Module 6: Factors affecting populations

Question 1

A population growth curve often involves 3 phases , which are …

Answer 1

1) period of slow growth-initially slow as birth rate begins to exceed death rate
2)period of rapid growth-expands rapidly as there are no significant restrictions on growth
3)stable state-eventually limiting factors begin to stop further growth so population size stabilises

Question 2

What is meant by an ecosystems carrying capacity?

Answer 2

the maximum population size an ecosystem can sustainably support

Question 3

What can happen to populations once they’ve reached carrying capacity

3 points

Answer 3

-birth and death rate tends to equalize
-population growth slows down , and size stabilises , it may fluctuate slightly
-population size might decrease rapidly if environmental conditions degrade

Question 4

What are limiting factors?

What 2 categories can limiting factors fall into?

Answer 4

conditions that prevent populations from increasing indefinitely by restricting access to essential resources

density independent and density dependent

Question 5

Define density dependent and density independent limiting factors

Answer 5

dependent-their impact increases as population size increases , eg resource competition

independent-impact remains constant regardless of population size and can lead to extinction, eg natural disaster

Question 6

Effect of migration on population size …

What effect does immigration have?
What effect does emigration have?

Answer 6

immigration-increases population size as organisms move into an area

emigration-decreases population size as organisms leave an area