EVOLUTION Darwin’s Observations

What did Darwin observe? Darwin saw huge amounts of biodiversity. He collected fossils, which are the remains of once-living organisms. – Fossils prove that there are lots of living things that have gone extinct. – This shows that life has changed over time. Scientists estimate that 99.9% of the species that have ever existed have already gone extinct

What did Darwin observe? He saw that each organism was uniquely suited to the life it lead Adaptations are combinations of physical characteristics and behaviors that enable an organism to survive in its environment They are the traits of survival – from the cellular level to the behavioral level

Fitness and Adaptations Darwin used the term fitness to describe the ability of an organism to survive and reproduce An organism’s evolutionary fitness is its success in passing genes to the next generation. It is not just about survival, but also passing on your genes

Fitness and Adaptations The more offspring an organism has, the more fit it is An adaptation is any genetically controlled trait that increases an individual’s ability to pass along of copies its genes. Adaptations increase fitness.

The Galapagos Islands Darwin learned the most from the Beagle’s visit to the Galapagos Islands, a group of islands off the coast of South America The islands are small, but very different from each other – even have drastically different climates Unique animal and plant life are found there

The Galapagos Islands

Species of the Galapagos

Peculiar Creatures Tortoises vary in a predictable way from island to island – shells are distinct Each island had unique bird life that looked similar but were actually different species – Darwin’s finches DarwinFinch.html DarwinFinch.html

What did Darwin observe? Darwin saw that plants and animals reproduce much faster than humans There had to be something limiting the animal and plant populations This meant that the majority of offspring of each species die, and only a few that survive succeed in reproducing

What is the solution? Darwin theorized that in nature, organisms struggle for survival. Only the fittest organisms can survive and reproduce (survival of the fittest) This is called natural selection – only the organisms with the best adaptations (best suited to their environment) will pass on their genes.