Charles Darwin

1. Charles Darwin

2. Was Darwin the First? • Darwin was not the first to present the concept of evolution • Word first appeared in 1647 • Ancient Greeks inferred that species had descended from a common ancestor • Darwin referred to evolution as “descent with modification” • Explained it as the differential survival of organisms following their naturally occurring genetic variation • Natural Selection

3. Early Influences on Darwin • Charles Lyell – geologist • Proposed that plant and animal species had arisen, developed variations over time and then became extinct • Also believed that earth’s physical landscape had changed over time • Thomas Malthus – proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another • Applied theory to humans, Darwin applied to all animal species

4. Galapagos Islands • Darwin’s trip on the Beagle stopped in the Galapagos • Contained endemic species, not found anywhere else on earth • The species there looked similar to mainland species • But somehow specialized to their particular environment • proposed that changes were dependent on the environment

5. Sequence • 1st: Adaptations  traits occur within organisms and allow them to be more successful in the environment • Darwin reasoned that the importance of these adaptations was to insure the survival of reproduction of the species • Successful adaptations help organisms to both survive and reproduce, so these adaptations are passed on to future generations • Natural Selection is the mechanism that explains how changes occur within a population with favorable variations for that particular environment surviving, reproducing and passing these variations on to the next generation • (environments are constantly changing)

6. Sequence • 2nd Speciation – organisms on the Galapagos Islands had become geographically separated from one another • Produced reproductive isolation so that there is no interbreeding between organisms of same species • separates the gene pools of the populations • Darwin theorized that within a populations of species, adaptations would arise because of reproductive isolation and would develop adaptations specific to their particular environment over time • Eventually this would lead to new species evolving on the different islands • Which is what was observed

7. Reproductive Isolation • All begins when a group becomes reproductively isolated from the rest • May be geographic, temporal or behavioral • It is most obvious in distant islands, such as the Galapagos or Hawaiian island • Mountains, rivers, lakes and other natural barriers can also geographically separate populations that once belonged to the same species

8. Types of Reproductive Isolations • Temporal isolation occurs when there is a time difference between two species • Such as one species of flower opening up for pollination in the morning and another at night • Behavorial isolation occurs when the behavior of one species does not match another • One mating song for one bird is not recognized by another • Geographic isolation is the most common method of separating two populations of a species • Depends on the animal involved as to what is needed to separate it

9. Finches • Classic example of speciation is the 13 species of finches on the Galapagos Islands • Each species, descended with modifications, from an ancestral species • Today, the different species of finches on the island have distinct habitats, diets and behaviors depending on the current climate conditions • Which determines what food is available to the birds

11. Darwin’s Book • The Origin of Species – Presents Darwin’s theory (1859) • Has undergone modification and expansion and is now supported by studies in genetics and molecular biology