1. Biological Evolution

2. What is Evolution Evolution is descent with modification
Microevolution = changes in gene (allele) frequency in a population from one generation to the next
Macroevolution = descent of different species from a common ancestor over many generations

3. Evolution Explained NOT simply change over time
Ex: Life cycle is NOT evolution
MUST involve DESCENT through GENETIC INHERITANCE
Change in a POPULATION over GENERATIONS of time
Underlying Concepts:
All organisms share a Common Ancestor
Occurs through Natural Selection

5. Natural Selection
Variation in traits: more than one allele for a trait; one allele may be more advantageous than another
Differential reproduction: NOT all individuals get to reproduce to their full potential
Heredity: adaptations are genetic
End result: more advantageous trait allows individuals to survive and produce more offspring

6. Natural Selection

7. Natural Selection

8. Natural Selection

9. Shift in Allele Frequency
Mutations can produce new phenotypes that may or may not be beneficial to the organism
If the new allele is beneficial, then those organisms will be more “fit” and therefore better able to reproduce.
Over generations of time, this will cause the new allele to become more frequent in the population.

13. Stabilizing Selection
Favors Intermediate phenotypes & eliminates BOTH Extremes
Reduces variation and maintains the current average
Ex = human birth weight

14. Directional Selection
Favors ONE Extreme & eliminates other phenotypes
Most common during times of environmental change or when moving to new habitats.
Ex: speed; faster is better so a population will tend to get faster over time.

15. Favors BOTH Extremes & eliminates Intermediates
Disruptive Selection
Favors BOTH Extremes & eliminates Intermediates
Occurs when environmental change favors an extreme phenotype; not as common.
Ex: Prey with distinctive markings; predation causes drift away from the “normal” phenotype in extreme directions.

16. Fitness
Fitness = how good a particular genotype is at leaving offspring in the next generation compared to other genotypes
FITNESS is INHERITED!
Fitness will increase one or more of the following:
Ability to Survive
Find a Mate
Produce Offspring
Fitness is NOT necessarily strongest, fastest, or biggest.
Ultimate Goal = transmit GENES to the next generation

19. Beak Lab Explanation
Varied food sources allowed many different beak structures to be beneficial; therefore allowing many phenotypes to reproduce
When food source was changed, only beaks with specific phenotypes (ADAPTATIONS) were able to get enough food to survive/reproduce.
Over generations of time, the non-beneficial phenotypes would die out and the beneficial phenotypes would become amplified.

22. Sexual Selection Special case of natural selection
Acts on an organism’s ability to obtain &/or successfully copulate with a mate
Organisms may go to extreme lengths for sex
Peacock tail
Elephant seals fight
Fruit flies dance
Some even die for it! (male praying mantis)

23. Artificial Selection
Artificial Selection = people (NOT nature) select which organisms get to reproduce
Farmers and breeders commonly cultivate crops using Selective Breeding

25. Adaptation
Adaptation = inherited characteristic in a population that increases fitness
Adaptation Types
Behavioral
Biochemical
Anatomical
An adaptation is NOT ACQUIRED during an organism’s lifetime

26. Lamarck = Acquired Traits (wrong)
Giraffes needed longer necks so they “grew” longer necks through repeated use. THIS IS INCORRECT!
Giraffes that INHERITED longer necks were better able to survive, so they passed those genes on to their offspring.
Darwin = Inherited Variation & Natural Selection (correct)

27. Adaptation Functional = Produced by Natural Selection
Heritable = MUST be able to be INHERITED (genetic trait)
Adaptive = increases the fitness of an organism

28. Speciation
Species is the biggest “gene pool” possible under natural conditions.
If the organisms can breed and produce fertile offspring, they are the same species.
German Sheppard + Chihuahua = puppy (fertile)
Horse + Donkey = Mule (sterile hybrid)
Horse & Donkey (NOT the same species)
Speciation produces 2 or more separate species caused by:
Geographic Isolation
Reproductive Isolation

29. Speciation of Fruit Flies

30. A population of wild fruit flies lays eggs on rotting bananas…

31. Disaster strikes: a hurricane washes the bananas and immature fruit flies out to sea. The bananas eventually wash up on the mainland. There are now 2 separate populations of fruit flies that cannot mate due to location.

32. Populations become different due to slightly different conditions on the island. This causes a shift in allele frequency in the island population because of selection pressures.

33. So we meet again: If another storm reintroduces the island fruit flies to the mainland fruit flies, they will not readily mate with each other due to differing courtship behaviors. The few that do mate produce inviable eggs because of genetic differences in the populations.

34. EVOLUTION DOES NOT WORK THIS WAY!!!
Misconceptions
What I NEED is a GOOD FUR COAT!
Natural Selection does NOT produce perfection.
An organism cannot “adapt” during its lifetime. It cannot “try” to change. That is NOT adaptation. Adaptations MUST be GENETIC!
Natural Selection is NOT random: variations that aid survival and reproduction are more likely to become common in the population
EVOLUTION DOES NOT WORK THIS WAY!!!

35. Why aren’t all harmful mutations eliminated from the population through Natural Selection?
Sickle Cell Anemia
1 wrong nucleotide base (mutation)
1 different amino acid that changes the shape of the hemoglobin protein
Autosomal Recessive
Heterozygotes have resistance to Malaria