Evolution January 9th

Question: How did the giraffe get its long neck? Why are there 9 subspecies of giraffes? Massai, reticulated, angolan

History of Evolutionary Thought In 1831, Charles Darwin, a 22-year-old naturalist, accepted a position aboard the ship HMS Beagle that began a voyage around the world. Darwin made observations of animals that inhabited the island - a study of biogeography tortoises iguanas finches

The Voyage of the Beagle

Darwin’s Theory of Evolution by Natural Selection Finches on the Galápagos Islands resembled a mainland finch but there were more types. Galápagos finch species varied by nesting site, beak size, and eating habits. Darwin proposed that each bird was descended from the mainland species. this idea is known as COMMON DESCENT

Charles Darwin and Alfred Wallace had similar ideas about how species changed over time….Natural Selection Characteristics (variations) are inherited More offspring are produced than can survive Those with the most favorable characteristics survive ADAPTATION

Descent with Modification Each generation will have more individuals with those traits than the previous generation.

Homo sapiens Canis lupus Giraffa camelopardalis Taxonomy is the science of classifying organisms. Carolus Linnaeus developed a binomial system of nomenclature - two-part names for each species GENUS SPECIES Giraffe camelopardalis angolensis (Angolan giraffe) Giraffe camelopardalis camelopardalis (Nubian giraffe) Giraffe camelopardalis reticulata (Reticulated giraffe) Homo sapiens Canis lupus Giraffa camelopardalis

Masai Giraffe: Giraffa camelopardalis tippelskirchi Thornicroft Giraffe: Giraffa camelopardalis thornicrofti

Biogeography study of the distribution of species and ecosystems in geographic space and through geological time A cladogram shows how these giraffes are related. Why are there so many different subspecies and why in distinct locations?

Are all of these giraffes descended from one common ancestor?

How does natural selection explain the finches on the Galapagos?

The Definition of Evolution Evolution is the change in allele frequencies, or a change in the gene pool, of a population. You don’t need to see an animal change physically, you only need to measure changes at the DNA level.

IMPORTANT!!! Individuals do not evolve. (they either live or die) These stickleback fish have different levels of armored scales. Individuals do not evolve. (they either live or die) *POPULATIONS EVOLVE* 2. Evolution does not have a direction. Organisms aren’t “trying” to be anything. 3. Fitness refers to an organism's ability to survive in their environment - it doesn’t necessarily mean “stronger”

3. Individuals differ in FITNESS (relative fitness) - fitness measures an organism’s reproductive success - it does not necessarily mean “stronger”. A black panther is the melanistic color variant of any Panthera species. Black panthers in Asia and Africa are leopards (Panthera pardus) and black panthers in the Americas are black jaguars (Panthera onca). Leucism refers to lighter varieties, like white tigers. White tigers are NOT albino.

Selection Strength How strong does the environment push for the survival or elimination of a polymorphism? Examples: White- Striped Clover & Rock Pocket Mouse

Divergent vs Convergent Evolution Phenotypes are similar, though these organisms are not closely related.

Variation (polymorphisms) Relative fitness (who survives selection?) The aye-aye survived!?? Review Evolution in 3 steps: Variation (polymorphisms) Relative fitness (who survives selection?) Reproduction and inheritance And the blobfish and naked mole rat?? See “Strange Animals”