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A Level Biology > Genetics > Flashcards

Genetics Flashcards

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1
Q

What is the importance of meiosis

A

sexual reproduction

crossing over leads to genetic variation

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2
Q

How does genetic variation occur

A

independent segregation of homologous chromosomes

new combination of maternal and paternal alleles by crossing over

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3
Q

what is a gene

A

length of DNA that codes for a polypeptide

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4
Q

what is a locus

A

position of gene on a chromosome

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5
Q

explain independent segregation

A

chromatids arrange randomly on the equator
homologous pair line up
4 pairs therefore 4 options

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6
Q

when does crossing over occur

A

between pro and metaphase 1

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7
Q

when does independent segregation occur

A

anaphase 1 and 2

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8
Q

how does prophase 1 leads to variety

A

crossing over is a random process and alleles

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9
Q

Why does selective breeding decrease genetic diversity

A

decreases the number of alleles

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10
Q

What is eugenics

A

selective breeding in humans

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11
Q

why do populations stay constant even though there’s more food

A

intraspecific competition within species and natural selection increases desirable allele frequency which, after e period of time, becomes the most common allele

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12
Q

what are the two types of selection

A

directional and stabilising

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13
Q

what is directional selection

A

favours individuals that vary in a direction from the mean when selection pressure applies such as a change in the environment

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14
Q

what is stabilising selection

A

favours average individuals, preserving characteristics of a population in a maintained environment

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15
Q

What will a stabilising selection do

A

eliminate extreme alleles

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16
Q

what 3 things can natural selection be based off

A

anatomical changes, physiological changes or behavioural changes

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17
Q

What is a genetic bottleneck

A

when a population suffers a drop in numbers and survivors possess fewer alleles than the original population

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18
Q

what is a disadvantage of having fewer alleles

A

less likely to adapt to changes making them vulnerable

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19
Q

give an example of genetic bottlenecking

A

Northern elephant seals that were hunted close to extinction

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20
Q

Name three things that increase genetic variability

A

migration, meiosis and mutations

21
Q

name three things that decrease genetic variability

A

natural selection, diseases and natural disasters

22
Q

give an example of industrial melanism

A

light peppered moths in the industrial revolution

23
Q

what is the founder effect

A

a few individuals from a population start a new population with a different allele frequency than the original, more diverse population

24
Q

how do we write the genus and species

A

underlined

25
Q

if the species is unknown what do we write

A

sp

26
Q

what is the genus written with

A

a capital letter

27
Q

what is the theory and practice of biological classification called

A

taxonomy

28
Q

what are the two types of classification

A

artificial and phylogenetic

29
Q

what is artificial classification

A

divides organisms according to differences that are useful to us at the same time

30
Q

what is phylogenetic classification

A

based on the evolutionary relationship between organisms and their ancestors

31
Q

what is a homologous characteristic

A

a characteristic that has similar evolutionary origins but may not have the same uses now eg pentadactyl limb

32
Q

what are the three domains

A

bacteria archaea eukarya

33
Q

what characteristics does bacteria have

A

unicellular
70s chromosomes
murein walls

34
Q

what characteristics does archaea have

A

no murein
single cell
DNA more similar to bacteria

35
Q

what characteristics does eukarya have

A

80s ribosomes
membrane bound organelles
no murein in cell walls

36
Q

on a phylogenetic tree where is the oldest species

A

at the base

37
Q

what are the older species on a tree

A

extinct

38
Q

name 5 reasons why it is hard to define species

A

they are not fixed and evolve
artificial selection causes much variation
many species are extinct with no fossil records
some species dont reproduce sexually
some species are isolated from one another and cannot interbreed

39
Q

what does courtship allow

A

animals to recognise their own species and identify a mate that is capable of breeding
allows easy inheritance of genes

40
Q

what happens in a ritual

A

male does the action and the female responds making a stimulus response chain

41
Q

biodiversity meaning

A

variety in living organisms in a particular area

42
Q

what is species diversity

A

the number of different species within one community

43
Q

what is genetic diversity

A

the variety of genes possessed by the individuals that make up one species

44
Q

what is ecosystem diversity

A

range of different habitats within one particular area

45
Q

what does biodiversity reflect

A

how well an ecosystem functions

46
Q

the higher the species diversity index the what

A

more stable the ecosystem

47
Q

how does making comparisons with dna help look at classification

A

dna determines proteins
proteins determines features
comparing dna helps determine evolutionary relationships

48
Q

what is interspecific variation

A

variation between species

49
Q

what is intraspecific variation

A

variation in a species

A Level Biology (11 decks)

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