OCR A Level Biology: Populations and Sustainability

Phases of a population growth curve

Lag, log, stationary

Limiting factor

Environmental resource or constraint that limits population growth

Reasons for slight increases and decreases in the stationary phase

Fluctuations in limiting factors

Examples of limiting factors

Interspecific competition, disease, temperature, light, pH, availability of water, humidity, predators

Types of limiting factor

Biotic, abiotic

Examples of biotic factors

Predators, disease, competition

Examples of abiotic factors

Temperature, light, pH, availability of water or oxygen, humidity

Carrying capacity

Maximum population size that an environment can support

Examples of density independent factors

Earthquakes, volcanic eruptions, fires, storms

Examples of interactions between populations

Predator-prey, interspecific competition, infraspecific competition

Competitive exclusion principle

When two species compete for the limited resources, the one that uses the resources most effectively will eliminate the other

Example of interspecific competition

Red and grey squirrels, grey squirrels can eat a larger variety of food and is larger so can store more fat

Stages of infraspecific competition

Resource is plentiful so population size increases, too many individuals so resources are limited, population decreases in size, less competition so population size increases, repeats

Predation

When one organism kills and eats another organism

Stages in a predator-prey relationship

Increase in prey population means more food for predators so more (than) survive, more predators so more predation so death rate of prey population increases, too small prey population so infraspecific competition in predators increases, predator population decreases in size, fewer prey killed, prey population increases

Limitations to the predator-prey relationship

Populations also affected by availability of other foods or other predators or abiotic factors

Conservation

Maintenance of species, genetic and habitat diversity through human action or management

Preservation

Protection of an area by restricting or banning human interference so the ecosystem is kept in its original stage

Economic reasons for conservation

To provide resources that humans need to survive, to provide an income for people through selling medicines or drugs or clothes or food

Social reasons for conservation

People enjoy natural beauty, means of relaxation and exercise through bird watching or walking or cycling or climbing

Ethical reasons for conservation

All organisms have a right to exist, some play important roles within their ecosystem, we should not have the right to choose which organisms survive, moral responsibility to future generations

Sustainable resource

A renewable resource that is being economically exploited in a way that will not diminish it or cause it to run out

Examples of resources being used in a sustainable way

Timber production, fishing

Methods of sustainable timber production

Coppicing, pollarding, clear-felling, selective cutting

Coppicing

Tree trunk is cut close to the ground, new shoots form from the cut surface, shoots cut eventually, more produced in their place, done rotationally

Benefits of rotational coppicing

Trees never grow enough to block out light, succession stopped, more species can survive

Pollarding

Coppicing but higher up

Why is pollarding done?

So larger mammals can't eat the new shoots as they appear

Clear felling

Areas of a forest are cleared and replanted

Selective cutting

Individual trees are selected and cut down

Methods of sustainable fishing

Quotas set by the Common Fisheries Policy, nets with large mesh sizes, only allowing commercial and recreational fishing at certain times of the year

Example of an ecosystem being used to balance the conflict between conservation and human needs

Masai Mara region in Kenya, Terai Region in Nepal, peat bogs

Main problems for the land in the Masai Mara

Intensive herding and tourism putting strain on soil, endemic vegetation and wildlife

How is conservation being done in the Masai Mara?

Big cat project tries to secure future of big cats, elephant project tracks movements of elephants to understand movements and provides anti-poaching education, lion project tries to understand exact movements of lions in time and space so local people can be advised on where and where to not graze their livestock

How is the conflict between human needs and conservation being resolved in the Masai Mara?

From the conservation there are employment possibilities, locals benefit from water conservation and access to renewable energy, education programs, female empowerment

Main problems in the Terai Region of Nepal

Natural resources at risk of being overused, clearing of large areas of forest exacerbates effects of monsoon flooding, soil erosion, loss of tourism, loss of biodiversity, illegal logging

How is conservation being done in the Terai Region of Nepal?

Development of local community forest groups, protection of endangered species, promote food production in the hills so it's not in the forest, improved irrigation for crops, rotational planting, nitrogen fixing crops

Benefits to the local people as a result of the conservation in the Terai Region of Nepal

Empowerment of women, employment, income, increased retail price for forest produce, more technical skills, sustainable flow of income to next generation

Main problems for peat bogs

Intensive land use, afforestation, peat extraction, land drainage, all dry out the bogs

Afforestation

The establishment of a forest or stand of trees in an area where there was no forest

How conservation of lowland bogs is being done

Ensuring that peat and vegetation is as undisturbed and wet as possible, surrounded by ditches to allow water run off to prevent flooding of nearby land, removal of seedling trees from the area as they take water from the bog, controlled grazing

Examples of environmentally sensitive ecosystems

Galapagos Islands, Antarctica, Snowdonia National Park, Lake District

Animals and plants in the Galapagos Islands

Giant tortoise, marine iguana, rock purslane, scalesia tree

Main problems in the Galapagos Islands

Fishing, twelvefold growth in tourism, introduced species which threaten native species, habitat destruction for buildings or roads, agriculture, increased pollution

Methods of conservation in the Galapagos Islands

Culling goats, cap tourism at 100000 people per year, price hikes

Animals and plants in Antarctica

Whales, seals, penguins, lichens, moss, algae

Main problems in Antarctica

Tourism, global warming, hunting of whales and seals, fishing, discharging of waste into the sea

Methods of conservation in Antarctica

Antarctic Treaty - scientific cooperation between nations, protection of the environment, conservation of plants and animals, designation and management of protected areas, management of tourism

Animals and plants in Snowdonia National Park

Coughs, cormorants, oystercatchers, pied flycatcher, wood warblers (Yay!), ospreys, buzzards, sparrowhawks, snowdon lily, oak, alder, wych elm

Main problems in Snowdonia National Park

Trampling of parks, overuse of cycling or walking parks, pollution due to waterspouts, mechanical equipment

Methods of conservation in Snowdonia National Park

Park Authority - Conserve natural beauty and wildlife and cultural heritage, promote opportunities for understanding and enjoyment of park, enhance economic and social wellbeing of community, Dinorwig power station is inside a mountain to preserve natural beauty

Animals and plants in the Lake District

Water voles, Natterjack Toads, bats, red deer, Golden eagle, osprey, red squirrels, vendace, purple saxifrage, dwarf juniper, dwarf willow, sundew

Main problems in the Lake District

Fewer native tree species, trampling of plants, overuse of cycling or walking paths

Methods of conservation in the Lake District

Park Authority - Conserve the region while enabling access for visitors, replanting native tree species