Chapter 5 Changes Over Time Section 1 Darwin’s Voyage

What is Evolution? Evolution is a change in a species over time.

Ways through which evolution occurs: Mutations Adaptation Natural Selection

Mutations Inheritable changes because of a mutation in the DNA code May be helpful or harmful Helpful mutations improve the species’ ability to survive, harmful mutations may decrease or have no effect on the species’ ability to survive.

Adaptations Adaptations are traits that help an organism survive. Example: beak shape

Natural Selection The survival and reproduction of the individuals in a population that exhibit the traits that are best suited for their environment. AKA: “Survival of the Fittest” Concept originated with Charles Darwin

Factors that influence the process of Natural Selection Overproduction Competition Variations

Overproduction Producing more offspring than can survive Ex. Dandelions overproduce their seeds to assure that at least some seeds will survive

Competition Offspring must compete with each other to survive Usually indirectly, ex. Turtles may fail to find enough to eat

Variations There are small variations or differences among the members of the same species. Mutations increase the amount of variations. Make certain individuals better adapted to their environment because of the helpful traits they possess.

Over a long period of time, natural selection can lead to evolution Helpful variations gradually accumulate in a species, while unfavorable ones disappear.

Isolation Occurs when some members of a species are cut off from the rest of the species. A new species forms when individuals remain separated from the rest of the species long enough to evolve new traits. Geographic isolation has occurred in the past because of continental drift.

Continental Drift