3.7 Genetics, Population, Evolution And Ecosystems

Question 1

What is a population?

Answer 1

Group of all organisms of the same species living in the same habitat

Question 2

What is a habitat?

Answer 2

Part of an ecosystem in which particular organisms live in

Question 3

What is a community?

Answer 3

All the populations of the different species in the same area at the same time

Question 4

What is an ecosystem?

Answer 4

A community and the non-living components of an environment (biotic and abiotic factors)

Question 5

What is a niche?

Answer 5

An organisms role within an ecosystem, including position in the food web and habitat. Each species occupies its own niche

Question 6

What is carrying capacity?

Answer 6

Maximum population size an ecosystem can support

Question 7

What are abiotic factors and examples?

Answer 7

•Non-living conditions
e.g temperature, oxygen, CO2 and light intensity

Question 8

What are biotic factors and examples?

Answer 8

Living conditions (impact of interactions between organisms)
e.g competition, predation, disease

Question 9

What are the different types of competition?

Answer 9

Interspecific: members of different species compete for the same limited resources and better adapted individuals survive

Intraspecific: members of the same species compete for resources and mates. Fitter individuals attract a mate

Question 10

What does a predator-prey relationship show?

Answer 10

•both population sizes will fluctuate
•at most times, more prey than predators so prey no. peaks more
•size of population changes in prey and then predators due to lag time

Question 11

How can you accurately represent a population?

Answer 11

•large no. of samples (representative 30+)
•random samples (avoids bias)

Question 12

Outline a random sampling method

Answer 12

1.lie 2 tape measures at a right angle to create a gridded area
2.use a random number generator to generate 2 coordinates e.g calculator
3.place a quadrat and collect data e.g total no.
4. Repeat at least 30 times (or until running mean as more reliable and allows for a statistical test to be done)
5.multiply to give estimate for total field area

Question 13

What are the 2 types of transects?

Answer 13

Belt: quadrat placed at every position along tape measure
Interrupted: quadrat placed at uniform intervals along the tape measure

Question 14

Outline a method for a line transect

Answer 14

1.place tape measure at right angles to e.g the shore line
2.place quadrat every 1 metre along the tape measure
3. Collect data
4. Repeat by placing another 30 transects along each e.g the beach at right angles to the shore line

Question 15

What is local frequency and ad/dis of using it to estimate abundance?

Answer 15

•% of squares in quadrat with species
Ad: •quick for large areas
•useful if too many to count or hard to identify individual
Dis: •poor accuracy as it doesn’t consider overlapping plants or size of plants

Question 16

What is density and ad/dis of using it to estimate abundance?

Answer 16

•no. of one species in a given area
Ad: •more accurate
•used to estimate species richness
Dis: •more time consuming

Question 17

What is % cover and ad/dis of using it to estimate abundance?

Answer 17

•proportion of ground occupied by the species
Ad: •quicker method than density
•useful if too many to count or difficult to identify
Dis: •subjective so limiting accuracy
•doesn’t consider overlapping plants or the size of the plant

Question 18

How is mark-release-recapture done to estimate population?

Answer 18

1.collect sample in each area and mark unobtrusively
2.allow time to re-integrate with rest of the population
3.collect second sample and count no. marked
4.estimate using equation =
S1X S2
———-
no. marked in S2

Question 19

What assumptions are made in mark-release-recapture?

Answer 19

•no immigration/migration
•no reproduction
•marking doesn’t increase predation
•population is large enough

Question 20

What is meant by uniformly distributed?

Answer 20

Same no. of organisms in each region/equally spread

Question 21

What is ecological succession?

Answer 21

Process by which communities change over time as a result of interactions between abiotic and biotic factors.
Proceeds with a series of stages with one community of organisms being replaced by another

Question 22

What is primary and secondary succession?

Answer 22

1)occurs in environment where there is no pre-existing vegetation or soil
2)occurs on substrate that previously supported vegetation before and ecological disturbance

Question 23

What is the process of succession?

Answer 23

1.pioneer species colonise first as they can tolerate hostile abiotic conditions
2.pioneer species reproduce, grow and die, this changes abiotic conditions to make it less hostile e.g increase the mineral nutrients in soil
3.this allows other new species to colonise and eventually outcompete the pioneer community and outcompete each other
4.over time new communities continue replacing previous communities and biodiversity increases (biomass and productivity increase)
5.eventually a stable climax community is reached

Question 24

What is deflected succession and what does it produce?

Answer 24

•occurs when the climax community is prevented from being reached e.g due to coppicing and grazing by animals
•it intervenes and prevents succession completing as large trees are prevented from growing
•this produces a sub-climax community called plagioclimax

Question 25

What are features of climax communities?

Answer 25

•same species present over a long time
•stable population
•abiotic conditions remain stable

Question 26

Why does a population decrease when temperatures change?

Answer 26

•use more energy to maintain right internal temperature
•less energy for growth and reproduction