E V O L U T I O N

Questions to Ponder TRUE/FALSE You can web your hands if you try. You can acquire traits in your lifetime that will help you survive. All organisms have the same chance for survival. All organisms need the same favorable trait. Evolution of most organisms occurs during their lifetime.

THEORIES OF EVOLUTION: LAMARCK VS. DARWIN

LAMARCK’S THEORIES: wrong Acquired trait: a trait NOT determined by genes, it arises during an organisms lifetime as a result of behavior and can be passed onto offspring

WRONGLamarck: Acquired Trait Example: giraffes evolved their long necks by stretching further to get leaves in trees and that this change in body shape was passed on. 

CHARLES DARWIN (1809-1882) voyage of the Beagle

The study of the Galapagos finches led Darwin to his TWO theories… Decent With Modification Natural Selection

Darwin’s Theories 1) Descent with Modification Newer forms appearing in the fossil record are modified descendents of older species All species had descended from one common ancestor

Descent With Modifications - tree of life that links all living things!

Modification by Natural Selection Describes how evolution occurs organisms in nature produce more than can survive THEREFORE living things face a constant struggle for existence

POPULATIONS HAVE VARIATIONS 2. Variation exists within populations because: - mutation - Crossing Over/Independent Assortment (make different gametes) - Sexual reproduction - Random fusion of two gametes Through mutation three variations of neck length exist: Short, Medium and long necks.

Let’s review Mutations Start here A

SOME VARIATIONS ARE FAVORABLE Having a high number of favorable traits gives the organisms an adaptive advantage 3. Non-random Survival and Reproduction -Individuals with traits best suited to their environment (favorable traits) survive and reproduce in high numbers The long neck giraffe has the “best advantage” and therefore reproduces more than the others

Fitness: organisms ability to survive and pass on its genes 4. These favorable traits have to be heritable (able to be passed down to offspring) Fitness: organisms ability to survive and pass on its genes SURVIVORS HAVE FAVORABLE TRAITS TO PASS TO OFFSPRING Long neck giraffes have baby long neck giraffes

POPULATIONS CHANGE OVER TIME 5. Adaption: The number of organisms with favorable traits increases Populations genetically change to become more suited to the environment The entire population of giraffes now ALL have long necks POPULATIONS CHANGE OVER TIME

Summary: Natural selection is not an active process: the environment “selects” the traits that are favorable and those that are not If the environment changes, so must the ...population **The environment decides which alleles are favored not the individual**

Evidence of Evolution 1) Fossil Record

Evidence of Evolution Comparative Anatomy Homologous Structures: same structure but different function

Evidence of Evolution Comparative Anatomy Analogous Structure: Same function but different underlying structures

Evidence of Evolution Comparative Anatomy Vestigial Structure - body part that is evolutionarily reduced or has no use

Evidence of Evolution Embryology

Evidence of Evolution Molecular Biology