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AQA A level biology <33 > Topic 7- Genetics, populations, evolution and ecosystems > Flashcards

Topic 7- Genetics, populations, evolution and ecosystems Flashcards

(63 cards)

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1
Q

what is genotype?

A

alleles that make up an organism

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2
Q

what is a phenotype?

A

observable characteristics of an organism resulting from the interaction between genotype and the environment

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3
Q

what is a gene?

A

length of DNA that codes for a particular polypeptide

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4
Q

what is the locus?

A

position of a gene on a particular DNA molecule

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5
Q

what is an allele?

A

different form of a gene

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6
Q

homozygous

A

two alleles the same

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7
Q

heterozygous

A

two different alleles

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8
Q

dominant allele

A

allele that expresses itself in the phenotype

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9
Q

recessive allele

A

allele not expressed

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10
Q

co dominant alleles

A

both contribute to phenotype

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11
Q

monohydrid inheritance

A

inheritance of singular gene

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12
Q

law of segregation

A

in diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete

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13
Q

dihybrid inheritance

A

two characteristics determined by two different genes located on different chromosomes are inherited

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14
Q

law of independent assortment

A

each member of a pair of alleles may combine randomly with either of another pair.

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15
Q

codominance

A

both alleles expressed in phenotype

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16
Q

multiple alleles

A

gene may have more than two alleles, but only 2 can be present in an individual

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17
Q

sex linkage

A

females- XX- same gametes
males- XY- two different gametes
any gene carried by X or Y chromosome is said to be sex-linked

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18
Q

autosomomes

A

other 22 chromosomes other than sex chromosomes

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19
Q

autosomal linkage

A

two or more genes carried on the same autosome
all linked genes remain together during meiosis assuming there is no crossing over
do not segregate according to Mendel’s law of independent assortment

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20
Q

epistasis

A

allele of one gene affects or masks the expression of another in the phenotype

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21
Q

chi-squared test

A

used to test null hypothesis
is a means of testing whether any deviation between the observed and expected numbers is significant or not

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22
Q

when can the chi-squared test be used?

A

sample size relatively large
data falls into discrete categories
only raw counts used

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23
Q

degrees of freedom

A

number of categories — 1
used to find critical value
compare to 0.05 (5%)

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24
Q

gene pool

A

all the alleles of all the genes of all the individuals in a population at a given time

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25
allele frequency
number of times an allele occurs within the gene pool
26
hardy-weinberg principle
used to calculate frequencies of alleles of a particular gene in a population
27
assumptions of hardy -weinberg principle
no mutations arise population isolated no selection population is large mating in population is random
28
hardy-weinberg equations
p+q=1 p^2+2pq+q^2=1
29
what causes genetic variation?
mutations meiosis random fertilisation of gametes
30
selection pressures
environmental factors that limit the population of a species
31
examples of selection pressures
predation disease competition
32
factors that natural selection rely on
1) organisms produce more offspring than can be supported by available food, light, space 2) genetic variety within the population of all species 3) variety of phenotypes that selection operates against
33
intraspecific competition
competition amongst individuals
34
interspecific competition
competition between different species
35
natural selection
those with the more advantageous allele survive they reproduce to produce more offspring with the advantageous allele allows population to evolve and adapt
36
stabilising selection
preserves average phenotype of population by favouring average individuals selection against extreme phenotypes
37
directional selection
changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean of the population selection for one extreme phenotype
38
disruptive selection
favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population
39
abiotic factors
non-living
40
biotic factors
living
41
ecosystems
dynamic systems made up of a community and all the non-living factors of its environment
42
population
group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed
43
carrying capacity
size of population of species an ecosystem supports
44
community
all the populations of different species living and interacting in a particular place at the same time
45
habitat
place where an organism lives
46
microhabitats
smaller units of a habitat with their own microclimate
47
niche
how an organism fits into the environment, including all the biotic and abiotic factors
48
competitive exclusion principle
no two species occupy exactly the same niche
49
abiotic factors influencing population
temperature light pH water humidity
50
predator
organism that feeds on another organism (prey)
51
predation
one organism consumed by another
52
effect of predator-prey relationship
predators eat prey reducing population of prey with fewer prey available the predators are in greater competition with each other for the prey left predator population reduced as some unable to obtain enough prey for survival fewer prey eaten so more survive and reproduce predator population increases with more prey available
53
point quadrant
horizontal bar supported by 2 legs ten holes at set intervals pin dropped through each species touching pin recorded
54
frame quadrant
square frame divided by string or wire into equally sized subdivisions placed in different locations abundance of each species in the quadrant recorded
55
mark-release-recapture
used to measure abundance of motile organisms known number caught and marked before being released back into the community given number of individuals collected randomly and the number of marked individuals recorded
56
estimated population size
(first sample x second sample)/number of marked individuals recaptured
57
assumptions of mark-release-recapture
1) proportion of marked to unmarked individuals in second sample is same as proportion of marked to unmarked as a whole 2) marked individuals distribute themselves evenly amongst remainder 3) few deaths or births 4) mark or label is not lost or rubbed off
58
succession
changes in species that occupy an area over time
59
stages of succession
1) colonisation of pioneer species in inhospitable environment 2) climax community created as biodiversity increases/ species flourish
60
features that emerge during succession
non-living factors become less hostile greater variety of habitats increased biodiversity more complex food webs increased biomass
61
secondary succession
occurs when land already occupied has been altered in some way
62
conservation
management of earths natural resources by humans in such a way that maximum use of them can be made in the future
63
main reasons for conservation
personal ethical economic cultural aesthetic

AQA A level biology <33 (12 decks)

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