The Theory of Evolution

1. The Theory of Evolution

2. Old Theories of Evolution • Jean Baptiste Lamarck(early 1800’s) proposed: “The inheritance of acquired characteristics” • He proposed that by using or not using its body parts, an individual tends todevelopcertaincharacteristics, which itpasseson to itsoffspring.

3. “The Inheritance of Acquired Characteristics” • Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

5. Popular Belief (Before Darwin) • Species were created at the same time and remained unchanged • Features may be passed on to allow survival of a species

6. Darwin’s Theory of Evolution • Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. • A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

7. History of Darwin’s Studies • Darwin went on an around-the-world trip on the HMS Beagle and traveled to the Galapagos Islands. • He particularly liked and observed the finches. He also observed the tortoises on different islands. • He observed each different group had its own niche. • He studied 13 different species and saw how they adapted to their environment.

9. Diversity in Finches

11. The Galapagos Islands • The smallest, lowest islands were hot, dry, and nearly barren sparse vegetation. • The higher islands had greater rainfall and a different assortment of plants and animals had rich vegetation.

12. The Galapagos Island Tortoises • Giant tortoises varied in predictable ways from one island to another. • The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

14. Charles Darwin - The Author • Wrote in 1859: “On the Origin of Species by Means of Natural Selection”

15. Natural Selection • Natural Selection leads to organisms that are well suited in particular environments. • Individuals with favorable traits are more likely to leave more offspring better suited for their environment • It provides a scientific explanation for the history of life on Earth as depicted in the fossil record and similarities evident within the diversity of existing organisms. 1.32

16. 5 Main Points • There is variation with a population. • Some variations are favorable. • Not all young produced in each generation survive. • Individuals that survive and reproduce are those with favorable variations. • Descent with Modification Ostriches are the fasted birds on land due to favorable traits such as long, powerful legs. 1.31

17. Evolution by Natural Selection • The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities • Survival of the Fittest-Individuals that are best suited to an environment (adaptations that enable fitness) survive and reproduce most successfully.

18. Summary • Each organism is unique, each has advantages and disadvantages in the struggle for existence • Species alive today descended with modification from species that lived in the past • All organisms on earth are united into a single family tree of life by common descent