Evolution Change over time; the process by which modern organisms have descended from ancient organisms

Evolution Only a theory?

Some basic definitions Fact: an observation that has been repeatedly confirmed (Plants need light for photosynthesis) Law: a descriptive generalization about how the physical world behaves (Laws of Motion) Hypothesis: a testable statement that can be used to build inferences and explanations

Some basic definitions Theory: a well- substantiated and accepted explanation that incorporates facts, laws, inferences and tested hypotheses. In science, you don’t get any better than a theory.

Spontaneous Generation- life produced from non-life Biogenesis-life arises only from life According to Jean van Helmont from the 3 rd century B.C., when grains of wheat are place in a container and left for 21 days, mice will form from the fermenting wheat. False

Animal Locomotion What different ways do these animals move? What traits does each animal have that help it move as it does?

Darwin’s Voyage

H.M.S. Beagle Sailed around the world in 1831 Darwin began to make observations about the species in the world

Darwin’s Observations An enormous number of species inhabit the earth Organisms are well suited to their environment Organisms have many ways to survive and produce offspring

Where Organisms Live Certain organisms live in some areas but not others –Rabbits and Kangaroos live in the same type of environment –Australia has Naturally Kangaroos but not Rabbits –England has Rabbits but not Kangaroos

Fossils Some fossils look like organisms that are alive today Other fossils look unlike any creature Darwin had ever seen Why do species disappear? How are organisms in fossils related to living species?

Galapagos Island Islands are close together with very different climates Darwin saw finches with different shaped beaks on different islands Could similar organisms on different islands once have been members of the same species? Fruit CactusSeeds Insects

Giant Tortoise

Evolution is not… Individuals do not evolve

Evolution is: Descent with Modification Each living species has descended, with changes, from other species over time Populations evolve over many generations

Types of Evolution Convergent evolution-two different lineages evolve similar traits –Dolphins & fishes –Wings of bees & bats Divergent evolution-a lineage splits to have organisms with different traits –Darwin’s finches –Adaptive radiation

CONVERGENT EVOLUTION

DIVERGENT EVOLUTION

How fast does evolution occur? Gradualism –Species change slowly over time Punctuated Equilibrium –Species can make rapid “leaps” in evolution Modern Synthesis –Parts of both are correct

Evidence for Evolution Fossils Anatomy –Homologous structures –Analagous structures –Vestigial structures Embryology DNA

Fossils Scientists have used the fossil record to construct a history of life on Earth. –Earth’s life forms appeared 3.5 billion years ago –Fossil indicate that life forms have change over time

Anatomy –Homologous Structures - different organisms sharing similar structures from the same evolutionary origin

Anatomy –Analogous Structures – different organisms sharing the same structure to perform similar functions from different evolutionary origins (evolved twice)

Anatomy Vestigial Structures – structures that have lost their function through evolution They once had a purpose

In humans, the pelvis and the femur, or thighbone, are involved in walking. In whales, the pelvis and femur are A.Homologous structures B.Vestigial Structures C.Acquired Structures D.Analogous Structures

Embryology Embryos of many organisms are alike in early stages of development. These similarities suggest that we are all related, but have developed differences

DNA Organisms that are closely related should have similar DNA Similar DNA indicates sharing a common ancestor at one time. Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

How similar is Human DNA to mouse DNA? A.60% B.48% C.23% D.7%