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ADAPTATIONS
•A heredity characteristic that helps an organism survive and reproduce in its environment
FITNESS
•Measure of ability to survive and produce more offspring relative to other members of a population
PRACTICE
Example: Duck A has 15 offspring whereas duck B has 6 offspring. Which bird has more fitness?
DARWIN’S EXPLANATION
•Darwin realized that animals have many offspring and some don’t survive
•The survivors are better suited to their environment
•He called this Natural Selection
STEPS OF NATURAL SELECTION
2. Genetic Variation Individuals vary within a population
New traits appear due to genetic mutations
STEPS OF NATURAL SELECTION
3. Struggle to SurviveOrganisms compete for resources (food, water, shelter, and mates)
Organisms have to get away from predators
STEPS OF NATURAL SELECTION
3. Struggle to Survive (continued)Some adaptations allow organisms to survive at a higher rate and individuals are “naturally selected” to survive and produce offspring
STEPS OF NATURAL SELECTION
4. Descent with ModificationOrganisms with the best adaptations will survive and reproduce passing these beneficial traits down to their offspring
IMPORTANT!
•Natural Selection acts on PHENOTYPES not genotypes
•As environments change, different traits will become beneficial
3. STRUGGLE TO SURVIVE
•There are lynxes in this environment that eat rabbits
•The rabbits that hop slowly are unable to get away from the lynxes