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)

natural selection trends

create 4 types of distributions

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)

• Shifts one direction –Ex: horses taller, wolves to dogs smaller

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)

Gall Weed Wasps /Downy Woodpeckers

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

speciation time frame – minimum of 50 generations– maximum of millions to billions of years

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

Local example of convergent evolution

Mudpuppy (amphibian)

Burbot (fish)

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…

Speciation Patterns

• Punctuated Equilibrium: episodes of speciation followed by long periods of no change.

• Adaptive Radiation: the diversification of one ancestral species into many descendants.