6.6 - C - Populations And Sustainability

Question 1

Define carrying capacity

Answer 1

The maximum number of population suppported by a particular habitat, determined by limiting factors.
(k).

Question 2

What do limiting factors do?

What significance do they have on determining the final size of a population?

Answer 2

Limit the growth of a population size.

They prevent populations from exceeding the carrying capacity.

Question 3

State and explain the 3 points of a population growth curve in order

Answer 3

The lag phase - small population size, slow reproductive rate, acclimatising to habitat, takes time for dispersed individuals to find each other to mate.
The log phase - reproductive rate is greater than death rate, population size increases rapidly, plenty of resources, little competition, little disease, few predators, no overcrowding, low environmental resistance (biotic and abiotic factors which limit population growth).
The stationary phase - reproduce rate = death rate - population size, remains stable, habitat can’t support larger population, it has reached carrying capacity (k).

Question 4

What does it mean if a limiting factor is density independent?
Include examples.

Answer 4

These act just as strongly, irrespective of the population. Eg: particularly low temperatures may kill the same proportion of individuals in a population, irrespective of the size.

Question 5

What does it mean if a limiting factor is density dependent?

Include examples.

Answer 5

The factor influenced population more strongly as population size increases. Eg: the availability of resources like food may decrease. Similarly, as population size increases, levels of parasitism and predation from other species may increase. The carrying capacity is the upper limit that these factors place on the population size.

Question 6

Explain k strategists.

Give examples.

Answer 6

Population size is determined by the carrying capacity.
Limiting factors exert an increasingly more significant effect as carrying capacity is reached, causing the population to gradually level out. Eg: larger animals and plants.

Question 7

List the characteristics demonstrated by k strategists

Answer 7

Low reproductive rate, slow development, late reproductive age, long lifespan, large body mass.

Question 8

Explain r strategists.

Give examples.

Answer 8

Population size increases very quickly.
Carrying capacity exceeded before limiting factors have an effect.
Once it is succeeded, there are no longer enough resources to allow individuals to reproduce or even to survive.
Build up of excess waste can poison the species (‘boom and bust’).
Eg: mice, insects, spiders, weeds.

Question 9

List the characteristics demonstrated by r strategists

Answer 9

High reproductive rate, quick development, young reproductive age, short life span, small body mass.

Question 10

What is the most important influence on population growth?

Explain it.

Answer 10

Physical rate (r) at which individuals can reproduce.
This type of growth is characteristic of species with short generation times (eg: bacteria) and of pioneer species.

Question 11

Explain the relationship between predator and prey

Answer 11

When the predator population increases, more prey are eaten.
The prey population then gets smaller, leaving less food for the predators.
With less food, fewer predators can survive and their population size reduces.
With fewer predators, fewer prey are eaten, and their population size increases.
With more prey, the predator population gets bigger, and the cycle starts again.

Question 12

Describe the effect that competition has on populations

Answer 12

More competition = less resources.
Higher death rate as less resources e.g. food to survive.
Slower rate of reproduction as fewer resources to reproduce.
Eg: fewer potential mates.

Question 14

Define and explain intraspecific competition

Answer 14

Competition between individuals of the same species.
As environmental pressures increase (factors become limiting) competition increases.
Those best adapted survive, reproduce and pass on their genes (others die).
This keeps the stationary phase fairly stable.

Question 15

Define interspecific competition

Answer 15

Competition between individuals of 2 or more different species

Question 16

Define competitive exclusion

Answer 16

A result of interspecific competition

Question 17

Explain why the competitive exclusion principle does not always apply in natural ecosystems

Answer 17

Because of the effects of other variables acting as limiting factors. Also variation between individuals in each species can lead to selection so that the two species evolve to be slightly different. In effect the two species are not competing in exactly the same niche.

Question 18

Define conservation.

Define preservation.

Answer 18

Maintaining biodiversity between species, including diversity between species, genetic diversity within species and maintenance of a variety of habitats and ecosystems.
Protecting and maintenance of habitats and ecosystems in their present condition, which are unused by humans to maintain natural
biodiversity.

Question 19

How have increasing human populations threatened biodiversity?

Answer 19

Over‐exploitation of wild populations for food.
Disrupting habitats with urbanisation and pollution.
Introducing non‐native species which competitively exclude native species.

Question 20

Define dynamic conservation

Answer 20

Preservation of organisms or environments that are at risk from human activity. This requires management and the creation of new habitats, which may need may need reclamation of land.

Question 21

What do management strategies depend on?

Answer 21

The specific characteristics of the ecosystem and the species involved

Question 22

State 7 management strategies

Answer 22

Reclaim ecosystems by reversing effects of human activity (can be difficult because we don’t always know what species were part of the original community and succession is likely to take a long time before it allows original communities to survive again)
Raise carrying capacity by providing more food.
Move individuals to enlarge populations or create corridors which
provide pathways which connect fragmented habitats, allowing species
to move between them.
Restrict dispersion of individuals by fencing.
Control predators and poachers.
Vaccinate individuals against disease.
Preservation of habitats by protecting against pollution or disruption or
restrict succession (coppicing, grazing etc.)

Question 23

What are the 3 reasons we should conserve?

Answer 23

Ethics
Economic
Social

Question 24

Ethically, explain why we should conserve.

Answer 24

Every species has value, humans have an ethical responsibility to look after them.

Question 25

Economically, explain why we should conserve.

Answer 25

Many species have direct economic value when harvested.
Others may have direct value that is as yet unrecognised, and may provide benefit in the future.
Many plant and animal species provide a valuable food source, and were originally domesticated from wild species.
Genetic diversity may be needed in the future to breed for diseases resistance and improved yield in organisms.
Natural predators of pests can act as biological control agents.
Species can have indirect economic value. Eg: insect species responsible for pollinating crop plants.

Question 26

Socially, explain why we should conserve.

Answer 26

Ecotourism and recreation in the countryside have significant social and financial value. This comes from aesthetics of the environment and nature. Ecotourism in particular depends on maintenance of biodiversity, and there is even a sizeable industry in natural history books, films and other media.

Question 27

What are trees examples of? How is this?

Answer 27

They are a biological resource. They are living and timber is of use to humans.

Question 28

What is clear-felling?

What is it used for?

Answer 28

Completely cutting down all of the trees in an area.

It is for large‐scale timber production.

Question 29

Explain the process of large-scale timber production

Answer 29

Clear-felling trees.
Trees take up water from the soil which stops the soil being washed away (soil erosion) and polluting rivers. Keep nutrient levels in balance in the carbon and nitrogen cycle. Clear‐felling leads to the opposite.
If trees are felled on a rotation of 50‐100 years then biodiversity can be increased but this isn’t cost‐effective.

Question 30

Define sustainable production

Answer 30

Harvesting in amounts which leave sufficient organisms to grow and replenish what has been harvested. It can be carried on indefintiely via replanting, coppicing etc.

Question 31

Explain how can we carry out sustainable forestry for large timber

Answer 31

Replant a tree for each one harvested.
Whole woodland must maintain its ecological function of biodiversity, climate, mineral and water cycles.
Local people should benefit from the forest.

Question 32

What balance is needed in sustainable forestry?

Answer 32

A balance is needed between making money and supplying plenty of wood and maintaining biodiversity.

Question 33

What needs to be ensured by foresters in order for each tree to yield the maximum amount of wood (and mean fewer trees need to be felled)?

Answer 33

Control pests and pathogens.
Only plant tree species which will grow well in the area.
Plant trees optimal distances apart to prevent too much competition for
light, water, minerals.

Question 34

Explain coppicing

Answer 34

Cutting a tree trunk close to the ground to encourage several
new, thinner, stems to grow.
Once they have grown, the new stems will be cut.
All this thin wood can be used for furniture, firewood etc but the trees
don’t die and so no replanting is needed.

Question 35

What is rotational coppicing used to harvest?

Explain the process.

Answer 35

Small timber.
Woodlands are divided up and different sections are coppiced on different years.
This means each section is at a different stage and coppicing can be done to provide a continuous supply of wood each year.
By the time they are ready to coppice the first section again, the shoots
should have regrown and be ready to be re‐cut.

Question 36

What are standards?

Answer 36

Trees left uncoppiced and cut to produce larger timber for planks
etc. ‐ these have more value.

Question 37

State the 2 methods of managing fish stocks

Answer 37

Fisheries

Aquaculture

Question 38

Explain what an aquaculture is.

How does this impact the wider environment?

Answer 38

Refers to the breeding, rearing, and harvesting of plants and animals in all types of water environments including ponds, rivers, lakes, and the ocean.
Restricts impact on oceanic fish stocks and is expected to feed more people than traditional fishing in future.

Question 39

Explain the 3 main principles of the Marine Stewardship Council for sustainable management

Answer 39

Over‐fishing must be avoided to stop extinction of species (aim to
maintain the population at its carrying capacity and only harvest
excess numbers).
No permanent damage to local habitats (maintains structure and function of ecosystem).
Always comply with local, national and global regulations (be flexible with these).

Question 40

What are the benefits and disadvantages of aquaculture rather than ‘capture fisheries’?

Answer 40

Benefits:restrictstheimpactoffishingonoceanicfishstocks;isa
cheapandplentifulproteinsourceforanincreasinghuman
population.
Disadvantages:populationssusceptibletopestsandpathogens;
possiblecauseofpollution.

Question 41

Where is the Terai region?
What is it comprised of?
Describe it

Answer 41

South Nepal.
Marshy grasslands, Savannah and forests. It’s densely populated, and home to endangered species. There are many national parks.

Question 42

State 2 reasons forests in the Terai region have been under pressure

Answer 42

Grazing from animals,

Over-exploitation of resources.

Question 43

State 2 reasons the forests in the Terai region are important to local communities

Answer 43

Fuel source,

Building materials.

Question 44

State 2 of the community forestry initiatives introduced by the WWF and Nepalese government.

Answer 44

Counteracting poachers,

Creating forest corridors between national parks.

Question 45

After national parks were created in 1945, worried about their tenure on the land, the Maasai took individual title over smaller portions of land. State one impact this had.

Answer 45

Constrained mobility of livestock

Question 46

State one advantage and one disadvantage of a partnership between conservancies and tourism in the Maasai Mara

Answer 46

+ finance for locals.

- land owners must move love stock, increasing stocking density outside reservoir.

Question 47

Where is the Maasai Mara?

Answer 47

Kenya

Question 48

State 4 effects of human activity on the Galápagos Islands

Answer 48

Habitat disturbance,
Over-exploitation of resources,
Effects of introduced species,
Managing the effects of human activity.

Question 49

Explain how habitat disturbance is an effect of human activity in the Galápagos Islands

Answer 49

Population increase had placed huge demands in water, energy and sanitation services. More waste and pollution produced. Oil demand increase.

Question 50

Explain how over-exploitation of resources is an effect of human activity in the Galápagos Islands

Answer 50

In the 1800s, 200,000 tortoises killed in less than 50 years. The Charles Darwin Research Station has a captive breeding programme to supplement tortoise numbers. Recent boom in fishing for exotic fish has depleted numbers.

Question 51

Explain how the effects of introduced species is an effect of human activity in the Galápagos Islands

Answer 51

They out-compete, eat and alienate native species and destroy their habitats, or bring diseases.

Question 52

Explain how managing the effects of human activity is an effect of human activity in the Galápagos Islands

Answer 52

In 1999, the Charles Darwin Research station adopted 2 strategies: to prevent the introduction and dispersion of introduced species and to treat the problems caused by them.

Question 53

State 3 effects of human activity on the Antarctic

Answer 53

Krill,
Protected areas,
Albatrosses and petrels

Question 54

Explain the effect of human activity on krill in the Antarctic

Answer 54

Krill are tiny, shrimp like organisms that are prey to bigger animals. They’re used to make nutritional supplements and for animal feed. Due to tech advances, krill harvesting is quick, easy and big. Natural predators can’t easily adapt to find krill elsewhere. To avoid over-exploitation, trigger level catch size in specific areas.

Question 55

Explain the effect of human activity on protected areas in the Antarctic

Answer 55

The southern ocean whale sanctuary is 80 to 90% of the world’s whale’s summer feeding grounds. Within this, it is illegal to hunt and kill whales. They monitor whaling activity and ensure the sanctuary is effective. There is an initiative to expand a network of marine protected areas, eg: Ross Sea.

Question 56

Explain the effect of human activity on albatrosses and petrels in the Antarctic

Answer 56

They are threatened by pollution, hunting and poaching for eggs, habitat destruction and introduction of non-native predators. Their biggest threat is long-life fishing. Birds try to eat and swallow hooks. Boats are using bird-scaring lines and streamers to reduce death count.

Question 57

State three human impacts and their solutions in Snowdonia National Park

Answer 57

Farmers dig open drainage ditches to dry the land. This causes poor water quality and rivers, the rain flows quickly through the habitat, increasing flood risk. However, drainage ditches can be blocked by hay bales.
Conifers planted as cash crops dry out more land as the trees absorb water and roads have to be built to transport the wood. However, the branches of cut trees are used to block drainage ditches to slow water flow and keep the land moist.
Mooreland burnt to provide various habitat for grouse, but when sheep graze, burning is stopped. Old heather burns easily, so accidental fires are high risk. However, people burn controlled fires before heather gets too old and dry.

Question 58

Outline 2 threats to biodiversity in the Lake District as well as their solutions

Answer 58

Spruce and pine in conifer plantations support limited biodiversity. However, recent initiatives have generated more varied planting and felling patterns, giving a mosaic of smaller stands of different aged trees.
Limestone pavement is a unique habitat characterised by solid blocks with fissures between them. However, the pavement is legally protected through the limestone pavement orders.