Download Using an example how does natural selection occur?

Monday, February 13
Bell Work:
Using an example how does natural selection occur? (not the elephant or the jaguar)
Other Evidence for Evolution
1
Fossils
­Provides evidence that evolution occurred, but the record is incomplete.
­Give clues to the organisms age, location, and environment at that time.
­Scientists can still understand overall picture of how most groups evolved.
Tiktaalik roseae…the missing link
• 4 to 9 feet long
• gills and fins of a fish
• But its fins included shoulders, elbows, and wrists, like the limbs of land animals. • a crocodile­style skull and the neck and ribs of an early land animal.
• The scientists say their "fish with elbows" represents a major link in the evolutionary chain leading from ancient fishes to amphibious land 2
• Debate over whether this creature was the first bird or a dinosaur with bird­like characteristics
Geography
­ Darwin noticed that animals and plants on the islands were similiar to those on the mainland.
­He hypothesized that some individuals from the mainland migrated to the islands.
­ Different ecosystems on different islands favored different traits and since the islands are too far apart for mating, interaction didn't occur.
­Biogeography­ study of the distribution or organisms around the world.
3
Embryology
All embryos look similar, no matter the species, which
suggests a common ancestor.
-Fish, reptile, mammals and birds have pharyngeal
pouches and tails.
-In fish, the pharyngeal pouches become gills in the
other organisms they become parts of the ears, jaw and
throat.
Homologous­ structural features that are similar in structure, but appear to have different functions
­suggest common descent
Example­ Bones of forelimbs of whales, crocs and birds all are similar in structure, but different in function.
Vestigial­ A body structure present in organisms that no longer serves a purpose.
­important so show evolution has occurred.
Example­ Pelvic bones in whales, wings on ostriches, appendix in humans. (once used to digest cellulose in plants, we don't each much cellulose now) 4
Analogous­ body parts that do not have a common structure, but similar functions.
­do not suggest a common ancestor
Example­ Bird and butterfly wings
Scientists use all possible evidence to interpret evolutionary relationships between species.
However, it is all subject to a scientists interpretation.
Cannot observe evolution occurring because of short life span.
5
6