ah Flashcards Preview

Evolution > ah > Flashcards

Flashcards in ah Deck (171)
Loading flashcards...
1

What is evolution

change in allele or genotype frequency overtime

2

evidence for evolution includes

direct observation (soapberry bug)
shared features
Fossil record
imperfect design
beiogeogrpahy

3

example of direct observation

soapberry bug
evolution of mouthpart morphology in relation to seed defense of host

4

example of shared features

anatomy - homologous
embryology - same molecular basis
biochemistry - evidence for one origin of life
molecular biology

5

example of fossil record evidence for evolution

trilobites - gradual change in number of ribs in 8 lineages over 3my (increase)
transitional forms - archeopteryx/titaalik roseae

6

example of imperfect design

left recurrent laryngeal nerve - x10 longer than could be goes to brain voice box via aorta as fish ancestor branchial arch in giraffe 5m long
human eye nerve in front of retina = blind spot

7

what are alleles

variants in populations but homologoous at the locus

8

in 1 generation of random mating what happens to HWE

is reached and remains for all generations

9

if hwe conditions not met what occurs

evolution

10

why is hwe important

math proof ev exist
evidence that in absence of any ev forces allele frequencies stay constant
predict frequency of disease carriers

11

hwe assumptions

diploid
sexual repr
non overlapping generation
mating random
infinitely large population
no mutation
no migration
Natural selection not occuring

12

what occurs if one of HWE assumption not met

evolution

13

what is mutation

any change in dna of organism
only heritable when in germ line
ultimate source of all heritable variation

14

describe luria delbruck experiment

bacteriophage plated with E.coli
some E>coli are resistant
found each plate of E.coli to be variable in mutant
showing bacteria mutations occur in the absence of selection

15

how may mutation per generation

10^-9/bp/generation

16

what are the dynamic of gene evolving under equal reversible mutation rates

will reach equilibrium as forward/back are equal
will be 50/50 between

17

what are the dynamic for gene evolving under unequal reversible mutation rate

equilibrium not at 50/50 value is determined by relative rate of forward/back

18

speed of mutation

v slow (10,000s of generations)
as on the order of mutation rate

19

what determines the long term dynamis of the population

backward mutation rate over the total mutation rate

20

what is natural selection

the main force of evolutionary change and the only mechanism which increases fitness

21

feature of natural selection

individuals vary in ability to survive and reproduce
acts on ptype
requires heritable variations
requires differential reproduction

22

forms of natural selection

directional (distirbution toward selection pressure)
truncation (all bar few do not survive)#
stabilising (at either end do not survive)
disruptive (optimum trait does not survive)

23

what is the long term outcome of gene evolving under natural selection

allele frequency changes by relative fitness value

24

describe dynamics of natural selction

occurs in 700 generations
becomes fixed at whichever allele favoured
fixes faster when favoured allele has higher initial frequency
heter adv = fix at equilibrium
hetero dis = depends how system starts

25

what is the difference with dominant and recessive allele dynamic in selection

have different selection coefficient regardless of initial allele frequency
dominant allele no lag phase bu longer to fix
recessive allele long lag phase but quick to fix

26

example of the difference with dominant and recessive allele dynamic in selection

peppered moth in manchester
mutant black and dominant
wt recessive
pollution decreased after 1950, after lag phase wt increase

27

what affects speed of selection

selection strength and initial allele frequency

28

what is genetic drift

stochastic changes in allele frequency caused by random sampling of gametes to form offspring in finite population

29

features of genetic drift

random
leads to loss of variation
if run indefinitely 1 allele will fix
stronger in smaller population
outcome of value of fixation depends on initial allele frequency

30

Natural selection and genetic drift on dominant allele

in low pop dominat allele lost as genetic drift
as increase population less allele lost
natural selection stronger bigger population