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Evolution and Human Behaviour (PSYC2537) > 2. Natural Selection > Flashcards

2. Natural Selection Flashcards

1
Q

What is the mechanism for evolution?

A

Natural selection

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2
Q

What do terms like ‘Darwinian’ mean?

A

Evolution via natural selection

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3
Q

What does lack of understanding of evolution lead to?

A

Misunderstandings or simplification of Darwinian theory

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4
Q

What is variation?

A

The differences within a population for certain characteristics

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5
Q

Types of characteristics

A

Continuous e.g. height, IQ, attractiveness in humans

Discrete e.g. eye colour, blood type

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6
Q

Variation occurs at 2 levels

A

Phenotype & genotype

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7
Q

What is a phenotype?

A

Observable characteristics of an individual

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8
Q

How are phenotypic traits created?

A

By cells (bones, muscle, brain, etc.)

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9
Q

What are cells made from?

A

Proteins that are strings of amino acids

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10
Q

What do genes do in terms of amino acids?

A

Genes encode the sequence of amino acids

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11
Q

In natural selection, what is actually selected?

A

The phenotype

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12
Q

Two types of genes

A

Recessive & dominant

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13
Q

Alternative forms of genes are called…

A

alleles

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14
Q

Organisms with two copies of the same allele are called…

A

haploid

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15
Q

Organisms with different alleles are called

A

diploid

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16
Q

How are genes assembled?

A

Genes are assembled into chromosomes in nucleus

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17
Q

How many chromosomes do humans have?

A

46 in 23 pairs

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18
Q

How is sex determined?

A

By chromosomes - females have XX and males have XY

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19
Q

What are genes made of?

A

deoxyribonucleic acid (DNA)

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20
Q

How are genes arranged?

A

Long chain molecule, two strands bound in double helix

Two strands bound by sequences of base pairs

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21
Q

What are the base pairs?

A

Adenine (A) pairs with Thymine (T)

Cytosine (C) pairs with Guanine (G)

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22
Q

How many base pairs make up a gene (or allele)

A

Approximately 27,000

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23
Q

How do amino acids make phenotypic traits?

A

Amino acids make proteins, and from there make phenotypic traits

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24
Q

Who was the first human to know his entire genetic code?

A

J. Craig Venter

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25
Q

How many base pairs, chromosomes and genes make up a human?

A

3.2 billion bade pairs over 23 chromosomes, making approximately 25,000 genes

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26
Q

What % of DNA is genes?

A

40%

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27
Q

What is 60% of DNA?

A

Non-coding, such as transposable elements, sequence repeats and junk

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28
Q

What % of our genes do we share with chimpanzees?

A

98%

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29
Q

What % of our genes do we share with bananas?

A

50%

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30
Q

How many base pairs difference between humans and chimpanzees?

A

Approximately 32 million

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31
Q

What characteristics must the 2% difference in DNA between chimpanzees and humans explain?

A

Bipedalism
Bigger brains
Hairlessness
Language(?)

32
Q

What are sex cells called?

A

Gametes

33
Q

Sexual reproduction

A

Sex cells (gametes) contain 1 of each chromosome
Split through meiosis, creates sperm and eggs
These then combine, make embryo
Chromosomes pair up, new genotype formed

34
Q

Why is sexual reproduction relevant?

A

It is a major source of variation between individuals of a species

35
Q

Different types of mutations

A

Single-base substitutions
Single sequence repeat expansions
Insertions

36
Q

How many new mutations do we carry in our DNA?

A

100-200

37
Q

What are mutations caused by?

A 
Mutagens: 
X-rays
Cosmic rays
Radioactive substances
Various chemicals
and even 'mutator' genes
38
Q

Are mutations good or bad?

A

Most are either neutral or damaging, but sometimes advantageous

39
Q

Why is heredity a necessary component for natural selection to occur?

A

Only traits that are inherited will be exposed to evolution by natural selection i.e. hair colour, but not hair length

40
Q

How ‘heritable’ are traits?

A

Different traits vary in heritability

41
Q

What genes are inherited will be partly based on…

A

sexual reproduction

42
Q

What is the study of heritability called?

A

Behavioural genetics

43
Q

How can we estimate heritability?

A

Twin studies

44
Q

Two types of twins

A

Monozygotic (MZ) - share 100% of genes

Dizygotic (DZ) - share 50% of twins

45
Q

What is included in twins’ assumed shared environment?

A

Diet
Home life
Parental relationships
Schooling

46
Q

What do concordance rates between twins show?

A

How much of trait is explained by genes and how much is explained by the environment

47
Q

If concordance rates are larger between MZ twins than DZ twins, what does this say about the size of the genetic component?

A

Genetic component will be large

48
Q

What does little difference between concordance rates in twins suggest?

A

That environmental influences are more important in determining phenotypic variation

49
Q

Geschwind et al. (2003)

A

Measured total volume of cerebral hemispheres in both MZ and DZ twins
MZ correlation was 0.87
DZ correlation was 0.56
Therefore the size of the genetic component (heritability) of size of brain structures is 0.62

50
Q

How can we use twin studies to calculate the effect of non-shared environment?

A

1 - concordance rate in MZ

51
Q

How can we use twin studies to calculate the effect of shared environment?

A

Concordance rate in MZ - heritability

52
Q

Problems with twin studies

A
  • Assumes shared environment is the same for twins
  • The nature of adoptive families
  • Adopted children have 9 months shared environment with their biological mother - prenatal effects (e.g. hormones/diet/drugs) may be large
53
Q

Greater the heritability, more likely that trait is…

A

adaptive

54
Q

TRUE OR FALSE: Traits with heritability >0 can be shaped by natural selection.

A

True

55
Q

TRUE OR FALSE: Heritability has to be 100% to say that a trait is genetic.

A

False

56
Q

What is the heritability of general intelligence?

A

Approximately 0.35

57
Q

What are pre-requisites for natural selection?

A

Variation and heredity

58
Q

TRUE OR FALSE: Evolution will only occur when there is some form of selection (i.e. natural, artificial).

A

True

59
Q

Selection relies on some form of…

A

competition

60
Q

Thomas Malthus

A

Published “An Essay on the Principle of Population” 1798
European population was growing exponentially
Limited resources - competition to survive

61
Q

What determines which traits are selected for?

A

Levels of competition and force of selection

62
Q

What are K-selected species?

A

few offspring
high likelihood to survive
long generations

63
Q

What are r-selected species?

A

more offspring
lower survival rates
short generations
e.g. fish

64
Q

How do selection pressures affect K-selected species and r-selected species differently?

A

r-selected species may be more rapidly and strongly affected
BUT
r-selected species can evolve quicker to cope with extreme selection pressures and can cope with rapidly changing environments

65
Q

Size of selection pressure in the environment will affect levels of…

A

competition and selection

66
Q

Examples of large selection pressures

A

Major catastrophe e.g. meteor striking the earth or lethal pandemic

67
Q

‘Endler’s guppies’ experiment: background

A

Guppies vary from stream to stream
Brightness of males attracts females BUT also predators
Where predator levels high –> drabber males selected for (camouflaged with gravelly floor)

68
Q

‘Endler’s guppies’ experiment: method

A

Guppies randomly assigned to ponds with either strong/weak/no predator
Before predator introduced, guppies became more colourful and spotty to attract females
After predator introduced, those in the ‘strong’ condition had less spots

69
Q

‘Endler’s guppies’ experiment: conclusion

A

Selection for predator avoidance was greater than selection by females for colourful males (due to size of selection pressure)

70
Q

What does ‘fitness’ mean?

A

number of copies of particular allele in subsequent generations

71
Q

What are the types of natural selection?

A

Purifying selection
Stabilising selection
Directional selection

72
Q

3 aspects of adaptation

A

RELIABILITY: Does trait develop in all members of species in normal environments?
EFFICIENCY: A good solution to a problem?
ECONOMY: Does it do so without great costs to the organism?

73
Q

Example of an adaptation

A

Imprinting

74
Q

The adaptationist stance

A

If a particular trait is common in a population, then it is the result of natural selection

75
Q

Which stance does evolutionary psychology take?

A

The adaptationist stance

Evolution and Human Behaviour (PSYC2537) (14 decks)

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