Natural Selection and Adaptations

Charles Darwin Born February 12, 1809 A “naturalist” by profession. Spent 5 years studying plants and animals from around the world on board the HMS Beagle.

Charles Darwin Some of his most important observations came from his studies on the Galapagos Islands.

Charles Darwin Darwin noticed: Many of the animals on the islands were similar but not identical to animals on the mainland. He found giant tortoises on the Galapagos islands, and nowhere else. Darwin thought maybe the animals in the Galapagos came from South America originally and then evolved.

Mainland South America Galapagos Islands Cormorants (sea birds) can fly. Cormorants are unable to fly. Iguanas have smaller claws for climbing. Iguanas have larger claws to grip rocks.

Charles Darwin He reasoned that each population had changed slightly to fit its unique environment on the islands.

Charles Darwin Darwin was especially interested in the variety of finches that he found on the different islands of the Galapagos.

Charles Darwin When the finches came to the islands from the mainland, they were all the same species. Because the populations were separated on the different islands, over many generations they began to look slightly different.

Charles Darwin The finches became more suited to their different habitats.

Charles Darwin Remember, selective breeding is ON PURPOSE breeding of plants or animals to get offspring with desired characteristics. This does NOT lead to a new species.

Charles Darwin Dogs last shared a common ancestor with wolves around 32,000 years ago. If wolves can evolve into a little Pekingese in less than 32,000 years, imagine what millions of years of evolution can do!

Natural Selection Darwin’s explanation of evolution is called the theory of natural selection. Natural selection states that organisms which are better suited to their environment tend to survive and produce more offspring, who are more likely to share those desirable traits.

Natural Selection Because there is variation within every species, some individuals will have traits that better allow them to survive and reproduce than others.

Natural Selection New traits (variations) arise in a species because of genetic mutations. Variation is necessary for evolution to occur.

Darwin’s Theory of Natural Selection

Natural Selection Animals produce more offspring than are able to survive to reproduce (because resources are limited). Nature “selects” the most fit organisms to survive and reproduce, so Darwin called his theory natural selection.

Four key steps in Darwin’s theory of natural selection: Overproduction Variation Inherited Variation Natural Selection

1. Overproduction Overproduction – Organisms produce more offspring than can be supported by the food, water, and shelter in an environment. Many will die due to predation, competition, and starvation.

2. Variation Offspring of a species vary in traits such as color and size.

3. Inherited Variation Traits are passed from parent to offspring. Sources of variation include mutations and sexual reproduction. Both adapations and undesirable traits can be passed from parent to offspring.

4. Natural Selection Natural Selection – Individuals with adaptations will have more offspring, and thus pass on these favorable traits, than individuals without those features.

Adaptations Adaptations are the desirable traits in a species that make it more likely to survive and reproduce. Not all traits are adaptations

Adaptations Adaptations are the final product of the long process of natural selection.

Adaptations Structural adaptations-characteristics of the physical body that help an organism survive and reproduce.

Adaptations Camouflage-coloring that blends with the environment and makes an organism difficult to see.

Adaptations Mimicry- when one species (the mimic) looks like another species (the model) in order to deceive a third species.

Adaptations Batesian mimicry is when the model organism is venomous or dangerous, but the mimic is not. Mullerian mimicry is when the model and the mimic are both venomous or dangerous.

Batesian Mimicry- King snake mimics the venomous coral snake Adaptations Batesian Mimicry- King snake mimics the venomous coral snake Coral Snake-Venomous King Snake-Harmless

Adaptations Mullerian Mimicry- Cuckoo bee mimics the Yellow Jacket wasp (both can sting) Cuckoo Bee Yellow Jacket

Adaptations The mimic octopus of Indonesia: http://www.youtube.com/watch?v=H8oQBYw6xxc&feature= related Batesian or Mullerian Mimicry?

Adaptations Behavioral adaptations- actions or behaviors that help an organism survive and reproduce

Adaptations Hibernation: when an animal or plant spends a period of time, usually the winter, in a state of dormancy (when growth, development, and physical activity are temporarily stopped)

Adaptations Migration-the seasonal movement of animals from one region to another.

1. Which of the following is necessary for evolution to occur? Selective Breeding Genetic Variation Populations on isolated islands None of the above

2. What is evolution? Adaptations to particular environments. Genetic change in a population over time. Natural selection Differences in traits.

3. Which of the following is not an example of an adaptation? Inbreeding Camouflage Mimicry Behavior