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A level OCR 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
how can fossils prove there are ecological links between species?
the sequence in which the organisms are found matches their ecological links to each other
26
how can scientists use fossils to show how closely related organisms have evolved from the same ancestors?
by studying the similarities in the anatomy of fossil organisms
27
are the oldest fossils in the lowest or highest rock layers?
lowest
28
what are strata?
layers of rock
29
why is the fossil record incomplete?
-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
why has the function of these pentadactyl limbs altered over time?
as a result of evolution from a common ancestor
31
what is comparative anatomy?
the study of similarities and differences in the anatomy of different living species
32
what is a homologous structure?
a structure that appears superficially different in different organisms, but has the same underlying structure
33
why would you expect the limbs in vertebrates to be different?
the limbs are used for a wide variety of functions so the bone structure is different for different functions
34
what is thought to be the explanation behind the common bone structure in vertebrates?
all vertebrates have evolved from a common ancestor, therefore vertebrate limbs have all evolved from the same structure
35
what is divergent evolution?
this describes how, from a common ancestor, different species have evolved, each with a different set of adaptive features
36
when might divergent evolution occur?
when a closely related species diversify to adapt to new habitats as a result of migration or loss of habitat
37
how do homologous features provide evidence for divergent evolution?
shows superficial structures that are different
38
what is comparative biochemistry
the study of similarities and differences in the proteins and other molecules that control life processes
39
what are the important molecules that are highly conserved within most species and what do they do?
-cytochrome C (protein involved in respiration) -ribosomal RNA
40
what is neutral evolution in terms of biochemistry?
states that most of the variability in the structure of a molecule does not affect its function
41
where does the variability occur to allow it to be neutral?
outside of the molecules functional regions
42
why is neutral evolution not affected by natural selection?
due to the fact that they have no effect on function, their accumulation is not affected by natural selection
43
what is the evidence that chimps are a humans closest living relative?
they have very similar DNA sequences, they have been found to share at least 985 of their DNA
44
why is ribosomal RNA commonly used to determine relationships between species?
it has a very slow rate of substitution
45
how do scientists discover how closely related two species are?
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
what do scientists then estimate after the molecular sequence has been compared?
the point at which two species last shared a common ancestor
47
species that are more closely related...
have more similar DNA and proteins
48
what is variation?
the differences between individuals within or between a species
49
describe discontinuous variation
-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
how many genes is discontinuous variation controlled by?
one
51
how is discontinuous variation represented?
bar chart
52
describe continuous variation
-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
how many genes is continuous variation controlled by?
many genes
54
how is continuous variation represented?
histogram
55
what is interspecific variation?
variation between members of different species
56
what is intraspecific variation?
variation between members of the same species
57
what are the causes of variation?
-genes -environment
58
give some examples of genetic variation
-eye colour -blood group -ear lobes
59
give some examples of both genetic and environemental variation
-height -weight -hair colour
60
give some examples of environmental variation
-language (accent) -scars
61
what are the different genetic causes of variation?
-alleles -mutations -crossing over -independent assortment -sexual reproduction -chances
62
how does alleles cause genetic variation?
individuals in the same population may inherit different versions of the same gene
63
how does mutations cause genetic variation?
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
how does crossing over cause variation?
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
how does independent assortment cause variation?
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
how does sexual reproduction cause variation?
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
how does chance cause variation?
individuals produced different from their parents. This is because they inherit different genes from each of the parents.
68
why are twins used in variation studies?
they have the same genetic makeup so any differences in characteristics can be said to be caused by the environment
69
why do differences in twins increase as they age?
they have an increased amount of different environmental influences

A level OCR Biology (9 decks)

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