1. Darwin Presents His Case (Ch 16.3)
Unit 4

2. Evolution by Natural Selection
The Origin of Species by Charles Darwin
Darwin took his own ideas combined with Malthus and Lamarck to produce a theory regarding evolution
Struggle for Existence
Malthus → the more individuals that are produced than can survive will need to compete for food, living space, and other limited necessities of life
Variation and Adaptation
Variations play a vital role in the ability for organisms to survive
Adaptation: any heritable characteristic that increases an organism’s ability to survive and reproduce in its environment
Structural Adaptation: changing the appearance to survive
Physiological adaptation: internal systemic responses
Behavioral adaptation: acting a certain way to survive

3. Types of Adaptation
Camouflage
Mimicry
` Behavioral

4. Evolution by Natural Selection
Survival of the Fittest
Lamarck → connection between the way an organism makes a living and the environment in which it lives
Fitness: describes how well an organism can survive and and reproduce in its environment
Highly adapted to environment and reproduces = high fitness
Low adaptations and little to no offspring = low fitness
Survival of the Fittest: the differences in rates of survival and reproduction
Survival = reproducing and passing on adaptations to offspring

5. Natural Selection
Natural Selection: organisms with variations most suited to their ecological environment survive and leave more offspring (environment influences fitness)
Natural Selections Occurs When:
More individuals are born than can survive (struggle for existence)
There is natural heritable variation (adaptation)
There is variable fitness among individuals (survival of the fittest)
Generation to generation, populations will continue to change until they become adapted to their environment
Natural selection does not make “perfect” organisms; it just makes organisms that can survive and reproduce in their living environment → If the environment changes, the species needs to adapt or runs the risk of becoming extinct

6. Natural Selection v. Artificial Selection
Artificial Selection (selective breeding)
Intentional reproduction of individuals that have desired traits
Breeding certain organisms to get the desired traits
Only certain individuals will produce offspring
Natural Selection
Organisms variations are best suited to their ENVIRONMENT
Organisms will adapt to their environment and the adaptive changes will be passed from parent to offspring
Only certain individuals will produce offspring

7. Common Descent
Parent + Parent = Offspring 1 → Offspring 1 + Offspring 1 = Offspring 2 → and so on…
Well adapted species will survive and reproduce in order to survive over time
Descent with Modification: species descend from a common ancestor but modify over time are modified in order to continue to survive through the generations
Lyell and Hutton → Deep time gave enough time for natural selection to act on the species
Darwin used the fossil record to prove descent with modification
Darwin created one of the first cladograms showing how species evolved from a common ancestor
Principle of Common Descent: all species -- living and extinct -- are descended from ancient common ancestors