EvolutionEvolution

I. Variation and AdaptationA. Species are interbreeding populations of

organisms which produce viable offspring.

B. Niche

1. 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

1. 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. Variation is the differences among members of a population.

B. Increased variation in a population increases a populations chance of survival

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

Artificial SelectionArtificial Selection

Artificial selection occurs Artificial selection occurs when humans select the best when humans select the best traits for plants and animalstraits for plants and animals Examples:Examples:

Disease-resistant cropsDisease-resistant crops Beefy cattleBeefy cattle Cows that produce more milkCows that produce more milk

AdaptationsAdaptations

Types of AdaptationsTypes of Adaptations

Mimicry – Organisms that copy the Mimicry – Organisms that copy the appearance of another species for protectionappearance of another species for protection

Types of AdaptationsTypes of Adaptations

Camouflage – When an organism blends in to its Camouflage – When an organism blends in to its surroundingssurroundings

Variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.

EvolutionEvolution

Evolution means a change over time Evolution means a change over time or descent with modificationor descent with modification

It occurs in It occurs in populationspopulations, not , not individuals in response to individuals in response to environmental pressuresenvironmental pressures

Natural selection is the Natural selection is the mechanismmechanism of evolution (the way it happens)of evolution (the way it happens)

Natural SelectionNatural Selection

Natural selection happens becauseNatural selection happens because::

1. Overproduction1. Overproduction – organisms produce – organisms produce more offspring than can survivemore offspring than can survive

Fun Facts: A fern plant may produce 50 million spores each year. Fun Facts: A fern plant may produce 50 million spores each year. If they all survived, in the second year they would nearly If they all survived, in the second year they would nearly cover North America. An oyster may shed 114,000,000 eggs cover North America. An oyster may shed 114,000,000 eggs in a single spawning season. If they all survived, the ocean in a single spawning season. If they all survived, the ocean

would be literally filled with oysters.would be literally filled with oysters.

Natural SelectionNatural Selection

2. Variation2. Variation – Within a – Within a population there are many population there are many differences between differences between organisms. These organisms. These differences are inherited.differences are inherited. Examples:Examples:

Color in flowersColor in flowers Length of antlers in elkLength of antlers in elk Height in humansHeight in humans Shape of beak in birdsShape of beak in birds

Natural SelectionNatural Selection

3. Struggle for existence3. Struggle for existence – There – There are limited resources, so living are limited resources, so living things must compete against each things must compete against each other to stay aliveother to stay alive

4. Survival of the fittest4. Survival of the fittest – Only the – Only the organisms best adapted to the organisms best adapted to the environment will liveenvironment will live

Natural SelectionNatural Selection 5. Populations evolve5. Populations evolve – Over time, the favorable – Over time, the favorable

adaptations are passed on and the entire population adaptations are passed on and the entire population changes changes