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OCR A level Biology > evolution > Flashcards

evolution Flashcards

1
Q

define evolution

A

theory that describes the way that organisms change over many years due to natural selection

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2
Q

define natural selection

A

the process by which organisms best suited to their environment survive and reproduce, passing on their alleles to their offspring

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3
Q

outline the relevance of Darwin

A

-in 1809 creationism was an overriding belief
-Darwin was a naturalist
-he rode in a ship named Beagle in 1931 for a round the world trip
-in Galapagos he studied finches
-he started to see that those best suited survived and passed on characteristics
-experimented on pigeon variation

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4
Q

what theory did Darwin propose?

A

proposed theory of natural selection

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5
Q

what theory did Lyell propose?

A

suggested fossils were evidence of animals from millions of years ago and the principle of uniformitarianism (earth was shaped by forces like erosion)

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6
Q

what theory did Wallace propose?

A

sent his theories of natural selection to Darwin for peer review- they were the same!

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7
Q

what happened when both Wallace and Darwin came up with the same theory?

A

their theory of evolution was proposed in a joint presentation to the Linnaean society

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8
Q

what was the name of the book that Darwin released?

A

The origin of species

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9
Q

why was ‘The origin of species’ controversial?

A

-went against creationism
-suggested man descended from apes

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10
Q

what are the stages of the process of natural selection?

A
  1. mutation
  2. variation
  3. selection pressure
  4. reproduction to pass on allele
  5. repeated over many generations
  6. allele increases in population
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11
Q

describe the mutation stage of natural selection

A

provides alleles (variation)

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12
Q

describe the variation in population stage in natural selection

A

variation within a species increases the species chance of survival if conditions change

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13
Q

what is a selection pressure?

A

factors that affect an organisms chance for survival

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14
Q

what are some examples of a selection pressure?

A

when one of these changes, this is a selection pressure:
-find food
-avoid predation
-survive harsh environments
-defend a territory
-find a mate
-raise young

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15
Q

describe the reproduction to pass an allele stage of natural selection

A

-all living things reproduce at a rate that is unsustainable to ensure that some survive to pass on genes
-those who have the advantageous characteristics are most likely to survive and reproduce and pass on the advantageous characteristic

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16
Q

what are some objections to the theory of natural selection?

A

-gaps in the fossil record
-surely natural selection would eliminate all exaggerated characteristics, but this can be explained by “sexual selection”
-went against creationism
-didn’t think the world was old enough

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17
Q

what are the evidence for evolution?

A

-palaeontology
-anatomy
-biochemistry

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18
Q

how is palaeontology evidence for evolution?

A

-shows evolutionary links
-found in different aged rocks
-shows similarities and differences in anatomy

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19
Q

how is anatomy evidence for evolution?

A

comparative, so the more similar the more closely related

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20
Q

how is biochemistry evidence for evolution?

A

-looks at DNA, protein structure and others
-the more similar the structure, the more closely related they are

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21
Q

how is a fossil produced?

A

when animal and plant remains are preserved in rocks

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22
Q

what is the fossil record?

A

a sequence of fossils from oldest to youngest, which shows that organisms have gradually changed overtime

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23
Q

what is the proof that life forms evolved over an extremely long period of time?

A

fossils of the simplest organisms are found in the oldest rocks, whilst fossils of more complex organisms are found in more recent rocks

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24
Q

how old are the oldest cyanobacteria fossils?

A

3.5 billion years old

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25
Q

how can fossils prove there are ecological links between species?

A

the sequence in which the organisms are found matches their ecological links to each other

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26
Q

how can scientists use fossils to show how closely related organisms have evolved from the same ancestors?

A

by studying the similarities in the anatomy of fossil organisms

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27
Q

are the oldest fossils in the lowest or highest rock layers?

A

lowest

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28
Q

what are strata?

A

layers of rock

29
Q

why is the fossil record incomplete?

A

-many organisms are soft bodied and decompose quickly before they can fossilise
-the conditions needed for fossils to form are not always present
-many fossils have been destroyed

30
Q

why has the function of these pentadactyl limbs altered over time?

A

as a result of evolution from a common ancestor

31
Q

what is comparative anatomy?

A

the study of similarities and differences in the anatomy of different living species

32
Q

what is a homologous structure?

A

a structure that appears superficially different in different organisms, but has the same underlying structure

33
Q

why would you expect the limbs in vertebrates to be different?

A

the limbs are used for a wide variety of functions so the bone structure is different for different functions

34
Q

what is thought to be the explanation behind the common bone structure in vertebrates?

A

all vertebrates have evolved from a common ancestor, therefore vertebrate limbs have all evolved from the same structure

35
Q

what is divergent evolution?

A

this describes how, from a common ancestor, different species have evolved, each with a different set of adaptive features

36
Q

when might divergent evolution occur?

A

when a closely related species diversify to adapt to new habitats as a result of migration or loss of habitat

37
Q

how do homologous features provide evidence for divergent evolution?

A

shows superficial structures that are different

38
Q

what is comparative biochemistry

A

the study of similarities and differences in the proteins and other molecules that control life processes

39
Q

what are the important molecules that are highly conserved within most species and what do they do?

A

-cytochrome C (protein involved in respiration)
-ribosomal RNA

40
Q

what is neutral evolution in terms of biochemistry?

A

states that most of the variability in the structure of a molecule does not affect its function

41
Q

where does the variability occur to allow it to be neutral?

A

outside of the molecules functional regions

42
Q

why is neutral evolution not affected by natural selection?

A

due to the fact that they have no effect on function, their accumulation is not affected by natural selection

43
Q

what is the evidence that chimps are a humans closest living relative?

A

they have very similar DNA sequences, they have been found to share at least 985 of their DNA

44
Q

why is ribosomal RNA commonly used to determine relationships between species?

A

it has a very slow rate of substitution

45
Q

how do scientists discover how closely related two species are?

A

the molecular sequence of a particular molecule is compared by look at:
-the order of DNA bases
-the order of amino acids in protein

46
Q

what do scientists then estimate after the molecular sequence has been compared?

A

the point at which two species last shared a common ancestor

47
Q

species that are more closely related…

A

have more similar DNA and proteins

48
Q

what is variation?

A

the differences between individuals within or between a species

49
Q

describe discontinuous variation

A

-individuals fall into a number of distinct categories
-based on features that cannot be measured across a range
-there are no inbetween values
-environment has no effect

50
Q

how many genes is discontinuous variation controlled by?

A

one

51
Q

how is discontinuous variation represented?

A

bar chart

52
Q

describe continuous variation

A

-complete range of measurements from one extreme to another
-get a normal distribution curve due to the graduation from one extreme to another
-significantly affected by environment

53
Q

how many genes is continuous variation controlled by?

A

many genes

54
Q

how is continuous variation represented?

A

histogram

55
Q

what is interspecific variation?

A

variation between members of different species

56
Q

what is intraspecific variation?

A

variation between members of the same species

57
Q

what are the causes of variation?

A

-genes
-environment

58
Q

give some examples of genetic variation

A

-eye colour
-blood group
-ear lobes

59
Q

give some examples of both genetic and environemental variation

A

-height
-weight
-hair colour

60
Q

give some examples of environmental variation

A

-language (accent)
-scars

61
Q

what are the different genetic causes of variation?

A

-alleles
-mutations
-crossing over
-independent assortment
-sexual reproduction
-chances

62
Q

how does alleles cause genetic variation?

A

individuals in the same population may inherit different versions of the same gene

63
Q

how does mutations cause genetic variation?

A

Changes to the DNA nucleotide sequence can cause changes to the tertiary structure of a protein. If this occurs in a somatic cell then just the individual is affected, if it occurs in the gametes it can be passed on to offspring. Both cause variation.

64
Q

how does crossing over cause variation?

A

Non sister chromatids will form chiasmata during prophase 1 of meiosis. This allows for the shuffling of alleles between the chromatids and increases variation.

65
Q

how does independent assortment cause variation?

A

Homologous chromosomes line up randomly in the equator of the cell during metaphase 1. This is then repeated when chromatids line up randomly in the equator in metaphase 2.

66
Q

how does sexual reproduction cause variation?

A

This can often be called random fertilisation as there are so many genetically different gametes produced by meiosis. Individuals will contain a unique genetic code.

67
Q

how does chance cause variation?

A

individuals produced different from their parents. This is because they inherit different genes from each of the parents.

68
Q

why are twins used in variation studies?

A

they have the same genetic makeup so any differences in characteristics can be said to be caused by the environment

69
Q

why do differences in twins increase as they age?

A

they have an increased amount of different environmental influences

OCR A level Biology (5 decks)

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