1. The History of Evolution
Darwin
Lamarck
Cuvier

2. We’ll talk more about these later.
Evolution
Defined: the process of biological change by which descendants come to differ from their ancestors.
5 factors that lead to evolution:
Genetic drift
Gene flow
Mutations
Sexual selection
Natural Selection
We’ll talk more about these later.

3. Species lion tiger liger
Species: group of organisms that can interbreed and produce fertile offspring
Different species rarely breed
Interspecies (between different species) breeding often results in sterile offspring
Ex: Horse x Donkey = Mule
Ex: Lion x Tiger = Liger
tiger
liger

4. horse
donkey
mule

5. Jean Baptiste de Lamarck
Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth.
Cause: environmental changes forced individuals to change
Problem: Traits acquired after fertilization cannot be passed to offspring
Early Belief: Giraffes & Long Necks
Long necks are result of stretching to reach leaves
Extra length was passed on to offspring

6. Geologic Change Early belief: “New” Observations
Earth ~6,000 years old
Life remained unchanged
“New” Observations
Rock layers (strata) contained differing fossils
Deeper fossils (older) less complex
Environmental changes thought to affect life characteristics
past geologic events can be explained by phenomena and forces observable today; the classical concept that 'the present is the key to the past'

7. Charles Darwin Observed:
Organisms have variations based upon environment
Similarities between extinct fossils & modern life
Marine fossils atop mountains
Natural Selection: Process where organisms with favorable traits survive and reproduce
Major concept in biology published in The Origin of Species (1859)

8. Finches are another example.
Finches with strong, thick beaks live in areas with a lot of large, hard shell nuts.
Finches with delicate beaks live in areas where small insects and fruits are readily available.

9. Adaptation & Variation
Variation: Inherited traits that make an individual different from others
Green, flat wings of the insect above
Adaptation: Variation increases the chance of survival
Ability to blend with environment

10. Butterflies won't
lay eggs on plants
with fake egg spots

11. Can you find
the geckos?

12. Gross....bird poop...or is it???

13. Causes of Genetic Variation
Genetic variation increases chances some organisms survive in changing environments
Gene Pool: All alleles within a population
Two main causes of genetic variation:
1) Mutations: Random genetic changes may affect phenotypes
2) Recombination: During meiosis, genes recombine in varying patterns

14. Variation: 4 Different Gametes
Chromatids
copied
Crossing-
over
Crossing-
Over
finished
Genetic variation!
Four differing chromatids

15. Quick Review Features of a species can evolve, or change over time
Natural selection is when favorable traits allow survival & reproduction
Variations allow an organism to be better suited to its environment