Genetic populations and ecosystems - POPULATIONS/SUCCESSION

Question 1

Definition of ecosystem

Answer 1

Dynamic systems made up of a community and all the non living factors of its environment

Question 2

Definition of community

Answer 2

All the populations of different species living and interacting in a particular place at the same time

Question 3

Definition of population

Answer 3

Several found within an ecosystem and are a group of individuals of the same species that occupy a particular habitat at a particular time and are able to interbreed

Question 4

Definition of habitat

Answer 4

The place where an organism lives and is characterised by the physical conditions and other types of organism present

Question 5

Definition of carrying capacity

Answer 5

The maximum number the population can grow to in a given space

Question 6

Give examples of abiotic factors

Answer 6

• Temperature
• Light intensity
• pH
• Humidity
• Wind speed
• Tidal range
• Wave speed

Question 7

Give examples of biotic factors

Answer 7

• Intraspecific competition (between members of the same species)
• Interspecific competition (competition between members of different species)
• Predation
• Disease

Question 8

What is the competitive exclusion principle?

Answer 8

No two species can occupy the same niche

Question 9

What term is used to describe populations of different species living in the same habitat? (PPQ 1 mark)

Answer 9

Community

Question 10

Explain the advantage of species occupying different niches (PPQ 1 mark)

Answer 10

Less interspecific competition for food

Question 11

What is meant by an abiotic factor? (PPQ 1 mark)

Answer 11

A factor that is physical/non biological/non living

Question 12

What is meant by the ecological term population? (PPQ 1 mark)

Answer 12

Total number of organisms/individuals of a species

Question 13

Why does temperature affect population size?

Answer 13

• Temperature affects enzymes
• Temp too low, slower rate of reaction
• Temp too high, enzymes denature and rate decreases

Question 14

Why does light affect population size?

Answer 14

• Light energy for photosynthesis
• Too low, less photosynthesis->less glucose=less respiration and less ATP for growth

Question 15

Why does pH affect population size?

Answer 15

Enzymes denature at extreme pH, decreasing rate

Question 16

Why does water affect population size?

Answer 16

Water for photosynthesis

Question 17

Why does humidity affect population size?

Answer 17

• Humidity affects transpiration
• Increased humidity results in less transpiration as diffusion gradient reduced

Question 18

Describe how you could estimate the size of the population of sundews in a small marsh (PPQ 5 marks)

Answer 18

• Use a grid
• Obtain random coordinates
• Count number in a quadrat
• Large sample and calculate mean/average number
• Calculate total umber of sundews

Question 19

Describe how the mark-release-recapture method could be used to determine the population of lizards at the start of an investigation (PPQ 3 marks)

Answer 19

• Capture/collect and release
• Leave time to disperse
• (N1 x N2)/N3

Question 20

Describe how you could use the mark-release-recapture method to estimate the number of lizards on an island (PPQ 4 marks)

Answer 20

• Capture/collect sample, mark them and release
• Method of marking lizards does not harm them
• Leave time for lizards to distribute
• (N1 x N2)/N3

Question 21

When is systematic sampling used?

Answer 21

To see the change/trend from one area to another

Question 22

What is the competitive exclusion principle?

Answer 22

When two species are competing for limited resources, the one that uses the resources more effectively will eliminate the other over time

Question 23

Definition of predation

Answer 23

When one organism is consumed by another

Question 24

Definition of succession

Answer 24

The changes that take place over time in the species that occupy a particular area

Question 25

What is a pioneer species?

Answer 25

The species that colonises an inhospitable environment

Question 26

Succession occurs in natural ecosystems. Describe and explain how succession occurs (PPQ 4 marks)

Answer 26

• Colonisation
• Pioneer species change the environment
• Environment becomes less hostile for other species
• Changes biodiversity
• Until climax community is reached

Question 27

What are two features of a climax community?

Answer 27

• Abiotic factors constant
• Same species present/stable community

Question 28

What is species diversity?

Answer 28

The number of different species (species richness) and the number of individuals of each species within any one community (species eveness)

Question 29

Give some examples of farming practises that have directly removed habitats and reduced species diversity

Answer 29

• Removal of hedgerows
• Creation of monocultures
• Filling in ponds and draining marshes
• Over grazing of land

Question 30

What is the realised niche?

Answer 30

An area that the organism lives in when biotic factors are considered

Question 31

What is the ecological niche?

Answer 31

An area with the right abiotic conditions that an organism can live

Question 32

Describe those features of a succession that would bring about an increase in the index of diversity (PPQ 3 marks)

Answer 32

• Initial environment is hostile
• Pioneer species colonise environment and make it more hospitable
• More species can grow
• More niches/habitats

Question 33

Suggest one ethical argument for maintaining biodiversity (PPQ 1 mark)

Answer 33

• Prevent extinction
• Prevent loss of habitats

Question 34

Suggest one economic argument for maintaining biodiversity (PPQ 1 mark)

Answer 34

Biodiversity may have financial importance in industries such as medicine and tourism

Question 35

Do abiotic factors exert a density-dependent or a density-independent effect on a population? (PPQ 1 mark)

Answer 35

• Density independent
• Abiotic factors are unaffected by number of living organisms