The Organization of Life

Section #2:Evolution

How do organisms become so well suited to their

environment?

• Charles Darwin (1859)• proposed his theory of evolution• observed that organisms in a

population vary slightly in form, function, & behavior from each other

• some of these differences are hereditary – passed from parent to offspring

Natural Selection

• the unequal survival and reproduction that results from the presence or absence of particular traits

• the environment exerts a strong influence over which individuals will survive and thus reproduce

• individuals with certain traits will have a better chance of surviving

Evolution of thicker fur in a population of deer:

Evolution

• Darwin proposed that over many generations, natural selection causes the characteristics of populations to change1. organisms produce more offspring than can

survive2. the environment is hostile and contains

limited resources3. organisms differ in the traits they have4. some inherited traits provide organisms with

an advantage5. each generation contains proportionately

more organisms with advantageous traits

Video Clip:Natural Selection

Adaptations

• an inherited trait that increases an organism’s chance of survival and reproduction in a certain environment

Video Clip:Adaptations

Coevolution

• the process of two species evolving together in response to long-term interactions with each other

Example:the lobelia flower has developed a structure to ensure that the Hawaiian honeycreeper bird gets pollen on its head when it sips the sweet nectar through its long curved beak

Artificial Artificial SelectionSelection

• the selective breeding by humans for specific characteristics

Resistance

• the ability of one or more organisms to tolerate a particular chemical designed to kill it

• Examples:– bacteria’s resistance to certain

antibiotics– insect’s resistance to pesticides– weed’s resistance to herbicides

Video Clip : Resistance