Evolution and Speciation Chapters 15 & 16 Evolution and Speciation
Let’s talk “evolution” first The theory of evolution (decent with modification) by natural selection What’s is a theory?
Misconceptions…
- Acknowledgment that life on Earth has changed - The First Hurdles - Acknowledgment that life on Earth has changed - Dominant religious beliefs stated that life was created at the same time as Earth. Newly discovered species were not at odds with this. The discovery of evidence of extinct species was a problem for this belief system. There was also an issue with time. Common religious belief, taking cues from religious texts, was that the world was in the neighborhood of 4000 years old.
All species have always existed… The First Hurdles… All species have always existed… Jean Baptist Lamarck Use and disuse Inheritance of acquired characters
All species have always existed… The First Hurdles… All species have always existed… Explained changes in life without requiring species to have gone extinct
Jean Baptist Lamark The mechanism for decent with modification (Evolution) is… Inheritance of Acquired Characteristics
Charles Darwin 1809-1882 HMS Beagle 1831 1859 – “On the Origin of Species”
the mechanism for decent with modification (Evolution) Natural Selection is … the mechanism for decent with modification (Evolution)
Misconceptions… Scientist don’t debate “if” they debate “how”
Misconceptions…
Misconceptions…
Natural Selection can only work on traits/structures already present. It is not perfect.
4 Parts of Natural Selection 1. Overproduction 2. Genetic Variation 3. Struggle to Survive 4. Differential Reproduction
1. Overproduction
2. Genetic Variation
3. Struggle to Survive
4. Differential Reproduction
Populations Adapt – Individuals Can’t (They acclimatize) Fitness = ability to make a hereditary contribution to the next generation Populations Adapt – Individuals Can’t (They acclimatize)
Evidence
Fossils
Fossil Record Strata & Superposition Relative Age vs. Absolute Age
Fossil Record Per the theory - You would expect older rock to contain mostly organisms that are less complex and less like current (living) organisms
Transitional Species in the Fossil Record
Transitional Species
Biogeography The study of the location of living organisms (and fossil remains)
Biogeography
Anatomical
Vestigial Structures
Convergent Evolution
Analogous Structures Similar purpose – different origin
Divergent Evolution Adaptive Radiation
Homologous Structures
Adaptive Radiation
Coevolution
Molecular
DNA & The Genetic Code
Embyrological
Embryonic Development
Explaining things… (some examples of natural selection at work)
Artificial Selection
Sexual Selection
Relaxed Selection – Backward Evolution?
Altruism
Chapter 16 – Seeing Evolution
Q: How do we see evolution? A: In populations Natural Selection acts on populations by changing the composition of the gene pool.
Gene Pool
Population Genetics Bell Curve – Ding! You’re most likely…just average!
Hardy-Weinberg Equilibrium No evolution if: 1. No net mutation occurs 2. Individuals do not leave or enter population. 3. The population is large 4. Individuals mate randomly 5. Selection does not occur
Non-random Mating Sexual Selection
Gene Flow Mutation Immigration (In) Emigration (Exit)
Genetic Drift – small population problems or founder effect
Types of Selection
Directional Selection
Directional Selection
Stabilizing Selection
Stabilizing Selection
Disruptive Selection
Disruptive Selection
Types of Selection
What is a species? Morphology Biological Species Concept
Speciation Involves Isolation (Reproductive or Geographic) Then adaptation
(Adaptation) (Isolation)
Isolation
Reproductive Isolation Prezygotic Postzygotic
Reproductive Isolation Prezygotic or Postzygotic? Hybrids… Horse = 64 Donkey = 62 Mule = 63 Liger and Tiglon
Reproductive Isolation
Reproductive Isolation
Allopatric Speciation “different homelands” Geographic Isolation
Sympatric Speciation “same homeland” Reproductive Isolation
Gradualism vs. Punctuated Equilibrium
Gradualism vs. Punctuated Equilibrium
Extinction
Phylogenetic Tree