Effects of human activities

Question 1

Explain warfarin resistance in rats.

Answer 1

The pesticide “warfarin” is an anticoagulant has been used on a large scale to control the rat population but rats have become resistant to this.

Question 2

How is there a link between rats diet and the degree of resistance to warfarin?

Answer 2

A dominant allele R at a single locus in rats confers resistance. However, this allele also confers a requirement for vitamin K:
1) Heterozygotes (Rr) are resistant to warfarin and have only a small requirement for vitamin K
2) Homozygotes (RR) are resistant to warfarin but have a massive requirement for vitamin K which is difficult to meet
3) Homozygotes (rr) are killed by warfarin but have a much better chance of survival that RR rats if warfarin is absent from the environment.
This means heterozygotes are favoured by selection.

Question 3

Why is disease easily spread amongst farm animals and how prevented?

Answer 3

They are often brought indoors so that they grow so are within crowded conditions so to prevent this broad-spectrum antibiotics are added to animals food.

Question 4

How has bacteria that were susceptible now become resistant?

Answer 4

Mutation occurring randomly within populations of bacteria which then confer an advantage in presence of that antibiotic. E.g. produce an enzyme, penicillinase, which renders penicillin ineffective.

Question 5

What greatens the selection pressure?

Answer 5

The greater the quantity and frequency of penicillin use as repeated exposure to antibiotics has led to more bacteria surviving and passing on resistant genes.

Question 6

How can resistance be passed on without even using an antibiotic?

Answer 6

From one organism to another on plasmids during conjugation (sexual reproduction) causing a disease-causing organism to become resistant.

Question 7

What is artificial selection?

Answer 7

1) It is carried out by humans to obtain plant or animals with the characteristics humans require
2) May take many years to develop organisms with required characteristics
3) Produces organisms belonging to the same species, which are often described as different breeds or varieties

Question 8

What are the two basic methods of artificial selection?

Answer 8

Inbreeding and outbreeding

Question 9

What is inbreeding?

Answer 9

It occurs when gametes of close relatives fuse. The problem with inbreeding is that it promotes homozygosity. That is, it increases the chance of a harmful recessive gene expressing itself, since there is a greater risk of double recessive individual occurring.

Question 10

What’s an example of inbreeding depression?

Answer 10

Plant species inbred over many generations show a degree of loss of vigour, size and fertility.

Question 11

What is outbreeding?

Answer 11

Occurs by crossing of unrelated varieties. Outbreeding promotes heterozygosity. It introduces hybrid vigour where the organism sometimes grow more strongly. It arises when the new sets of chromosomes are complementary in their effects. Occasionally crosses have occurred between plants of different species e.g. development of modern wheat.

Question 12

What is the typical breeding programme to increase milk yield in cattle?

Answer 12

1) Test the milk yield of selected high milk yielding cows.
2) Select the cow with the highest milk yield (A)
3) Select a bull descended from a cow with a high milk yield (B)
4) Cross cow A and bull B and select female calves
5) Wait for these calves to mature then test their milk yield
6) Select the cow with the highest milk yield (C) then repeat these steps over several generations.

Question 13

How does human activity increase extinction?

Answer 13

Massive destruction of habitats throughout the world has brought around agriculture, urban development, forestry, mining and environmental pollution. Coral reefs destroyed so one third of the planet’s marine fish that rely on them die.

Question 14

What are the main reasons for endangered species?

Answer 14

1) Loss of habitat
2) Overhunting by humans
3) Competition from introduced species.
4) Deforestation
5) Pollution
6) Drainage of wetlands

Question 15

Why is there a need for species reservation?

Answer 15

Species are a potential source of food, useful chemicals or disease-resistant genes.

Question 16

What does breeding achieve?

Answer 16

It increases genetic uniformity with the loss of rarer alleles.

Question 17

Why may extinction of plant species be such a big loss?

Answer 17

Because among the many trees and shrubs are some with medicinal properties so the extinction could lose certain gene pools.

Question 18

What steps have been taken in order to prevent extinction from occurring?

Answer 18

1) Stocks of seeds of “traditional” varieties of plants are stored in seed banks
2) The establishment of sperm banks
3) The founding of rare breeds societies to maintain old less commercial varieties of animals.
4) The protection and breeding of endangered species in specialised zoos
5) Reintroduction programmes, e.g. Red Kit in mid Wales
6) Global organisations, such as the World-Wide Fund for Nature, mount continuing campaigns to promote public awareness
7) International co-operation restricting trade e.g. in ivory and whaling
8) In the UK, the Countryside Commission is the government body that promotes nature conservation. This produces a range of publications, it proposes schemes of management for each of the major ecosystems types, endeavouring to conserve species directly and it establishes nature reserves managed by wardens.

Question 19

Why has legislation been introduced?

Answer 19

To protect endangered species and to prevent overgrazing, overfishing, hunting of game, collection of birds’ eggs, picking of wild flowers and plant collecting.

Question 20

What are the aims of ecotourism?

Answer 20

1) Minimise the negative impacts of tourism
2) Contribute to conservation efforts
3) Employ local people and give money back to the community
4) Educate visitors about the local environment and culture
5) Co-operate with local people to manage natural areas
6) Provide a positive experience for both visitor and host

Question 21

What environmental impacts did agricultural exploitation have?

Answer 21

1) To make larger fields to enable machinery that was needed to prepare the soil and harvest crops, many hedgerows were removed
2) In the larger fields, single crops were grown (wheat/barley) which leads to monoculture reducing species diversity. By growing the same plot year after year then it means that the yield progressively declines. This is due to mineral depletion (intensive cultivation necessitated a huge increase in the use of inorganic fertilisers) and an increase in pests and diseases (necessitating the use of pesticides to remove insects and other pests).

Question 22

Why are schemes in place for farmers?

Answer 22

To encourage farmers to manage their farms for biodiversity. this means that some land is given over to conservation and the farmers receive a grant to compensate them for reduced income. The loss of hedgerows has been reversed as they are important as provide habitats for insects and birds that live and feed on them. Also they allow birds and mammas to move from one area to another helping to maintain the biodiversity of the woodlands.

Question 23

What are the reasons for deforestation?

Answer 23

1) Demand for timber as a building material
2) Wood is used as a fuel
3) land is cleared for farming
4) New roads are built to provide a transport infrastructure
5) Demand for paper and packaging.

Question 24

What are the consequences of deforestation?

Answer 24

1) Climate change: rate a which carbon dioxide is removed from the atmosphere by the process of photosynthesis is being reduced by cutting down forests.
2) Destruction of natural habitats lead to a reduction in biodiversity. If natural habitats are cut down it could also lead to the loss of medicinal properties.
3) Soil erosion: Digging and ploughing loosens the topsoil, assisting in the process of soil erosion. The removal of vegetation affects regional climate mainly by reducing rainfall this accelerating desertification. Deforestation of the watershed causes lowland flooding

Question 25

What results heavy rain sweeping exposed soil to the flood plains below?

Answer 25

The removal of vegetation on higher slopes. This is due to the lower slopes have plants and leaf litter which act as a sponge soaking up heavy rainfall and water would gradually be released into the soil. Instead due to the absence of plants only evaporation occurs. This is generally slower than transpiration in returning water vapour to the atmosphere so soil conditions become wetter.

Question 26

What is coppicing?

Answer 26

The cutting down of trees close to the ground and then leaving them for several years to re-grow.

Question 27

What is selective cutting?

Answer 27

Felling only some of the largest trees leaving the others in place. This is important on steep slopes where the total removal of trees would leave the soil very vulnerable to erosion. It also helps to maintain nutrients in the forest soil reducing the nutrient loss, and minimises the amount of soil that is washed into nearby waterways.

Question 28

What is long rotation time?

Answer 28

Leaving each part of the forest for many years before re-harvesting it.

Question 29

How can efficiency be increased in regards to good forestry practice?

Answer 29

1) Planting trees the optimum distance apart. Planting them too close together would result in intra-specific competition. This means the trees would grow tall and thin producing poor timber quality
2) Controlling pests and diseases. If trees grow well this results in a high quality harvest of timber. this means that fewer trees need to be felled. best use is made of the land reducing the total area od land required.
3) Cutting timber in such a way that similar number of trees are removed year after year for long periods of time, the forest ecosystem can be maintained. This means that the habitats are left intact and species are able to live in the forest even though timber is being extracted.
4) Preservation of native woodlands to maintain and enhance biodiversity. There is a need to plant more native species to provide wide range of habitats for the great variety of species that live there.

Question 30

What is overfishing?

Answer 30

The rate at which fish are harvested exceeds the rate at which they reproduce.

Question 31

What is drift netting?

Answer 31

Suspending a net from floats stretched between two boats so that fish swim into it.

Question 32

What is trawling?

Answer 32

Dragging a large net through the water, catching whatever happens to be in the way.

Question 33

Why are the holes in the net important for the conservation of fish stocks?

Answer 33

Because the very small mesh nets catch young fish before they have become sufficiently mature to reproduce.

Question 34

How can wildlife be effected by overfishing?

Answer 34

The overfishing of a particular species has “knock-on” effect along the food chain. E.g. as herring is eaten by cod, if herring are overfished the cod population suffers as well. Also krill are small shrimps that are very important to the trophic levels in food chain. This is because they are the main food source for the great whales, and also supplement the diets of seals, penguins, squid and fish. So by overfishing krill means the starvation of whale population.

Question 35

How to reduce overfishing?

Answer 35

1) Imposing quotas on catches based on scientific estimates of the size of the fish stock
2) Restricting the net mesh size. Correct mesh size should be used in all nets to ensure that fish of the correct age are caught and to prevent as much as possible “accidental” catches of other fish. larger mesh nets allow juvenile fish to escape and so survive to reproduce
3) International agreements limiting catches
4) Enforcing closed seasons for fishing
5) Enforcing exclusion zones

Question 36

What are the problems with fish farming?

Answer 36

1) Farmed salmon is often kept very densely stocked. In this state the fish can more easily become diseased and these diseases can spread to wild fish. Huge amounts of antibiotics are required to keep the fish moderately healthy.
2) The pesticides used to control fish parasites are also known to harm marine invertebrates. Eutrophication can result when fish excreta, waste food and fertiliser are carried in the water to the wider community around the rearing pens.
3) When fish escape the farmed fish interbreed with wild fish and potentially weaken wild stocks. there is also the problem of pollution in the water and seabed around fish farms. Farmed salmon, which are carnivorous, eat three times their bodyweight in fish feed which is made from other fish. This is not the best use of resources from an environmental point of view. Another problem with all salmon is that they can contain high levels of dioxins and polychlorinated biphenyls (PCBs)

Question 37

What are the two main reasons for the rise in carbon dioxide in atmosphere?

Answer 37

1) The burning of fossil fuels (accounts for about 70% increase)
2) Deforestation (accounts for about 30% increase). Forests help maintain balance of carbon dioxide and oxygen in atmosphere which is important as carbon dioxide is a “greenhouse gas”. It absorbs the radiation from the earth and if it accumulates it leads to “global warming”.

Question 38

What do greenhouse gases do?

Answer 38

It forms a layer in the atmosphere acting like glass in a greenhouse. These gases allow high-energy solar radiation to pass through to the Earth’s surface. Much pf this energy is “bounced back” towards space as low energy hear which is absorbed is absorbed and trapped by gases.

Question 39

What is the greenhouse effect?

Answer 39

It’s a natural process and without it earth’s temperature would be too low to sustain life.

Question 40

What are the possible consequence of global warming?

Answer 40

1) Some melting of polar icecaps resulting in flooding in coastal areas.
2) Increased frequency of droughts, hurricanes and cyclones and also forest fires
3) In tropical areas of the world, decrease availability of water might lead to the formation of deserts
4) Increased crop yields, but insect pest populations might also increase
5) Climate change will have serious effects on world food production with massive reductions in the grain crops of North America and Central Asia. This would have serious economic and political consequences.
6) Increasing carbon dioxide in the oceans decreases the pH which threatens fish populations, coral reefs, etc.
7) Genetic engineering research is on-going to develop drought-resistant crops. A gene that controls water efficiency in plants has been identified but it will take many years of research to develop the idea further.

Question 41

What is biofuel?

Answer 41

Any kind of fuel that is biological in origin. In recent years the biofuel (oil substitute) has come to mean ethanol and diesel made from crops including corn, sugarcane and rapeseed. In forms such as wood, wood chippings and straw, biogas (methane used in small scale to power generators) from animals excrement.

Question 42

How is ethanol for fuel made?

Answer 42

Through fermentation .

Question 43

Are biofuels climate-friendly?

Answer 43

Yes as they reduce greenhouse gas emissions as burning the fuel release carbon dioxide by growing the plants it absorbs a comparable amount of the gas from atmosphere. However energy is used during farming and processing the crops.

Question 44

What’s the worry about converting to biofuels?

Answer 44

Reduction of biodiversity as farmland already consists of monocultured crops so will reduce habitat for animals and wild plants.

Question 45

What are technical problems of biofuels?

Answer 45

Current technologies limit production as only specific parts of plant can be used. the tough cellulose plant cell walls needed to be pre-treated before it can be fermented.

Question 46

What are the harmful effects of nitrate-containing fertiliseds?

Answer 46

1) In soil- on agricultural land the increased use of fertiliser has reduced species diversity on grassland. fertilisers increases the growth of grasses and plants such as nettle which shade out smaller plants
2) Leaching into water- of nitrates and phosphates from surrounding land is a slow, natural process during which the concentration of salts builds up in bodies of water. in lakes and rivers the salts normally accumulate until equilibrium is reached where they are exactly counterbalanced by the rate at which they are removed. However, sewage and fertilises are an additional source of these salts and their leaching from the land into the water may result in eutrophication of lakes and rivers.

Question 47

What happens when nitrate-containing fertiliser get into water?

Answer 47

1) Algal bloom so the water becomes green and light is unable to penetrate to any depth.
2) The plants in the deeper regions of the lake are unable to photosynthesise and therefore die. There is a general decrease in animal species diversity as they rely on the plants and food for shelter
3) The short-lived algae soon fie and are decomposed by saprobiontic bacteria which use a lot of oxygen creating a biochemical oxygen demand (BOD). The water in all but the very upper layer becomes deoxygenated, so that fish and other oxygen-requiring species die
4) Anaerobic bacteria in the water may reduce nitrate to nitrite (toxic)

Question 48

What strict legislation do farmers with high nitrate levels in water have to do?

Answer 48

1) restrict the amount of fertiliser applied to soil
2) Only apply fertiliser at a time when the crops are actively growing
3) Leave a strip at least 10 metres wide next to watercourses
4) Dig drainage ditches