Effects of human activities Flashcards
(48 cards)
Explain warfarin resistance in rats.
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.
How is there a link between rats diet and the degree of resistance to warfarin?
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.
Why is disease easily spread amongst farm animals and how prevented?
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.
How has bacteria that were susceptible now become resistant?
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.
What greatens the selection pressure?
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.
How can resistance be passed on without even using an antibiotic?
From one organism to another on plasmids during conjugation (sexual reproduction) causing a disease-causing organism to become resistant.
What is artificial selection?
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
What are the two basic methods of artificial selection?
Inbreeding and outbreeding
What is inbreeding?
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.
What’s an example of inbreeding depression?
Plant species inbred over many generations show a degree of loss of vigour, size and fertility.
What is outbreeding?
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.
What is the typical breeding programme to increase milk yield in cattle?
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.
How does human activity increase extinction?
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.
What are the main reasons for endangered species?
1) Loss of habitat
2) Overhunting by humans
3) Competition from introduced species.
4) Deforestation
5) Pollution
6) Drainage of wetlands
Why is there a need for species reservation?
Species are a potential source of food, useful chemicals or disease-resistant genes.
What does breeding achieve?
It increases genetic uniformity with the loss of rarer alleles.
Why may extinction of plant species be such a big loss?
Because among the many trees and shrubs are some with medicinal properties so the extinction could lose certain gene pools.
What steps have been taken in order to prevent extinction from occurring?
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.
Why has legislation been introduced?
To protect endangered species and to prevent overgrazing, overfishing, hunting of game, collection of birds’ eggs, picking of wild flowers and plant collecting.
What are the aims of ecotourism?
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
What environmental impacts did agricultural exploitation have?
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).
Why are schemes in place for farmers?
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.
What are the reasons for deforestation?
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.
What are the consequences of deforestation?
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
