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Biology > Topic 4: Diversity and selection > Flashcards

Topic 4: Diversity and selection Flashcards

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1
Q

What are homologous pairs?

A

Pairs of chromosomes that are the same in size with the same genes but different versions of these genes known as alleles

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2
Q

What is a zygote?

A

When 2 gametes fuse together during fertilisation a zygote forms- fertilised egg

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3
Q

What is random fertilisation?

A

Any sperm can fertilise any egg- its random. Random fertilisation produces zygotes with different combinations of chromosomes to both parents. Increases genetic diversity.

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4
Q

What happens before meiosis I?

A

DNA unravels and replicates so there are 2 copies of each chromosome- chromatids. DNA condenses to form double-armed chromosomes, with sister chromatids held together by the centromere

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5
Q

What happens in meiosis I?

A

Homologous pairs separate, halves number of chromosomes

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6
Q

What happens during meiosis II?

A

Centromere divides to separate pair of sister chromatids, produces 4 genetically different haploid cells

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7
Q

What happens during crossing over?

A

Homologous pairs have parts of chromatids that twist and swap over one another., These chromatids stull have the same genes but different combination of alleles. Means each of the 4 cells produced by meiosis II has chromatids with different alleles. Introducing genetic variation.

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8
Q

What is independent segregation?

A

One maternal and one paternal chromosome in a homologous pair. When they separate in meiosis !, it’s completely random which chromosome from each pair ends up in which cell. So the 4 daughter cells produced by meiosis have completely different combinations of these maternal and paternal chromosome. Introducing genetic variation.

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9
Q

Outline the differences between meiosis and mitosis.

A
  1. Mitosis produces diploid cells meiosis produces haploid
  2. Mitosis produces 2 genetically identical cells and meiosis produces 4 cells that are genetically different to one another
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10
Q

What is a mutation?

A

Change in the DNA base sequence of chromosomes

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11
Q

Substituion mutation

A

one base is substituted for another. Doesn’t always lead to a change in the amino acid sequence due to the degenerative nature of DNA where 1 amino acid can be coded for by more than 1 DNA triplet

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12
Q

Deletion mutation

A

removal of a base causes frameshift

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13
Q

What are mutagenic agents? Give examples

A

Increase the rate of mutations e.g. UV radiation and ionising radiation

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14
Q

What is chromosome non-disjunction?

A

Failure of the chromosome to separate properly. E.g Downs syndrome is caused by a person having an extra copy of chromosome 21 or part of it. It means that during meiosis one cell gains an extra copy of the chromosome and another gets none. The cell with the extra copy can fuse with another gamete to produce a zygote that now has 3 copies of chromosome 21.

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15
Q

What is genetic diversity?

A

The number of different alleles of a gene in a species or a population

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16
Q

What if there is a low genetic diversity?

A

Population may not be able to adapt to change in the environment and may be wiped out a by a single event

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17
Q

Give 2 ways in which genetic diversity can be increased within a population

A
  1. Mutations in the DNA forming new alleles
  2. Different alleles being introduced into population when individuals from another migrate into it and reproduce. This is known as gene flow
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18
Q

What is a genetic bottleneck?

A

A large reduction in a population, large number die before they can reproduce. Reduces number of alleles in the gene pool and so genetic diversity. Survivors reproduce and a larger population forms.

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19
Q

What is the founder effect?

A

Describe what happens when a few organisms start a new colony from only a small number of alleles in the initial gene pool. The frequency of alleles differ e.g. a allele that was rare in the original population may become more common and this may lead to a higher incidence of genetic disease.

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20
Q

What is natural selection?

A

When an allele codes for a characteristic that is advantageous its frequency within the population increases over time.

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21
Q

Describe the process of natural selection.

A
  1. Within a population there is differential reproductive success between the organisms, those with a more advantageous allele are more likely to survive and reproduce and pass on the beneficial allele to offspring
  2. Frequency of beneficial allele within the population increases over generations
  3. these organisms are more likely to survive and reproduce
  4. over generations this can lead to evolution as the advantageous allele becomes more common in the population
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22
Q

What is an adaptation? What are the 3 types?

A

Adaptations are features that help organisms to survive in their environment.
1. Behavioural- the way an organism acts
2. Anatomical- structural features of the body
3. Physiological - processes inside the body

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23
Q

What is directional selection? Give an example

A

Where individuals with alleles for extreme characteristics are more likely to survive and reproduce. This is can be caused by an environmental change. E.g. antibiotic resistance where resistant bacteria are more likely to survive and reproduce without competition, passing on the allele that gives antibiotic resistance to their offspring. After some time most of the organisms will carry the resistant allele

24
Q

What is stabilising selection? Give an example

A

Occurs when organisms with alleles towards the middle of the range are more likely to survive and reproduce. Occurs when environment isn’t changing and it reduces the range of characteristics. For example human birth weight, small babies find it difficult to regulate their body temperatures whilst large babies have more complicated births. Conditions are favourable for medium sized babies

25
Q

Give 4 aseptic techniques you need to use

A
  1. Disinfect work surfaces before you start to work and disinfect them after finishing to prevent contamination
  2. Carry out near busen burner, hot air rises and so do any microbes which can be moved away from your culture
  3. sterilise a wire inoculation loop before and after use by passing it through the flame for 5 seconds this is to kill any microbes
  4. Briefly flame the neck of the bottle containing the bacteria culture after its opened or before its closed- this causes the air to move out of the container, preventing unwanted organisms from falling in
26
Q

Describe an experiment you can carry out to test the effectiveness of antibiotics

A
  1. Take a wire inoculation loop that has been sterilised in aflame to transfer the bacteria broth onto an agar plate. Use the loop to spread the bacteria
  2. Place sterile paper discs soaked with different antibiotics on to the agar, these can be at different concentrations. Place a negative disc that has been soaked in sterile water
  3. Place a lid on to the petri dish and seal (no all the way), invert and you place it at under 25 degrees Celsius for about 24 hours. This allows bacteria to grow and where it doesn’t a zone of inhibition forms, this is where bacteria hasn’t grown. The larger this is the more effective the antibiotic.
27
Q

What is phylogeny?

A

Study of the evolutionary history of groups of organisms. It tells you how closely related they are.

28
Q

What is taxonomy?

A

Science of classification and it involves naming organisms and placing them into groups

29
Q

8 levels of groups used to classify organisms

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

30
Q

What is the meaning of species?

A

Species is a group of organisms that are able to reproduce to give fertile offspring

31
Q

What is the binomial system?

A

Naming system used for classification. First part of the name is genus second is the species

32
Q

What is courtship behaviour?

A

It is carried out by organisms to attract a mate of the same species.

33
Q

How can courtship behaviours be used to classify organisms?

A

It is species specific, only members of the same species do and respond to courtship behaviours. This ensures that only same species recognise the behaviour and prevents interbreeding and more successful reproduction to produce fertile offspring.

34
Q

How can courtship behaviours be used to classify organisms?

A

It is species specific, only members of the same species do and respond to courtship behaviours. This ensures that only same species recognise the behaviour and prevents interbreeding and more successful reproduction to produce fertile offspring. The more closely related a species are to each other the more similar the courtship behaviour

35
Q

How can genome sequencing be used to clarify evolutionary relationships?

A

The entire DNA base sequence of organisms can be determined and compared to the DNA base sequence of another. The more similarities there are between DNA base sequences of one organism and another the more closely related they are considered to be

36
Q

How can amino acid sequencing be used to clarify evolutionary relationships?

A

Proteins are made up of amino acids. This can be coded for by the base sequence in DNA. Related organisms have similar DNA base sequence and so similar amino acid sequences in the proteins.

37
Q

How can immunological comaprisons be used to clarify evolutionary relationships?

A

Similar amino acids will bind the same proteins. If antibodies to a human version of a protein are added to isolated samples from other species, any protein that is like the human version will also bind e.g. bound antibodies often form a precipitate the more that forms the more antibodies the protein binds

38
Q

Give 2 ways in which gene technologies are more accurate at determining genetic diversity rather than just looking at frequency of observable characteristics

A
  1. Different alleles of the same gene will have slightly different DNA base sequences, comparing DNA base sequence can allow us to determine the different alleles in a population
  2. different alleles can produce slightly different mRNA base sequences and may produce proteins with slightly different amino acid sequences, so these can also be compared
39
Q

What is variation?

A

Variation is the differences that exist between individuals, this can be between species or within species

40
Q

What are the 2 main factors affecting variation?

A
  1. Genetic- different species have different genes and so there is variation between species and the same species have the same genes but different alleles
  2. Environmental e.g. climate
41
Q

Why do we take population samples?

A

It’s too time consuming and difficult to catch all individuals in a group

42
Q

How can you ensure that there is no bias in a sample?

A

It should be random e.g. if you are looking at a plant species you can divide a field into a grid system and using a number generator to make coordinates to select sample site

43
Q

What does standard deviation measure?

A

Spread of values about the mean. E.g. if the values are closer to the mean then the graph is steep and so standard deviation is small

44
Q

What is the equation used to measure standard deviation?

A

See page 248

45
Q

What is biodiversity?

A

Variety of organisms living in an area

46
Q

What is a habitat?>

A

A place where an organism lives

47
Q

What is a community?

A

All the populations of different species in an area

48
Q

At what scales could you view biodiversity?

A

Local and global

49
Q

What is species richness?

A

Measure of the number of different species in a community

50
Q

How is the index of diversity measured?

A

Takes into account population size and species richness

51
Q

What is the equation for Index of diversity?

A

see page 250

52
Q

Give 5 ways in which agriculture has reduced biodiversity

A
  1. Woodland clearance, direct loss of trees and tree species, any habitats and animals can lose food source, this means they may die or migrate, leading to loss of biodiversity
  2. Hedgerow clearance- this reduces biodiversity for the same reasons when lots of smaller fields are converted into few of bigger ones
  3. Monoculture- planting the same type of plant, single type reduces biodiversity and the number of habitats and food source
  4. Herbicides- kill unwanted plants, any species that survive on them as a food source can be affected
  5. Pesticides- kill unwanted pests, any species that feed on them can also be affected and also reduces diversity of pests
53
Q

Give 3 conservation schemes

A
  1. Giving legal protection to endangered species
  2. Making areas Sites for scientific Interest and Areas of outstanding natural beauty to restrict particularly agricultural development
  3. Environmental Stewardship scheme encourages farmers to conserve biodiversity e.g. leaving margins in their fields to allow wild flowers to grow.
54
Q

What is the null hypothesis?

A

Suggests that there is no correlation between 2 factors you are investigating

55
Q

When is the null hypothesis rejected?

A

When your value is higher than the critical value

Biology (8 decks)

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