OCR GCE Biology (A) Module 6.6 Populations & Sustainability

Carrying capacity is:

The maximum population size that can be maintained over a period of time in a particular habitat

A limiting factor is:

The factor whose magnitude (amount) slows down the rate of a natural process

k-strategists are:

Species whose population size is determined by the carrying capacity (e.g. kangaroos, elephants)

r-strategists are:

Species whose population grows so quickly that it can exceed the carrying capacity (e.g. rodents such as rats, locusts)

Density dependent limiting factors are:

Limiting factors that act more strongly on a population as the population increases (e.g. availability of food, availability of nesting sites)

Density independent

Limiting factors that work just as strongly regardless of the size of the population (e.g. low temperatures may kill organisms irrespective of how many organisms are present)

k-strategist species (e.g. kangaroos, elephants) exhibit characteristics such as:

Low reproductive rate, slow development, late reproductive age, long lifespan, large body mass

r-strategist species (e.g. rodents such as rats, locusts) exhibit characteristics such as

High reproductive rate, fast development, young reproductive age, short life span, small body mass

Fast growing weeds such as Poppies and Groundsel are plant examples of
k-strategists or r-strategists?

r-strategists

Slow growing plants such as Oak trees are plant examples of k-strategists or r-strategists?

k-strategists

As populations grow in number, in which phase is there a slow increase in numbers due to the few individuals acclimatising to their new habitat?

Lag phase

As populations grow in number, in which phase is does the rate of reproduction exceed the rate of mortality, and resources are plentiful?

Log phase

Interspecific competition is:

Competition between individuals of different species

Intraspecific competition is:

Competition between individuals of the same species

Predation can act as a ........................... ..................... on a prey's population size.

Limiting factor

During predator / prey interactions, when prey numbers fall, there is a time lag for predator numbers falling. This is because:

It takes time for the lack of food (prey) to increase death rate (and decrease birth rate) of the predator species

As food resources become limiting, individuals of the same species will compete for food. Those individuals that survive are:

Best adapted to obtaining food, survive and reproduce

Intraspecific competition will keep the population of a species relatively stable because:

If the population size drops, competition reduces and the population size increases. If the population size increases, competition increases and the population size drops

The relationship between Snow Shoe Hare and Lynx, is an example of a:

Predator / prey relationship
(interspecific competition)

When two protoctistan species: Paramecium caudatum and Paramecium aurelia are grown separately, each species population size reaches their:

Carrying capacity

When Paramecium caudatum and Paramecium aurelia are grown together, the P. caudatum population crashes because:

The two species show interspecific competition. The two species' niches overlap, resulting in the most 'fit' species surviving at the expense of the less 'fit' species (the competitive exclusion principle)

Experiments in the laboratory between the flour beetle species Tribolium confusum and Tribolium castaneum could not be exactly replicated in the wild because:

A wide range of uncontrolled variables exist, that may fluctuate on a daily or annual basis. These variables act in addition to simple interspecific competition

Allelopathy is:

Some plants exude chemicals (e.g. from their roots) that interfere with the growth of competing plants nearby

Resources that are commonly competed for by species are:

Light, space, nutrients, food, water, and nesting sites

Conservation is:

The maintenance of biodiversity, including diversity between species, genetic diversity within species, and maintenance of a variety of habitats and ecosystems

Preservation is:

The maintenance of habitats and ecosystems in their present condition, minimising human impact

Threats to biodiversity include:

Over-exploitation of wild populations for food
(e.g. over fishing of Cod), habitat disruption and fragmentation, introducing alien invading
species into a an ecosystem

Successful conservation requires consideration of the:

Social and economic costs to the local economy and effective education and liaison with the community

Examples of management strategies for successful conservation are:

Raise carrying capacity by providing extra food, move individuals to enlarge populations, restrict dispersal of individuals by fencing, control predators and poaching

Mowing, grazing and coppicing help preserve habitats because they:

Restrict the process of succession

Economic reasons for conservation are:

Many plant and animal species provide a valuable food source and can be harvested and sold

Economic and social reasons for conservation include:

Genetic diversity of wild strains of crops or livestock may be needed in the future to breed disease resistance. Wild plants may be sources of drugs needed by society in the future

Wild species that may have an indirect economic or social benefit to humans are:

Insects that pollinate crop plants. Soil invertebrates and bacteria that maintain 'healthy' soil for crops to grow

Ecotourism may aid conservation because:

The money raised by people paying for 'eco-holidays' can be used to fund conservation strategies, thus maintaining biodiversity

Ecotourism may hinder conservation because:

Not all of the money generated is used for conservation. The wild animals watched become desensitised to humans - changing their natural behaviour.

The difference between direct and indirect financial value of a species is:

The first refers to the value of the species for what it can be harvested for (e.g. as a food source), the second refers to the value of its presence, and how it affects other factors (e.g. pollinators, soil bacteria)

Sustainable management means

The management and exploitation of natural resources, that maintains biodiversity whilst ensuring supplies of products, and maintaining their economic benefits

Timber production can be small-scale of large-scale. An example of small-scale timber production is:

Coppicing
Pollarding

Timber production can be small-scale of large-scale. An example of large-scale timber production is:

Clear-felling
Selective cutting of trees

Coppicing is:

Cutting the stem of a deciduous tree (e.g. Hazel) is cut close to the ground. New shoots grow from the cut surface into narrow stems, that can be harvested

Pollarding is:

Cutting the stem of a deciduous tree (e.g. Willow) just above head height (away from grazing animals). New shoots grow from the cut surface into narrow stems, that can be harvested

Coppicing increases biodiversity in a woodland by:

Increasing the amount of light that can penetrate to the woodland floor. Spring flowering plants (e.g. Primrose) can photosynthesise, before being shaded by the tree's canopy of leaves

Clear felling can destroy habitats because:

It reduces the soil mineral levels, leaves soil susceptible to erosion. The eroded soil can run-off into waterways and pollute them

Modern, sustainable forestry uses these principles to maintain sustainability:

Replace every harvested tree with another tree, the whole forest is maintained for maximum biodiversity
(e.g. by not planting trees too close together)

Modern, sustainable forestry practices try to maximise the growth of each tree to supply the maximum amount of wood. Examples of these practices are:

Control of pests and pathogens
Plant species suitable for the soil and climate
Plant trees at an optimal distance apart

The Marine Stewardship Council has proposed three principles to support sustainable fishing. These are:

Avoid over-fishing; maintain the structure, productivity, function and diversity of the habitat; fisheries must adapt to changes and comply with regulations

How does 'aquaculture' differ from 'capture fisheries'?:

The first is where fish are either bred in tanks or sea-pens and stocks are replenished by regularly introducing juvenile fish. The second is harvesting adult fish from nature without replenishment of stock

Disadvantages of aquaculture are:

The fish may be susceptible to pest an diseases as they are more intensively reared. May be a source of pollution.

An example of successful conservation alongside human development is the Terai region.
This region is in which country?

Nepal

An example of successful conservation alongside human development is the Maasai Mara.
This region is in which country?

Kenya

The habitats that make up the Terai region are:

Marshy grasslands, savannah (grassland), and forests

Endangered species that are found in the Terai region are:

Bengal tiger
Greater One-horned rhinoceros

Threats to the forests of the Terai region are:

Expansion of agriculture, grazing from farm animals, over-exploitation of forest resources, and replacement of traditional crop varieties with modern ones

Conservation strategies of the Terai region are:

Introduction of community forestry initiatives, creation of forest corridors between National Parks, and control of poachers and
illegal tree-felling

Threats to the Maasai Mara include:

High endemic poverty (i.e. many of the local people are extremely poor). Intensification of agriculture that left wildlife in small,
unconnected patches of habitat

Conservation strategies of the Maasai Mara include:

Partnership between conservation bodies and tourism enable cash to be paid for land to be
set aside for conservation

One negative effect of land conservancies in the Maasai Mara is:

Livestock is moved out of an area during the tourist season, which increases pressure on that land due to the high stock density

Limited livestock grazing can have a beneficial effect on the Maasai Mara because:

Invasive species are not allowed to take-over. This creates habitats suitable for a greater number of plant and animal species in the area

Conservation initiatives that take into account the needs of the local people are often successful because:

The people see the benefit to themselves and the habitat, so are more likely to be
fully committed to the project

Similarities between the strategies adopted in the Terai region and the Maasai Mara are:

Both acknowledge the importance of local people and work with them; both have conservation with development aspects.

Humans have tried to control their effects on the Galapagos islands by decreasing habitat disturbance. Problems of habitat disturbance include:

Increasing human population placing huge demands on water, energy and sanitation services. More waste and pollution produced. Natural areas lost to agriculture

Humans have tried to control their effects on the Galapagos islands by decreasing over-exploitation of resources.
Problems of over-exploitation of resources include:

Tortoise population decreased as they were used as a food source. Decrease in exotic fish population due to fishing. Decrease in shark populations due to the
shark-fin soup market.

Humans have tried to control their effects on the Galapagos islands by decreasing the effects of introduced species
Problems of introduced species include:

Cats hunt lava lizards and young iguanas. Goats feed on Galapagos Rock-purslane. The invasive Red Quinine tree outcompetes native plants, resulting in loss of nesting sites for the Galapagos petrel

Strategies to manage the effects of humans on the Galapagos include:

Prevent the introduction of non-native species. Controlled release of biological control (e.g. Ladybirds).
Culling feral goats

Humans have tried to control their effects on the Antarctic by managing Krill population size.
Problems associated with Krill population decrease are

They are a food source for seals, whales and penguins.
Penguins do not migrate far so cannot seek alternative food sources.
They are used to make animal (livestock) feed.

Conservation strategies to avoid over-exploitation of the Krill population in the Antarctic are:

Particular areas have a 'trigger level' in catch size. Once reached, fishing must be conducted equally over all areas, up to the catch limit

Humans have tried to control their effects on the Antarctic by protecting certain areas.
Problems associated with not protecting areas are:

Uncontrolled whaling of the 80-90% of the world's summer feeding grounds of whales

Humans have tried to control their effects on the Antarctic by conserving Albatrosses and Petrels.
Problems associated with not protecting these birds are:

Threat to their habitat from pollution hunting and poaching for eggs. Long-line fishing (using baited hooks) inadvertently catches and kills many individuals

Conservation strategies to avoid Albatross and Petrel population decreases in the Antarctic are:

The use of bird-scaring lines. Fish at night when the birds to not hunt. Use weighted lines so they sink out of the bird's reach faster

Threats to biodiversity of the Lake District include:

Spruce and conifer plantations support limited biodiversity. Invasive species (e.g. Rhododendron) outcompete native species. Damage to cliff habitats by walkers

Threats to biodiversity of the Snowdonia National Park include:

Farmers drain land causing poor water quality in rivers. Burning moorland stopped when sheep were grazed on the land; this decreases biodiversity

A conservation strategy to increase biodiversity in Snowdonia National Park is:

Controlled burning of moorland