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biology > genetics, populations, evolution and ecosystems > Flashcards

genetics, populations, evolution and ecosystems Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

genotype

A

genetic constitution of an organism (alleles it has for a gene)

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2
Q

phenotype

A

expression of genes and their interaction with the environment

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3
Q

allele definition

A

different versions of a gene found at the same locus on a chromosome

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4
Q

dominant allele definition

A

an allele that will always be expressed in the phenotype

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5
Q

recessive allele definition

A

an allele that is only expressed in the phenotype if no dominant allele is present

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6
Q

homozygous definition

A

a pair of homologous chromosomes carrying the same alleles for a single gene

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7
Q

heterozygous definition

A

a pair of homologous chromosomes carrying two different alleles for a single gene

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8
Q

codomiant alleles definition

A

both alleles are equally dominant and expressed in the phenotype

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9
Q

monohybrid inheritance definition

A

one phenotypic characteristic is controlled by a single gene

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10
Q

dihybrid inheritance definition

A

two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time

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11
Q

sex-linkage definition

A

a gene whose locus is on the X chromosome

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12
Q

multiple alleles definition

A

more than two alleles for a single gene

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13
Q

autosomal linkage definition

A

genes that are located on the same chromosome

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14
Q

epistasis definition

A

when one gene modifies or masks the expression of a different gene at a different locus

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15
Q

expected ratio of monohybrid cross of two heterozygous alleles

A

3:1

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16
Q

why are males more likely to express a recessive sex-linked allele?

A
  • most sex-linked alleles on X chromosome
  • males only have one X chromosome
  • so only carry a single allele
  • whereas women must be homozygous recessive
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17
Q

which parent do males inherit sex-linked characteristics from?

A

their mother as she has the X chromosome, if she is heterozygous for sex-linked alleles, she is a carrier

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18
Q

what is recessive epistasis?

A

where two homozygous recessive alleles mask expression of another allele

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19
Q

what is dominant epistasis?

A

where one dominant allele masks the expression of other alleles

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20
Q

ratio of recessive epistasis

A

9:3:4

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21
Q

ratio of dominant epistasis

A

12:3:1

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22
Q

expected ratio of dihybrid cross

A

9:3:3:1

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23
Q

what are the two only possible gametes for cases of autosomal linkage?

A

homozygous dominant or recessive

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24
Q

when does autosomal linkage produce 4 gametes?

A

when crossing over has occured

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25
Q

gene pool definition

A

all of the alleles of all the genes within a population at one time

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26
Q

allele frequency definition

A

the proportion of an allele in a gene pool

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27
Q

what is the hardy-weinberg principle?

A

allows us to estimate allele frequency and if the frequency is changing

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28
Q

assumptions of the hardy-weinberg principle

A
  • no mutations
  • no migration
  • no selection
  • random mating
  • large population
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29
Q

two hardy-weinberg equations

A

p+q=1
p2+2pq+q2=1

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30
Q

what does p equal in H-W?

A

frequency of the dominant allele

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31
Q

what does q equal in H-W?

A

frequency of the recessive allele

32
Q

what does p2 equal in H-W?

A

frequency of homozygous dominant (genotype)

33
Q

what does 2pq equal in H-W?

A

frequency of heterozygous (genotype)

34
Q

what does q2 equal in H-W?

A

frequency of homozygous recessive (genotype)

35
Q

genetic factors causing variation?

A
  • mutation
  • random fertilisation
  • crossing over
  • independent segregation
36
Q

why does natural selection occur?

A

predation, disease and competition

37
Q

how does natural selection cause a change in a population’s gene pool?

A
  • advantageous alleles more likely to be passed on through survival and reproduction
  • frequency of unfavourable allele decreases
38
Q

process of natural selection

A
  • mutation causes allele
  • advatangeous allele more likely to survive selection pressures and therefore reproduce
  • pass gene onto generations
  • increase alle frequency over time
39
Q

types of selection

A

stabilising, directional and disruptive

40
Q

disruptive selection

A

both extreme traits have selective advantage so middling phenotype becomes less frequent over time

41
Q

what can disruptive selection lead to?

A

speciation

42
Q

speciation definition

A

the process that results in the creation of a new sepcies

43
Q

allopatric speciation definition

A

when populations become separated geographically leading to reproductive isolation

44
Q

allopatric speciation process

A
  • variation due to random mutation
  • species become geographically isolated
  • different selection pressures
  • gene pools are kept separate
  • change in allele frequency
  • no longer create fertile offspring
45
Q

sympatric speciation

A

when populations become reproductively isolated

46
Q

sympatric speciation process

A
  • random mutation
  • gene pools separate
  • change in allele frequency
  • no longer create fertile offspring
47
Q

genetic drift definition

A

change in allele frequency within a population between generations

48
Q

what does genetic drift lead to?

A

evolution

49
Q

evolution definition

A

change in allele frequencies in a population due to chance rather than environmental factors

50
Q

why does genetic drift affect small populations more than large ones?

A
  • small populations have a smaller gene pool
  • any change in frequency becomes pronounced very quickly
51
Q

population

A

group of organisms of the same species living in the same habitat

52
Q

habitat

A

part of an ecosystem in which organisms live

53
Q

community

A

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

54
Q

ecosystem

A

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

55
Q

ecological niche

A

organisms specific role in the ecosystem

56
Q

carrying capacity

A

maximum population size an ecosystem can support

57
Q

abiotic factors

A

non-living factors of an ecosystem

58
Q

biotic factors

A

living factors of an ecosystem

59
Q

examples of abiotic factors

A

temperature, oxygen concentration, carbon dioxide concentration, light intensity, pH and soil conditions

60
Q

four abiotic factors that affect population growth

A
  • temperature
  • light
  • pH
  • water/humidity
61
Q

intraspecific competition

A

competition between organisms of the same species (e.g mates and resources)

62
Q

interspecific competition

A

competition between organisms of different species (e.g habitat and food)

63
Q

typical pattern of predator-prey relationships

A
  • prey eaten by predator
  • predator pop increases and prey pop decreases
  • fewer prey means more competition for food
  • predator pop decreases
  • fewer predators increases prey pop
  • always more prey than predators
  • across specific time
64
Q

sampling methods for non-motile organisms

A

quadrats and transects

65
Q

when are transects used?

A

when distribution is uneven

66
Q

when are quadrats used?

A

random sampling

67
Q

quadrats process

A
  • lie two tape measures at right angles to create gridded area
  • use random number generator for coordinates
  • place quadrat and collect data
  • repeat 30 times
  • calculate a mean
68
Q

transect process

A
  • place the tape measure at a right angle to environment
  • place the quadrat every 5 metres’every position across tape measure
  • collect data
  • repeat by placing another 30 transects
  • calculate a mean
69
Q

when is mark-release-recapture used?

A

when sampling motile organisms

70
Q

MRR process

A
  • initial sample of population is collected
  • individuals are marked and released and number is recorded
  • marking must not impact survival
  • allow sample to redisperse
  • second sample is collected
  • total number captured in second sample and number recaptured is recorded
71
Q

MRR equation

A

(number in 1st sample x number in 2nd sample)/number in 2nd sample previously marked

72
Q

assumptions of MMR

A
  • marked individiuals distrubute evenly
  • no migration in or out
  • few births or deaths
  • method of marking doesnt affect survival
  • mark does not come off
73
Q

why are ecosystems described as dynamic?

A
  • populations constantly rise and fall
  • any small change can have a large effect
  • abiotic and biotic factors may alter conditions
74
Q

succession definition

A

change in ecological community over time

75
Q

succession process

A
  • colonisation by pioneer species
  • pioneer species changes abiotic factors/environment
  • makes environment less hostile for new species
  • increases/changes biodiversity
  • climax community is when stable state is reached
76
Q

conservation definition

A

protection and management of species and habitats in order to maintain biodiversity

biology (21 decks)

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