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Biology Year 2 > classification, variation and evolution > Flashcards

classification, variation and evolution Flashcards

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1
Q

the different types of variation and their descriptions

A

Continuous: controlled by a number of genes character shows a gradation from one extreme to the other

Discontinuous: controlled by a single gene
no intermediate forms
characteristics are clear cut and easy to tell apart

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2
Q

Heritable variation

A

results from genetic changes due to sexual reproduction

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3
Q

three processes that result in heritable variation

  1. what do these processes generate
A

the mixing of two different parental genotypes in cross-fertilization

the random assortment of homologous chromosomes in metaphase 1

crossing over between homologous chromosomes during prophase 1

  1. new allele combinations
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4
Q

what generates novel long-lasting variations

A

only mutations

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5
Q

non-heritable variation

A

environmental influences that determine phenotypic variation

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6
Q

what causes non-heritable variation in humans

A

diet
exercise….etc

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7
Q

what causes non-heritable variation in plants

A

temperature
light
availability of inorganic ions

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8
Q

what happens if organisms of identical genotypes are subject to different environmental influences

A

they show considerable variety

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9
Q

interspecific competition
what is this type of competition illustrated by

A

competition between individuals of different species

predator-prey relationships

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10
Q

intra-specific competition

this type of competition is the basis of the origin of species by?

A

competition between individuals of the same species

Natural Selection

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11
Q

if a population reproduces sexually, then it has a large number of variations. true or false

A

true

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12
Q

gene pool

A

all the alleles of all the genes of all the individuals in a population at any one time

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13
Q

allele frequency

A

a measure of the relative frequency of an allele on a genetic locus in a population

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14
Q

under which circumstances does the gene pool remain stable

A

if the environment is stable

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15
Q

what happens in a population if there is a sudden change of the environment

A

some phenotypes become more advantageous than others

they are therefore selected for whilst the disadvantaged phenotypes will be selected against

therefore the gene pool changes over time and certain alleles become more frequent than others

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16
Q

selection pressures

A

external factors that affect the frequency of certain alleles within a gene pool

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17
Q

selection

A

the process by which organisms better adapted to their environment survives and breed, while those less well-adapted fail to do so.

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18
Q

after selection, the better-adapted organisms are …………………… to pass on their ……………………….. to ………………………………

A

more likely
characteristics
succeeding generations

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19
Q

give four examples of selective agents

A

supply of food
breeding sites
climate
human impact

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20
Q

what does the selection pressure determine

A

the frequency of an allele in a gene pool

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21
Q

what is the hardy-weinberg equation for predicting genotype frequencies?

where p^2 represents?
q^2 represents?
2pq represents?

A

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

the frequency of homozygous dominant alleles

the frequency of homozygous recessive alleles

the frequency of heterozygote alleles

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22
Q

the hardy-weinberg principle suggests that the frequency of dominant and recessive alleles will remain constant in a population if five conditions are true.

what are the 5 conditions?

A

there is a large population

the population is isolated, so there is no emigration and immigration

there is no selection for or against any phenotype

there is random mating throughout the population

there are no new mutations

23
Q

will there be evolution if the conditions under which the hardy-weinberg principles apply do not change?

A

no there would not

24
Q

natural selection

A

refers to when organisms which are better adapted to their environments are likely to survive and reproduce to produce fertile offspring

25
Q

processes leading to natural selection

A

variation due to new (random) mutations

overproduction (the production of a large number of offsprings)

struggle for survival, whereby only the fittest survive

the individuals that survive reproduce, passing on their characteristics to their offsprings

the offspring therefore gain a selective advantage

over many generations, individuals that once belonged to the same species may give rise to two different groups, which are significantly distinct to belong to separate species

26
Q

species

A

a group of similar individuals that are able to interbreed and produce fertile offspring, and it is reproductively isolated from other such groups

27
Q

speciation

A

features of behaviour, morphology or genetics which serve to prevent breeding between species

28
Q

name factors that can cause changes in the equilibrium of a gene pool

A

genetic drift
mutations
natural selection

29
Q

founder effect

A

when a population is isolated on an island or a new habitat, the founder members are a small sample of the original population

30
Q

how does founder effect cause a genetic drift

A

the founder members may have very different allele frequencies to the original population by chance
so if the population size remains small, they may undergo a genetic drift

31
Q

bottleneck effect

A

effects resulting from a disaster that drastically reduces population size, like earthquakes and volcanic eruptions

32
Q

types of speciation and their descriptions

A

2 types
allopatric: speciation resulting from geographical features

sympatric: speciation resulting from habitat changes, morphology, breeding mechanisms and behavioural changes

33
Q

what happens to the population in allopatric speciation

A

the population becomes physically split in separate demes

34
Q

adaptive radiation

A

this is where present day species have all descended from a common ancestor and have over time occupied different niches via natural selection

35
Q

reproductive isolation

A

when organisms inhabiting the same area become reproductively isolated into two groups where there are no physical barriers

36
Q

give 4 barriers to breeding

A

temporal or seasonal isolation
behavioural isolation
mechanical isolation
gamete isolation
hybrid sterility
hybrid unviability

37
Q

seasonal or temporal isolation

A

when the breeding season or time of activity of two closely related populations don’t exactly correspond

38
Q

behavioural isolation

A

where traits develop which are very specific to closely related species, thereby preventing them from mating

39
Q

morphology

A

when closely related species are unable to physically mate due to incompatibility between their genitals

40
Q

hybrid sterility

A

this is when the set of chromosomes from each parent are different and can therefore not pair up in meiosis 1 and produce gametes

41
Q

give an example of a case of hybrid sterility

A

horses and donkeys reproducing to produce sterile mules

horses have 64 chromosomes and donkeys have 62, their offspring has 63 chromosomes

mules are sterile because their parental chromosomes cannot pair up in prophase 1 of meiosis 1, because they are not homologous

so meiosis in fails and gametes are not produced

42
Q

how do plants deal with the problem of hybrid sterility

A

plants can reproduce asexually to produce a colony of sterile hybrids

occasionally, the hybrids undergo mutations to become polyploid, meaning they double their chromosome set

now their chromosomes can pair up in prophase 1 of meiosis, making them a new species of fertile, mutant hybrids

43
Q

biodiversity

A

the number of species and the number of individuals of each species in a given environment

44
Q

the three main reasons for which biodiversity can vary

A

succession
natural selection
human influence

45
Q

ecological succession

A

the observed process of change in the species structure of an ecological community over time

46
Q

adaptive radiation

A

this occurs when a species colonises an area with several niches available

47
Q

adaptation

A

organisms specialising to suit the environment they live in

48
Q

why do organisms adapt

A

so that they are uniquely able to exploit their own niche
thereby ensuring that their niche is different enough to that of others, to avoid competition

49
Q

behavioural adaptation

A

these are actions by the organism which help them to survive or reproduce

50
Q

physiological adaptation
give example of a physiological adaptation

A

these are internal workings within the organism which helps it to survive or reproduce

fish, birds and whales are able to drink salt water, whereas humans cannot

51
Q

a low level of diversity from the simpson’s diversity index suggests?

A

dominance by just one or few species
that a change in one species is more likely to affect the others
the community is unstable and could be able to withstand change

52
Q

what are the measures taken to ensure the data is accurate when calculating the species density of a grassland

A

do a random sampling
use a reliable number of quadrats
identification of species
standardisation of techniques
sure that the species are not larger than the quadrat

53
Q

a gene’s position on a chromosome

A

locus

54
Q

polymorphism

A

it results from multiple alleles for the same gene

Biology Year 2 (21 decks)

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