Chapter 7, Section 1: Darwin’s Theory

Charles Darwin A naturalist Studied plants and animals Traveled on a ship called the Beagle in the southern hemisphere Best known for his studies on the Galapagos Islands

More on Darwin He was amazed by the diversity of wildlife (diversity means how many different kinds of living things there were) Species = a group of similar organisms that can mate with each other and produce fertile offspring He studied fossils, the preserved remains of animals from the past

Darwin’s Findings Organisms on the Galapagos islands were similar to those in South America But there were also differences (i.e. smaller claws on the mainland iguanas; larger claws on the island ones) He hypothesized that both species were related, but each had an adaptation, or special trait that helped it survive in its environment TABLE TALK: How would larger claws help island iguanas?

As he traveled, he also noticed that the different species of finches had different beaks, depending on what they ate.

Table Talk: Summarize Darwin’s work in the Galapagos Islands.

Evolution The gradual change in a species over time Darwin came up with the theory of evolution – He believed in natural selection: only the strongest survive to reproduce See DiscoveryEducation videos, “Charles Darwin’s Journey to the Galapagos Islands” (1:47) and “Natural Selection: Examples from the Galapagos” (3:26)

How Do the Strongest Survive? Variation Overproduction Competition Environmental conditions The differences among individuals of the same species Many offspring Some organisms make it; some don’t (ex.: too many eating the same food) Ex.: the best soil, cleanest water, choice nesting sites end See Brain Pops: Darwin/Natural Selection