Genetics and Variation - Ecosystems

Question 2

define discontinuous variation

Answer 2

organisms fit into distinct categories with no overlaps

controlled by a small number of genes

largely unaffected by environment

Question 3

define environmental variation

Answer 3

variation where the environment determines where an organism lies within the limits

genes also set limits

usually due to polygenes

Question 4

what is an example of environmental variation?

Answer 4

height or weight

Question 5

define continuous variation

Answer 5

no categories to place individuals

controlled by polygenes

significantly affected by environment

forms a normal distribustion curve

Question 6

define selection pressure

Answer 6

factors that cause competition for survival eg predators, disease

Question 7

define genetic drift

Answer 7

the change in frequency of an allele in a population over time

Question 8

where does genetic drift occur most often?

Answer 8

in smaller populations

Question 9

what is the difference between the founding population and new population in genetic drift?

Answer 9

founding population has a small no. individuals with small no. alleles

new population has non-representative allele frequencies compared to parent population

Question 10

define speciation

Answer 10

the evolution of a new species

Question 11

what are the 3 steps of speciation?

Answer 11

gene pool isolation

evolution due to environment

reproductive isolation - organisms can no longer breed with members of original species to produce fertile offspring

Question 12

what are the 2 causes of speciation?

Answer 12

allopatric speciation

sympatric speciation

Question 13

when does allopatric speciation occur?

Answer 13

when organisms are geographically separated and each population experiences different selection pressures

Question 14

when does sympatric speciation occur?

Answer 14

random mutations occur that cause an organism to be reproductively isolated from other organisms

normally requires organism to be able to reproduce asexually

Question 15

what are the 4 causes of reproductive isolation?

Answer 15

seasonal changes

mechanical changes

behavioural changes

chromosomal changes

Question 16

define ecology

Answer 16

the study of organisms in their environment

Question 17

define abiotic factors

Answer 17

non-living parts of an environment

Question 18

define biotic factors

Answer 18

living parts of an environment

Question 19

define a community

Answer 19

a group of different species that live in the same place at the same time

Question 20

what is an ecosystem?

Answer 20

biotic and abiotic factors and a community of organisms in a specific area

Question 21

what is an environment?

Answer 21

the conditions that surround an organism, including both abiotic and biotic factors

Question 22

what is a habitat?

Answer 22

the location where an organism lives

Question 23

define niche

Answer 23

the role a species has in its environment, governed by adaptation to both biotic and abiotic conditions

Question 24

what is a population?

Answer 24

all of the members of a species living together in the same place at the same time

Question 25

what is a species?

Answer 25

organisms that look similar and can breed together to produce fertile offspring

Question 26

when is random sampling used?

Answer 26

to estimate a population size where organisms are evenly distributed

Question 27

what is the method for using quadrats?

Answer 27

1. divide the area into a grid by placing 2 tape measures along the sides, assign each square coordinates
2. use random number generator to choose coordinates
3. estimate % cover, count organisms present or indicate if organism is present
4. repeat

Question 28

what are the 2 types of quadrats?

Answer 28

frame quadrats and point quadrats

Question 29

when is transect sampling used?

Answer 29

when organism distribution has spatial variation

Question 30

what is spatial variation?

Answer 30

when organisms are distributed over two environments

Question 31

what is the method for using transect sampling?

Answer 31

1. place line marked at regular intervals across the area
2. place a quadrat at each interval
3. count or calculate % cover of organisms within the quadrat
4. repeat with more transects and calculate average of organisms at each interval

Question 32

what does quadrat sampling measure?

Answer 32

the abundance of species in a given area

Question 33

what is the mark-release-recapture method of sampling?

Answer 33

1. catch, count and mark a sample of animals
2. release the animals back into their habitat
3. after a period of time, catch a new sample
4. count number of marked animals recaptured
5. calculate population size - (total of 1st sample x total of 2nd sample) divided by no. marked animals recaptured

Question 34

when can mark-release-recapture sampling be used?

Answer 34

when there is a large sample size

when between the 2 samples:

there is little to no migration, immigration and reproduction

marked organisms can effectively re-mi with the rest of the population

marking does not influence behaviour or increase predation risk

Question 35

what is the carrying capacity?

Answer 35

the maximum sustainable size of a population