Population ecology

Question 1

Community

Answer 1

Population of living species living and interacting at the same time in a particular place.

Question 2

Habitat

Answer 2

Place where organism lives

Question 3

Niche

Answer 3

How organism fits into an environment. Abiotic and biotic factors that the organism is adapted to to survive.

Question 4

Population size varies as a result of…

Answer 4

Effect of abiotic factors, interactions between organisms (interspecific competition and predation).

Question 5

Abiotic factors

Answer 5

Temperature - can affect enzymes.
Light - increase speed of growth or how many seeds produced.
pH - effects enzymes
Water and humidity - effects transpiration

Question 6

Intraspecific competition

Answer 6

Competition between individuals of same species

Question 7

Interspecific competition

Answer 7

Individuals of different species. Normally one has competitive advantage over other, leading to increase of one and decrease of other population. No two species can occupy same niche.

Question 8

Effect of predator-prey relationship on population size

Answer 8

• Predators eat prey, reducing population of prey
• Fewer prey, predators in greater competition.
• Predator population reduced.
• Fewer prey eaten, population increase.
• Cycle

Question 9

What to consider when using quadrats

Answer 9

Size - larger species need larger quadrats and where possible when population is spread out using more smaller quadrats.
Number of sample quadrats- more = more reliable results but more time.
Random sampling

Question 10

How to random sample

Answer 10

Two long tape measures at right angles.
Get coords using random number gen.
Place quadrat at coord.

Question 11

Systematic sampling

Answer 11

Stretch tape and placing a quadrat regularly.

Question 12

How to ensure reliable results

Answer 12

Large sample size (many quadrats used), mean taken of all samples.

Question 13

Release and recapture formula

Answer 13

Pop size = (number in first sample * number in second) / number of MARKED individuals recaptured

Question 14

Release and recapture assumptions

Answer 14

Proportion of unmarked is same in sample as population.
Marked individuals distribute themselves evenly.
Population has definite boundary so no immigration or emigration.
Few deaths and births.
Marking is not toxic or washed off.

Question 15

How does one stage link to another in succession

Answer 15

Alters environment in a way less suitable for existing species so new species outcompete existing one.
Alters environment to be more suitable for other species with different adaptations.

Question 16

First stage of succession

Answer 16

Pioneer species make up pioneer community.

Question 17

Characteristics of pioneer species

Answer 17

Asexual reproduction.
Wind dispersed seeds or spores to reach isolated situations.
Rapid germination.
Photosynthesis.
Fix nitrogen from atmosphere.
High tolerance to extreme conditions.

Question 18

Climax community

Answer 18

Stable equilibrium with climate, depends on place.

Question 19

During succession, common features are…

Answer 19

Abiotic environment becomes less hostile.
More habitats and niches
Increased biodiversity.
Higher biomass

Question 20

Secondary succession

Answer 20

Land is altered and succession to a climax community happens more rapidly.

Question 21

Conservation

Answer 21

Preventing succession to another stage. E.g. a countryside of fields prevented from turning into woodlands by grazing.

Question 22

Species

Answer 22

Group of individuals that can breed to produce fertile offspring

Question 23

Why is most of sun’s energy not converted to organic matter by photosynthesis

Answer 23

Much of sunlight reflected
Not all wavelengths of light can be absorbed
Limiting factor of photosynthesis limits rate
The light does not hit chlorophyll molecule

Question 24

GPP (gross primary production)

Answer 24

The chemical store of energy in a plant in a given area over given time

Question 25

NPP (net primary production)

Answer 25

GPP - respiratory losses

Question 26

Why is low amount of energy transferred at each stage in food chain

Answer 26

Some of organism not consumed.
Some is not digestible and left in faeces.
Some lost in urine.
Heat from respiration

Question 27

Why do most food chains have at most 5 tropic levels

Answer 27

Relative inefficiency of energy transfer.

Question 28

How does speciation occur

Answer 28

Two groups become separated and reproductively isolated so that gene flow is reduced. Each group experiences different selection pressure so frequency of alleles changes due to natural selection and 2 populations can no longer interbreed.