Evolution

Question 1

What causes evolution?

Answer 1

Accumulation of genetic variation

Question 2

History of Evolution

Answer 2

Greeks –> Carolus Linnaeus (hierarchy based on common features, animalia, chordata etc.)

Lamarckism (living beings could acquire characteristics over their life and pass these down)

Nicolaus Steno (fossils showing evolution)

Mary Anning (species could go extinct)

Darwin (theory of natural selection)

Darwin (sexual selection)

Question 3

Evolution Definition (CD)

Answer 3

The cumulative change in the genetic composition of a population or species over time

Question 4

The 3 pillars of Darwinian Theory of Evolution

Answer 4

• Species are not immutable
  ○ Population show phenotypic variation and species can change over time
  ○ Difference in and between species
  
  • Descent with modification occurs
    ○ Related species, which share a common ancestor, diverge from one another gradually over time
  • Natural selection
    ○ Differences in phenotypes of individuals cause some of them to survive and reproduce more
    ○ Not all organisms produce offsprings, the more adapted to the environment you are, the more offspring you can produce, increasing genetic/phenotypic occurrence

Question 5

Explain natural selection? What does it act on?

Answer 5

Individuals with phenotypes most suited to the environment (fittest) are more likely to produce offspring.

Natural selection is the driver of evolution and acts on heritable variation within a population

Question 6

What is a phylogeny? What groups/relationships can it represent?

Answer 6

A phylogeny is a physical representation of evolutionary relationships of species

Monophyletic:
includes the common ancestor and all descendants (a clade)

Polyphyly
does not include common ancestor

Paraphyly
includes the common ancestor, but not all the descendents

Question 7

Terminology of phylogeny

Answer 7

Nodes
represent the msot recent common ancestor

Terminal Branch
leads to taxonomic group *only one species

Internal branch
leads to many other groups/species

Question 8

Macro and microevolution

Answer 8

macroevolution:
explains the evolutionary changes among large taxonomic groups above the species level

includes:
origin, diversificationa dn extinciton of species over long periods of time

Question 9

Convergent evolution

Answer 9

when two species evolved separately but formed similar morphological traits

Question 10

What are the 6 agents of evolutionary change? What do they do?

Answer 10

The 6 agents of evolutionary change are:
- mutation
- gene flow
- genetic drift
- natural selection
- non-random mating
- recombination

They effect and cause evolution in species

Question 11

Mutation- what is it?

Answer 11

Changes in an organisms DNA that can introduce new alleles. They have to be heritable (to the germ line cells) and can then contribute to the allele frequency in populations, changing the overall species

Question 12

How do mutations arise?

Answer 12

During DNA replication there can be mistakes, they can also occur from mutagens (chemicals that cause mutations) or radiation damage

There are 2 sources of external damage
- exogenous (UV, radiation, chemicals etc.)
- endogenous (reactive oxygen species, hydrolysis, alkylation, endonucleases)

If the mistake isnt repaired this can cause mutation

Question 13

What are the types of Mutations

Answer 13

1. point mutation
   single base change
2. insertion/deletion
   DNA of different sizes is inserted/deleted from an existing sequence
3. Frameshift
   a section is added or deleted, causing everythign to be moved over (codons)
4. larger mutations
   DNA is copied an extra time, flipped aroumd, chromosomes are gained or lost (aneuploidy). They are less common because they lead to death more often

Question 13

positive and negative mutations are known as?

Answer 13

advantageous and deleterious

Question 14

Somatic and Germline mutations

Answer 14

germline
affects gametes
passed on through sexual reproduction

somatic
affects all of the daughter cells of a single cell
not heritable (can be passed down through plants and vegetative reproduction)
cancer

Question 14

How often do mutations occur for evolution to occur?

Answer 14

○ If the mutation rate is too low then there is no evolution or adaptation (risk of extinction in new conditions)
○ If its too high then too many functional alleles are effected
○ 10-8 mutations per nucleotide per generation (of single nucleotide changes)
○ 50-70 changes per individual at birth
○ 3.2x109 nucleotides in the human genome
○ Almost 4 times more mutations from the father than mother (because of Y chromosome mutations)

Question 15

How do mutations cause evolution?

Answer 15

New alleles arise by mutations, which are created by change in the nucleotide sequence of an organism’s DNA. Mutation creates genetic variation that selection can act upon, which can result in increasing the frequency of adaptive traits, or removing maladaptive traits from the population

Question 16

Non-random mating

Answer 16

General term used to describe when an individual does not choose mates at random.

Animals can dominate others in order to breed, or pick mates based on certain criteria, therefore changing allele frequency to favour the genes required to fit these criterie

Plants often self-germinate, resulting in increase homozygosity

this decreases genetic variation

Question 16

What is Genetic Drift?

Answer 16

the populations alleles are separating slowly from their original combo due to random chance e.g. they are drifting

effects smaller populations because there are less things to change to make a bigger impact

It REMOVES variation, rather than adding it

Question 16

Natural selection as an agent of evolutionary change

Answer 16

Natural selection changes the frequency of genes and alleles in a population and is therefore an agent of evolutionary change

It can help increase beneficial mutations to the environment and sift out maladaptive traits

it a microevolutionary process that shapes the phenotypes of an organism to match its environment

Question 17

Gene Flow

Answer 17

Isolated populations accumulate genetic differences over time, through genetic drift, selection and mutation

These can lead to reproductive isolation and speciation

Gene flow counteracts the effects of population subdivisions

Gene flow is the process of the spread of genetic variation across geographical areas due to migration, hybridisation or gamete dispersal

Increases genetic variation and can homogenise allele frequencies across the landscape between connected subpopulations

Question 18

What needs to happen for gene flow to occur?

Answer 18

individuals must be able to disperse, interbreed and produce viable offspring

The populations can be isolated at one point, but gene flow can only occur when there is some way for them to reproduce again

Question 19

What does the impact of gene flow depend on?

Answer 19

1. The genetic difference berween populations
   if there isnt a lot of difference, then there isnt a lot of stuff to change/disperse, and vice versa
2. the level of migration/movement and hybridisation
   if there isnt a lot of interaction, then the distribution of genetic material will be slower and vice versa

Question 20

Recombination

Answer 20

Recombination is the exchange of genetic material that occurs when two chromosomal pairs cross over in meiosis.

This results in the exchange or mixing of the chromosomal regions to create new genetic combinations

Particular combinations of traits may be beneficial. Since recombination creates new combinations of alleles at different genes, and recombination frequencies can vary between genes, the ease at which recombination occurs can affect the speed at which evolution occurs.

Question 21

Intependent assortment

Answer 21

Paternal and maternal chromosomes inherited by the individual will assort into gamete cells independently during meiosis, creating novel combinations of alleles at different loci

Question 22

Molecular clocks and phylogenies

Answer 22

molecular clocks can be used to estimate when two species last shared a common ancestor

you can look at morphological changes, protein changes and amino acid sequence changes, however, protein and amino acid sequence changes are more accurate and useful

Question 23

cladograms vs phylograms vs ultra metric trees

Answer 23

cladograms show clades and topology

phylograms show how much change occurs (longer length is more change)

ultra metric trees use genes adn real time plots

Question 24

adaptive traits

Answer 24

Particular structures, physiological processes or behaviours that make an organism bettwe able to survive and reproduce

arise through mutation, creating new variation for selection to act upon

can also be passed between related species via hybridisation

Question 25

examples of adaptive traits (4)

Answer 25

1. pollinators
   two different types of the same flower attract different pollinators and are seperated by prezygotic reproductive isolation
2. bee pollinated
   nectar guides, wide corollas, inserted anthers and stigma
3. bird pollinated
   red and reflexed petals, narrow tubular corolla, exerted anthers and stigmas