BI111 Week 4-5

Dawrins observations and inferences 1

• observation : populations have a great capacity to grow, but are ultimately limited by resource availability

  • inference : compétition between individuals in a population for resources

Darwins observations and inferences 2

• observation: individuals vary within populations in heritable traits related to competitive success (ultimately survival)

  • inference: some individuals more likely to survive and reproduce than others

Darwins observations and inferences 3

• observation: individuals may also vary within populations in heritage traits related to reproductive competitive success

  • inference: some individuals more likely to reproduce than others

Adaptive Evolution (natural selection)

• a populations characteristics change over time as advantageous traits become more common

change in allele frequencies over time

• evolution encompasses all types of changes brought about by selection processes and chance events

Domesticated species and adaptation

• depending on environnent, different phenotypes are adaptive or deleterious

• traits (with genetic basis) that might otherwise put individuals at a competitive disadvantage may be desirable to humans and thus become favoured by selective breeding

Darwin’s pigeon

• artificial selection is an analogous process (similarity of function and superficial resemblance of structures that have different origin) to natural selection

anagenesis

• accumulation of changes in linages, with no change in number of species

cladogenesis

• accumulation of changes in 2 or more descendant species

Rate of Speciation

• refers to the speed that new species arise

Misconception

• selection will produce perfectly adapted species

Maladaptation can arise from;

• mutation

• genetic drift/inbreeding

• variation in selection, heterozygote advanatage

• gene flow

Homologies

• resemblance due to recent common ancestor

  • E.g bones that support wings of bats, birds and pterosaur all look like modifications of the pentadactyl limb

Homoplasties

• resemblance due to similar selective pressures to fill niche

Analgous

• Analogous structures in biology are like having different tools that do the same job but are made differently.

  • For example, a bird's wing and an insect's wing both help them fly, but they're built differently and didn't come from a common ancestor. They evolved separately to solve the same problem of flying.

Principle of monophyl

• all groups in a clade include common ancestors and all its descendants

Monophyletic Taxon

• include ancestor and descendant

Polyphletic Taxon

• species from different evolutionary lineage (tricked by superficial similarities)

Paraphyletic taxon

• include ancestor and some of its descendants

Rooted

• tail gives directionality where it changes what order

Unrooted

• not knowing where first split occurred, maybe know some connections

scaled

• length is important

  • long arms mean more different

  • short means they’re the same

Unscaled

• no difference