Chapter 22Evidence for Evolution

• How has evolution risen in status to the level of THEORY, the same level as gravity or plate tectonics?

• Through repeated observations from many areas of life sciences.

Evidence of Evolution

• What is probably the first evidence that living things have changed over time?

• What additional clues have been added since then?

Beaks as Evidence

• Darwin saw finches on the Galapogos Islands (and tortoises, and armadillo fossils in South America, and lots more).

• What did he notice about these finches?

• “ …from an original paucity of birds in this archipelago, one species has been…modified for different ends.” see page 455 Can someone rephrase this?

• Are you able to see things in a different way than they have traditionally been seen?

Industrial Melanism

• Peppered moth story

• See peppered moth sim

• See details of how the experimental method was implemented (pg 456) (mark/ recapture).

• How does this relate to the Clean Air Act?

• What types of selection can you attribute this to?

Artificial Selection

• There are some dramatic examples of artificial selection to be found on page 458--459. Give 2 examples and include details.

Selection Ponderables

• Does selection act on genotypes or phenotypes? • Which is more likely to be selected against,

deleterious mutations that are dominant or those that are recessive? Why?

• Can selection create perfect organisms?– (Human’s backs are evolved from 4-legged

ancestors and not fully compatible w upright posture, so many older people have backpain)

Evolution of Horses

• Compare the profile of the house cat with the early horse on page 462.

• What climatic conditions accompanied the change the feet and teeth of horses?

Fossil Evidence

• How can the age of fossils be determined?– Relative Dating– Absolute Dating

Fossil Evidence

• We found orange juice with 1/8 of its original 32P in the lab cabinets during cleanup. 32P has a half-life of about 14 days.

How long had the orange juice been there?

• That is 3 half-lives, so about 3 x 14= 42 days. Drink Up!

Anatomical Evidence

• Homologous structures– Structures that have different functions but

arrived from same body part.– Human arm, bat wing, porpoise flipper

• Development– “Ontogeny recapitulates phylogeny”.– Developing embryo tells a story

• gill pouches, tail, fur (lanugo)

Anatomical Evidence

• Did you know there are pelvic bones in snakes? In whales? Why?– Vestigial structures

• What vestigial structures do humans have?– Appendix

• What our new understanding of genetics tell us about our model of evolution?

Molecular Record

• The more amino acid (or DNA base pair) differences, the greater the evolutionary distance.

• The ‘trunk’ of the tree represents similar traits or molecules (depending on how tree was made). Each branch represents a divergence. (See page 466)

Convergent Evolution

• Two separate groups (branches on evolutionary tree) display similar characteristics.

• Ex: Placental mammals often have a marsupial “cousin”: wolf / tasmanian “wolf”.

Island Evolution

• An ideal location to study evolution. Organisms can be seen that are similar to the mainland species that they are nearest, but with traits adapted to a specific island.

Response to criticism

• Discuss one criticism/ response.