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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

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
Q

allele frequency

A

number of times an allele occurs within the gene pool

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26
Q

hardy-weinberg principle

A

used to calculate frequencies of alleles of a particular gene in a population

27
Q

assumptions of hardy -weinberg principle

A

no mutations arise
population isolated
no selection
population is large
mating in population is random

28
Q

hardy-weinberg equations

A

p+q=1
p^2+2pq+q^2=1

29
Q

what causes genetic variation?

A

mutations
meiosis
random fertilisation of gametes

30
Q

selection pressures

A

environmental factors that limit the population of a species

31
Q

examples of selection pressures

A

predation
disease
competition

32
Q

factors that natural selection rely on

A

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
Q

intraspecific competition

A

competition amongst individuals

34
Q

interspecific competition

A

competition between different species

35
Q

natural selection

A

those with the more advantageous allele survive
they reproduce to produce more offspring with the advantageous allele
allows population to evolve and adapt

36
Q

stabilising selection

A

preserves average phenotype of population by favouring average individuals
selection against extreme phenotypes

37
Q

directional selection

A

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
Q

disruptive selection

A

favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population

39
Q

abiotic factors

A

non-living

40
Q

biotic factors

A

living

41
Q

ecosystems

A

dynamic systems made up of a community and all the non-living factors of its environment

42
Q

population

A

group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed

43
Q

carrying capacity

A

size of population of species an ecosystem supports

44
Q

community

A

all the populations of different species living and interacting in a particular place at the same time

45
Q

habitat

A

place where an organism lives

46
Q

microhabitats

A

smaller units of a habitat with their own microclimate

47
Q

niche

A

how an organism fits into the environment, including all the biotic and abiotic factors

48
Q

competitive exclusion principle

A

no two species occupy exactly the same niche

49
Q

abiotic factors influencing population

A

temperature
light
pH
water
humidity

50
Q

predator

A

organism that feeds on another organism (prey)

51
Q

predation

A

one organism consumed by another

52
Q

effect of predator-prey relationship

A

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
Q

point quadrant

A

horizontal bar supported by 2 legs
ten holes at set intervals
pin dropped through
each species touching pin recorded

54
Q

frame quadrant

A

square frame divided by string or wire into equally sized subdivisions
placed in different locations
abundance of each species in the quadrant recorded

55
Q

mark-release-recapture

A

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
Q

estimated population size

A

(first sample x second sample)/number of marked individuals recaptured

57
Q

assumptions of mark-release-recapture

A

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
Q

succession

A

changes in species that occupy an area over time

59
Q

stages of succession

A

1) colonisation of pioneer species in inhospitable environment
2) climax community created as biodiversity increases/ species flourish

60
Q

features that emerge during succession

A

non-living factors become less hostile
greater variety of habitats
increased biodiversity
more complex food webs
increased biomass

61
Q

secondary succession

A

occurs when land already occupied has been altered in some way

62
Q

conservation

A

management of earths natural resources by humans in such a way that maximum use of them can be made in the future

63
Q

main reasons for conservation

A

personal
ethical
economic
cultural
aesthetic

AQA A level biology <33 (12 decks)

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