7- Populations in Ecosystems =)

Question 1

Explain the meaning of the ecological term ‘population’. (1)

Answer 1

organisms of one species in an ecosystem

Question 2

Explain the meaning of the ecological term ‘community’. (1)

Answer 2

organisms of all species in an ecosystem

Question 3

Give two conditions necessary for results from mark-release-recapture investigations to be valid. (2)

Answer 3

1. x immigration/ migration
2. x reproduction
3. marking x influence behaviour/ ↑ vulnerability to predation
4. sample large enough

Question 4

Mock 2 q9d

The mark-release-recapture method can be used to estimate the size of a fish population.
Explain how. (4)

Answer 4

1. capture sample, mark , release
2. ensure marking x harmful/ affect survival
3. allow time for fish to randomly distribute before collecting second sample
4. pop = n1 x n2 / nm

Question 5

Suggest why the mark-release-recapture method can produce unreliable results in very large lakes. (1)

Answer 5

↓ chance of recapturing fish/
unlikely fish distribute randomly

Question 6

The sundew is a small flowering plant, growing in wet habitats such as bogs and marshes. The soil in bogs and marshes is acidic and has very low concentrations
of some nutrients. The sundew can trap and digest insects.
Describe how you could estimate the size of a population of sundews in a small marsh. (5)

Answer 6

1. use a grid
2. random coordinates from computer
3. count no. in each quadrat
4. large sample + cal mean
5. mean no. x total area = total

Question 7

The Dengue virus is carried from one person to another by a mosquito. One method used to reduce transmission is the Sterile Insect Technique (SIT)- releasing large numbers of sterile (infertile) male into the habitat.
Explain how using the SIT could reduce transmission of dengue. (2)

Answer 7

• Compete w/ fertile males to mate/for
  food/resources (intraspecific competition)
• x reproduce/breed

Question 8

The release of radiation-sterilised mosquitoes has not been very successful in controlling the transmission of dengue.
Suggest one reason why. (1)

Answer 8

Radiation affected their attractiveness to mate/ survival

Question 9

What is it called, how an ecosystem supports a certain size of population of a species? (1)

Answer 9

Carrying capacity

Question 10

Suggest two reasons for conserving rainforests. (2)

Answer 10

1. conserve species/ biodiversity
2. conserve habitats
3. ↓ climate change
4. source of medicines
5. ↓ erosion
6. tourism