chapter 2- evolution of populations Flashcards
what is evidence for evolution
Direct observation
fossil record- gives us some evidence that species must have evolved
homologous structures- give us some aspect of unity of life
convergent evolution
What is convergent evolution
similar characteristics that evolved independently in two lineages, can be homologous or analgous
How does convergent evolution happen
in response to similar environmental pressures
How can homologous or analogous characteristics be visualized
on a phylogeny
How do you know what species share ancestors on a phylogeny
by seeing how close to the root it is
What is microevolution
ind. posses heritable genetic differences on which natural selection acts resulting in evolution. changing allele frequencies in a population
What are the 4 mechanisms of evolution
natural selection
genetic drift
gene flow
mutation
what is gene flow
means the movement of genes. In some cases, small fragments of DNA may pass from one individual directly into the germline of another, migration
what is genetic drift
Any random change to the allele frequency of a population due to a chance event.
What does the hardy weinberg model describe
a non evolving population
HWE equation
p2+ 2pq+ q2= 1
What does the HWE examine
what happens to allele frequencies when these evolutionary mechanisms are not working,
_ acts on inds, _ acts on a population
natural selection, evolution
_ is the unifying theory of all of biology
Evolution
What are patterns of natural selection on phenotypes
Directional selection, disruptive selection, stabilizing selection.
what does directional selection show
selection for a rare phenotype that differs from mean of population
what does disruptive selection show
selection against the common intermediate phenotype and favouring extreme phenotypes. there is no mean or middle section, favouring 2 extreme phenotypes.
Stabilizing selection
favouring a common intermediate phenotype
Biological Species Concept
- Produce viable, fertile offspring (at least potentially)
- Breeding with other species is prevented (reproductive isolation)
Morphological species concept
(look different), = unique combination
of traits
Ecological species concept
(unique environmental niche)
Phylogenetic species concept
(monophyletic groups only identified), traits that are unique to descendants of a common ancestor
Speciation:
evolutionary process of divergence of one species into
two species
Allopatric speciation
geographical isolation through the formation of a physical
barrier, Uplift of mountain range splits a population
