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AQA A Level Biology 2018 > Diversity, Classification And Variation > Flashcards

Diversity, Classification And Variation Flashcards

1
Q

What are gametes?

A

Sex cells

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2
Q

Gametes fuse together to form.x

A

A zygote.

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3
Q

Normal body cells have …

A

The diploid number of chromosomes - 2n

Each cell contains two of each chromosomes - one from mum and one from dad.

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4
Q

Gametes have …

A

A haploid number of chromosomes - only one copy of each chromosomes.

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5
Q

At fertailisation,

A

Two haploid cells fuse together to form the normal diploid number of chromosomes.

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6
Q

Meiosis

A

1) DNA unravels and replicates = two copies of each chromosome called chromatids.
2) DNA condensed to from double armed chromosomes each made from 2 sister chromatids joined by a centromere.
3) Meisois 1 - chromosomes arrange in homologous pairs and they’re separated halving the chromosome number
4) Meisois 2 - the pairs of sister chromatids that make up each chromosome are deprecated.
5) 4 haploid gamete cells are produced.

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7
Q

What happens during Meiosis 1?

A

Homologous pairs of chromosomes come together and pair up - chromatids twist around eachother and bits of chromatids swap over = different combos of alleles

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8
Q

2 events which leads to genetic variation during Meiosis:

A
  • crossing over of chromatids

- independent segregation of chromosomes

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9
Q

Explain what happens during independent segregation:

A

When the homologous pairs are separated in the first division, it’s completly random which chromosomes from each pair ends up in which daughter cell - 4 daughter cells have diff combos of chromosomes.

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10
Q

Three differences between Mitosis and Meiosis:

A

Mitosis produces cells with same number of chromosomes as parent cell = Meiosis produces half.

Mitosis is genetically identical = meiosis is not.

Mitosis produces 2 daughter cells = meiosis produces 4

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11
Q

What is chromosome mutation?

A

When something goes wrong and the cells produced contain variations in the numbers of whole chromosomes of parts of chromosomes.

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12
Q

Chromosome mutations lead to…

A

Inherited conditions because the errors are present in the gametes.

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13
Q

One type of chromosome mutation:

A

Non-disjunction - failure of the chromosomes to seperate properly - DOWN’s SYNDROME.

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14
Q

Down’s syndrome is caused by…

A

A person having an extra copy of chromosome 21.

The resulting zygote has 3 copies of chromosome 21.

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15
Q

What are mutations?

A

Changes to the base sequence of DNA.

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16
Q

2 mutations:

A

Substitution
One base is substituted with another

Deletion
One base is deleted

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17
Q

Why do mutations affect a gene?

A

Because the order of DNA bases in a gene determines the other of amino acids in a particular protein - a change would change the sequence of amino acids it coded for and the protein.

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18
Q

Not all mutations affect the order of amino acids…

A

Because the degenerate nature of the genetic Code means that some amino acids are coded for by more than one DNA triplet.

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19
Q

Will deletion always lead to changes in the amino acid sequence?

A

Yes because the number of bases present will change which causes a shift in all the base triplets after it.

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20
Q

What do mutagenic agents do?

A

They increase the rate of mutation.

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21
Q

Examples of Mutagenic Agents:

A

UV radiation, ionising radiation etc.

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22
Q

What is Genetic Diversity?

A

Is the variety of different alleles of a genes in a species or population.

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23
Q

How can Genetic Diversity be increased? (2)

A
  • mutations in the DNA.

- different alleles being introduced into a population because of migration - GENE FLOW.

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24
Q

What is a Genetic Bottleneck?

A

An event that causes a big reduction in a population.

It reduces the number of different alleles in the gene pool and so reduces Genetic Diversity.

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25
Q

What is the Founder Effect?

A

A type of Genetic Bottleneck.

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26
Q

What happens in the Founder Effect?

A

When just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool.

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27
Q

The Founder Effect results in…

A

A higher incidence of genetic disease.

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28
Q

Describe Natural Selection:

A

Random mutations cause variation in a population of species. Species with the advantage are able to survive, reproduce and pass on their genes increasing the beneficial allele from generation to generation.

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29
Q

Whats a Behavioural Adaptation?

A

Ways an organism ACTS that increase its chance of survival and reproduction.

30
Q

What is a Physiological Adaptation?

A

Processes inside an organism’s body that increase its change of survival.

31
Q

What are Anatomical Adaptations?

A

Structural features of an organism’s body that increase its chance of survival.

32
Q

What is Directional Selection?

A

Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.

E.g. bacteria evolving antibiotic resistance.

33
Q

What is Stabilising Selection?

A

Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce.

34
Q

What is Phylogeny and what does it tell us?

A

The study of the evolutionary history of groups of organisms.

Tells us who’s related to whom and how closely related they are.

35
Q

Phylogenetic trees show…

A

Evolutionary Relationships.

36
Q

What is Taxonomy?

A

The science of classification.

Involves naming organisms and organising them into groups making it easier to identify and study them.

37
Q

There are 8 groups. Each group is called…

A

A taxon.

38
Q

What is a species?

A

A group of similar organisms able to reproduce to give fertile offspring.

39
Q

Name the 8 groups.

A 
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
40
Q

What is the Binomial Naming System?

A

First part of the name is the genus name and the second is the species.

Homo sapiens

41
Q

Why’s the Binomial system good?

A

To avoid confusion of using common names e.g. breaks language barriers.

42
Q

What is Courtship Behaviour?

A

The way organisms act to attract a mate of the right species.

43
Q

Courtship behaviour is..

A

SPECIES SPECIFIC - only members of the same species will respond to that courtship behaviour.

44
Q

The more closely related species are, what is significant about their courtship behaviour?

A

The more similar it is.

45
Q

Give 3 ways in which Techniques can clarify Evolutionary Relationships:

A
  • Genome Sequencing
  • Comparing Amino Acid Sequence
  • Immunological Comparisons
46
Q

What is Genome Sequencing?

A

When the entire base sequences of an organism is determined and compared to the DNA base sequence of another organism.

Closely related = more similarities.

47
Q

What is Comparing Amino Acid Sequencing?

A

Proteins are made up of amino acids and the sequence of amino acids in a protein is coded for by the base sequence in DNA.

More closely related = similar amino acid sequences.

48
Q

What is Immunological Comparisons?

A

Similar proteins will also bind to the same antibodies.

49
Q

How has the way Genetic Diversity is assessed changed?

A

In early years, it was assessed by the frequency of OBSERVABLE CHARACTERISTICS in a population.

Now, we can measure genetic diversity directly by DNA base sequences etc.

50
Q

What is Variation?

A

Differences that exist between individuals.

There’s variation between species and within species.

51
Q

Variation can be caused by: (2)

A

Genetic factors

Or

Environmental factors

52
Q

To study variation, what do you need to do?

A

You have to sample a population as you cannot look at a whole population.

53
Q

What do the samples have to be like?

A
  • random so it’s not biased e.g. can use a random number generator to find co-ordinates.
  • results should be analysed statistically to make sure the variation observed isn’t just due to chance.
54
Q

What is Biodiversity?

A

The variety of living organisms in an area.

55
Q

What is Habitat?

A

The place where an organism lives.

56
Q

What is the Community?

A

All the populations of different species in a habitat.

57
Q

How can Biodiversity be considered? (2)

A
  • Local Biodiversity

- Global Biodiversity

58
Q

What is Local Biodiversity?

A

You could consider the variety of different species living in a small habitat local to you.

59
Q

What is Global Biodiversity?

A

You could consider the variety of species on Earth.

It would vary in different parts of the world.

60
Q

What is Species Richness?

A

A measure of the number of different species in a community.

61
Q

How can species richness be worked out?

A

By taking random samples of a community and countering the number of different species.

62
Q

What is Index of Diversity?

A

It’s when both the number of species in a community AND the abundance of each species is taken into account.

63
Q

Agricultural practices

How do they affect Biodiversity?

A

They reduce it.

64
Q

Give 3 examples of Agricultural Practices which reduce Biodiversity:

A
  • pesticides - kill pests which means any species that eat pests will lose food and also decrease.
  • hedgerow removal - this is done to increase the area, destroys habitat.
  • monoculture - when farmers have fields containing only one type of plant - a single type reduces biodiversity directly and supports fewer organisms.
65
Q

What do Conservationists try to do?

A

Protect Biodiversity.

66
Q

Give 2 examples of Conservation Schemes:

A
  • giving legal protection to endangered species.

- The Environmental Stewardship Scheme - encourages farmers to conserve biodiversity.

67
Q

How can you test the effect of antibiotics?

A

You use an Agar plate with bacteria on it - use sterile for pets to place paper disks soaked with different antibiotics.

Incubate the plate allowing the bacteria to grow and measure the zone of inhibition.

68
Q

The size of an inhibition zone tells you…

A

How well an antibiotic works.

The larger the zone = the more the bacteria were inhibited from growing = more effective the antibiotic.

69
Q

What are Aseptic Techniques used to do?

A

Prevent contamination of cultures by unwanted microorganisms.

70
Q

Give 3 examples of Aseptic Techniques which can be used:

A
  • regularly disinfect work surfaces to minimise contamination.
  • work bear a Bunsen flame - hot air rises and keeps microbes in the air away.
  • minimise the time spent with the kid of the agar plate to reduce the chance of airborne microorganisms contaminating the culture.

AQA A Level Biology 2018 (17 decks)

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