Download - Evolution in Populations Wyoming, wolf was killing livestock, legally hunted Newfoundland
Genetic variation in populations
2 main sources of variation (create biodiversity):omutation – a random change of DNA in certain
cells; many failo recombination – during meiosis (forming of
egg/sperm), new allele combos are given to offspring; produces a random shuffling of genes
Possible source of variation:ohybridization – crossing of different species which
creates new varieties (possible source)
normal distribution
• bell curve• average is the highest• extreme population is
much less• human height
directional selection
• nature favors one of the extremes
• bell curve shifts (right or left)
• This then becomes “normal”
• Ex: drug resistant bacteria (less resistance to more)
stabilizing selection• the average becomes
even more favored• bell curve becomes
tightened• Ex: Gall flies in
goldenrod (woodpeckers eat large larvae) (wasp larvae eat small larvae)
disruptive selection
• Both extreme phenotypes become favored by nature
• The average drops out• could lead to a new
species• Ex: Lazuli bunting
mating patterns(extreme blue feathers – dominate)(blue-brown mix get outcompeted)(brown feathers are left alone)
Sexual Selection (two types)quality control for all populations…
• intersexual (between genders)– females choose mates based on physical traits
Ex: bird (males) - songs/colorful feathers
• intrasexual (within same gender) – males fight for the females; winner gets all the
females
biodiversity is the # different species; changes when new species form or extinctions happen
gene flow - alleles move from one population to another; if gene flow stops, each population will evolve separately and develop greater genetic differences because of natural selection
How new species form (11.5)
speciation theory - two main parts (mutation, isolation)
1. genetic mutations are passed in sex cells to the next generation; increases genetic diversity (70% fail) Do not help survival
Peppered Moth
2. isolation – prevents gene flow; separate species
evolve• geographic - separated by some geographic boundary
(ex: ocean/mountain/desert)
• temporal - different breeding season:– fall (Brown Trout) – spring (Rainbow Trout)
• behavioral - blue vs. red-footed boobies; different mating dances
Patterns of Evolution (11.6)
convergent evolution – different species evolve to adapt in a similar environment– analogous structures: tail fin of fish, reptile, and
mammal all function the same
Divergent evolution – when closely related species evolve in different habitats to become increasingly different. Example: Homologous Structures look same/different function.
Red Fox Kit Fox.
Beneficial Relationships in evolution
• Coevolution: two or more species evolve in response to changes in each other.
http://video.nationalgeographic.com/video/animals/bugs-animals/ants-and-termites/ant_acaciatree/
Species become Extinct
• Background Extinctions- happen continuously but at a very low rate
• –roughly same as speciation.
• Mass Extinctions – more rare, happen on global scale –geologic events Ex: Meteor –
• Dinosaurs Humans causing…