1. 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

2. 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.

3. What changes populations?
Evolutionary Forces
What changes populations?

4. 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

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

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

7. 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

8. 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!

9. 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!

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

11. 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.

12. Sexy = fitness markers

13. 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?

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

15. 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

16. Any Questions??