Question

MCAT Mini-Tutorial: Introduction to Speciation, Symbiosis, & Phylogeny

Answer 1

\({\bf{Speciation:}}\)
- species concept: species is defined as a group organisms that cannot interbreed with other groups to produce viable fertile offspring [this is not the only species definition but it is the one most commonly used]
- reproductive barrier: physical/chemical obstacles/mechanisms that interfere with formation of viable offspring, can be pre-zygotic or postzygotic
- allopatric speciation: speciation from geographic isolation
- sympatric speciation: speciation within populations that are in contact
> possible causes: polyploidy, changes in ecological niche/habitat, sexual selection, gene transfer

\({\bf{Symbiosis:}}\) relationship between two species that live in association and provide benefit to at least one species within the group
- mutualism: both benefit
- commensalism: only one benefits, the other is unaffected
- parasitism: one benefits at the expense of the host

\({\bf{Phylogenetics:}}\) study of the evolutionary relationships/history between organisms, based on morphology, physiology, and genes
- phylogenetic tree: diagram that illustrates the evolutionary relationships between organisms
> can be rooted or unrooted (shows direct ancestry vs not)
> branch length represents evolutionary distance
> the ends/nodes of the branches are species that still exist

- taxonomy: organization of organism into hierarchical classes
> domain kingdom phylum subphylum class order family genus species
> mnemonic device: dumb king Peter sometimes comes over for great soup

- molecular clock: system to estimate when two species diverged, ex. DNA mutations
- punctuated equilibrium: long periods of evolutionary stability with short periods of rapid change

- divergent evolution: ancestor diverges into two species that become more different over time
- convergent evolution: two distinct species that become more similar b/c of similar pressures
- parallel evolution: sub-type of convergent evolution in which two closely related members develop similar characteristics not shared by the ancestor
- analogous: traits that arise from independent evolution
- homologous: traits from evolution linked to a common ancestor

Answer 2

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 2nd Edition Barron's Prep book for the new MCAT