Chapter 24 P2

Question 1

predation.

Answer 1

• is where an organism (the predator) kills and eats another organism (the prey).
• For example, tigers prey on water buffalo and deer.
• Predation is a type of interspecific competition, operating between prey and predator species.
• Predators have evolved to become highly efficient at capturing prey, for example, through sudden bursts of speed, stealth, and fast reactions.
• Likewise, prey organisms have evolved to avoid capture through camouflage, mimicry, or defence mechanisms such as spines.
• Prey organisms have had to evolve alongside their predators (and vice versa) - if evolution had not occurred, one or both of the species may have become extinct.

Question 2

Predator-prey relationships

Answer 2

• The sizes of the predator and prey populations are interlinked.
• As the population of one organism changes, it causes a change in the size of the other population.
• This results in fluctuations in the size of both populations.
• Predator-prey relationships can be represented on a graph (Figure 2).
• In general all predator-prey relationships follow the same pattern.
• The peaks and troughs in the size of the prey population are mirrored by peaks and troughs in the size of the predator population alter a time delay.

Question 3

Stage one

Answer 3

An increase in the prey population provides more food for the predators, allowing more to survive and reproduce. This in turn results in an increase in the predator population.

Question 4

Stage two -

Answer 4

The increased predator population eats more prey organisms, causing a decline in the prey population. The death rate of the prey population is greater than its birth rate.

Question 5

Stage three

Answer 5

The reduced prey population can no longer support the large predator population.
Intraspecific competition for food increases, resulting in a decrease in the size of the predator population.

Question 6

Stage four

Answer 6

• Reduced predator numbers result in less of the prey population being killed.
• More prey organisms survive and reproduce, increasing the prey population - the cycle begins again.
• Rarely in the wild is the link between the predator and prey population as simple as this.
• Other factors will also influence the population size - for example, the availability of the food plants of the prey or the presence of other predators.
• Fluctuations in numbers may also result from seasonal changes in abiotic factors.

Question 7

Canadian lynx and snowshoe hare

Answer 7

• When a predator feeds on just one type of prey, there is an interdependence between the predator and prey populations.
• This means that changes in the population of one animal directly affect the population of the other.
• The Canadian lynx and snowshoe hare have an interdependent relationship.
• This relationship has been widely studied - data exist for over 200 years, as records were kept for the number of lynx furs that were traded in Canada.
• The data collected is shown in Figure 3.

Question 8

Conservation

Answer 8

• Conservation means the maintenance of biodiversity through human action or management.
• This includes maintaining diversity between species, maintaining genetic diversity within a species, and the maintenance of habitats.
• Conservation involves the management of ecosystems so that the natural resources in them can be used without running out.
• This is known as sustainable development.
• For example, the Forest Stewardship Council ensures that forests are managed so that they provide a sustainable source of timber.
• Their mission is to promote socially beneficial, environmentally appropriate, and economically viable management of forests across the world.
• Conservation approaches also include reclamation

Question 9

reclamation

Answer 9

• this is the process of restoring ecosystems that have been damaged or destroyed.
• For example, a habitat may be destroyed by floods, or as a result of a new building project.
• Reclamation also involves techniques such as controlled burning of areas of a forest, which can halt succession and increase biodiversity
• Conservation is dynamic and needs to adapt to constant change.

Question 10

Preservation

Answer 10

• Preservation is the protection of an area by restricting or banning human interference, so that the ecosystem is kept in its original state.
• It is most commonly used when preserving ecologically, archaeologically, or palacontologically sensitive resources, which can easily be damaged or destroyed by disturbances.
• When lands are preserved, visitation (along with most other activities) is not allowed, except by those who manage and monitor such areas.
• Newly discovered caves, called virgin caves, are pristine.
• These may contain very sensitive geological formations or unique ecosystems - walking from one cave to another can cause irreparable damage, for example, through direct crushing or by the movement of dirt around the cave system.
• Such damage can be avoided by barring entrance to caves altogether thus preserving these unique habitats.
• Only through preservation can the integrity of these ecosystems be guaranteed.
• However, this can result in no one being able to enjoy the caves and some argue that there is no point in having a resource that cannot be used.
• In reality it is objects and buildings that are more commonly preserved, whereas the natural environment is conserved.
• Examples of preserved habitats include areas set aside in nature reserves and marine conservation zones where human interference is prohibited.

Question 11

Conservation of gray bats

Answer 11

• The gray bat is an example of a species which has been successfully supported through a series of conservation measures.
• Inhabiting a small number of caves across the south-eastern US, the gray bat became endangered following the human exploitation of its habitat, and through pesticide bioaccumulation.
• Following the collection of data about bat numbers and particular habitat requirements, a series of measures were introduced to support the remaining population, which is currently estimated to be around one million:
• In 1982, the gray bat was placed on the International Union for Conservation of Nature (IUCN) endangered species list.
• Caves supporting gray bat populations were gated, preventing human access but allowing bats to freely enter and leave the caves.
• The exploitation of land around the caves, which provide the bats with their food sources, was strictly controlled.
• This included limiting the use of pesticides in these regions.
• A programme of education was launched for those who inhabited the areas surrounding regions which supported a bat population

Question 12

Importance of conservation economic

Answer 12

to provide resources that humans need to survive and to provide an income. For example, rainforest species provide medicinal drugs, clothes, and food that can be traded.
Other forests are used for the production of timber and paper

Question 13

Importance of conservation social

Answer 13

many people enjoy the natural beauty of wild ecosystems as well as using them for activities which are beneficial to health by providing a means of relaxation and exercise.
Examples of these activities include bird watching, walking, cycling, and climbing.

Question 14

Importance of conservation ethical

Answer 14

all organisms have a right to exist, and most play an important role within their ecosystem. Many people believe that we should not have the right to decide which organisms can survive, and which we could live without.
We also have a moral responsibility for future generations to conserve the wide variety of existing natural ecosystems.

Question 15

24.5 Sustainability
Specification reference: 6.3.2

Answer 15

• An increasing global human population results in the need for more resources.
• To survive at a basic level you require uncontaminated food and water supplies, shelter, clothing, and access to medical care when the need arises.
• To live in the manner to which you are accustomed, many more resources are required.
• To cope with the increased human demand for resources, intensive methods have been used to exploit environmental resources.
• This can result in the destruction of ecosystems, a reduction in biodiversity, and the depletion of resources.

Question 16

Sustainable use of resources

Answer 16

• The world’s natural resources have conflicting demands placed upon them.
• To conserve natural resources for future generations, sustainable management of the natural environment is necessary.
• A sustainable resource is a renewable resource that is being economically exploited in such a way that it will not diminish or run out.

Question 17

The aims of sustainability are to:

Answer 17

• preserve the environment
• ensure resources are available for future generations
• allow humans in all societies to live comfortably
• enable less economically developed countries (LEDCs) to develop, through exploiting their natural resources
• create a more even balance in the consumption of these resources between more economically developed countries (MEDCs) and LEDCs.

Answer 18

• Alongside the sustainable management of resources, existing resources should be used more efficiently.
• This helps to prevent finite resources being used up so quickly.
• For example, many products can be reused - others, such as aluminium cans, can be recycled into new products.
• As technology improves, alternatives may be developed that could case the strain on current finite resources.
• However, these new resources may take many years to develop, be more costly, and have negative environmental effects of their own.

Question 19

Sustainable timber production

Answer 19

The sustainable management of forests is possible. This allows for the maintenance of a forest’s biodiversity, while sustaining both our supply of wood to meet demands and the economic viability of timber production.
The techniques used depend on the scale of timber production.

Question 20

Small-scale timber production

Answer 20

• To produce sustainable timber on a small scale, a technique known as coppicing is often used.
• This is a technique where a tree trunk is cut close to the ground.
• New shoots form from the cut surface and mature.
• Eventually these shoots are cut and in their place more are produced.
• These shoots have many uses, including fencing.
• In most managed woodlands, rotational coppicing takes place.
• The woodland is divided into sections and trees are only cut in a particular section until all have been coppiced.
• Coppicing then begins in another area allowing time for the newly coppiced trees to grow.
• This process continues until you reach the trees that were first coppiced.
• These will now have grown to mature-sized trees, and the cycle begins again.
• Rotational coppicing maintains biodiversity as the trees never grow enough to block out the light.
• Hence, succession cannot occur and so more species can survive.
• An alternative technique to coppicing which may be used is pollarding.
• The technique is similar to coppicing, but the trunk is cut higher up so deer and other animals cannot eat the new shoots as they appear.

Question 21

Large-scale timber production

Answer 21

Sustainable timber production on a large scale is based around the technique of felling large areas of forest. The felled trees are destroyed and will not regrow.
To ensure that production is sustainable, timber companies:

Question 22

To ensure that production is sustainable, timber companies:

Answer 22

• Practise selective cutting, which involves removing only the largest trees.
• Replace trees through replanting rather than waiting for natural regeneration. This also helps to ensure that the biodiversity and mineral and water cycles are maintained.
• Plant trees an optimal distance apart to reduce competition. This results in higher yields as more wood is produced per tree.
Manage pests and pathogens to maximise yields.
• Ensure that areas of forest remain for indigenous people.

Question 23

major disadvantage of large scale timber production technique is

Answer 23

that habitats are destroyed, soil minerals are reduced, and the bare soil which is left is susceptible to erosion. Trees are important for binding soil together, removing water from soil, and maintaining nutrient levels through their role in the carbon and nitrogen cycles.

Question 24

Sustainable fishing

Answer 24

• As well as the increased demand for fuel and buildings created as a result of population growth, the demand for food is ever-increasing.
• Fish provide a valuable source of protein within the human diet.
• However, overfishing has led to the populations of some species of fish decreasing significantly.
• These fish populations are then unable to regenerate, meaning that they will no longer be able to provide us with a food source in the future.
• To try to overcome this problem international agreements are made about the number of fish that can be caught.
• An example of this is the Common Fisheries Policy in the EU.
• Fishing quotas provide limits on the numbers of certain species of fish that are allowed to be caught in a particular area.
• The aim is to maintain a natural population of these species that allows the fish to reproduce sufficiently to maintain their population.

Question 25

Other techniques that have been used include:

Answer 25

• The use of nets with different mesh sizes. For example, mesh sizes can be made sufficiently large enough that immature fish can escape.
Only mature fish are caught, thus allowing breeding to continue.
• Allowing commercial and recreational fishing only at certain times of the year. This protects the breeding season of some fish species and allows the fish levels to increase back to a sustainable level. For example fisherman are only allowed to catch red snapper in the Gulf of Mexico between May and July.
• The introduction of fish farming to maintain the supply of protein food, whilst preventing the loss of wild species. For example, tilapia are among the easiest and most profitable fish to farm due to their diet, tolerance of high stocking densities, and rapid growth.
In some regions, the fish are placed in rice fields at planting time where they grow to edible size when the rice is ready for harvest.

Question 26

Overfishing of North Sea cod

Answer 26

As a result of increasing boat numbers and improvements in technology, ever larger numbers of fish have been removed from the sea. In recent years, the number of cod caught in the North Sea has declined as the cod population has fallen. As a result of the near collapse of some fish populations, the European Union introduced fishing quotas to conserve fish stocks. These regulations also placed limits on the mesh size of the nets. By increasing the size of the holes in nets, only mature, full-sized fish can be caught. Immature fish can escape.

Question 27

Ecosystem management -
Masai Mara

Answer 27

The Masai Mara National Reserve (MMNR) in southern Kenya is an example of an ecosystem that is actively managed to balance the needs of humans and the need for conservation. The reserve was established as a wildlife sanctuary in 1961, and covers around 1500 km? - it is situated approximately 1500-2000m above sea level.

Question 28

Ecosystem
The MMNR

Answer 28

• The MMNR is primarily a savannah ecosystem, divided by the main Mara river.
• The fertile regions close to the river are a combination of rich grasslands and woodland - further from the river are open plains with scattered shrubs and trees.
• The region is famous for its annual zebra and wildebeest migrations and is home to a wide range of large mammals, including buffalo, elephants, leopards, lions, and black rhinos.
• In the past, the region was dominated by the acacia bush.
• This provided a habitat for the tsetse fly which is a carrier of African trypanosomiasis (sleeping sickness).
• To attempt to reduce incidences of the disease, government workers and indigenous communities have cleared major tracts of acacia over the last 50 years.
• Elephants, fire, and cattle grazing have further reduced the presence of acacia and other woody plants.

Question 29

Farming
Grazing

Answer 29

• Traditionally the Masai Mara has been used by local tribes for livestock grazing.
• In the past, the Masai practised a traditional method of farming known as semi-nomadic farming.
• Tribes frequently moved depending on climate variation and the presence of tsetse flies.
• This allowed vegetation time to recover from animal grazing whenever the farmers moved on to another area.
• Grazing is now limited to areas on the edge of the reserve, as local tribes are prevented from entering the park.
• Populations have grown in these marginal areas.
• Larger herds graze the grassland areas, and more trees are removed for fuel.
• As the vegetation is removed, the risk of soil erosion increases.

Question 30

Cultivation

Answer 30

The level of cultivation around the region of the Masai Mara has increased in recent years. As grassland has been converted into cropland, natural vegetation is removed, and nutrients in the soil are used up.
Over time this leads to a reliance on fertilisers for effective crop growth.