species diversity and ecological stability

Question 1

outline and explain species diversity in extreme environments

Answer 1

1) often dominated by abiotic factors so species diversity is low
2) few food species mean that changes to one food species will have a big impact on number of predators
3) this creates cycles of population rise and fall

Question 2

outline and explain species populations in less extreme environments

Answer 2

1) higher biodiversity therefore have a more stable environment with less fluctuations
2) population dominated by biotic factors
3) examples of stable ecosystems are tropical rainforests and coral reefs

Question 3

how can biodiversity of an area be measured

Answer 3

the Simpson’s diversity index

Question 4

how can the total number of species be estimated

Answer 4

• using the past rate of discovery, the gradual reduction in rate of finding new species can be used to estimate total number of species yet to be discovered and therefore the total number of species which exist

Question 5

what causes a population to increase

Answer 5

when reproduction rate is high and death rate is low

Question 6

what causes a population to decrease

Answer 6

when death rate is higher than birth rate

Question 7

define birth rate

Answer 7

the number of births per 1000 individuals in a given unit of time

Question 8

define death rate

Answer 8

the number of deaths per 1000 individuals in a given time- usually controlled by environmental factors such as disease or predation

Question 9

what is the difference between r- select and k-select species

Answer 9

r- species which can respond rapidly to low survival rates, the reach sexual maturity quickly and produce many young such as mice or locusts

k- species which recover slowly from a decline in population, reach sexual maturity later, produce few young but often live a long time such as whales or elephants

Question 10

define maximum sustainable yield

Answer 10

the greatest exploitation that is possible without causing unsustainable long term population decline

Question 11

how can a population be worked out

Answer 11

births + immigration- deaths- emigration

Question 12

what are the differences between density dependent factors and density independent factors

Answer 12

1) factors where the chance of survival depends on population density for example food supply, disease, predation
2) factors where population density has no effect on chances of survival for example floods or forest fires

Question 13

define carrying capacity

Answer 13

the greatest population that an area can support without damaging or over-exploiting the environment
- if carrying capacity is exceeded density dependant factors increase causing increased deaths until population falls back below

Question 14

outline predator-prey relationships on population size

Answer 14

1) when prey population increase their is increased food availability for predators
2) therefore predator populations rise
3) the high predator pop causes prey pop to decline
4) the low prey pop increasing environmental resistance as food supply decreases
5) therefore predator pop declines
6) cycle repeats

Question 15

draw and label a sigmoidal population growth curve

Question 16

when might artificial population control be used

Answer 16

1) when the breeding rate of an endangered species is low= captive breeding and release
2) when non-native species are introduced reducing native species= culling
3) when a native predator population becomes overpopulated and needs to be culled to avoid ecological damage

Question 17

provide an example where a native species must be culled to avoid ecological damage

Answer 17

1) wolves of Scotland had been exterminated
2) therefore red deer populations increased
3) this means the deer pop has to be culled to prevent too higher a population which would lead to overgrazing