Populations & Sustainability (OCR A Level Biology): Flashcards

Competition for the same resources between individuals from different species.

Competition for the same resources between individuals of the same species.

1. The sizes of both populations are limited, because each species has access to fewer resources and therefore less chance of survival and reproduction. This usually occurs when the two species are similarly well-adapted to the habitat.

1. One population decreases while the other increases, because one species out-competes the other for resources. This usually occurs when one species is better adapted to the habitat.

Red and grey squirrels compete (interspecific competition) for the same habitat, nesting sites and food.

Grey squirrels are better adapted: they eat a wider range of foods, are larger, and store greater amounts of fat over winter.

This increases their chances of surviving the winter and reproducing successfully, so they out-compete the red squirrels, whose population falls.

True

False — intraspecific competition is between members of the same species; competition between different species is interspecific.

Competition that occurs when individuals of the same species compete for the same resources (e.g. food and shelter). "Intra" means within.

Competition between different species for the same resource. "Inter" means between.

The maximum population size that an environment can support, reached when resources become limiting and the population can no longer grow.

• Intraspecific interactions occur between individuals of the same species

• Interspecific interactions occur between different species, e.g. competition and predation

Both act to limit the size of populations.

When resources are plentiful, the population increases.

As the population grows, more individuals compete for the same resources (e.g. food and shelter).

Eventually resources become limiting and the population can no longer grow — the carrying capacity has been reached.

• The red squirrel was outcompeted for food and shelter (interspecific competition)

• The grey squirrel also carries parapoxvirus, which is harmless to itself but can be fatal to the red squirrel

• Protecting the red squirrels' habitats and food

• Giving the red squirrel legal protection

• Reintroducing the pine marten, a natural predator of the grey squirrel

When two species occupy very similar niches, one is slightly better adapted and outcompetes the other; the less well-adapted species must move to a different niche (and may evolve to adapt to it) or die out.

A resource (e.g. a fruit tree) is divided up (partitioned) to satisfy the needs of different feeders, so the species are not competing directly but coexisting on different parts of the resource.

Closely related species in the same region occupying similar niches differentiate to minimise niche overlap and avoid competitive exclusion.

A predator is a consumer that kills and eats other animals; the animals that are eaten are the prey.

• The number of predators increases as there is more prey available

• The number of prey decreases as there are now more predators

• The number of predators decreases as there is now less prey available

• The number of prey increases as there are now fewer predators

• The cycle then repeats

In a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both.

Intraspecific competition occurs between individuals of the same species competing for the same resources.

On a fruit tree, the fruit may be grazed by one species and the leaves by another. The two species coexist on different parts of the same resource rather than competing directly.

Each finch species has a different beak size and shape: finches with stronger beaks eat large, tough seeds, while those with smaller beaks eat smaller, softer seeds. This reduces competition between the species.

False — interspecific competition occurs between different species; competition within the same species is intraspecific.

True

The maintenance of biodiversity and sustainability by:\n\n- Allowing changes to the profile of organisms in an ecosystem\n\n- Allowing human activity alongside other species in a managed way

The maintenance of habitats and populations exactly as they are now, making no allowance for usage by humans.\n\nIt takes place in small geographical areas with little or no human population and allows no human intervention, e.g. areas of Arctic tundra where mineral mining has been prohibited.

Conservation allows managed human activity and changes to the organisms present, while maintaining biodiversity and sustainability.\n\nPreservation maintains habitats and populations exactly as they are, allowing no human intervention or usage.

Humans have focused on conservation rather than preservation, as conservation allows managed human activity alongside the protection of biodiversity.

In order to avoid outcompeting species and forcing them into extinction, humans must adopt the role of environmental custodian, managing habitats and species to ensure sustainability and biodiversity for future generations.

A species that has a larger impact on its ecosystem than others relative to its abundance.\n\nWhen a keystone species is lost, there are several knock-on effects throughout the ecosystem.

• They graze in an extreme way, knocking over and eating several species of tree; this destruction of vegetation helps to maintain the ecosystem\n\n- Their dung provides a habitat for many important fungi and insect species\n\n- When elephants were hunted legally for ivory, their numbers fell and scientists observed a major negative impact on the savannah

A more diverse ecosystem is better able to survive and adapt to environmental changes or threats.\n\nFor example, if a species-rich lake warms due to global warming, some fish species cannot cope but others can; those that cope survive, reproduce and continue contributing to the ecosystem.

• Plants absorb carbon dioxide, reducing the greenhouse effect and climate change\n\n- Microorganisms break down organic waste produced by larger organisms\n\n- Transpiration of plants contributes to the water cycle, providing irrigation and drinking water\n\n- Fungi and bacteria drive the nutrient cycle, returning nutrients to the soil for further plant growth\n\n- Plants are producers, acting as a direct and indirect energy source for humans

• Medicines: many drugs originate from plants, fungi and bacteria (e.g. the anti-cancer drug paclitaxel from Yew trees); undiscovered drugs may still exist in nature\n\n- Ecotourism: tourists spend money to see wildlife in National Parks, boosting the economy and providing jobs\n\n- Science and technology: e.g. the enzyme used in DNA sequencing was first found in a thermophilic bacterium from a Yellowstone hot spring

Tourism directed towards natural environments, in which visitors travel to and spend money in areas such as National Parks to see wildlife.\n\nIt contributes to a country's economy and provides employment, giving an economic incentive to conserve ecosystems.

Aesthetic:\n\n- Humans find pleasure in the beauty of nature, which provides inspiration for photographers, poets, musicians and artists\n\nEthical:\n\n- Humans have a moral obligation to prevent the loss of biodiversity caused by human activity and have no right to cause the extinction of other species\n\nSocial:\n\n- People enjoy activities in nature together (e.g. birdwatching, walking, climbing), benefits that would be lost if environments are not conserved

As humans are the most intelligent species on the planet, the responsibility falls upon them to protect and value all organisms, and to prevent the manmade loss of biodiversity for the good of future generations.

False — preservation maintains habitats exactly as they are, allowing no human intervention; it is conservation that permits managed human activity.

True — a keystone species has a disproportionately large impact on its ecosystem, so its loss triggers several knock-on effects.

The ability of an ecosystem to maintain (or ideally increase) its biodiversity whilst simultaneously providing humans with the resources they need over a long period of time.

• The resource must be allowed sufficient time to replenish before being harvested, so that it does not run out

• No harm should be done to the ecosystem, its surrounding areas, or the species living within it

• Practices that boost biodiversity are promoted

• The long-term future of the ecosystem must be guaranteed

• Leaving enough fish in the ocean so stocks can replenish

• Protecting habitats and marine food webs that fish rely on

• Allowing human communities that catch and process fish to maintain their livelihoods

• Establishing fishing quotas

• Agreeing areas where fishing is banned (e.g. spawning grounds) and where it is permitted

• Regulating the mesh size of nets so undersized/juvenile fish can escape

• Limiting the size of the fishing fleet by issuing licences

• Inspecting the catch as boats return to port

• Banning damaging practices (e.g. gillnets) and promoting low-bycatch methods such as trolling

Gillnets are static nets that catch anything that swims by, causing high bycatch. Trapped fish struggle and die in distress, so banning them protects non-target species and marine food webs.

A sustainable fishing method that uses hook-and-line (rather than large nets), reducing bycatch and damage to the seabed. It is different from trawling.

• There is a very wide area of ocean for the authorities to patrol

• High demand and profit potential have made poachers more daring and willing to break the law

• Fast-growing conifers, e.g. spruce, pine, fir, larch

• Slower-growing broad leaf trees, e.g. oak, beech, hazel

They form an effective monoculture. The trees are densely planted, creating deep shade, and needle litter builds up at floor level. Together these conditions prevent many other species from establishing.

• Using felling methods other than clear-felling to introduce variety

• Creating clearings, firebreaks and edge habitats

• Using selective felling and strip felling

• Leaving naturally dead trees in situ to attract other species

A sustainable felling technique in which trees are felled close to the ground, leaving the stump in place. New shoots grow from the stump and can be harvested again later. Woodland can be coppiced on rotation, and the extra light reaching the ground creates more diverse woodland.

A sustainable felling technique similar to coppicing, but the trees are cut 2-3 metres above the ground, leaving the mature trunk in place. This means herbivores are less likely to reach and eat the new shoots as they grow.

Because the tree is cut 2-3 metres above the ground rather than close to it, herbivores are less likely to be able to reach and consume the new shoots as they grow.

Densely planted coniferous plantations create an effective monoculture, which contributes to their low biodiversity.

False — that describes pollarding; coppicing fells trees close to the ground.

True

Rapid human population growth since the 18th century has increased the demand for:

• food

• space for infrastructure and farming

• clean water

• resources

Meeting this increasing need for resources places growing pressure on other species.

• Climate change

• Introduction of non-native species

• Hunting by humans

• Degradation and loss of habitats

Burning fossil fuels on a large scale increases the level of carbon dioxide in the atmosphere.

The raised carbon dioxide concentration results in higher average global temperatures.

• Changes in weather patterns

• Melting polar ice caps

• Rising sea levels, causing flooding and salination of soil in coastal areas

• Rising ocean temperatures and acidity

These effects change the habitats of some species, putting their survival at risk.

More of the polar bears' habitat melts away earlier each year.

This means they must swim further to reach the seal populations they prey upon for food, making survival harder.

A species that has been introduced (deliberately or accidentally) to an area outside its natural range, e.g. via travel, keeping pets, growing garden plants, or biological pest control.

Non-native species often have no natural competitors, predators or pathogens to limit their population growth.

Without natural population control their populations can grow very quickly, negatively affecting native species through competition and disease.

• Travel, e.g. marine species in the ballast water of ships

• Keeping animals as pets, e.g. cats introduced to Australia

• Growing attractive plants in gardens, e.g. Rhododendron ponticum in the UK

• Introduction of biological pest control, e.g. cane toads in Australia

Hunting can cause overexploitation of a natural resource.

If populations are hunted so much that they are unable to recover, extinction may result, e.g. the passenger pigeon, dodo and Pyrenean ibex.

Harvesting animals for food must be carried out in a sustainable way to ensure that extinctions do not occur, e.g. by implementing sustainable fishing practices.

Humans cut down forests and drain wetlands to create farmland, as well as polluting water, soil and air.

• Prohibiting the import and export of species

• Restricting certain areas from being used for agriculture, housing and infrastructure

• Requiring environmental tests before building on undeveloped land

• Reducing sources of greenhouse gases, e.g. burning fossil fuels for electricity, heat or transport

• Increasing the capacity of "sinks" that store greenhouse gases, such as oceans, forests and soil

As habitat area is reduced, a species must compete for the remaining habitat and search for other suitable habitats.

Eventually the range can become so small that the species cannot survive and becomes extinct.

True

False — burning fossil fuels increases atmospheric carbon dioxide, raising average global temperatures.

The protection and management of species and habitats (ecosystems) in a sustainable way.

Using resources in a way that meets the needs of humans alive now without reducing the ability of future humans to meet their own needs.

As the human population increases and countries become more economically developed, the demand for natural resources (land, water, wood, fossil fuels) also increases.\n\nThis has a harmful effect on aquatic and terrestrial ecosystems, the atmosphere and climate, damaging the species and habitats within them.

Because these practices may appear to limit them in certain ways (e.g. financially) in the short-term, even though careful management of natural resources is needed for long-term sustainability.

• Farms became more specialised, growing one crop or raising one type of livestock (monoculture)\n- A switch to growing cereal crops rather than vegetables\n- Fields were made bigger to fit large machinery, by removing hedgerows and stone walls\n- More land turned to arable use by draining wetland and filling in ponds\n- The use of pesticides and fertilisers increased massively

The range and variety of genes, species and habitats within a particular region.

• Rewilding areas by removing human interference and reintroducing native species\n- Promoting and encouraging organic farming\n- Re-establishment of hedgerows\n- Planting of wildflower field margins

The fertilising, draining and sowing of these two species means other plant species are outcompeted, or the changed land is no longer a suitable habitat for them.\n\nThis results in low species richness, supporting fewer insect and bird species than natural, uninterfered grazing land.

Ploughing and harvesting are the times when food (invertebrates, spilt grain and weed seeds) is plentiful for birds.\n\nAutumn sowing greatly shortens the gap between harvesting and ploughing (from _{5-6 months to} 1-2 weeks), so there is only a very short period when food is plentiful. Scientists believe this will reduce the diversity of farmland birds.

Organic farming:\n\n- Highly restricts the use of pesticides and inorganic fertilisers, producing food free from harmful chemicals\n- Thought to boost biodiversity (though there is currently little scientific evidence for this)\n- Is less productive but more sustainable than intensive farming

• The monoculture of crops reduces plant diversity, removing bumblebee habitats and food (pollen and nectar)\n- Pesticides can harm bumblebees even though they are not the target species\n\nEvidence remains inconclusive as to whether these methods are the overriding cause of the decline.

Conservation practices can be expensive, labour- and time-intensive, and can reduce crop and livestock yield.\n\nFor example, stopping pesticide use increases bumblebee numbers but also increases pest species, reducing yield and profit. The farmer must then charge more in a competitive market, making the conservation-farming balance hard to achieve.

The EU has several grant schemes set up to encourage farmers to use more environmentally friendly techniques, offsetting any profit lost due to lower yields.

False — organic farming is less productive but more sustainable than intensive farming.

True — these species only grow on drained, fertilised land, so other plants are outcompeted, giving low species richness.