Evolution
I. Variation and Adaptation A. A. Species are interbreeding populations of organisms which produce viable offspring.
B. Niche An organisms niche is the place it survives and the role the organism plays in the environment. 2. Niches include all the environmental factors to which populations are adapted (living and non- living)
C. Adaptation If the niche changes, then the organism must move, change (adapt) or die 2. Adaptation is an inherited trait which increases a organisms chance of survival and reproduction.
D. Variation A. A. Variation is the differences among members of a population. B. B. Increased variation in a population increases a populations chance of survival C. C. Inherited variation is a change in genome cause by mutation or the recombining of the genetic code.
E. Sources of Genetic Variation 1. Mutation- change in the sequence of DNA May change an organisms phenotype Random change 2. Sexual Reproduction- Gene Shuffling - Chromosome segregation and crossing-over
Examples In the desert, animals are brown and white and generally blend in with the sand. What would happen to a population of bright red bugs? In the snow, animals tend to be white and light colors. What would happen to a red fox? In the heat of the desert, could a polar bear survive?
Artificial Selection Artificial selection occurs when humans select the best traits for plants and animals Artificial selection occurs when humans select the best traits for plants and animals Examples: Examples: Disease-resistant crops Disease-resistant crops Beefy cattle Beefy cattle Cows that produce more milk Cows that produce more milk
Adaptations
Types of Adaptations Mimicry – Organisms that copy the appearance of another species for protection Mimicry – Organisms that copy the appearance of another species for protection
Types of Adaptations Camouflage – When an organism blends in to its surroundings Camouflage – When an organism blends in to its surroundings
Variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.
Evolution Evolution means a change over time or descent with modification Evolution means a change over time or descent with modification It occurs in populations, not individuals in response to environmental pressures It occurs in populations, not individuals in response to environmental pressures Natural selection is the mechanism of evolution (the way it happens) Natural selection is the mechanism of evolution (the way it happens)
Natural Selection Natural selection happens because: Natural selection happens because: 1. Overproduction – organisms produce more offspring than can survive Fun Facts: A fern plant may produce 50 million spores each year. If they all survived, in the second year they would nearly cover North America. An oyster may shed 114,000,000 eggs in a single spawning season. If they all survived, the ocean would be literally filled with oysters.
Natural Selection 2. Variation – Within a population there are many differences between organisms. These differences are inherited. 2. Variation – Within a population there are many differences between organisms. These differences are inherited. Examples: Examples: Color in flowers Color in flowers Length of antlers in elk Length of antlers in elk Height in humans Height in humans Shape of beak in birds Shape of beak in birds
Natural Selection 3. Struggle for existence – There are limited resources, so living things must compete against each other to stay alive 3. Struggle for existence – There are limited resources, so living things must compete against each other to stay alive 4. Survival of the fittest – Only the organisms best adapted to the environment will live 4. Survival of the fittest – Only the organisms best adapted to the environment will live
Natural Selection 5. Populations evolve – Over time, the favorable adaptations are passed on and the entire population changes 5. Populations evolve – Over time, the favorable adaptations are passed on and the entire population changes