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Biology > 4. Genetic Variation, Natural Selection, Diversity > Flashcards

4. Genetic Variation, Natural Selection, Diversity Flashcards

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1
Q

Why do organisms show genetic variation?

A
  1. Random mutations
  2. Meiosis
  3. Random fertilisation
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2
Q

Continuous variable

A

Individuals can lie anywhere between two extremes

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3
Q

Discrete variable

A

Individuals fall into categories

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4
Q

Population

A

All of the organisms of the same species living in a particular area at a particular time

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5
Q

Gene pool

A

The total number of different alleles in a population at a particular time.
A population with a wider variety of alleles has a greater genetic diversity

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6
Q

Allele

A

Different versions of a gene.

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7
Q

How do new alleles arise?

A

Due to mutations

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8
Q

Phenotype

A

The characteristics an organism has as a result of its combination of alleles

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9
Q

Species

A

Organisms that can interbreed to produce fertile offspring

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10
Q

What is the only way competition for resources can be established?

A

If organisms produce more offspring than can be supported by the available resources

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11
Q

Population graph axes & shape

A

x = time
y = number of individuals of a species
shape = S shaped (like cumulative freq graph)

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12
Q

3 stages of a population graph

A
  1. Slow growth
  2. Rapid growth: no natural selection so no competition for resources (plenty of them)
  3. Stable population: now competition for resources, leading to natural selection
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13
Q

What is carrying capacity and how is this shown on a population graph?

A

The maximum population that the environment can support
Shown where the graph levels off

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14
Q

Natural selection depends upon the following factors:

A
  1. Producing more offspring than can be supported by available resources
  2. Genetic variation within the population
  3. Genetic variation leads to different phenotypes which may be advantageous or disadvantageous
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15
Q

3 different phenotypes

A

Physical
Behavioural
Biochemical

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16
Q

Examples of physical phenotyes

A

Colour

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17
Q

Examples of behavioural phenotypes

A

Hedgehogs rolling into balls

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18
Q

Examples of biochemical phenotypes

A

Haemoglobin’s affinity for oxygen changes in different environments

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19
Q

Natural selection in a nutshell

A
  1. More organisms born than can survive
  2. Variation amongst organisms: some have alleles that make them better adapted to the environment than others
  3. Selection pressure act on the population & organisms compete for limited resources
  4. Better adapted organisms out-compete the less well-adapted ones and so survive & breed, passing on their advantageous alleles to future generations
  5. Over many generations the advantageous alleles become more common in the gene pool, whilst disadvantageous ones become less common
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20
Q

Two types of selection pressures

A

Biotic & abiotic

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21
Q

Examples of biotic selection pressures

A

Predators
Prey
Disease
Habitat
Mates

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22
Q

Examples of abiotic selection pressures

A

Sunlight
Minerals
Temperature
Water
Physical space

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23
Q

The two types of selection on evolution are…

A
  1. Stabilising selection
  2. Directional selection
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24
Q

Normal distribution graph axes & shape

A

x = the variable (e.g. height)
y = frequency
shape = hump/mountain

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25
Q

Explain shape of normal distribution graph

A

Hump: most individuals have characteristics around the mean value
Plateaus at the ends because fewer individuals have extreme characteristics

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26
Q

What is stabilising selection?

A

Selection against extremes of the phenotype range

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27
Q

Where does stabilising selection occur?

A

Stable environments/when the environmental conditions are stable

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28
Q

What is directional selection?

A

Selection for one extreme of the phenotypic range

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29
Q

Where does directional selection occur?

A

When the environmental conditions change

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30
Q

A notable example of directional selection is…

A

antibiotic resistance!
Use of antibiotics puts directional selection pressure on the bacterial population

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31
Q

What are antibiotics?

A

Chemicals that target molecules & structures ONLY found in prokaryotic cells (70S ribosomes/murein cell wall)
They can also be enzyme inhibitors targeting bacterial enzymes

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32
Q

Reasons for antibiotic resistance

A
  1. Antibiotics used to treat illnesses that are trivial/short lived
  2. Doctors accept patients’ demands for antibiotics even if they aren’t necessary
  3. Not finishing a course of antibiotics
  4. Stockpiling antibiotics from previous prescriptions then using them in smaller doses
  5. Using them in agriculture to prevent disease particularly in intensively reared animals
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33
Q

Describe what a petri dish used to test for antibiotic resistance looks like

A
  1. Disks of paper soaked in different antibiotics
  2. Bacteria growing on agar plate
  3. Clear space around disks indicate no bacteria growing there, so the larger the area around a disk of paper is the more effective of an antibiotic it is
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34
Q

Example of stabilising selection

A

Human birth weights

35
Q

Define taxonomy

A

The study of classification

36
Q

Define classification

A

Grouping living organisms

37
Q

Define artificial classification system

A

Grouping organisms according to differences that are seen as useful or important and that time

38
Q

Define analogous characteristics (and give an example)

A

Similar functions but different evolutionary origins (e.g. wings in insects & birds; eyes in land mammals vs. crustaceans)

39
Q

Define natural classification system

A

Hierarchical (groups within groups/order)
Based on shared homologous characteristics which have been derived from evolutionary ancestors

40
Q

Another name for natural classification system is…

A

phylogenetic classification system

41
Q

What is the advantage of a natural system over an artificial system?

A

Natural systems are based on evolutionary origins rather than visual observations

42
Q

Define homologous characteristic (& give an example)

A

Body parts of organisms that have the same anatomical features thus indicating a common ancestor or developmental origin
(e.g. forelimbs of humans, cats, bats)

43
Q

How can we find out how closely related two species are?

A

Through comparing the same gene in different species (comparing DNA sequences), specifically through comparing nucleotide sequence of the gene or the amino acid sequence of the protein

44
Q

Why is cytochrome C an ideal gene that could be used to compare different species?

A

Cytochrome C is an important gene for a protein used in respiration. The vast majority of species have a version for the cytochrome C gene.

45
Q

The seven taxa/groups in order:

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
(do keep penis clean or forget good sex!!!)

46
Q

The three domains are:

A
  1. Bacteria
  2. Archaea
  3. Eukarya
47
Q

5 characteristics of bacteria domain

A
  1. prokaryotic
  2. no membrane-bound organelles
  3. 70s ribosomes
  4. cell walls made of murein
  5. unicellular
48
Q

5 characteristics of archaea domain

A
  1. prokaryotic
  2. contain genes and proteins that are more similar to eukaryotic cells
  3. membrane structure different from bacteria
  4. cell walls not made from murein
  5. RNA polymerase very different from bacteria
49
Q

3 features of eukarya domain

A
  1. contain membrane bound organelles such as mitochondria and chloroplasts
  2. contain a nucleus
  3. 80s ribosomes`
50
Q

The 4 kingdoms within the eukarya domain are…

A
  1. Protoctista
  2. Fungi
  3. Plants
  4. Animals
51
Q

Protoctista feature

A

Not multicellular (e.g. algae amoeba)

52
Q

Fungi features

A
  1. Chitin cell wall
  2. Saprotrophic nutrition: secrete extracellular enzymes to digest stuff then absorbed back inside
53
Q

Plants features

A
  1. All multicellular
  2. Photosynthetic
  3. Cellulose cell wall
54
Q

Animals features

A
  1. All multicellular
  2. No cell wall
  3. No photosynthesis
55
Q

Define species

A

Can interbreed to produce living and fertile (viable) offspring

56
Q

Problems with the definition of a species

A

Doesn’t apply to organisms that reproduce asexually
Some plants can be hybridised to produce new species that can produce fertile offspring too!

57
Q

Advantage of binomial naming system over using common names

A

Overcomes language barriers
Avoids muddling things up

58
Q

Courtship behaviour overview

A

Courtship behaviour is an important example of an inborn (genetic) behaviour that is essential for reproduction, and therefore the survival of a species.

59
Q

4 main purposes of courtship behaviour

A

Identify a mate of the same species
Identify a mate that is capable of breeding
Synchronises mating with female’s fertility cycle
Forms or strengthens a pair bond

60
Q

Define phylogeny

A

The study of the evolutionary relationships between organisms

61
Q

What are phylogenetic trees nowadays based off of?

A

Comparisons of gene or protein sequences

62
Q

What do intersections/junctions in phylogenetic trees represent?

A

Common ancestor

63
Q

The three aspects of biodiversity are…

A

Species diversity
Genetic diversity
Ecosystem diversity

64
Q

The two aspects of species diversity are…

A

Species richness
Relative number of individuals of each species

65
Q

Define species richness

A

Number of different species in an area

66
Q

Formula for species diversity (Simpson’s diversity index)

A

N(N-1) / Σn(n-1)

N = total # of organisms of all species
n = total # of organisms of each species

67
Q

9 ways in which agriculture could impact biodiversity

A
  1. Destruction of natural habitats to provide land for agriculture
  2. Monoculture
  3. Selective breeding: reduces genetic diversity
  4. Crops out-compete other species
  5. Space available for other species is reduced
  6. Pesticides kill other species
  7. Eutrophication
  8. Over grazing
  9. Removal of hedgerows to farm large fields
68
Q

Why might maintaining biodiversity be in the farmer’s best interests?

A

Insects are required for pollinating plants which is how plants reproduce (agriculture)!

69
Q

How can farmers help to maintain biodiversity without impacting on their ability to produce enough food?

A
  1. Maintain hedges instead of fences
  2. Reduce pesticide use - use biological control instead
  3. Don’t overuse fertilisers: use crop rotation to maintain soil quality
  4. Maintain existing ponds
  5. Plant trees
70
Q

What are the limitations of using observable characteristics to investigate diversity?

A

• Physical characteristics can change according to environment e.g. skin colour
• Organisms can have similar characteristics but by chance/coincidence: these are analogous not homologous

71
Q

What is now the best way of investigating diversity?

A

Using molecular characteristics - comparing DNA, mRNA and amino acid sequences in specific proteins

72
Q

Process of immunological comparisons of proteins (using humans and rabbits as an example)

A
  1. Human serum containing human proteins is injected into rabbit
  2. Rabbit immune system recognises human proteins as foreign, and produces antibodies specific to the human proteins
  3. Rabbit serum contains antibodies produced by the rabbit
  4. Rabbit serum injected into serum from blood of other species
  5. The more similar the other species’ proteins are to human proteins, the more the rabbit antibodies bind to them and produce precipitate
73
Q

Interspecific vs intraspecific variation

A

Interspecific: differences between different species of organisms
Intraspecific: differences between members of the same species

74
Q

Quantitative investigations of variation within a species involve:

A
  1. collecting data from random samples
  2. calculating a mean value of the collected data and the standard deviation of that mean
  3. interpreting mean values and their standard deviations
75
Q

Why is sampling often used when investigating diversity?

A

Investigating small parts rather than the whole ecosystem: ecosystems are massive!
Rarely possible to record data about every individual in a population

76
Q

Define representative sample

A

A sample that captures the full picture of an ecosystem

77
Q

What measures can be taken to ensure that sampling is representative?

A
  1. Random sampling: avoids sample bias
  2. Large sample: enough quadrats
  3. Use statistical analysis of data from the sample
78
Q

What does it mean if standard deviation bars overlap on a graph?

A

Differences between mean is NOT significant

79
Q

How to calculate degrees of freedom

A

(n1 + n2) - 2

80
Q

When do you reject the null hypothesis?

A

Calculated value BIGGER than tabulated value

81
Q

What does it mean when you reject the null hypothesis at the x% significance level?

A

Less than x% probability that the differences between the two sets of data are due to chance

82
Q

What does a small p value for a T test mean?

A

We can be certain that the pattern we’re seeing isn’t due to chance, but rather a solid relationship.

83
Q

Define genetic diversity

A

Number of different alleles in a population

Biology (42 decks)

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