1. 15-3 Darwin Presents His Case

2. Variation and Artificial Selection
Variation – an appearance of an inherited trait that makes them different from others.
This led to understanding more about heredity and how parents pass traits to their off spring. This also led to the understanding of a process called artificial selection
Artificial selection is where nature provides the variation and humans select those variation that they found useful.
This process does aid in breeding animals and choosing certain crop seeds in farming.

5. Evolution by natural selection
Struggle for existence: members of each species compete regularly for food, living space and other necessities.
In this struggle those organisms that are faster, fitter or have a particular characteristically advantage, tend to catch more prey, survive and reproduce.
Fitness: the ability of an individual to survive and reproduce in its specific environment.
Adaptation: any inherited characteristic that increases an organisms chance in survival. Porcupines sharp quills. Plants and photosynthesis, animals that live and hunt in groups.

6. Survival of the fittest – Natural Selection
Individuals that are best suited to their environment, with adaptations and characteristics that enable fitness, will survive and reproduce most successfully.

7. Decent with modifications
Every living species has descended, with changes, from other species over time.
It also means that all living organisms are related to one another.
During long periods of time, natural selection produces organisms that have different structures, establish different niches, and as a result animals look different today than their ancestors
Darwin referred to this principle as Decent with modifications.

8. Homologous Body Structures
A. Homologous – structures that have different mature/adult forms but develop from the same clumps of cells in embryos. This shows that all 4 limbed vertebrates have descended, with modifications, from common ancestors. B. Example – forelimbs

9. The forelimbs look strikingly different and vary greatly in function, they are very similar in skeletal structure and they derive from the same structures in the embryo, same cluster of cells.

11. Analogous Structures C
Analogous Structures C. Analogous – features have similar appearance and function, but different embryological origin. D. Example – wings on birds and insects Same purpose = flight, but are different in structure and embryo development.

13. 2. Vestigial Structures
A. Structures that animals/humans still inherit but are useless and can be removed without harming the organism and it can still survive.
B. Examples: Tailbone, Appendix, Nictitating eye membrane, Tonsils, molars,

15. 3. Similarities in Embryology
A. Similarities in early embryonic stages of vertebrates are evidence that vertebrates share a common ancestry.
B. In no stage of development does a gorilla look like an adult fish. But in early stages all vertebrates are similar, fading as development continues.

16. Who’s who? Choices: human chicken tortoise dog

17. Did you get any correct?

18. 4. Similarities in Macromolecules A
4. Similarities in Macromolecules A. Darwin hypothesized that more-similar forms of organisms have a more recent common ancestor than do less-similar forms B. Amino acid sequence in human and gorilla hemoglobin differ by one amino acid 1. Human and frogs differ by 67 amino acids 5. Patterns of evolution A. Coevolution – change of two or more species in close association with each other 1. Predators and prey sometimes co--evolve. 2. Plants and animals can co-evolve.

19. Analogous structures are associated with convergent.
B. Convergent evolution – sometimes organisms that appear to be very similar, such as a shark and a porpoise( similar to a dolphin) are not closely related. This occurs when 2 organisms independently evolve similar traits as a result of having to adapt to similar environments.
Analogous structures are associated with convergent.

20. Shark, porpoise and dolphin all show convergent evolution

21. The wings of three vertebrates (pterodactyl, bird and bat) show convergent evolution. Their outer forms are similar, even though they are based on different bone arrangements and use different surface structures. (analogous structures)

22. 1. It’s a response to differing habitats and can result in new species
C. Divergent evolution – two or more related populations or species become more and more dissimilar
1. It’s a response to differing habitats and can result in new species

24. a. Adaptive radiation – Organisms diverged in response to what is available to them in their habitats. Finches on Galapagos islands

25. Summary of Darwin’s Theory
1. Organism differ and some of this variation is heritable.
2. Organisms produce more offspring then can survive and this causes organisms to compete for limited resources.
3. Each unique organism has different advantages and disadvantages in the struggle for existence. Individuals best suited to their environment survive and reproduce most successfully. These organisms likely pass their heritable traits to their offspring. Some will die or leave fewer offspring, this process of natural selection causes species to change over time.
4. Species alive today are descended with modification from ancestral species that lived in the distant past. This process, by which diverse organisms evolved from common ancestors, unites all organisms on Earth into a single tree of life.