1. Chapter 15 – Evolution: Theory & Evidence

2. Theories of Evolution Jean Baptiste Lamarck
Proposed that similar species descended from a common ancestor
Acquired Traits – Hypothesized that organisms “picked up” traits during their lifetime

3. I really want some leaves!
Lamarck’s theory
At first, there are only short-necked giraffes. They try harder to reach the leaves.

4. So their necks get longer because they use them more.
I really want some leaves!
Lamarck’s theory
So their necks get longer because they use them more.

5. Lamarck’s theory

6. Lamarck’s theory

7. And then their babies have long necks, too!
Lamarck’s theory
And then their babies have long necks, too!

8. Darwin’s theory
At first, there are some long-necked giraffes and some short-necked giraffes. Only the long necked can reach the leaves.

9. The short-necked giraffes are more likely to die of hunger.
Darwin’s theory
The short-necked giraffes are more likely to die of hunger.

10. Darwin’s theory
The long necked giraffes have babies that will also have long necks when they grow up.

11. Write/Pair/Share What is another possible reason for giraffe necks to have evolved for length? Write at least 2 lines!

12. Natural Selection
Charles Darwin & Alfred Wallace both suggested the theory of natural selection
Natural Selection – organisms best suited for the environment reproduce more successfully than others
The favorable trait increases in a population
Making a population the smallest unit able to evolve

13. Charles Darwin H.M.S. Beagle
Read books by Charles Lyell (geologist) placing an emphasis on uniformitarianism
Darwin observed various habitats and considered that these changes of earth played a part in the adaptation of organisms

14. Darwin’s Data Traveled all over the world Galapagos Islands
Collected species of all types of animals
Compared animals from each destination
Galapagos Islands
Collected beetles and finches
13 species of finches
Observed tortoises

15. Darwin’s Finches
Based theories on the 13 species of finches collected in the Galapagos
Hypothesized that the finches all evolved from a common ancestor (originating in South America)
The environments of each island produced different challenges
The finches would have to overcome these different environments to survive.

17. Darwin’s Theories Descent with Modification
Newer forms in the fossil record are modified descendants of older species
Reproduction allows species to change over time
Proposed that ALL organisms descended from a few ancestors with changes

18. Natural Selection HOW descent with modification occurs
Influenced by Thomas Malthus
Populations can double and redouble
Human population is limited by adverse conditions
Theorized that the environment was the limiting factor for populations
Some organisms have traits that make them better fit to respond to certain environmental pressures
Organisms better fit reproduce more and pass on the favorable traits
Individuals in a population would respond to environmental changes differently because they are not identical
A population adapts BECAUSE the favorable trait from a few individuals is passed down

19. REMEMBER Natural selection is not an ACTIVE process
Meaning that you can’t MAKE yourself change
Traits (ALLELES) MUST be present in a population for evolution to occur
Variation exists among individuals in a species.
Individuals of species will compete for resources
Some competition would lead to the death of some individuals while others would survive
Individuals that had advantageous variations are more likely to survive and reproduce.

20. Evidence of Evolution The Fossil Record What is a fossil?
A fossil is the remnants of an organism
Found in sedimentary rock
Types of fossils:
Mold – imprint in rock in the shape of the organism
Cast – a rock-like model of the organism

21. Distribution of Fossils
Nicholas Steno – Law of Superposition
Successive layers of rock or soil were deposited on top of one another
Lowest strata (stratum) is the oldest
Observing these strata allows them to determine the relative age of a fossil and the absolute age

22. Studying Fossils
The fossil record tells us that organisms appeared for awhile and then died off
Mass Extinctions
Evidence in fossils shows us that there are periods where large numbers of species disappeared
Caused by environmental changes

23. Transitional Species
Organisms that have features that are intermediate between hypothesized ancestors and current species.
Hypothesis that whales descended from land mammals based on a sequence of transitional forms.

24. Don’t believe me???
Whale Evolution

25. This is what Darwin did with the finches, turtles and beetles!!!
Biogeography
Scientists study the distribution of fossils and living relatives to help determine how organisms have changed
Similarities between fossils and living organisms allows us to make connections with our ancestors
This is what Darwin did with the finches, turtles and beetles!!!

26. Comparative Anatomy & Physiology
Examining the structure & function of organisms
Homologous Structures
Same structure but has a different function
Evolved from a common ancestor

27. Analogous Structure Same function but different structure
Evolved from a different ancestor but faced similar pressures

28. Vestigial Structures
Organ or structure that was useful to an ancestor but now has no use to the current organism
Examples
Appendix in humans
Pelvic and limb bones in snakes
Leg bones in whales

29. Macromolecules Genetic Evidence Embryology
Examination of major macromolecules in organisms (specifically proteins)
Genetic Evidence
DNA and RNA - Similarities in these molecules are evidence that organisms evolve from common ancestors
Embryology
Early stages of development are strikingly similar in organisms
The more closely the development, the more closely they are related

30. Fish, salamander, tortoise, chick, hog, calf, rabbit and human

31. Evolution in Action
Interactions between species and environmental pressures continue to drive evolution

32. Types of Evolution
Co evolution – Change of two or more species in close association with each other
Predators and prey, parasites and hosts
Flowers and pollinators

33. Darwin’s Orchid
Darwin’s Moth

34. Convergent Evolution– unrelated species evolve due to similar environmental pressures
Shark and porpoise, bird and bee

35. Divergent Evolution – two or more related species evolve from a common ancestor
Species DIVERGE (separate)
Adaptive radiation – many species evolve from a common ancestor
Artificial selection – divergence is sped up by choosing the parents of offspring (found in dogs)

36. Parallel Evolution
Similar to convergent but this happens in SAME environment
When two different species in the same type of environment develop the same adaptations for survival, it is considered parallel evolution