1. Interest Grabber When Is a Flipper a Wing?
Section 15-3
When Is a Flipper a Wing?
All living things are related. Some relationships are easy to see— your pet cat may not roar like a lion, but it clearly resembles one. Other relationships are less obvious.
Interest Grabber

2. Interest Grabber continued
1. On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect.
2. Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many?
3. Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer.
Interest Grabber continued

3. 15.3 – Darwin Presents His Case

4. Darwin’s Publication
After Darwin’s journeys he wrote and published a book called On the Origin of Species
In this book he proposed his thoughts on how evolution happened called natural selection

5. Objective: Summarize Darwin’s theory of evolution by natural selection
Influences on Darwin
Thomas Malthus—(Essay on the Principle of Population, 1798)
plants and animals produce more offspring than can survive.
human overpopulation would lead to decreasing living standards if left unchecked.
Charles Lyell ( )
Assumed natural forces in past same as today (erosion, sedimentation, etc.)
Uniformitarianism (idea originally proposed by James Hutton but popularized by Lyell)
"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work".Charles Darwin, from his autobiography. (1876)
"I am well aware that this doctrine of natural selection is open to the same objections which were at first urged against Sir Charles Lyell’s noble views on ‘the modern changes of the earth, as illustrative of geology;’ but we now very seldom hear the action, for instance, of the coast waves, called a trifling and insignificant cause, when applied to the excavation of gigantic valleys or the formation of the longest lines of inland cliffs. Natural selection can act only by the preservation and accumulation of infinitesimally small inherited modifications, each profitable to the preserved being; and as modern geology has almost banished such views as the excavation of a great valley by a single diluvial wave, so will natural selection, if it be a true principle, banish the belief of the continued creation of new organic beings, or of any great and sudden modification in their structure.” Charles Darwin, from the Origin of Species, 1859

6. Evolution by Natural Selection
Darwin proposed that as populations grew that there would be a struggle for existence
A key factor in the above would be survival of the fittest
Successful adaptions enable organisms to be better suited for environment
Those adaptations are then passed on to next generations
Those that are adapted best for their environment will have more offspring and those that are not will either die or have few offspring
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7. Note: It is species that evolve, not individuals.
Natural selection
Some members of a species have characteristics that enable them to survive, produce more offspring than others, and pass these characteristics on.
(Species—a group of similar organisms capable of reproducing with one another).
Fitness—the relative ability of an organism to survive and transmit its genes to the next generation.
Adaptation—a characteristic that increases the chances an organism will survive and reproduce in its environment.
3 Types:
Morphological/Structural
Behavioral
Biochemical
Note: It is species that evolve, not individuals.
Gene pool—the entire collection of genes among a population of organisms.
Population genetics—the study of gene pools and their changes.

8. Natural Selection
Observations
Populations tend to be constant
Naturally occurring variations—small differences between members of a species
Inferences
If more offspring are born, yet population is constant, then there is competition for food, water, light, etc.
Some variations are helpful and others aren’t. Natural selection eliminates those that aren’t.
Good variations are adaptations
If variations are selected, then organisms may change—given enough time this may result in a new species.

9. Causes of Variation Recombination of genes during mating.
Genotype—the genetic makeup of an individual.
Phenotype—the visible characteristics of an organism
“Crossing-over”
Mutation
What is crossing over?
Bivalent
Chiasma (site of crossing-over)
Centromere

10. Natural Variation vs Artificial Selection

11. Descent with Modification
Darwin proposed that over long periods of time organisms developed different structures to adapt to different environments
As a result species today look different from their ancestors
Common Descent
All species-living and extinct-were derived from same ancestors

14. The Fossil Record
Archaeopteryx

15. Lucy

16. Geographic Distribution of Living Species
Section 15-3
Beaver
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu

17. Observations/Experiments that Support Natural Selection
Intermediate fossil forms
Archaeopteryx indicates that birds probably evolved from reptiles.
Changing populations
Artificial selection (domestication)
Antibiotic resistant bacteria
Anol Lizards in the Bahamas, Etc.
Homologous structures—2 organisms w/parts that have similar organization that is functionally unnecessary (meaning the similarity is unnecessary but the trait in question may be, and usually is, functional).
Indicates a common ancestor
May or may not have similar function today
Whale fin & our forelimb

18. Homologous Structures
The forelimbs of vertebrates are homologous structures.
Homologous Structures

19. Vestigial structures—parts that are no longer useful.
Analogous structures (for contrast with homologous structures— analogous structures are not evidence for common descent)—2 organisms w/parts that have similar function, but different internal structure.
Did not come from a recent common ancestor
Whale vs. shark fin
Insect vs. bird wing
Vestigial structures—parts that are no longer useful.
Appendix—human
Snakes with nerves to their “legs”
Birds have genes that code for a reptilian mouth and tail.

20. 5 Main Assumptions of Darwin
Overpopulation—Tendency to have more offspring than can survive
Variations—within a species there are variations—hair, color, height, etc.
Inheritance of variations
Not all survive. Struggle for existence. Competition for resources.
Survival of the fittest, the best adapted.

21. Homologous Body Structures
Section 15-3
Turtle
Alligator
Bird
Mammals
Typical primitive fish

22. Vestigial Organs

23. Similarities In Early Development

24. Concept Map Evidence of Evolution includes The fossil record
Geographic distribution of living species
Homologous body structures
Similarities in early development
which is composed of
which indicates
which implies
which implies
Physical remains of organisms
Common ancestral species
Similar genes