Evolution by Natural Selection

Scientific Theory An explanation of natural phenomenon supported by a large body of scientific evidence obtained from many different investigations and observations.

Evolution A gradual change in a species (populations) through adaptations over time. Adaptation = some phenotypic feature or trait that improves an organism’s likelihood of survival and reproduction. In Georgia, there is a popular hunting area of forest called the Poopycack forest, where the Poopy Deer lives. This species of deer has 6 ears. How might this adaptation have occurred and how is it beneficial? What would you expect to happen to the Poopy Deer population in the next 1000 years?

Charles Darwin “Theory of Evolution by Natural Selection” Proposed that new species could develop through a process called Natural Selection During his travels aboard HMS Beagle, made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time

Darwin’s Voyage Darwin studied animal species in the Galapagos Islands and found they each had unique adaptations

Darwin’s Studies Galapagos finches demonstrate different adaptations to eat different kinds of foods Galapagos tortoises are the biggest in the world

Natural Selection Acts on Phenotype rather than Genotype Those better suited for their environment will survive Those least suited to their environment will die faster, leaving fewer offspring

Genetic variation is essential! Mutations _________ promote genetic variation, which helps ensure a species survival Like crossing over!

How does a great number of species ensure that at least some organisms survive major changes in the environment? Those who are better at adapting will survive major changes in the environment

Natural Selection A mechanism for change in a population Natural Selection (NS) is responsible for most evolutionary change by selectively changing genetic variation through differentiated survival and reproduction. Goal - To be fit enough to survive and reproduce Three types of NS

Stabilizing Selection Favors average individuals in a population Those individuals have a “selective advantage”. Reduces variation in a population

Directional Selection Favors one of the extreme variations of a trait Can lead to rapid evolution of a population

Disruptive Selection Favors both extreme variations of a trait Leads to evolution of two new species

Speciation A process of producing two individual species from one Members of the population no longer interbreed within their natural environment

Evidence for Evolution: 1. Fossil record A piece of organism or imprint left behind. Fossils show that species have changed over time. 2. Vestigial structures Body structures that have shrunken and are not used anymore. 3. Homologous structures Structures that share a common ancestry and look/behave similarly. 4. Embryology 5. DNA homology, Amino Acid homology, Mitochondrial DNA, Photosynthetic Plant cells

Evidence For Evolution Fossils Provide a record of early life and evolutionary history

Geologic Strata (sedimentary layers) and Carbon Dating Defining age of fossils! Geologic Strata (sedimentary layers) and Carbon Dating Carbon-14 (remember isotopes?) Used to date any object composed of carbon Radioactive carbon decays over time check amount of C14 left in sample, enabling you to tell age of object

Did you know that whales have feet? Well, sort of….

Fossils help us determine whale evolution 60 million years ago 50 million years ago 40 million years ago Yesterday

Vestigial Structures Human tail-bone, wisdom teeth, appendix (they have no purpose) Snake feet, Whale feet

Homologous Structures (derived from a common ancestral feature) Limb adapted to function means the same!

Analogous Structures-similar in function but not structure

Evidence For Evolution Embryology Similarities among the young embryos suggest evolution from a distant, common ancestor Biochemistry Comparing DNA and RNA

How do we know what happened when? Radiometric dating relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly Stratiography provides a sequence of events from which relative dates can be extrapolated Molecular Clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates.

DNA/Amino Acid Homology (Means the same!) DNA/Amino Acid Homology Human 5’A-T-C-T-T-A-C-G-A-A-T-C-A-T-G-C-C-C-T-A-A-C-T-T-C-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ Whale 5’A-C-C-T-T-A-C-C-A-A-T-C-A-T-T-C-C-C-T-A-A-C-T-T-A-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ Frog 5’A-C-C-A-T-G-C-G-T-G-T-C-A-T-C-C-C-C-G-A-G-C-T-T-C-G-G-T-A-T-T-A-C-G-C-A-A-G-C-3’ Gorilla 5’A-T-C-T-T-A-C-G-A-A-T-C-A-T-G-C-C-C-T-A-A-C-A-T-C-G-G-C-A-T-T-A-C-G-C-T-A-G-C-3’ Can you create a cladogram from the information above?

http://www.youtube.com/watch?v=faRlFsYmkeY