4.4. Variation and evolution

Question 1

what factors prod variation bet individuals??

Answer 1

both genetic & environmental factors prod variation

Question 2

types of variation??

Answer 2

continuous & discontinuous
heritable & non-heritable

Question 3

discontinuous variation?

Answer 3

-type of variation that can be categorised e.g. blood grp
-a characteristic can only appear in discrete values
-influenced by 1 or 2 genes & environmental factors have little effect

Question 4

continuous variation??

Answer 4

-type of variation that cannot be categorissed e.g. height
-prods a continuous range in which a characteristic can take any value
-infulenced by multiple genes & is often significantly affected by environmental factors

Question 5

compare heritable & non-heritable variation??

Answer 5

heritable variation is the genetic differences bet individuals whereas non-heritable variation is acquired differences in the phenotypes of individuals that cannot be inherited

Question 6

evolution??

Answer 6

-change in allele freqs in a gene pool of a pop over time
-occurs due to natural selection

Question 7

how does natural selection cause change in allele freqs over generations?

Answer 7

organisms w/ advantageous characteristics are more likely to survive & pass their favourable alleles to offspring, freq of unfavourable alleles decreases

Question 8

selection pressures??

Answer 8

-environmental factors that drive evolution by natural selection & limit pop sizes
-they can change the freq of alleles in a pop

Question 9

examples of selection pressures??

Answer 9

predation
disease
comp for food habitats mates
environmental conditions e.g. temp

Question 10

how can allele freqs be expressed??

Answer 10

expressed as a percentage or proportion of the total number of all alleles for that gene

Question 11

2 types of comp??

Answer 11

-interspecific
-intraspecific

Question 12

interspecific comp??

Answer 12

type of comp that takes place bet member of diff species

Question 13

intraspecific comp??

Answer 13

type of comp takes place bet members of same species

Question 14

gene pool??

Answer 14

all of the diff vers of genes(alleles) in the individuals that make up a pop

Question 15

genetic drift??

Answer 15

variations in allele freqs in small pops due to chance (rather than as a result of selection pressures)

Question 16

founder effect??

Answer 16

when a small number of individuals become isolated forming a new pop w/ a limited gene pool, allele freqs not reflective of og pop

Question 17

Hardy-Weinberg principle??

Answer 17

a model that allows the estimation of freq of alleles in a pop, & whether allele freq is changing overtime

Question 18

assumptions made by Hardy-Weinberg principle??

Answer 18

no mutations occur to create new alleles
no migration in or out of pop
no selection alleles are all equally passed onto the next gen
random mating
large pop

Question 19

Explain the Hardy-Weinberg eqn for calc allele freq??

Answer 19

freqs of each allele for a characteristic must add up to 1.0 giving the eqn: p + q = 1.0
p=freq of dominant allele & q=freq of recessive alle

Question 20

explain the Hardy-Weinberg eqn for calc genotype freq??

Answer 20

freqs of each genotype for a characteristic must add up to 1.0 giving the eqn: p^2 + 2pq + q^2 = 1.0
p^2=freq of homozygous dominant, 2pq=freq of heterozygous & q^2= freq of homozygous recessive

Question 21

define speciation??

Answer 21

formation of new species due to evolution of 2 reproductively separated pops

Question 22

why nay speciation occur??

Answer 22

genetic drift in isolated pop
founder effect
natural selection

Question 23

2 types of speciation??

Answer 23

allopatric speciation
sympatric speciation

Question 24

term for speciation that occurs when 2 pops become geographically isolated??

Answer 24

allopatric speciation

Question 25

term for speciation that occurs when 2 pops w/in same area become reproductively isolated??

Answer 25

sympatric speciation

Question 26

geographical isolation??

Answer 26

a physical barrier such as a river or mountain separates 2 pops of the same species

Question 27

potential isolation mechanisms in sympatric speciation??

Answer 27

morphological isolation
seasonal isolation
behavioural isolation
gametic isolation
hybrid sterility
hybrid inviability

Question 28

morphological isolation??

Answer 28

reproductive isolation of 2 pops due to incompatibility of their reproductive systems

Question 29

behavioural isolation??

Answer 29

reproductive isolation of 2 pops due to diff in their behaviour such as mating rituals

Question 30

seasonal isolation??

Answer 30

reproductive isolation of 2 pops due to diff in their breeding seasons

Question 31

hybrid inviability??

Answer 31

post-zygotic barrier
successful fertilisation but embryo cannot develop into a living organism

Question 32

hybrid sterility??

Answer 32

formation of sterile hybrid offspring from reprod of individuals of diff species

Question 33

why may reprod of individuals of diff species prod sterile offspring??

Answer 33

chromosome sets from each parents differ so unable to pair up during meiosis

Question 34

example of sterile hybrid and a fertile hybrid??

Answer 34

sterile hybrid - mule
fertile hybrid - wheat

Question 35

gametic isolation??

Answer 35

pre-zygotic barrier
successful fertilisation does not occur