Module 6: Populations And Sustainability

Question 1

Population growth curve diagram

Answer 1

Lag phase:

• reproductive rate is slow
• population size is small
• takes time for individuals to find each other to mate
• acclimatising to habitat

Exponential phase:

• reproductive rate is greater than death rate
• pop size increases rapidly
• plenty of resources
• little disease
• few predators
• no overcrowding

Stationary phase:

• reproductive rate = death rate - population size, remains stable
• habitat cannot support larger population
• it has reached its carrying capacity (k)

Question 2

Explain the meaning of the term carrying capacity

Answer 2

The maximum number of population supported by a particular habitat, determined by limiting factors.

Question 3

What are limiting fators which limit the growth of a population size?

Answer 3

• food

• water
• space
• light
• oxygen
• effects of predators
• disease
• competitions

Question 4

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

Answer 4

They prevent populations form exceeding the carrying capacity.

Question 5

What is the difference between conservation and preservation?

Answer 5

Conservation ‐ maintaining biodiversity between species, genetic diversity within species and a variety of habitats and ecosystems.

Preservation ‐ protecting land which is unused by humans to maintain natural biodiversity.

Question 6

How have increasing human populations thretened biodiversity?

Answer 6

• over‐exploitation of wild populations for food
• disrupting habitats with urbanisation and pollution
• introducing non‐native species which competitively exclude native species

Question 7

How is conservation a dynamic process?

Answer 7

Dynamic conservation: 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.

Conservation can involve establishing protected areas, e.g. SSSIs (sites of special scientific interest) or National Parks, and can provide legal protection for endangered animals or plants.

Conservation can also take place ex‐situ in places such as zoos or botanical gardens.

Question 8

Conservation strategies

Answer 8

‐ 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 9

Coppicing

Answer 9

Question 10

Discuss the economic, social and ethical reasons for conservation

Answer 10

Effective conservation requires consideration of the social, ethical and economic costs to the local community, as well as effective education and liaison with the community.

Economic: Drug resistance, drought resistance

Social:

Question 11

Why are trees a biological resource?

Answer 11

They are living and their timber is of use to humans.

Question 12

What is clear-felling?

Answer 12

Clear-felling is completely cutting down all the trees in an area.

Trees take up water from soil and stop it being washed away and polluting rivers. Keeping nutrient levels in balance in the carbon and nitrogen cycles. Clear-felling leads to the opposite.

If trees are felled 50 -100 years this can increase biodivserity but this isn’t cost effective.

Question 13

What is sustainable production?

Answer 13

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.

• Replant a tree for every one harvested.
• Local people should benefit.
• A balance is needed between making money and supplying plenty of wood and maintaining biodiversity.

To ensure each tree yield the maximum amount of wood (and mean fewer trees need to be felled) foresters:

• 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 14

What is coppicing?

Answer 14

Coppicing is 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 15

What is rotational coppicing?

Answer 15

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.

‘Standards’ are trees left uncoppiced and cut to produce larger timber for planks etc. ‐ these have more value.

Question 16

How can fish stocks be managed?

Answer 16

• Fisheries
• Aquaculture

Question 17

What is aquaculture?

Answer 17

• A strategy to manage fish stocks
• 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
• expected to feed more people than traditional fishing in future

Question 18

The Marine Stewardship Council has 3 main principles for sustainable management - what are they?

Answer 18

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

Question 19

What are the benfits and disadvantages of aquacultures rather than capture fisheries?

Answer 19

Benefits: restricts the impact of fishing on oceanic fish stocks; is a cheap and plentiful protein source for an increasing humanpopulation.

Disadvantages: populations susceptible to pests and pathogens; possible cause of pollution.

Question 20

Explain examples demonstrating how environmental resources and the effects of human activities have been managed

Answer 20

The lake district:

Impact by humans:

Question 21

Examples of balancing the conflict between conservation and human needs

Answer 21

The Terai Region:

• The Terai region in Nepal is home to endangered sepcies e.g. Bengal tiger.
• There are many national parks.
• Forrests in the Terai region have been under pressure form expansion of agriculture into forest areas, grzing from fram animals, over exploitataion of forest resources.
• Rural livelihoods are dependent on these forests: they provide fuel, animal feed, building materials etc.
• WWF introduced community forest initiatives in which local people had rights to exploit the forests as well as responsabilities to look after it.
• Community groups created forest corridors between national parks, which are essential to the survival of tigers, as well as counteracting poachers and illegal felling.

Peat bogs:

• Peat bogs form some of the Uks most scarce wetland habitats.
• These support a high biodiveristy and provide an important feeding and stopping-off point for migrating birds.
• Pressure from expansion of agriculture, forestry and landfill meant that lowland peat bogs now cover 1/10^th of what they used to.
• The UK biodiversity Action Plan (UKBAP) aims to conserve and enhance biodivseristy.
• UKBAP has idnetified cerain peat bogs for restoration and aims to end the commercial use of peat in the UK.

Question 22

How have humans have put species endemic to the Galapagos islands at risk of extinction?

Answer 22

• fragmentation and destroyed habitats by deforestation to build e.g. roads and houses.
• land also used for farming.
• more people have increased levels of pollution. For example eutrophication in water and oil spills in sea.
• humans have hunted and over fished certain species e.g. giant tortoise
• competition from introduced species e.g. red quinine tree outcompetes native scalesia tree/ e.g. goats outcompete giant tortoise for its food supply • predation by introduced species e.g. cats eat iguanas
• diseases pathogens introduced e.g. bird flu
• AWP for other specific organisms affected