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A Level - Biology > 9: Diversity, classification and variation > Flashcards

9: Diversity, classification and variation Flashcards

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1
Q

What are gametes?

A

Sexual haploid cells

Sperm cells in men, eggs in women

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2
Q

How can the number of chromosomes be described in a normal body cell?

A

Diploid
46 chromosomes, 32 pairs
One is maternal, one is paternal

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3
Q

What occurs at fertilisation?

A

Haploid sperm and egg fuse to form a zygote with the diploid number of chromosomes
1/2 maternal, 1/2 paternal

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4
Q

What is random fertilisation?

A

Any sperm can fertilise any egg
Produces different combinations of chromosomes
Increases genetic diversity

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5
Q

Where does meiosis take place?

A

Reproductive organs

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6
Q

Why is it important that the cells produced by meiosis are haploid?

A

To ensure the correct amount of chromosomes when the gametes fuse

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7
Q

What occurs just before meiosis?

A

Unwinding and replication of DNA

Creates two copes of each chromosome

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8
Q

What is formed when DNA is copied before meiosis?

A

Two sister chromatids are joined by a centromere

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9
Q

Describe the meiosis process

A

Replication of DNA
Prophase I - chromosomes pair with corresponding homologous chromosome
Metaphase & Anaphase I - Homologous pairs line up on spindle and the pairs are separated
Telophase I - splitting to form two cells
Metaphase & Anaphase II - Line up and the chromatids separate
Telophase II - splits to form four total cells
Produces 4x haploid cells with 23 chromosomes

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10
Q

What is a homologous pair?

A

Chromosomes that have the same genes and the same size
Different alleles
One pair maternal and one paternal

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11
Q

What are the three reasons why sexual reproduction gives varied offspring?

A 
Crossing over (prophase I)
Independent assortment (metaphase I)
Random fertilization
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12
Q

What is the structure formed when homologous pairs of chromosomes come together and pair up?

A

Bivalent/tetrad

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13
Q

What is crossing over?

A

In prophase I, homologous pair of chromosomes form bivalents/tetrads
Chromatids twist around and chromatids swap over Chromatids now contain the same genes but different combinations of alleles

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14
Q

What is the product of crossing over?

A

Four daughter cells formed by meiosis contain chromatids with different alleles

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15
Q

What is independent assortment?

A

Homologous pairs separated in meiosis I,
Completely random which chromosome from each pair ends up in which daughter cells
Daughter cells have different combinations of maternal and paternal chromosomes

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16
Q

What are the differences between mitosis and meiosis in the number of chromosomes?

A

Mitosis produces daughter cells with the same number of chromosomes
Meiosis produces daughter cells with half the number of chromosomes

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17
Q

What are the differences between mitosis and meiosis in the genetic similarity to the parent cell?

A

Mitosis daughter cells are genetically identical to one another and parent cell
Meiosis daughter cells are genetically different from one another and the parent cell

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18
Q

What are the differences between mitosis and meiosis in the number of cells produced?

A

Mitosis produces two daughter cells

Meiosis produces four daughter cells

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19
Q

What is the process whereby there are errors in meiosis?

A

Chromosome mutation

Leads to inherited conditions due to errors in gametes

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20
Q

How is down’s syndrome formed?

A

Non-disjunction - a failure of the chromosomes to separate properly
Occurs in meiosis I and II
Extra copy of chromosome 21 as separates improperly - 3 copies

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21
Q

What is a gene mutation?

A

Change in the DNA base sequence of chromosomes

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22
Q

What are the types of errors in gene mutation?

A

Substitution - one base is substituted with another
Deletion - one base is deleted
Addition - one base is added

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23
Q

Why do not all mutations affect the order of amino acids?

A

Degenerate nature means some amino acids are coded for by more than one triplet
Mutations therefore will not always lead to different amino acids

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24
Q

Why does deletion result in a different order of amino acid?

A

Changes the number of bases present as one less is made

Causes a frameshift in all the base triplets after it

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25
Q

What are mutagenic agents?

A

Things that increase the rate of mutation

UV radiation, ionising radiation, asbestos

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26
Q

What is the definition of genetic diversity?

A

Total number of different alleles in a population

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27
Q

What is the definition of a population?

A

Number of individuals of the same species living in the same place

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28
Q

What is the definition of a species?

A

Individuals that have the same genes and can breed to form fertile offspring
Belong to the same gene pool

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29
Q

How is genetic diversity increased in a population?

A

Mutations in the DNA

Different alleles introduced as individuals from another population migrate into them and reproduce

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30
Q

What is the genetic bottleneck?

A

An event that causes a big reduction in a population
Reduces number of different alleles and genetic diversity
Survivors reproduce

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31
Q

What is the founder effect?

A

Few organisms from a population start a new colony and only a small number of different alleles
Frequency of alleles are different in the new colony

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32
Q

What are Darwin’s principles?

A

Greater number of alleles in a population:
Greater the genetic diversity
Greater the chance the species will survive an environmental change
Greater the chance natural selection can occur

33
Q

Describe natural selection

A

Different reproductive success in a population mean some are more likely to survive
They reproduce more and pass on their beneficial alleles
Greater population of next generation inherit beneficial alleles
More likely to survive and reproduce
Frequency of beneficial allele increases and over generations leads to it being common in the population

34
Q

Why do adaptations lead to a population being better adapted?

A

Behavioural adaptations - how the organism acts
Physiological adaptations - processes inside the body
Anatomical adaptations - structural features of an organism

35
Q

What are the three selective forces?

A

Competition
Predation
Disease

36
Q

What are polygenes?

A

Several genes that influence one characteristic

37
Q

What are the types of selection?

A

Stabilising selection

Directional selection

38
Q

What is directional selection?

A

Individuals with alleles of an extreme type
Occurs in response to environmental change
Favours individuals at one side of the mean/median
Graph shifts in that direction - range is not changed

39
Q

What is stabilising selection?

A

Favours average individuals
Occurs when the environment is stable
Range decreases but the median is the same

40
Q

What is a gene pool?

A

All genes and alleles of a population

41
Q

What are aseptic techniques?

A

Conditions whereby you attempt to reduce the contamination of the microorganism

42
Q

Give some examples of aseptic techniques?

A

Disinfect work surfaces
Work under the dome of sterility - hot air rises and takes microbes away
Sterilise equipment

43
Q

What is phylogeny?

A

The study of the evolutionary history of groups of organisms

44
Q

What is taxonomy?

A

The science of classification

Involves the naming and organisation of organisms

45
Q

What is the lowest level of classification?

A

Species

46
Q

What do species have in common?

A

Similar physical/biochemical
Similar immunologically (antibodies)
Occupy the same ecological niche
Similar courtship behaviour (genetically determined)

47
Q

What is a hierarchy?

A

Groups within larger composite groups which do not overlap

48
Q

What are the eight groups in the hierarchy?

A 
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
49
Q

What are the three domains?

A

Archea domain
Bacteria domain
Eukarya

50
Q

Why is courtship behaviour done?

A

To attract a mate of the right species

51
Q

How and why is courtship behaviour specific?

A

Only the same species will do and respond the courtship behaviour
Done to prevent interbreeding and making it more successful (produce fertile offspring)

52
Q

How is the relation between a species and their courtship behaviour related?

A

The more closely the species are, the more similar their courtship behaviour

53
Q

Why is courtship necessary?

A 
To allow survival of the species
Ensure no interbreeding
Identifying a sexually mature and fertile mate
Form a pair bond to raise the young
Synchronise mating so both are ready
54
Q

What are the courtship actions?

A

Male actions elicits two different responses:
No thanks - male gives up
Yes please - next courtship action

55
Q

What is a male said to do to cause a response in the female?

A

Provide a stimulus

56
Q

What does nomenclature mean?

A

Naming system

57
Q

What is the binomial naming system?

A

First name is the genus of the organism - starts with a capital
Second name is species - lower case
All in italics BUT cannot be written so should be underlined in exams
If no species known then should put “sp” for the second name

58
Q

What is the name of the human using the binomial naming system?

A

Homo sapiens (italics or underlined)

59
Q

What is artificial classification?

A

Classification based on the characteristics which they have

Does not compare genetically similarity

60
Q

What are analogous features?

A

Same function but different evolutionary origin

E.g bird and bee wings

61
Q

What are homologous structures?

A

Same basic structure and evolution origin but may have different functions

62
Q

What are the ways which evolutionary relationships which can be investigated?

A

Compare observable features
Compare DNA base sequences
Compare mRNA
Compare proteins

63
Q

What are the advantages of using observable features to investigate evolutionary relationships?

A

Adv.- Features are due to DNA coding structural proteins and enzymes
Dis.- environment affects observable characteristics
observable characteristics are polygenic so they show a continuous variation

64
Q

What is continuous variation?

A

Can be varied in different ways

E.g. hair colour can be a number of different colours

65
Q

Why is comparing DNA base sequences done?

A

Adv. - Closely related species have similar DNA sequences
When one species gives rise to another during evolution the DNA will initially be similar
Dis,- mutation will cause the DNA to change
over time more mutations accumulate

66
Q

What are the two ways to compare DNA base sequences?

A

DNA sequencing

DNA hybridisation

67
Q

What is DNA/genome sequencing?

A

Computers used to compare the order of bases

Closely related species have a higher % of similar bases

68
Q

What is DNA hybridisation?

A

DNA is cut into short pieces
DNA from one species is labelled then mixed with unlabeled DNA from other species
Heated to separate their strands
Cooled to allow strands to combine with others that have complimentary base sequences
Hybrid strands have half labelled and are separated by increasing temp.
More H-bonding occurs with more base pairing so the higher the temp. before it breaks the more similar the base sequences

69
Q

What is comparing mRNA done?

A

mRNA is copied from DNA

mRNA of a gene is common to two species can be sequenced and compare how similar the gene is

70
Q

Why is mRNA comparison preferable to sequencing DNA?

A

mRNA is out of the nucleus in the cytoplasm

mRNA is one gene instead of thousands in DNA

71
Q

Why is comparing proteins effective?

A

Closely related species have similar amino acid sequences for the same protein

72
Q

What are the two ways to compare proteins?

A

Count similarities/differences between amino acids of a protein common to both species
Immunological comparisons

73
Q

What are the immunological comparisons of proteins?

A

Antibodies can bind to proteins to form a precipitate
Similar proteins will bind to the same antibodies
If the same antibody binds to the protein in a different species are closely related
Compare the amount of precipitate formed

74
Q

What is variation?

A

Differences that exist in between individuals

75
Q

Why is a sample taking necessary?

A

Collecting info. on the whole population would be too time-consuming or impossible

76
Q

Why does a sample have to be random?

A

To prevent bias

Makes sample more representative

77
Q

What does analysing data include?

A

Describing data
Drawing conclusions
Explaining reasons for any differences

78
Q

What is standard deviation used for?

A

Shows the spread of the data

Overlap shows no difference

A Level - Biology (22 decks)

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