Chapter 24 - Populations and ecosystems

What are 4 examples of environmentally sensitive ecosystems?

1. Antarctica
2. Snowdonia
3. Lake District
4. Galapagos Islands

What is a population?

All the organisms of one species in a habitat

What is interspecific competition?

Competition for resources between different species

What is intraspecific competition?

Competition for resources between members of the same species

What pattern can intraspecific competition follow and what does this mean?

Can be cyclic, so greater resources mean a larger population

What 2 things can interspecific competition affect?

1. Distribution
2. Population of both species (both will usually decrease)

What is carrying capacity?

The maximum stable population size of a species that an ecosystem can support

What is population density?

Number of individuals per unit area of a chosen habitat

What are the 4 most basic factors which affect population density?

1. Birth rate
2. Death rate
3. Immigration rate to habitat
4. Emigration rate from habitat

What 2 types of factors can affect population size?

1. Density dependent
2. Density independent

What are 3 examples of density dependent factors which affect population size?

1. Predation
2. Disease
3. Competition

What are 2 examples of density independent factors which affect population size?

Climate or catastrophe

What type of feedback are predation cycles an example of?

Negative feedback

What are the 5 phases of a population growth curve?

1. Lag phase
2. Log phase
3. Stationary phase
4. Stable phase
5. Death phase

What happens during the lag phase of a population growth curve?

Population growth begins slowly from a few individuals

What happens during the log phase of a population growth curve?

Exponential growth in ideal conditions

During what phase of a population growth curve is maximum growth rate reached?

Log phase

What happens during the stationary phase of a population growth curve?

Growth rate begins to slow as factors become limiting

What happens during the stable phase of a population growth curve?

Population stable

During what stage of a population growth curve is carrying capacity reached?

Stable phase

What normally prevents populations from undergoing uncontrolled exponential growth?

Limiting factors

What happens during the death phase of a population growth curve?

The population crashes and the process of the curve restarts

What causes the death phase of a population growth curve?

A sudden change in the environment which lowers carrying capacity

What is a limiting factor?

An environmental resource or constraint which limits population growth

What is the competitive exclusion principle?

No two species can occupy the same niche in the same habitat at the same time, so the species which uses resources more efficiently will ultimately eliminate the other

What happens when two species are competing for the same food source but one is better adapted than the other?

The less well adapted one is outcompeted

What is predation?

An interaction in which one organism kills another for food

What are the 3 stages of the effects of intraspecific competition on population size?

1. When a resource is plentiful in a habitat, all organisms have enough to survive and reproduce, causing a rise in population size
2. Increased population means more organisms have to share available resources. As resources are now limited, the population decreases in size
3. Less competition exists due to smaller population, so growth occurs again

What type of competition is almost all predation?

Interspecific

What can happen if a predator or prey species does not evolve?

They could go extinct

Do all predator-prey relationships show the same pattern?

In general yes

What are the stages of a predator-prey relationship?

1. Increase in prey population causes more food for predators, so predator population rises
2. Increased predator population eats more prey, so prey population decreases
3. Reduced prey population can no longer support predator population, so it falls
4. Reduced predator population causes prey population to increase as less are killed

Why are predator-prey relationships rarely as simple as the model?

There are other biotic and abiotic factors to consider

What is conservation?

The protection and management of an ecosystem so that natural resources can be used before running out

What is preservation?

The protection of ecosystems so that they are kept exactly as they are

What type of process is conservation and why?

A dynamic one, as it needs constant adaptation to changes within the ecosystem

What is reclamation?

Restoring ecosystems which have been damaged or destroyed

What is preservation commonly used to preserve?

Sensitive resources and species

What are 3 examples of commonly preserved ecosystems?

1. Marine conservation zones
2. Nature reserves
3. Newly discovered caves

What 2 things are maintained in conservation?

Habitats and genetic diversity within a species

What are 4 classes of reasons for the importance of maintaining biodiversity?

1. Economic
2. Ecological
3. Ethical
4. Social

What are 5 techniques used as part of conservation?

1. Managing land
2. Taking steps to encourage new habitats
3. Removing animals to captivity
4. Growing plants in cultivation
5. Reclamation

What is a technique humans can use to encourage new habitats?

Controlled habitats

Is anything removed from a preserved area?

No

What are 3 threats to biodiversity?

1. Habitat loss
2. Introduced species
3. Overexploitation

What are 3 reasons wild populations may be overexploited by humans?

1. For food
2. For sport
3. For commerce

What are 3 reasons habitats may be disrupted by humans?

1. Intensive agricultural practices
2. Increased pollution
3. Building

What is a sustainable resource?

Renewable resource that is being economically exploited in such a way that it will not diminish or run out.

What are 5 methods used for conservation?

1. National parks
2. Green belts (areas of green land)
3. SSSIs (Sites of Special Scientific Interest)
4. Legal protection
5. Ex Situ conservation

What is sustainable management of the environment necessary for?

Conservation of natural resources for future generations

What are the 5 aims of sustainability?

1. Preserve the environment
2. Ensure resources are available for future generations
3. Allow humans in all societies to live comfortably
4. Enable LEDCs to develop through exploiting their natural resources
5. Create even balance in consumption of resources between LEDCs and MEDCs

What technique is used to produce sustainable timber on a small scale?

Coppicing

What is coppicing?

Cutting tree trunks near the ground, which allows new shoots to form from the cut stumps and mature, before these shoots too are cut.

What is a use of the shoots from coppicing?

Fencing

What type of coppicing is used in most managed woodlands?

Rotational coppicing

How does rotational coppicing maintain biodiversity?

The trees never grow enough to block out the light, so succession can take place

What is rotational coppicing?

Only certain sections of a forest are coppiced at a time in a cyclical fashion, so once you get back to the original section new shoots have appeared

What is the difference between coppicing and pollarding?

In pollarding the trunk is cut higher up

What is an advantage of pollarding over coppicing?

Deer and other animals cannot eat the shoots

What are 3 disadvantages of large-scale timber production?

1. Habitats are destroyed
2. Soil minerals are reduced
3. Bare soil left is susceptible to erosion

What 5 techniques to companies use to do sustainable large-scale timber production?

1. Selective cutting of only the largest trees
2. Managing pests and pathogens to maximise yields
3. Ensure areas of forest remain for indigenous people
4. Plant trees an optimum distance apart to reduce competition and maximise yield per tree
5. Replace trees through replanting rather than wait for natural regeneration

What are 4 examples of techniques used to guarantee sustainable fishing?

1. Use of catch quotas
2. Use of nets with different mesh sizes
3. Allowing fishing only at certain times of the year
4. Introducing fish farming to reduce loss of wild species

What 2 things are balanced in the Masai Mara nature reserve?

Need for conservation and needs of humans

What country is the Masai Mara nature reserve in?

Kenya

What type of ecosystem is the Masai Mara primarily?

Savannah

What divides the Masai Mara?

The Mara river

What plant which once dominated the Masai Mara has been largely cleared over the last 50 years?

Acacia bush

Why was the Acacia cleared so aggressively in the Masai Mara?

It provided a habitat for the tsetse fly, which causes sleeping sickness

What 4 things have reduced Acacia coverage in the Masai Mara?

1. Elephants
2. Cattle
3. Fires
4. Efforts by the government

What have local tribes traditionally used the Masai Mara for?

Livestock grazing

What traditional farming method did the local tribes in the Masai Mara?

Semi-nomadic farming

What 2 things traditionally caused tribes to move in the Masai Mara?

1. Tsetse flies
2. Climate variation

What was an advantage of the Masai Mara tribes' traditional semi-nomadic farming?

Allowed vegetation to recover from animal grazing

How is grazing now limited in the Masai Mara?

Limited to the edge of the park as tribes are not allowed in

What are some disadvantages of the new grazing practices in the Masai Mara?

More trees removed for fuel, larger herds graze grasslands, risk of soil erosion increases with reduced vegetation

How has cultivation changed in the Masai Mara recently?

It has increased

What 2 negative things have happened as a result of increased cultivation in the Masai Mara?

1. Nutrients in soil used up
2. Reliance on fertiliser developed over time due to lack of soil nutrients

What provides most of the economic input of the Masai Mara?

Tourism

What is ecotourism?

Tourism directed towards natural environments, to support conservation and observe wildlife

What does ecotourism reduce?

The impact of tourism on natural habitats

What are the 3 key principles of ecotourism?

1. Ensure that tourism does not exploit the natural environment or local communities
2. Consult and engage with local communities on planned improvements
3. Ensure that infrastructure improvements benefit local people as well as visitors

Why can ecotourism have a negative impact on the environment?

Tourist movements such as repeated use of hiking trails, or use of mechanised transport, may contribute to soil erosion or other habitat changes

What species were protected by conservation and preservation efforts in the Masai Mara?

Black Rhinos

What caused people to be lured into Rhino poaching in the Masai Mara?

The large amounts of money on offer combined with their poverty

What caused a large decline in the Black Rhino population of the Masai Mara?

Illegal poaching

What are currently being undertaken in the Masai Mara?

Scientific research project

What are 4 examples of balancing the needs of humans and wildlife in the Masai Mara?

1. Elephants can threaten cultivation and eat crops so land can be fenced, but as this can affect migration it must be done in moderation
2. Legal hunting used to cull excess animals, but with constant monitoring of numbers
3. As livestock is threatened by migratory wildlife the needs of both must be managed
4. Expanding human population means more home and land for livestock needed, so must be managed as not to reduce wildlife density

What and where is the Terai region?

A rich agricultural region of Southern Nepal

Why are natural resources at risk of being overused in the Terai?

High population density and prevalence of agriculture

What are there large areas of in the Terai region?

Thick forests

What is the soil like in the Terai region?

Very fertile

Why have large areas of the Terai forests been cleared and what for?

Agriculture or to sell the timber, largely as a result of poverty and corruption

What is the Terai climate like?

Hot and humid in summer

How biodiverse is the Terai region?

Very biodiverse

What problem in the Terai region has been exacerbated by deforestation?

Flooding during the monsoon season

Why would the near complete loss of forest in the Terai be devastating for the local population as well as wildlife?

They rely on the forests for tourist income and timber for construction and fuel

What 2 examples of sustainability can be seen in the Terai region?

1. Sustainable forestry
2. Sustainable agriculture

What 2 groups have helped sustainable forestry in the Terai region?

1. Nepali government
2. Local worker cooperatives

What have been 6 successes of sustainable forestry in the Terai region?

1. Significant improvement in forest conservation
2. Improved soil and water management
3. Increase in retail price of forestry products
4. Securing biodiversity of forested areas
5. Sustainable wood fuel sources
6. Employment and income generation through forest protection

What have been 6 sustainable agriculture techniques used in the Terai region?

1. Growth of nitrogen fixing plants to improve soil fertility
2. Growing resistant crops
3. Improved irrigation
4. Promoting production of fruits and vegetables in lesser used mountains to lower intensification
5. Multiple cropping
6. Improved fertilisation techniques