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biology > genetics, populations, evolution and ecosystems > Flashcards

genetics, populations, evolution and ecosystems 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
gene pool definition
all of the alleles of all the genes within a population at one time
26
allele frequency definition
the proportion of an allele in a gene pool
27
what is the hardy-weinberg principle?
allows us to estimate allele frequency and if the frequency is changing
28
assumptions of the hardy-weinberg principle
- no mutations - no migration - no selection - random mating - large population
29
two hardy-weinberg equations
p+q=1 p2+2pq+q2=1
30
what does p equal in H-W?
frequency of the dominant allele
31
what does q equal in H-W?
frequency of the recessive allele
32
what does p2 equal in H-W?
frequency of homozygous dominant (genotype)
33
what does 2pq equal in H-W?
frequency of heterozygous (genotype)
34
what does q2 equal in H-W?
frequency of homozygous recessive (genotype)
35
genetic factors causing variation?
- mutation - random fertilisation - crossing over - independent segregation
36
why does natural selection occur?
predation, disease and competition
37
how does natural selection cause a change in a population's gene pool?
- advantageous alleles more likely to be passed on through survival and reproduction - frequency of unfavourable allele decreases
38
process of natural selection
- mutation causes allele - advatangeous allele more likely to survive selection pressures and therefore reproduce - pass gene onto generations - increase alle frequency over time
39
types of selection
stabilising, directional and disruptive
40
disruptive selection
both extreme traits have selective advantage so middling phenotype becomes less frequent over time
41
what can disruptive selection lead to?
speciation
42
speciation definition
the process that results in the creation of a new sepcies
43
allopatric speciation definition
when populations become separated geographically leading to reproductive isolation
44
allopatric speciation process
- 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
sympatric speciation
when populations become reproductively isolated
46
sympatric speciation process
- random mutation - gene pools separate - change in allele frequency - no longer create fertile offspring
47
genetic drift definition
change in allele frequency within a population between generations
48
what does genetic drift lead to?
evolution
49
evolution definition
change in allele frequencies in a population due to chance rather than environmental factors
50
why does genetic drift affect small populations more than large ones?
- small populations have a smaller gene pool - any change in frequency becomes pronounced very quickly
51
population
group of organisms of the same species living in the same habitat
52
habitat
part of an ecosystem in which organisms live
53
community
all the populations of different species in the same area at the same time
54
ecosystem
a community and the non-living components of an environment (biotic and abiotic)
55
ecological niche
organisms specific role in the ecosystem
56
carrying capacity
maximum population size an ecosystem can support
57
abiotic factors
non-living factors of an ecosystem
58
biotic factors
living factors of an ecosystem
59
examples of abiotic factors
temperature, oxygen concentration, carbon dioxide concentration, light intensity, pH and soil conditions
60
four abiotic factors that affect population growth
- temperature - light - pH - water/humidity
61
intraspecific competition
competition between organisms of the same species (e.g mates and resources)
62
interspecific competition
competition between organisms of different species (e.g habitat and food)
63
typical pattern of predator-prey relationships
- 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
sampling methods for non-motile organisms
quadrats and transects
65
when are transects used?
when distribution is uneven
66
when are quadrats used?
random sampling
67
quadrats process
- 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
transect process
- 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
when is mark-release-recapture used?
when sampling motile organisms
70
MRR process
- 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
MRR equation
(number in 1st sample x number in 2nd sample)/number in 2nd sample previously marked
72
assumptions of MMR
- 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
why are ecosystems described as dynamic?
- populations constantly rise and fall - any small change can have a large effect - abiotic and biotic factors may alter conditions
74
succession definition
change in ecological community over time
75
succession process
- 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
conservation definition
protection and management of species and habitats in order to maintain biodiversity

biology (21 decks)

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