this is now limited to areas on the edge of the reserve (growth in population)
  • larger herds grazing and more trees removed
  • risk of soil erosion increases
• cultivation:
  
  • level of cultivation has increased in recent years
  • grassland converted into crop land and natural vegetation removed (nutrients in soil used up)
  • leads to the reliance on fertilisers for crop growth

Question 26

What is Masai Mara’s ecotourism?

Answer 26

• this is tourism directed towards natural environments to support conservation efforts and observe wildlife
  
  • aims to reduce the impact that tourism has on environments (less invasive)
• key principles include:
  
  • ensures that tourism does not exploit the natural environment
  • consult/engage with local communities on planned developments
  • ensure that infrastructure improvements benefit local people and visitors
• ** it can negatively impact the ecosystem due to the repeated use of hiking trails, mechanised transport (soil erosion) **

Question 27

What is the conservation/research of Masai Mara?

Answer 27

• black rhinos are one of the most endangered animals in Africa and appear on the IUCN critically endangered list
• despite the trade being illegal, rhino horn is in great demand for use in medicine in South East Asia
  
  • in 1972, over 100 rhinos lived in the Masai Mara, by 1982, illegal poaching meant that only a handful remained
  • an active protection and conservation programme was established to encourage a balance of needs of local communities and wildlife
  • programme included employment of reserve rangers and provision of communication equipment, vehicles and infrastructure
  • helped to prevent poachers from entering the reserve and by mid 1990s, rhino numbers had increased significantly

Question 28

What is the research of Masai Mara?

Answer 28

• Michigan State university:
  
  • studying the behaviour and physiology of the predator spotted hyena
• Subalusky and Dutton:
  
  • completing a flow assessment for the Mara River basin
  • aim to identify the river flows needed to provide for the millions of humans and to sustain the ecosystem
• Mara predatory project:
  
  • catalogues and monitors lion population throughout the region, aim to identify the population trends trends and responses to changes in land management, human settlements, livestock movements and tourism
• Mara-Meru cheetah project:
  
  • aim to monitor the cheetah population and evaluate the impact of human activity on cheetah behaviour + survival

Question 29

How is a balance maintained between animal and human populations in Masai Mara?

Answer 29

• increasing wildlife density also threatens pastoral and cultivation lifestyles
• elephants threaten cultivation, large ones lead to crop trampling and damage to homesteads, other grazing animals may eat the crops
  
  • to prevent this, land may be fenced (but could have a negative effect on the natural migration)
• legal hunting is used to cull animals
  
  • can successfully maintain population numbers and bring in considerable amounts for conservation work
  • numbers must be constantly monitored to ensure levels are sufficient to maintain the natural balance within the ecosystem
• livestock also faces threats to migratory wildlife
  
  • e.g. during annual wildebeest migration, wildebeest may outcompete cattle for grass, diseases introduced to domesticated animals, domesticated cattle eat vegetation that is used by migrating zebras and wildebeest, spreading disease from domestic to wild animals
• as human population expands, more homes are required as well as land for cattle and agriculture
  
  • evidence shows wildlife density significantly decreasing as the density of the built environment increases

Question 30

What is the Terai region’s ecosystem?

Answer 30

• region is fertile and is the main agricultural area
  
  • high population density so its natural resources are at risk of being overused
• hot and humid in summer months
  
  • fertile alluvial soil (rich in plant nutrients)
• high biodiversity:
  
  • many subtropical plants and areas of thick forest with animals like Bengal tiger and Indian rhinoceros
• many depend on the Terai forests for livelihoods
  
  • it is an important source of national income
  • as a result of poverty/corruption forest has been cleared/used for timber
• removal of large plants has increased the effects of monsoon flooding (causing severe disruptions)
  
  • if this continues, communities would be left with very small parts of the forest
  • this would affect not only the wildlife but also the population (income, harvesting, burning as fuel)

Question 31

How are Nepal’s forests managed sustainably?

Answer 31

• its aim to provide the Nepali state with considerable income for development and livelihood for local people
  
  • achieved through national legislation/development of local forestry groups
• local groups develop own plans, set harvesting rules/rates and prices, determine how income is distributed/spent
  
  • they can work together effectively to gain Forestry Stewardship Council certification

Question 32

What are the successes for the community forestry groups?

Answer 32

• significant improvement in conservation of forested regions
  
  • increased area and improved density
• improved soil and water management across region
• increase in retail price of forestry products
  
  • greater economic input to the region
• employment and income generation through forest protection (as well as production of non-timber forest products)
• sustainable wood fuel sources
  
  • contribute 3/4 of local household energy needs
• securing biodiversity of forested areas

Question 33

How is sustainable agriculture promoted in Nepal?

Answer 33

• promoting production of fruits/vegetables in hill/mountain regions:
  
  • avoids further intensification of Terai
• improving irrigation facilities
• multiple cropping:
  
  • more than one crop is grown on a piece of land each growing season
• growth of nitrogen-fixing crops such as pulses and legumes:
  
  • enhances fertility of soil
• growing crop varieties resistant to various soil/climatic/biotic challenges:
  
  • through use of genetic engineering/modern biotechnology
• improving fertilisation techniques to enhance crop yields:
  
  • using manure to improve nutrient content of soil
• ** Terai region is managed in a way such that both the biodiversity of the region and the economic welfare of its residents is secure **

Question 34

What are peat bogs?

Answer 34

• region of wet, spongy ground that contains decomposing vegetation (takes thousands of years to form)
  
  • undisturbed peatland = carbon sink (store of CO2)
  • once dried it can be used as a fuel
  • burning peat releases CO2 into the atmosphere
• also important for farmers/gardeners who use it to improve soil structure/increase acidity
  
  • it has favourable moisture-retaining properties (prevents excess water from killing roots when soil is wet)
  • despite having nutrients,it is not fertile
• ** commercial peat extraction is a danger to the ecosystem **

Question 35

What is the ecosystem of peat bogs?

Answer 35

• peat forms when the plant material is inhibited from fully decaying acidic and anaerobic conditions
  
  • normally occurs in wet/boggy areas and composed of wetland vegetation like mosses, sedge and shrubs
• plants that grow include: sphagnum moss, bog cotton and heathers
  
  • adapted to grow and thrive in wet conditions with few nutrients
  • contain large amounts of insects e.g. butterflies, moths and dragonflies
• lack of predators and human disturbance makes some peatland ideal for birds to nest and bring up chicks
• abundance of insects, spiders and frogs plus nutritious veg and berries provides food for many species
  
  • large areas of open ground are ideal hunting grounds for birds of prey
• the greatest decline of peat bogs has occurred through:
  
  • afforestation (establishment of a forest in an area where there was no forest)
  • peat extraction
  • agricultural intensification (land drainage)

Question 36

How are lowland bogs conserved?

Answer 36

• conservation is important for flood management, erosion control downstream and carbon storage
• ensuring the peat and vegetation of bog surface is as undisturbed and as wet as possible
  
  • most bogs surrounded by water to allow for surface run off and preventing floods or nearby land
  • in restoring bogs, ditch blocking may be required for a period of time to raise the water table to bog surface
• removal of seedling trees from the area
  
  • trees have a high water requirement due to transpiration
  • so any tree seedling that may remove water from peatland should be removed to maintain water level
• using controlled grazing to maintain biodiversity
  
  • ensures a diverse wetland for structure and species composition
  • provides a wide range of habitats for many rare insect species
• organisations that work to preserve these ecosystems include:
  
  • The Wildlife Trusts
  • Natural England
  • Royal Society for Protection of Birds (RSPB)
  • their works may strike a balance between land use and maintenance of a sustainable and biodiverse ecosystem

Question 37

What are environmentally sensitive ecosystems?

Answer 37

• ecosystems which are fragile and less resistant to changes than others
  
  • human activities like tourism can lead to losses of biodiversity in this region
• similar management techniques used:
  
  • limiting areas tourists can visit
  • controlling movement of livestock
  • introducing anti-poaching measures
  • replanting of forests and native plants
  • limiting hunting through quotas and seasonal bans

Question 38

What organisms are present at the Galapagos Islands?

Answer 38

• animals
  
  • majority are reptiles and only one species of land mammal (rice rat)
  • Galapagos giant tortoise, grows to over 150 cm long
  • flightless cormorant (reduced wings were better for fishing underwater, when flight was not needed to escape predators)
  • marine iguana (advantageous mutation,ability to swim effectively, appear black/grey allowing ectotherms to bask in the sun and raise their body temperatures to 36°C before swimming in the cold sea)
• plants: (three distinct regions)
  
  • coastal zone = salt-tolerant species e.g. mangrove and saltbush
  • arid zone = drought-tolerant species like cacti
  • humid zone = dense cloud-forest (support populations of mosses/liverworts)

Question 39

How have human activities been controlled at the Galapagos Islands?

Answer 39

• due to whaling trade, fragile ecosystem was disrupted by:
  
  • allowing domestic animals to roam freely
  • chopping forests for fire to render down whale fat
  • removing wild tortoises
  • goats introduced also outcompeted the giant tortoises present on the island
• conserved through:
  
  • introduction of park rangers across the islands
  • limiting human access to particular islands
  • controlling migration to and from islands
  • strict controls over movement of introduced animals e.g. pigs
• ** protects the flora and fauna of the islands for future generations **

Question 40

What organisms are present in Antarctica?

Answer 40

• average temp below -30°C
  
  • summer = 24 hrs of total sunlight
  • winter = 24 hr of total darkness
• animals:
  
  • all endotherms (can maintain constant temp. regardless of environment) require thick layers of blubber to insulate from the cold, including whales, penguins and seals
  • female emperor penguins lay eggs in June and spend winter at seas
  • males stay on land (keeping egg warm by covering with flab of abdominal skin)
  • largest invertebrate is wingless midge (small fly) called Beligica Antarctica (around 5mm in size and can only be viewed under a microscope)
• plants:
  
  • algae
  • lichens
  • moss
  • they grow in favourbale niches e.g. sand, soil, rock and on weathered bones and feathers of dead animals
  • ** not many plants due to the extreme environmental conditions **

Question 41

How have human activities been controlled in Antarctica?

Answer 41

• human activity effects:
  
  • planet wide activities like global warming and ozone depletion
  • hunting of whales/seals and fishing of some Antarctic species has depleted stocks of these organisms
  • soil contamination (around scientific research stations)
  • discharging waste into sea (human sewage)
• Antarctic treaty was established in 1961 to protect its unique nature and allows for:
  
  • scientific cooperation between nations
  • protection of the Antarctic environment
  • conservation of plants and animals
  • designation and management of protected areas
  • management of tourism

Question 42

What organisms are present at Snowdonia National Park?

Answer 42

• animals:
  
  • coast and estuary birds (choughs, cormorants, oystercatchers
  • forest birds (pied flycatchers, redstart, wood warblers)
  • moorland and mountain birds (ospreys, buzzards, sparrow hawks)
  • over 40 species of land mammal present
• plants:
  
  • supports equally diverse range of plant species
  • e.g. Snowdon lily, arctic-alpine plants (evolved to cope with extreme conditions)
  • oak, alder, wych elm

Question 43

How have human activities been controlled at Snowdonia National Park?

Answer 43

• Snowdonia National Park created in 1951 to conserve biodiversity of the region
  
  • home to over 25 000 people (many work on the land)
  • attracts several million visitors each year (climbing, cycling, water sports are popular activities)
• key purposes of Park authority:
  
  • conserve and enhance natural beauty, wildlife, and cultural heritage
  • promote opportunities for understanding/enjoyment of park
  • enhance economic and social well-being of communities within park
• Dinorwig power station is pumped-storage hydroelectric power station
  
  • helps to meet demands of the National Grid
  • to preserve the nature, it is located inside the mountain Elidir Fawr (minimised impact to the environment)

Question 44

What organisms are present at the Lake District?

Answer 44

• includes regions of moorland and fell (16 lakes dammed by glacial moraines)
  
  • dales and fringes of the lakes provide a rich variety of habitats, including areas of ancient woodlan
• animals:
  
  • water voles
  • natterjack toads
  • no. of species of bat
  • red deer
  • birds of prey
• plants:
  
  • habitats that exist above tree line support diverse range of arctic-alpine plant communities
  • includes purple saxifrage, alpine cinquefoil
  • specialised trees have evolved in these harsh habitats (dwarf jumper/willow)
  • sundew (carnivorous plant), insects trapped within its sticky leaves and enzymes are secreted to digest the insect (releases nutrients for the plant)

Question 45

How have human activities been controlled at the Lake District?

Answer 45

• LD National Park Authority is similar to Snowdonia’s
  
  • conserve the region while enabling access for many visitors each year
  • this is done through the active management of the countryside (replanting native plant species)
  • secures the fragile ecosystem for many generations