Populations

Question 1

Define population

Answer 1

A group of organisms living in the same space at the same time which have the potential to interbreed

Question 2

What is the gene pool?

Answer 2

All the alleles of all the genes of all the population at any one time

Question 3

What is the allele frequency of a population?

Answer 3

The number of times an allele occurs within a gene pool

Question 4

What are the hardy weinberg equations?

Answer 4

P^2 + 2pq + q^2 = 1

P+ q = 1

Question 5

What assumptions need to be taken when using the hardy Weinberg equations

Answer 5

Large enough sample
Random mating
No selective advantages
No mutations

Question 6

Give three causes of genetic variation

Answer 6

Mutations
Meiosis - crossing over and independent segregation
Random fertilisation

Question 7

What is infraspecific competition?

Answer 7

Competition within a species

Question 8

Describe the steps of natural selection

Answer 8

Mutations create alternate allelles
Greater genetic variation
Selection pressures favour the survival of certain individuals
Selected individuals more likely to reproduce
Next generation have a higher allele frequency of selected allele, some alleles may be selected against to the point of being removed from the gene pool

Question 9

Describe disruptive selection

Answer 9

Selection favours both extremes
E.g. Fur length
Winter favours long, summer favours short
Mid length never selected for

Question 10

What is speciation?

Answer 10

Where two populations become separated from each other, meaning natural selection occurs differently in each
Creates new organisms

Question 11

Describe a genetic bottle neck

Answer 11

Large rapid decrease in a population
Leads to reduction in gene pool
Only some survive

Question 12

What are the two types of speciation?

Answer 12

Allopatric - two populations are geographically separated, i.e. By flooding, climatic conditions give rise to new species
Sympatric - speciation in the same place, e.g. Different courtship dances or anatomical differences

Question 13

Define ecosystem

Answer 13

Biotic an abiotic features within a certain area and the interactions between them

Question 14

Define community

Answer 14

All the populations of all the species within a habitat at one time

Question 15

Define biological niche,

Answer 15

How an organism fits into the environment i.e. Its relation to biotic and abiotic factors.
No 2 species can fit the same niche when resources are limited

Question 16

What is a habitats carrying capacity?

Answer 16

The maximum population size maintained by a habitat

Question 17

What are the two types of transect?

Answer 17

Standard grid

Point quadrat - pins go through top which lead down to plant

Question 18

What is a belt transect?

Answer 18

Tape measure placed along length of area investigated

Place quadrat every x meters

Question 19

Give three ways of measuring abundance in an ecosystem

Answer 19

Frequency - number of quadrats that have the species in (good for hard to count organisms)
Percentage cover - % of a quadrat covered by the plant (good for speed)
Simple counting

Question 20

Describe the mark release recapture technique

Answer 20

Capture and mark a sample of organisms
Release and leave for a suitable time
Recapture them

Calaculate population by: (first sample x second sample) / those recaptured

Question 21

What assumptions need be made when using mark release recapture

Answer 21

Re- disperse evenly
No births or deaths since 1st capture
Closed habitat

Question 22

Describe primary succession

Answer 22

Hostile enviroment inhabited by a pioneer species which is heavily adapted to the enviroment e.g. Asexual reproduction, rapid germination photosynthetic, nitrogen fixing
Pioneer species dies, through decomposition it improves soil fertility
Nutrients allow a small community to be supported ( pioneer species reduces hostility)
More decomposition causes more complex organisms to be able to grow
Stable climax community is formed