3.7 Mass extinction and Biodiversity

Question 1

What is biodiversity?

Answer 1

biodiversity is the term used to describe the millions of different species of animals, plants and microorganisms on earth

Question 2

What is biodiversity important for?

Answer 2

providing different sources of food
supplying sources of medicines
stability of ecosystems
providing economic value

Question 3

DONT FORGET

Answer 3

biodiversity is the variety of living things on earth

Question 4

What is extinction?

Answer 4

living species naturally become extinct and are replaced by others

Question 5

What is mass extinction?

Answer 5

a mass extinction is a rapid decrease in the number of species on Earth
25-70% of all species may cease to exist over a period of tens of thousands of years e.g. the extinction of the dinosaurs
when organisms die their remains may be preserved as fossils providing a record of their existence
fossil evidence has shown that several mass extinction events have occurred in the past and that the holocene extinction which began 11500 years ago is still ongoing

Question 6

What is speciation?

Answer 6

a mass extinction leaves may unfilled niches and the surviving organisms may take advantage of these
new species evolve from a common ancestor to fill these empty niches as happened when mammals diversified into the empty niches occupied by dinosaurs

Question 7

What follows a mass extinction?

Answer 7

a period of recovery as biodiversity is lowly regained

Question 8

What is the background extinction rate a measure of?

Answer 8

measure of how often extinctions happen naturally without the interventions of humans

a broad estimate of the extinction rate can be calculated by measuring the number of species that become extinct over a certain period of time

this is easier for large, visible species such as mammals, but very difficult for less visible species such as bacteria, fungi and insects

Question 9

What are megafauna?

Answer 9

species of very animals

e.g. wooly mammoth

Question 10

What contributes to these mass extinctions?

Answer 10

climate changes, as well as hunting by humans, are likely to contribute to these extinctions

Question 11

what made it impossible to recover?

Answer 11

their slow reproduction

Question 12

Why is the current rate of species extinction is much greater than the background rate?

Answer 12

due to the rapidly increasing rate of ecosystem degradation by humans, which endangers the survival of many species

Question 13

What are the main causes of ecosystem degradation by humans?

Answer 13

deforestation - cutting down forests to make way for agriculture
pollution of air, water and land
over exploitation of resources for example overfishing and overhunting
destruction of habitats - the removal of hedgerows

Question 14

what are the role of humans in the extinction of polar bears?

Answer 14

activities such as deforestation and fossil fuel burning which lead to global warming

Question 15

what are the role of humans in the extinction of siberian tiger?

Answer 15

low genetic diversity and poaching by humans

Question 16

what are the role of humans in the extinction of black rhinoceros?

Answer 16

habitat destruction and poaching by humans

Question 17

What are the three elements which together can provide a measure of biodiversity?

Answer 17

genetic diversity
species diversity
ecosystem diversity

Question 18

What is genetic diversity?

Answer 18

the number and frequency of alleles in a population of a species of animal or plant are estimated
the higher the number and frequency of alleles, the greater the biodiversity

Question 19

What happens when a particularly population dies out?

Answer 19

then alleles are lost and genetic diversity decreases

Question 20

why is lack of genetic diversity an issue?

Answer 20

because if environmental conditions change, the species may not be able to adapt
e.g. a lack of genetic diversity lead to the irish potato famine since only two varieties of potatoes were planted and neither was resistant to the fungus responsible for the blight

Question 21

What is species diversity?

Answer 21

the number of different species of living organism in an ecosystem are estimated using sampling techniques

the relative abundance of a species of how many individuals there are compared to other species in an ecosystem can also be estimated in this way

Question 22

TOPTIP

Answer 22

sampling techniques include
quadrats
line transect
pitfall traps
tree beating 
sweep netting

Question 23

What is ecosystem diversity?

Answer 23

a record is made of the number of different types of ecosystem that exist within an area, the higher the ecosystem diversity for that region.

Question 24

TOPTIP

Answer 24

different types of ecosystem include:
woodland
soil
fresh water
marine
beach
moorland
mountain
tree 
hedge grassland

Question 25

What is the biodiversity in habitats related to?

Answer 25

related to the area of the habitat

Question 26

Biodiversity drops more quickly than..?

Answer 26

than the reduction of habitat size

Question 27

What does this mean when habitats are fragmented?

Answer 27

the impact is disproportionately high

Question 28

How are small fragments known as habitat islands created?

Answer 28

the breaking of tracts of rainforest by logging roads or by the creation of patches of agricultural land decreases the overall biodiversity by creating small fragments

Question 29

What does the species diversity of a habitat island depends on what?

Answer 29

on its area and the degree of isolation from other habitats

Question 30

DONT FORGET

Answer 30

high species diversity results in a stable ecosystem with complex food webs while low species diversity gives an unstable ecosystem with simple food webs: one small change could cause many species to die