Charles Darwin & The Theory of Evolution.

1) Consider This… “Individual organisms live, reproduce and die. Individuals, however, do not evolve; populations do. Evolution is the change in gene frequency that occurs in a population over time.” Audesirk, T. & Audesirk G. Biology – Life on Earth. 4th edition. © 1996 Population: all the individual members of a particular species living in a given area.

2) Charles Darwin 1831 At only 22 years old, this British nature lover went for a 5-year cruise onboard her majesty’s Beagle ship. He sailed around the world to look at stuff. The most famous stop being the Galapagos islands off the coast of South America.

Biodiversity VARIATION!

Beaks differ

Abundant babies!!!!! OVERPRODUCTION!

Blue feet? ADAPTATIONS ?

3) Darwin’s Notes Observation 1:Overproduction – Organisms make more offspring than can survive. Observation 2: Resources are Limited. Conclusion 1: Competition for survival and reproduction among species. Observation 3: Individuals Differ from one another within a species’ population. Conclusion 2: Fitness – the most well-adapted individuals from one generation will usually leave the most offspring.

4) Twenty Years Later Darwin finally publishes his book On the Origin of Species, sharing his theory of Evolution by Natural Selection (1859).

5) Darwinian Terms Natural Selection- Nature selects who stays!! This is what drives evolution. Evolution- change in population genotypes from one generation to the next. a.k.a. change over time.

Variation- Differences between individuals of the same species. Adaptation- A trait that helps an organism to survive & reproduce (born with it). Adaptations are favorable variations. Variation- Differences between individuals of the same species. Examples: color, shape, size, behavior, chemistry. Variations come from: Mutations. Meiosis Cross Over (challenge topic)

Populations will have a pool of genes. A gene pool is all the genes that occur in a population.

Evolution, part II Oh yea, PROVE IT!

Introduction: Recall that a scientific theory is testable; and explains many observations. A claim must have evidence. In other words, show sound reason, or be logical. So…Show me the proof that biological evolution accounts for the origin of species.

1) Fossils Fossils are the remains of past life dug up from the earth’s crust. Fossil formation is rare. Most fossils form in sedimentary rock. Examples of Fossils: Bones, teeth, molds, casts, impressions. Because the Earth’s crust is layered over time, younger fossils are found closer to the top.

1a) Fossil Record If you piece together all the millions of fossils that scientists have dug up and sequence them by time (age), you have the Fossil Record. How do you know a fossils age? Relative dating Top vs. Bottom layers. Radioactive dating Unstable element decay of nearby rocks.

2) Embryology Looking at the early development of one organism and comparing it to another allows scientists to make inferences about their evolutionary relationship. Embryo: Not yet born, developing multicellular organism. Inference: using clues to make a conclusion.

3) Homologous Structures Definition: similar structures that related species have inherited from a common ancestor. Example: dolphin’s flipper, bird’s wing, dog’s leg.

4) Biochemistry Results from DNA & protein analysis further support the theory of evolution by natural selection.

5) Class Discussion Which is more likely to form a fossil Jellyfish or crab? Why are there gaps in the fossil record? How do you interpret an evolutionary tree diagram?

6) Summary Evolution by means of natural selection explains the history of life on earth. This claim is supported by an abundance of evidence. Key Concepts are: Species share common ancestors. Descent with modification: (perpetual change) Nature chooses which species stay (extant) and which go (extinct).

7) High School Challenge Describe the role that geographic isolation can play in speciation. Speciation = new species formation. Research: Allopatric speciation Vicariant vs. founder effect. Sympatric speciation

Darwin’s Work 1. Variation: There is Variation in Every Population. 2. Competition: Organisms Compete for limited resources. 3. Offspring: Organisms produce more Offspring than can survive. 4. Genetics: Organisms pass Genetic traits on to their offspring. 5. Natural Selection: Those organisms with the Most Beneficial Traits are more likely to Survive and Reproduce.

The History of Evolutionary Thought Plato (Greek philosopher 427-347 B.C.E.)- Aristotle (Plato’s student 384-322 BCE)-

Evidence Proof Fossils Comparative Anatomy Comparative Embryology Vestigial Structures Comparative Biochemistry

High School Challenge Lamarck v. Darwin Hardy-Weinberg equation Who is Jean-Baptiste Lamarck & how did his take on evolution differ from Darwin’s? Hardy-Weinberg equation p2+2pq+q2=1; p+q=1