Evolution mid term (ch 1-8)

Aristotle

Proposed scala nature ( believe species were fixed )

Erasmus Darwin

Proposed evolutional change “single living filament

Lamarck

Proposed theory of inheritance of acquired characteristics

Patrick Matthew

Proposed circumstance adaptive law → similar to darwin idea

Lyell

Proposed that Geological formations result from slow, gradual processes (uniformitarianism and gradualism )

Darwin

Proposed evolution by natural selection and that species descended from a common ancestor

Wallace

Darwin’s friend who came to the theory of natural selection independently

Problems with darwin theory

1. Complex structure: eye 

2. Could not explain traits of little importance : example the limb

1. Lack of understanding of how variation persists in the face of natural selection:

Natural selection

Individuals with advantageous traits that survive and reproduce with more successful traits passing it on to offspring

Artificial selection

human choose which individual with the desired traitor to reproduce

Genotype

the genetic makeup of an organism

Locus

a unique physical location on the chromosome where the gene exist

Gene

A sequence of DNA that codes for a trait

Allele

An alternative version of a specific gene

Phenotype

An observable characteristic of an organism caused from the interaction of genotype with its environment

Component of natural selection (evolve)

Variation , Variation need to be heritable and Difference in reproduction success

Mutation

Generate variation → occurs randomly

Evolutionary unit

the population evolves not individual

Genetic drift affects what group

1. Population size matters → smaller pop is more affected

2. Selection is more efficient in large pop

Directional selection

favors individual with one extreme version of a trait

Diversifying or disruptive selection

favors individual at both extreme ends

ex: birds with small beaks or large beak are successful

Stabilizing selection

favors intermediate phenotype trait reducing variation

example: Average-sized babies are more likely to survive compared to very small or very large babies.

Natural selection constraints

1. Physical constraints,

2. rapid change in environment 

3. Natural selection lacks foresight (mutations are random even if favorable).

Modern synthesis

The Modern Synthesis showed that both discrete and continuous traits follow the same genetic principles.

Phylogeny

shows relationship among population in a group or taxa

Phylogeny nodes

Populations

Pedigree

track genetic traits

Pedigree nods

individuals , each nods has two ancestor

Monophyletic group

group including common ancestor + its descendents

Paraphyletic

group includes a common ancestor and some of its descendants

polyphyletic

a group that does not share a common recent common ancestor

Phylogram branch length

this means the amount of evolution change (longer = more change)

Analogous traits

similar traits evolved independently due to similar selective pressure

example bats and birds wing

Convergent evolution

when two or more pop become more similar to one another because they are exposed to the same condition

Divergent

when closely related pop diverge from one another because Natural selection acts

Vestigial traits

traits with unknown function but believed to be functional in the past

Synapomorphies

A shared derived trait that groups organisms together * new trait

Homoplasy

similar trait in species but independent origin

Symplesiomorphy

shared ancestral trait that appears in only one of the sister taxa

Parsimony

minimum number of evolutionary change is better

Fitch algorithm

helps calculate parisony, sum number of changes per trait , if there is one trait similar don’t count it

Bootstrap

test phylogeny tree strength by randomly reusing data many time to see what patter consistently show up, Acceptable support level 70% - 80%, very supported 90% - 95%

Bootstraps steps

1. Original data 2. Randomly pick traits and reorder them or repeat them ect, 3. The new table is made using resampled table 4. Repeated many times

Odds Ration

measures how strong data supports claude being monophyletic likelihood of tree X likelihood of tree Y

Odd ration HO

no difference between trees

Reject HO (odds ratio)

P < 0.05 tree X has a significant higher likelihood then tree Y

Fail to reject HO (odds ratio)

P > 0.05 The tree are equally supported by the data

Law of segregation

Each individual has 2 gene copies at each loci these gene copes segregate during gametes production so only 1 gene copy goes into each gamets 

Law of independent assortment

Alleles of genes assort independently of one another 

Epigenetic inheritance

Heritable mechanism altering gene expression withou changing DNA Sequence

Source of variation

• mutation 

• recombination 

• migration 

• lateral gene transfer 

Mutation location

Somatic : not heritable

ex: cancer 

Sex cells : heritable 

Synonymouse mutiation (silent)

Base change but no amino acid changes

Nonsynonymous mutation

Base change alter amino acid sequence (can cause problems) 

Missense Mutation

a base pair changes codon to encode a different amino acid 

nonsense (NO!)

A base pair change that creats a stop codon

Frameshift (mutation)

insertion/deletion of nucleotides not in multiple of 3 

disruption of reading frame

In Frameshift

Insertion/deletion in multiple of 3 may not disrupt reading

Most mutation are…

deleterious or neutral few are beneficial

synonymous : netural 

Nonsense: deleterious