Factors affecting biodiversity

Question 1

Why should we care about a loss of biodiversity?

Answer 1

• We need to preserve a balanced ecosystem for all living organisms to live in a balanced equilibrium.
• All species in an ecosystem are interconnected in some way.
• The removal from of one species can have a big effect on others - food webs, habitats etc.
• Ws as humans relay on the biodiversity of many other species - for food, timber, fuel, sources of new medicines.

Question 2

What are the main ways that human activity can lead to a decrease in biodiversity?

Answer 2

• Deforestation.
• Converting more land to agriculture.
• Causing climate change.

Question 3

How does deforestation affect biodiversity?

Answer 3

• This is the permanent removal of huge numbers of trees in an area.
• If specific tree species are targeted and removed, this causes a loss of tree species diversity.
• Destroys habitats and removes food supplies for animal species, so the number of animal species declines.. knock on effect along food chains.
• Forces animals to move to other areas if they are to survive .
• Loss of trees causes soil erosion - loss of soil - difficult for any other plants to grow, results in bare soil, no habitats.
• Trees regulate the balance of oxygen and carbon dioxide in the atmosphere and they also regulate the water cycle by taking up huge quantities of water, then releasing it slowly back to the atmosphere by transpiration.

Question 4

How does monoculture reduces biodiversity?

Answer 4

• Growing one type of crop over a huge area = very little genetic diversity in crop.
• Reduces habitats for animals.
• Reduces variety of food available for animals.
• Use of pesticides kills other plant species and insect species which may be beneficial.
• Whole food webs disrupted.

Question 5

How does selective breeding reduce biodiversity?

Answer 5

Farmers choose particular crop plants or farm animals with desirable characteristics.
These are then used for breeding
Their offspring are then studied to see which ones have inherited these desirable characteristics, and the best ones are again chosen for breeding.
This is repeated over many generations.
In results in all of the organisms being very similar to each other/ very little genetic variation/ reduces gene pool/ fewer different alleles in the population.

Question 6

Why is it useful for farmers to use monoculture?

Answer 6

If the crop is just one species, and they are all genetically similar, it means that the plants will all grow at the same rate, have the same nutrient requirements, be ready to harvest at the same time , be consistent in the product that can be sold to consumers.
Much easier for farmers to manage and bigger profit margins.

Question 7

Other farming practices that reduce biodiversity.

Answer 7

Removal of hedgerows- Increases area of land for crop growth but destroys habitats for birds, rodents, hedgehogs.
Use of chemical pesticides - May kill “non-target” species such as wild plants which provide habitats and food.

Question 8

How might global warming affect biodiversity?

Answer 8

• Melting of polar ice caps could lead to extinction of the few plant and animal species living in these regions.
• Rising sea levels from melting ice caps and the thermal expansion of oceans could flood low-lying land, reducing available terrestrial habitats.
• Higher temperatures and less rainfall would result in some species failing to survive, leading to drought-resistant species (xerophytes), becoming more dominant.
• Insect life cycles and populations will change as they adapt to climate change. Insects are key pollinators of many plants, so if the range of an insect changes, it could affect the lives of the plants it leaves behind, causing extinction.

Question 9

Factors that increase genetic biodiversity.

Answer 9

mutations - Random spontaneous changes to the DNA base sequence which give rise to new alleles.
Free interbreeding - between different populations- allows more mixing between of alleles/ more allele combinations/ gene flow.

Question 10

Factors that decrease genetic biodiversity.

Answer 10

SELECTIVE BREEDING – for example farm animals and crop species are in-bred to have
certain useful characteristics. This is also true when pedigree animals (dogs) are bred
from a limited number of individuals. This means that they all have very similar alleles
and very little genetic variation
[2] CAPTIVE BREEDING PROGRAMMES – such as zoos, wildlife parks, botanical gardens.
Only a small number of individuals are available to breed from, so the resulting offspring
all have very similar alleles.
[3] ARTIFICIAL CLONING – widely used in plant breeding, to produce thousands of plants
that are all genetically the same, e.g. for sale in garden centres
[4] NATURAL SELECTION – See previous notes, species evolve over time, to have the
alleles which are “advantageous” to that environment at that time. Other less
advantageous alleles will reduce in the population, and may be lost. This means that if the
environment then changes, some of the alleles that were lost might have been useful!
[5] GENETIC BOTTLENECKS – Where a few individuals within a population survive an event
such as a disease pandemic, or habitat destruction. The gene pool is greatly reduced
because it then only consists of the alleles present in the survivors – these are the only
alleles that can be passed on to offspring
[6] THE FOUNDER EFFECT – Where a small number of individuals migrate away from the
main population and create a new population which is “geographically isolated” from the
original one. The gene pool for this new population will be small and it may not contain
as many different alleles as the original population did (reduced genetic variation)