7.4 Populations in Ecosystems

Question 1

Define an Ecosystem

Answer 1

A dynamic system consisting of a community and the abiotic factors

Question 2

Define a population

Answer 2

The number of organisms of one species in an ecosystem

Question 3

Define a community

Answer 3

Organisms of all populations in an ecosystem

Question 4

Define a habitat

Answer 4

The place where an organism lives

Question 5

Define a niche

Answer 5

How an organism fits into it’s enviroment

Question 6

Define carrying capacity

Answer 6

Maximum population size a habitat can support, over an extended period of time

Question 7

What abiotic limiting factors affect carrying capacity

Answer 7

• Temperature
• Light intensity
• Soil pH
• Water avaliability

Question 8

What biotic limiting factors affect carrying capcity

Answer 8

• Interspecific competition for food
• Intraspecific competition for food
• Predation

Question 9

What are the 3 ways to estimate a population size

Answer 9

• Random sampling
• Systematic sampling
• Mark-Release-Recapture

Question 10

Describe how to use random sampling to estimate a population size

Answer 10

• Divide area into grid with co-ordinates
• Obtain random co-ordinates from a random number generator, and use this to place quadrats
• Count the number of individuals/percentage cover in each quadrat
• Take a large sample, and find the mean number/percentage cover
• Total individuals for area = mean x number of qudrats that fit into area

Question 11

Describe how systematic sampling is used to estimate a population size

Answer 11

• Lay tape measure perpendicualar to starting point
• Take samples at random intervals (e.g 1m) with a quadrat
• Count number of individuals/percentage cover in each quadrat
• Repeat with a large number of quadrats

Question 12

When estimating population size, howe are samples representative with bias eliminated

Answer 12

• Large sample
• Random number generator used to select individuals

Question 13

Describe how to estimate a population size using the Mark-Release-Recapture Method

Answer 13

• Capture sample, mark each individual and release
• Ensure marking doesn’t harm or affect survivial of organism
• Allow time period for organism to randomly and evenly distribute
• Collect second sample
• Population = no. marked in 1st x no. marked in 2nd / number recaptured

Question 14

What assumptions are made during the Mark-Release-Recapture Method

Answer 14

• No migration
• Constant population (no reproduction or deaths)
• Marking doesn’t influence behaviour or increase vulnarability to predators

Question 15

What is important about the marking for the Mark-Release-Recapture method

Answer 15

Must not harm or affect the survival of an organism

Question 16

W

Equation used when estimating population size using the Mark-Release-Recapture method

Answer 16

Question 16

Describe the process of succession

Answer 16

• Colonisation from pioneer species
• Pioneer species change the enviroment and conditions, by providing food for other species
• Enviroment becomes less hostile for new species, and less suitable for previous species
• Pioneer species outcompeted as succession continues
• Biodiversity increases
• Climax community reached

Question 17

What is the difference between primary and secondary succession

Answer 17

• Primary occurs from an inorganic starting point (sand dunes)
• Secondary occurs from an area cleared of organisms, but with soil present

Question 18

What is deflected succession part of, and why is it used

Answer 18

• Part of conservation
• Prevent climax community being achieved

Question 19

What are the features of a climax community

Answer 19

• Population stable over a long period of time
• Community stable over a long period of time
• Abiotic factors constant over a long period of time