3.8 Threats to Biodiversity

Question 1

What is exploitation?

Answer 1

exploitation is the harvesting of a natural resource

e.g. forests for timber and animals such as fish for food

Question 2

What has over exploitation been responsible for?

Answer 2

the decline of several natural resources since they are harvested a greater rate than they can be replaced

Question 3

What happens to the alleles when a particular population becomes extinct?

Answer 3

then their alleles are lost and genetic diversity decreases

Question 4

what happens if over exploitation is reduced before the population becomes extinct?

Answer 4

then this can lead to recovery and genetic diversity will increase again

Question 5

How can over exploitation lead to the bottleneck effect?

Answer 5

loss of genetic diversity can be critical for many species
the remaining members of the population will be very similar therefore inbreeding and poor rates of reproduction result
small populations with reduced genetic diversity are less capable of adapting to a changing environment
this can lead to a phenomenon known as the bottleneck effect

Question 6

DONT FORGET

Answer 6

ecosystem degradation endangers the survival of many species

Question 7

DONT FORGET

Answer 7

a major cause of modern species extinction is the loss of habitats often as a result of the actions of humans

Question 8

What is the bottleneck effect?

Answer 8

some populations can be reduced drastically as a result of fire, drought, overhunting or disease epidemic for example
if the surviving population is very small, it might have lost most of its genetic variability
if the survivors are genetically similar, their inbreeding can lead to further loss of variation and the species might not be able to adapt to environmental change in the future

Question 9

Example - elephant seals?

Answer 9

the northern elephant seal, whose population was drastically reduced by over hunting in the nineteenth century has recovered in recent years although genetic diversity of the modern population is very low

Question 10

Example - cheetahs?

Answer 10

example of species that has experienced bottleneck effect
scientists speculated 10000 years ago as last ice age drew to a close, large numbers of cheetah died out leaving very small populations in asia and africa. all the cheetahs now living are descended from this handful of individuals
in most species related individuals share about 80% of the same genes. with cheetahs this figure rises to approximately 99%. this genetic inbreeding in cheetahs has led to
- low survival rates
- greater susceptibility to disease
- poor reproductive rates

Question 11

When does habitat fragmentation occur?

Answer 11

occurs when humans take over an ecosystem
forests have been cleared for agriculture and housing and to use the timber that they yield
this practice leaves behind remnants of the original habitat called habitat fragments

Question 12

What do edge species do to the biodiversity?

Answer 12

edge species that live at the edges of habitat fragments often colonise the centres of smaller fragments and can cause declines in the number of other species, reducing overall biodiversity
the collective habitat fragments support lower species richness and abundance than the original habitat.

Question 13

What do habitat corridors allow species to do?

Answer 13

the creation of corridors of habitat between the fragments might allow species to recolonise them following local extinction
the species are able to move, feed and even mate along the corridors

Question 14

What has the habitat corridors been used for?

Answer 14

applied to hedgerows linking forest fragments on agricultural land and the creation of motorway on agricultural land and the creation of motorway underpasses/overpasses for wildlife

Question 15

Why may this not increase biodiversity?

Answer 15

because they do not provide for species that require continuous habitat with no breaks.
There is also the suggestion of a negative effect because they could allow the spread of disease between fragments

Question 16

What is an indigenous population?

Answer 16

an indigenous population is one which is native to a particular ecosystem and is present naturally without human intervention

Question 17

What is an introduced species?

Answer 17

is a non native species that has arrived in a new geographical area due to human activity, either accidentally or intentionally

Question 18

What happens when a non native species spreads and what is it called ?

Answer 18

When a non native species spreads within wild communities, becomes established and can maintain its population through reproduction, it is known as a naturalised species

Question 19

What are invasive species?

Answer 19

invasive species are naturalised species which can spread rapidly and eliminate native species

Question 20

How can invasive species have a negative impact on their environment?

Answer 20

since the absence of their usual predators, parasites, pests, disease, and competitors enables them to flourish and outcompete native species or hybridise with them

Question 21

DONT FORGET

Answer 21

Remember the cane toad in australia

Question 22

examples of scottish invasive species?

Answer 22

giant hogweed and rhododendron are a threat to our native biodiversity
the grey squirrel which was introduced to Britain in the nineteenth century competes more successfully for both food and habitats and has caused a decline in the native red squirrels

Question 23

What is the earth covered by?

Answer 23

a blanket of gases which allows entry from the sun to reach the earths surface where some of it is converted to heat energy
most of the heat is re-radiated towards the ground by greenhouse gases in the atmosphere
this is a natural effect that keeps the Earth’s temperature at a level necessary to support life

Question 24

DONT FORGET

Answer 24

Even a small change in the temperature of the atmosphere can have a significant effect on our climate

Question 25

How is anthropogenic climate change caused by?

Answer 25

human activity

Question 26

What is global warming?

Answer 26

human activities - particularly burning of fossil fuels (coal, oil and natural gas) agriculture and land clearing are generating more greenhouse gases
Greater concentrations of greenhouse gases will trap more heat and raise the earth’s surface temperature

Question 27

Why is it important for scientists to be able to predict the impact of climate change on biodiversity in the future?

Answer 27

so that strategies can be developed for the conservation of species

Question 28

What do computer models do?

Answer 28

stimulate the climate and predict the temperature, rainfall, extreme weather events and their effects on the distribution of species
these models can only speculate future events and may not be completely accurate but the real challenge is to find ways of reducing the generation of greenhouse gases.