Foundations of Bio Lecture 34

gene flow

movement of alleles between populations; occurs when individuals leave one population, join another, and breed; equalized allele frequencies; reduces genetic differences between populations

gene flow and fitness

doesn’t always reduce; can replenish alleles in population that lost alleles due to genetic drift

mutation

generates genetic diversity (ultimate source); creates new alleles, not just new combos; random with respect to fitness of individual; if did not occur, evolution would stop; alone is inconsequential

point mutations

change in single base pair in DNA; result in same or similar polypeptide

chromosome-level mutations

change in the number or composition of chromosomes, such as gene and genome duplication

lateral gene transfer

movement of genes between different species; important source of genetic variation, especially in prokaryotes

beneficial alleles

alleles that increase fitness of individuals; will rapidly increase in frequency in a population due to natural selection by directional selection; rare mutation

neutral alleles

alleles that have no effect on fitness; subject to evolution by genetic drift; common mutation

deleterious alleles

alleles that lower fitness; cause random changes in genes; eliminated by purifying selection

mutations and prokaryotes

significant evolutionary force in prokaryotes because they have short generation times

phylogeny

the branching evolutionary history of a group of organisms

phylogenetic tree

simplified diagram of branching evolutionary history

systematics

a biology discipline that characterizes and classifies relationships among all organisms on Earth

tree of life

most universal phylogenetic tree; complete, evolutionary history of life; one of greatest unifying concepts in biology that all life is connected through evolutionary history

uses of phylogenetic trees (3)

taxonomy, medicine (studying spread of disease), identifying species that are a conservation priority

taxonomy

naming species

taxa

higher-level groups; always located on branch tips, never in the tree, because none of the taxa are ancestors of others

sister groups

closely related taxa; share a recent common ancestor

nodes

represent speciation events (splits); branching order of nodes along time axis indicates when lineages last shared a common ancestor

branches/ clade

part of tree; descendants of a single common ancestor; can rotate at each node and won’t affect tree; each one represents a taxon

root

common ancestor of all represented taxa