Module 6 Populations and Sustainability

Question 1

Factors determining population size

Answer 1

• Carrying capacity is the maximum stable population size of a species that an ecosystem can support.
• Every individual in a species has the potential to reproduce and contribute to population growth, but abiotic and biotic factors may prevent this from happening.
• Limiting factors will lead to environmental resistance. Abiotic factors include light intensity, water availability, temperature and pH. Biotic factors include predation, intraspecific and interspecific competition.
• Interspecific competition is when individuals of different species compete for the same resources. If both species are similarly well adapted, both population sizes will be limited. If one species is better adapted, it will out compete the other for the resource.

Question 2

Interactions between populations

Answer 2

• Populations tend towards stable sizes.
• Intraspecific competition is when members of the same species compete for the same resources. This limits the population size an ecosystem can support, as there are not enough resources available.
• Interspecific competition is when members of different species compete for the same resources.
• There are different effects of competition. Competitive exclusion is when less well adapted species are forced to move and find a new niche.
• Resource partitioning is when a resource is divided up to satisfy all needs of the feeders. In this way species don’t directly compete and instead coexist.
• Character displacement is when species differentiate to avoid niche overlap and competitive exclusion.
• Predation results in predator-prey relationships. Populations rise and fall in cycles. As the number of predators increases, the number of prey falls, which causes the number of predators to fall, so the number of prey increases.

Question 3

Conservation/preservation

Answer 3

• Humans are environmental custodians.
• Conservation allows human activity to manage biodiversity and sustainability through changes to the profile of organisms. Humans have focused on conservation.
• Preservation is maintaining habitats exactly as they are now with no usage from humans.
• There are many economic, social and ethical reasons for conserving biodiversity. A more diverse ecosystem is more likely to survive and adapt to changes to environmental conditions. Loss of keystone species can cause issues for the entire ecosystem. Plants absorb CO2 from the atmosphere, bacteria contribute to nutrient cycles, and plants are producers in the food web.
• Economic reasons for conservation include ecotourism, contributions to science and technology and the discovery of medicines from plants, fungi and bacteria.
• Humans take pleasure in the beauty of nature and feel they have a moral obligation to prevent loss of biodiversity.
• There are also many activities that people can do together in nature.

Question 4

Management of environmental resources

Answer 4

• Rapid human population growth and consumption of natural resources is a biotic factor contributing to a loss of biodiversity.
• Human activity may be leading to mass extinction. Rising temperatures, melting ice caps and rising sea levels caused by climate change as a result of increased levels of CO2 in the atmosphere. `
• Increased competition is caused by a lack of resources as an effect of introducing non-native species with no natural competition and loss of habitat. Increased hunting can endanger vulnerable species.
• In Snowdonia, eradication projects work to get rid of the non-native R. ponticum which outcompetes native species.
• Areas of high biodiversity must be conserved but also meet human’s needs through careful management.
• More food is required at a faster rate, and this has led to farming practices that decrease biodiversity, such as use of insecticides and monocultures of cereal crops.
• Biodiversity can be increased through hedgerows, rewilding and organic farming. It is important to find balance between profit and high yield and maintaining biodiversity.
• In the Masai Mara region, there is a high biodiversity of species. People use the land to raise livestock, which has led to a conflict with predators and damage to the ecosystem by overgrazing.
• This has been solved by encouraging local people to work in conservation and ecotourism projects. Local people are employed to monitor the lions, so that livestock can be moved out of the way.
• In the terai region, people are dependent on natural resources provided by the forest. Agriculture has destroyed forests and lead to conflict with wildlife. Conservationists work with local people to protect against poachers, use the forest in a sustainable way and build wildlife corridors. Tiger populations have slowly recovered.
• Peatbogs are waterlogged ground where the decomposition of plant matter is incomplete. This forms peat which is a store of carbon, that can be burned as fuel and release CO2 into the atmosphere. Peat bogs are being restored through filling in drain ditches, removing tree seedlings and controlled grazing.