F215:03:07 What affects population size? Flashcards Preview

F215:03 Ecosystems and sustainbility > F215:03:07 What affects population size? > Flashcards

Flashcards in F215:03:07 What affects population size? Deck (24):
1

Describe how a population grows

a. The lag phase, there may be few individuals and they are still acclimatising. The rate of reproduction is low, so growth in population size is slow
b. log phase, resources are plentiful and conditions are good. Rate of reproduction is fast and exceeds mortality. Population size increases quickly
c. Stationary phase, population has levelled out at the carrying capacity, rate of reproduction and mortality are equal. Population remains stable, or fluctuates slightly in response to small environmental changes

2

Describe the lag phase

there may be few individuals and they are still acclimatising. The rate of reproduction is low, so growth in population size is slow

3

Describe the log phase

resources are plentiful and conditions are good. Rate of reproduction is fast and exceeds mortality. Population size increases quickly

4

Describe the stationary phase

Stationary phase, population has levelled out at the carrying capacity, rate of reproduction and mortality are equal. Population remains stable, or fluctuates slightly in response to small environmental changes

5

What is a carrying capacity?

The maximum population size that can be maintained over a period of time in a particular habitat

6

What are k-strategists?

Species whose population size is determined by the carrying capacity

7

What happens to k-strategist populations as the population size gets closer to the carrying capacity?

limiting factors exert a more and more significant effect, which causes the population size to eventually level off

8

What happens if a population size grows so quickly that it exceeds the carrying capacity of the habitat before the limiting factors start to have an effect?

They create a 'boom and bust' population growth
Once the carrying capacity has been exceeded, there are no longer enough resources to allow individuals to reproduce or even survive
An excessive build up of waste products also may start to poison them

9

What are r-strategists?

Species that create a 'boom and bust' population growth

10

What is the most important influence on a population growth of r-strategists?

the rate at which the species can reproduce

11

Give some typical examples of some r-strategists species

- species with a short generation times e.g. bacteria
- pioneer species

12

Why do pioneer species colonise a disturbed habitat before k-strategists?

Because of their quick population growth curve, but move on to other habitats when limiting factors start to have an effect

13

In reality what do r- and k-strategists represent?

They represent two ends of a continuum of strategies adopted by living things

14

What type of succession begins from a disturbed habitat?

Secondary succession

15

Are k-strategists or r-strategists more likely to be members of a climax community? Explain your answer

k-strategists, as their population size is determined by the carrying capacity, it stabilises at the carrying capacity. A climax community is a stable population

16

Give some examples of limiting factors

limited resources:
food
water
light
oxygen
nesting sites
shelter
the effects of other species:
parasites
predators
intensity of competition for resources

17

What is a limiting factor?

anything thats magnitude limits the rate of a natural process
It is usually the factor in the shortest supply

18

Describe the theoretical relationship between a population of a predator and its prey

1. when the predator pop increases, more prey is eaten so reduces
2. There is less food for predators, so fewer predators survive
3. So there is fewer prey being eaten their population increases
4. with more prey, the predator population gets bigger
5. cycle continues

19

What makes the theoretical relationship between a population of a predator and its prey less realistic?

This relationship suggests there are no other limiting factors
and the predator eats only one type of prey
Although in the wild the relationship is similar, but not quite such a defined shape

20

List 5 biotic and 4 abiotic factors that could act as limiting factors

biotic: predation, competition, parasitism, nesting sites, shelter
abiotic: temp, water, light, oxygen

21

Compare the death rate and the reproduction rate in the lag phase

Almost equal, reproduction rate slightly higher

22

Compare the death rate and the reproduction rate in the log phase

reproduction rate higher

23

Compare the death rate and the reproduction rate in the stationary

Equal

24

Explain the connection between limiting factors and carrying capacity

The carrying capacity is the maximum population size that can be maintained over a period of time in a particular habitat
Limiting factors are those that prevent the carrying capacity being any bigger than it is