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First year B > L42-45 evolution > Flashcards

L42-45 evolution Flashcards

1
Q

Evolution

A

a change in a population over generations as a result in genomic variation.

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2
Q

Name the 4 key evolutionary process

A

(1) Mutation
(2) Migration (“gene flow”)
(3) “Genetic drift”
(4) Natural selection

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3
Q

Natural selection

A

The non-random increase in frequency of DNA sequences that increase survival and a non-random reduction in deleterious sequences.

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4
Q

Continuous variables

A

height, mass, skin colour, hair colour , result of polygenic inheritance.

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5
Q

Graph of normal distribution curve of phenotype

A

Bell-shaped curve

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6
Q

Directional selection

A

One extreme of the phenotype range is selected for, this causes a progressive shift in the mean value.

*European black bears increased mass during ice age since larges body masses lost less heat.

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7
Q

Disruptive selection

A

Two extreme versions of the phenotypes are selected for at the expense of the intermediate versions.

*occurs when two different habbitats/ resource types become avaliable. Can result in population being split into two distinct groups

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8
Q

Stabilising selection

A

Average phenotype is slected for and extremes of phenotype are slected against; leads to reduction in genetic diversity.

*human birth mass between 3-4kg. Babies with lower masses more suseptible to disease; those with greater mass have difficulties during birth.

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9
Q

Is natrual slection more rapid in eukaryotes or prokaryotes?

A

Prokaryotes, since they can transfer information horizontally, this results in faster evolutionary change than in organism which only use vertical transfer

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10
Q

Horizontal gene transfer

A

Genes are transfered between individuals in the same generation.

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11
Q

Vertical gene transfer

A

Genes are transferred from parent to offspring as a result of sexual or asexual reproduction.

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12
Q

Species

A

A group of organisms capable of interbreeding and producing fertile offspring. These organisms don’t often breed with other groups.

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13
Q

Speciation

A

generation of new biological species by evolution as a result of isolation, mutation and selection.

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14
Q

Name the two types of speciation

A
  • Allopatric speciation

- Sympatric speciation

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15
Q

Allopatric speciation

A

Gene flow between two (or more) populations is prevented by a geographical barrier (rivers, mountain range, desert, sea)

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16
Q

Sympatric speciation

A

two (or more) populations live in close proximity in the same environment but still become genetically isolated due to a behavioural or ecological barrier. *promoted by disruptive selection.

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17
Q

Aristotle ‘great chain of being:’

A
  • It is the view point that nature is a continum
  • sense that small organisms are primitive and have naturally developed towards larger more advanced life

3 principles:

1) Every life imaginable exists on Earth
2) each species differs from its closest relative by an almost imperceptible degree
3) All species have a place on the great chain (god on top)

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18
Q

Lamarckism

A

The idea that parts of the body that are used regularly become stronger and those which are not deteriorate. The second principle is the inheritance of acquired characteristics, this is the theory that changes in offspring generation occur as a result of characteristics acquired during parents life.

for example parent acquires muscle due to physical work and is therefore passed on to offspring
for example parent acquires muscle due to physical work and is therefore passed on to offspring

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19
Q

Give faults with Lamarckism

A

Does not describe (or predict) evolutionary relationships (incl. divergence) No known mechanism for “striving”

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20
Q

hierarchical classification system

A

Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species

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21
Q

Darwin Observations:

A
  • Variation
  • Heritability
  • Competition
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22
Q

Darwin Observations: Variation

A

Members of a population often vary in their

traits

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23
Q

Darwin Observations:Heritability

A

Traits are inherited from parents to offspring

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24
Q

Darwin Observations: Competition

A

All species are capable of producing more offspring than the environment can support, leading to competition to survive and reproduce

25
Q

Describe the nature of inheritance

A

-Natural selection: Individuals whose inherited traits give them a higher probability of surviving and reproducing will leave more offspring and these favourable traits will therefore be passed onto the next generation.

26
Q

Evolutionary process: Mutation

A

-The genetic composition of the populations changes due to permanent change in nucleotide sequence caused by:

(1) Point mutations (single base changes)
(2) Insertion/deletions (“Indels”)
(3) Gene duplication
(4) Translocations
(5) Inversions

Mutations are random with respect to resulting phenotypic type however:

(1) Different sequences/part of the genome vary in their mutation rate (and mutation rate evolves)
(2) Certain classes of mutants more common that others
(3) Certain outcomes of mutation more common than others

27
Q

Evolutionary process: Migration/Gene flow

A

The transfer of alleles from one population to another, resulting from the movement of fertile individuals or gametes

28
Q

Evolutionary process: Genetic drift

A

A process by which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in smaller populations

29
Q

Bottleneck effect

A

Genetic drift that occurs when the size of a population is reduced, by a natural disaster or human actions. Typically the surviving population is no longer genetically representative of the original population.

30
Q

Explain why how there is no link between phenotype and survival

A

A lot of genetic change is phenotypically neutral, the third codon position is often synonymous, there is no change to the amino acid coded for

31
Q

Genetic Drift on a molecular level

A

Can compare the rate of non- synonymous substitutions (one base for another) to that of synonymous substitutions this can be used to understand the role of selection at molecular levels.

32
Q

Give the equation for comparing non- synonymous substitutions (one base for another) to that of synonymous substitutions

A

dn/ds

where

dn: non-synonymous substitutions per non synthesis site
ds: synonymous substitutions per non synthesis site

=1 suggest drift
<1 suggests “purifying selection” (against change)
>1 suggest “positive” selection (for change)

33
Q

Evolutionary process: Natural Selection

A

The non-random increase in frequency of DNA sequences that increase survival and a non-random reduction in deleterious sequences.

Proposition that this is due to the fact that:

1) Individuals vary in traits that are partly heritable
2) Some of these traits may be associated with successful reproduction

(1) + (2) together lead to genetic change from one generation to the next = evolution

34
Q

Conditions for Natural Selection to not occur

A
  • No heritable variation in traits

- No associations between traits and reproduction

35
Q

Evolutionary Fitness

A

number of copies of your genes that get passed to the next generation

36
Q

Two types of Natural selection in terms of evolutionary fitness

A

Direct Fitness: Measured in terms of your own offspring, more offspring = more copies of genes get passed onto next generation

Indirect Fitness: Genes carried by offspring of relative

Inclusive fitness = Direct fitness + Indirect fitness

37
Q

Natural selection: name the components of evolutionary fitness

A

(1) Survival (Viability selection)
(2) Number of offspring (fecundity selection)
(3) Number or quality of mating partner(s) (sexual selection)

38
Q

Microevolution

A

Evolutionary change below the species level, change in the allele frequency in a population over generations

39
Q

Macroevolution

A

Evolutionary change above the species level.

e. g:
- The origin of a new group of organisms through a series of speciation events

-the impact of mass extinctions on the diversity of life and its subsequent recovery.

40
Q

Macroevolution displays on the phylogenetic tree

A

Organisms show phylogenetic relationships predicted by descent with modification.

Relationship trajectories:

  • Parallel = related species
  • Convergent= unrelated species
41
Q

How does speciation contradict creationism

A

Individual creation of species is contradicted by the messy nature of specie relationships – ]

e.g. sibling species, “species flocks”, hybridisation

42
Q

Describe “poor design”

A
  • The testis wraps around the ureter and hangs outside the body, if one had the power to design a human this would be an illogical design, more keep the original positioning of the testis inside the body.
  • Laryngeal nerves :positioned in the giraffes neck such that there is a 4-5m detour
43
Q

Explain the fallacies with following statement:”Why aren’t chimpanzees evolving into humans?”

A

Chimps and humans are as “evolved” as each other, just down different phylogenetic (and phenotypic) trajectories.

44
Q

Give an example of evolution by Natural Selection

A

The peppered moth:

Two different form:

1) Light-coloured (typica)
2) dark-coloured (Melanic due to carbonaria mutation)

Bird predation selected against the Melanic moth causing a Natural directional shift in favour of they Typica moth, over time this led to a loss of the carbonaria mutation

45
Q

Describe challenges posed by evolution in real time

A

Evolution of drug resistant pathogens:

-Wide and extensive use of Penicillin, however bacteria existed which were resistant to this drug, these bacteria produced the enzyme penicillnase which could destroy penicillin therefore rendering it ineffective as a treatment. Therefore there antibiotics which where nit destroyed my penicillin were developed and utilised however overtime the bacteria developed a resistance. The same was true for Methicillin. Quick development of resistance in bacteria due to ability to evolve quickly via horizontal gene transfer.

This causes a Global heal concern since pathogens are developing resistance quicker than we cam develop new antibiotics.

46
Q

Multi-cellular organisms

A

collections of highly-related cells that work together to pass on their genes

47
Q

What is Cancer?

A

Cells evolving due to uncontrolled somatic replication. As a result mutations arise in cells that start to reproduce independently, creating tumours.

48
Q

Convergent Evolution

A

The evolution of similar features in independent evolutionary linages

49
Q

How is evolution measured?

A

We cannot see an organisms genetics to measure a genetic change, however we can identify and measure a change in phenotypic characteristics, these characteristics and present due to underlying genetics and therefore it is possible to infer evolution by natural selection

50
Q

Problems with inferring evolution based on phenotypic change

A

The phenotype of a population can change independently to genetic change as a result of:

(1) change in climatic conditions
(2) change in species range (incl. in response to humans)
(3) changes in inter-spp and intra-sp interactions (e.g. loss of predators/competitors = changes in food or habitat use)

51
Q

Sexually antagonistic selection

A

a trade-off between MALE fitness and FEMALE fitness

52
Q

Equation to determine strength of selection in the wild:

A

R=h^2S

R = response
h = Heritability 
S = Selection differential
53
Q

Heritability definition

A

Heritability is a measure of the inheritance of the trait

54
Q

Heritability equation

A

h^2 = Va / Vp

h = heritability

Va = additive genetic variance

Vp = total phenotypic variance

55
Q

Adaptive Radiation

A

Period of evolutionary change in which groups of organisms from many new species whose adaptations allow them to fill different ecological roles in their communities

56
Q

Darwin’s Finches

A

A drought caused there to be a change in seed availability, It was found that finches which survived this period correlated to those which has larger bills and hence could crack harder seed , the remaining breeding partners therefore had larger bills and this characteristic is heritable and was therefore passed onto there offspring. This is an example of directional natural selection.

57
Q

Coevolution

A

The joint evolution of two interacting species, each in response to selection imposed by the other.

58
Q

Examples of coevolution pars

A

hosts-parasites
predators-prey
flowers-pollinators
males-females…

59
Q

Give an example of coevolution

A

Darwin’s orchid has a nectary 20-35cm deep, Darwin therefore predicted there would be a moth with a tongue longer than any moth was known to have at the time. This moth wasn’t discovered until many years later but existence could be predicted due to the principle of coevolution.

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