Review: Essence of Darwin’s ideas Natural selection Variation exists in populations Over-production of offspring more offspring than the environment can support Competition and differential survival (struggle to survive) for food, mates, nesting sites, escape predators successful traits = adaptations Differential reproduction adaptations become more common in population

Evolution is not goal-oriented An evolutionary trend does not mean that evolution is goal-oriented. Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well Remember that for humans as well! Evolution is not the survival of the fittest. Rather it is the survival of the just good enough.

What changes populations? Evolutionary Forces What changes populations? 2007-2008

Forces of evolutionary change Natural selection traits that improve survival or reproduction will accumulate in the population adaptive change Genetic drift frequency of traits can change in a population due to chance events random change

Natural Selection Selection acts on any trait that affects survival or reproduction predation selection physiological selection sexual selection

Predation Selection Predation selection act on both predator & prey behaviors camouflage & mimicry speed defenses (physical & chemical)

Physiological Selection Acting on body functions disease resistance physiology efficiency (using oxygen, food, water) biochemical versatility protection from injury HOT STUFF! Some fish had the variation of producing anti-freeze protein 5.5 mya The Antarctic Ocean freezes over

Physiological selection Dogs pee on trees…Why don’t trees pee on dogs? NH3 plant nutrient animal waste One critter’s trash is another critter’s treasure!

Survival doesn’t matter if you don’t reproduce! Sexual Selection Acting on reproductive success attractiveness to potential mate fertility of gametes successful rearing of offspring Survival doesn’t matter if you don’t reproduce!

It’s FEMALE CHOICE, baby! Sexual selection It’s FEMALE CHOICE, baby!

The lion’s mane… Females are attracted to males with larger, dark manes Correlation with higher testosterone levels better nutrition & health more muscle & aggression better sperm count / fertility longer life But imposes a cost to male HOT! Is it worth it?? Even though it’s very hot to have a large mane the benefit of attracting mates and successfully producing & rearing young since you have that large mane outweighs the costs. Females who chose these males were more “successful” (more, healthier young) and therefore had a greater opportunity to pass on the trait of being attracted to longer darker manes to their daughters and the trait of having longer, darker manes to their sons.

Sexy = fitness markers

Is there a testable hypothesis in there? Sexual selection Acts in all sexually reproducing species the traits that get you mates sexual dimorphism influences both morphology & behavior can act in opposition to natural selection Jacanas Is there a testable hypothesis in there?

Coevolution Two or more species reciprocally affect each other’s evolution predator-prey disease & host competitive species mutualism pollinators & flowers

DIRECTIONAL SELECTION STABILIZING SELECTION Effects of Selection Changes in the average trait of a population DIRECTIONAL SELECTION STABILIZING SELECTION DISRUPTIVE SELECTION giraffe neck horse size human birth weight rock pocket mice

Any Questions??