Populations and sustainability

Draw and describe the population growth curve

• Phase 1: At first there is a slow development: birth rate > death rate.

• Phase 2: Then there is a period of rapid growth of the population size, due to few limiting factors on the population growth resulting in increasing numbers of organisms living and surviving.

• Phase 3: The stable phase. Further population growth is limited due to external constraints leading to fluctuations in population growth. This is where carrying capacty is met.

What is carrying capacity?

Where the population has reached its maximum size that the environment can support - the carrying capacity is not subject to any more succession

What are the factors that can limit population growth?

Abiotic factors:

• nutrients, oxygen, pH etc.

Biotic factors:

• Intra/inter-specific competition

• Finding a mate, predator prey relationships etc.

Define immigration and emigration

Immigration - the movement of organisms into an area

Emigration - the movement of organisms out of an area

What is interspecific competition?

Competition between different species

What is intraspecific competition?

Competition within the same species

Describe predation as a biotic factor

Predation is a biotic factor that can influence population size. Many predators have evolved ways to catch their prey e.g. speed and stealth. Likewise, prey has evolved ways to avoid capture e.g. camouflage, stings and mimicry.

Explain what a predator-prey graph shows

As the prey population increases in size (birth rate > death rate), there is more food for the predator, and thus the predator population will increase.

However, as the predator population begins to increase (birth rate > death rate), the prey population will begin to decrease (death rate > birth rate) due to increased predation.

Due to a decrease in the prey population (death rate > birth rate), the predator has less food and the population of predator will decrease (death rate > birth rate).

Predator prey graphs fluctuate due to the availability of food to the predator, through the population of prey and over predation by the predator.

What is the ‘competitive exclusion principle’?

When two sifferent speces that occupy similar niches, compete with each other leading to one species population to supplant the other species - both species cannot coexist

Define conservation

The maintenance or management of nature by human intervention to protect species or habitats

Define preservation

Leaving the environment alone by restricting human access to keep the ecosystem untouched

What are the reasons for Conservation?

• Economic - ecotourism / a potential source for medicines

• Social - aesthetic / use for excersize and enrichment

• Ethical - preserve biodiversity and stop extinction / support the ingigenous population

What are the aims of sustainability?

• Preserve the environment

• Ensure resources are available for future generations

• Allow humans in all socities to live comfortably

• Enable less economically developed countries to develop through exploiting their natural resources

• Create a more even balance in the consumption of these resources in more economically developed countries and less economically developed countries

Describe the process of copicing

The trunk cut close to ground level, several new shoots will grow from cut surface, process is repeated after a certain time, you need to protect young shoots from grazers, can be repeated indefinitely

What are the advantages of coppicing?

• New stems grow more rapidly than saplings

• Lifespan of tree is extended

• Provides a variety of light levels

• Fewer large trees means tehre is more light for smaller plants

• Provides a variety of habitats - maintains biodiversity

• Maintains soil quality

• Prevents succession

• Large machinery is not needed so there is less disturbance

What is selective felling?

The cutting down of mature trees in a forest. This allows other trees to grow to maturity and also leaves enough for habitats for animals.

What is rotational felling?

This consists of planting a site and then felling the trees when they have reached maturity. Depending on tree species this usually takes between 8 and 20 years.

What is strip felling?

The cutting down of selected trees in a forest in a strip. This allows other trees to grow to maturity and also leaves enough habitat for animals.

What are the methods for sustainable fishing?

• Introduce quotas - limits the number of certain species of fish that can be caught.

• Certain hole size in the nets to allow smaller fish to escape and reach maturity and therefore breeding age.

• Fishing is only allowed at certain times of the year allowing the population to reach a sustainable level.

Describe the conflict between conservation and human needs in the Masai Mara region in Kenya

• Poaching has lowered animal population numbers

• Park rangers have been employed and provided with the necessary equipment

• Elephants trample on crops therefore farm land is fenced off

• Legal hunting of overpopulated species is allowed at certain times

Describe the conflict between conservation and human needs in the Terai region of Nepal

• Forests are being cleared to make products

• There has been an increase in the retail price of forestry products leading to greater economic input into the region

• More sustainable wood fuel sources

• Promotion of fruits / vegetables from other areas

• Improved irrigation from cops

• Use more nitrogen fixing plants

Describe the conflict between conservation and human needs in peat bogs

• Used for fertilisers

• Takes thousands of years to form

• It supports rare species of plants

• No large trees are planted nearby (they will remove the water)

• No grazing of sheep or cattle

Describe the effects of human activies on the animal and plant populations and how these are controlled in the Galapagos Islands

• Habitat/ecosystem destruction - for buildings and roads

• Deforestation of land - used for farming, overgrazing by introduced species

• Increase in boats

• More pollution - sewage in the sea and oil spills

• Overfishing or over-hunting

• Competition from introduced species

• Introduction of new pathogens and diseases

Describe the methods to control the human impact in the Galapagous Islands

• Introduction of park rangers

• Limiting human access to particular islands

• Stricter control on migration and introduction of animals

Describe the effects of human activies on the animal and plant populations and how these are controlled in the Galapagos Islands

• Whale and fish populayions have been impacted through overfishing and whaling. There are now bans on whaling and restrictions on fishing.

• Waste must be taken with you when you leave.

• Boats can’t dump their ‘waste’ into the sea.

Describe the effects of human activies on the animal and plant populations and how these are controlled in Snowdonia National Park and the Lake District

• Visitors encouraged to use paths to protect native species

• Litter is encouraged to be placed in bins / taken home with you

• Speed limits on the boats