4.3 Evolution and Adaptation

Evolution

• Long periods of time• Millions of years• Species change over time• Due to genetic mutation of traits• Mutations passed to offspring• New offspring make populations

Charles Darwin

• 1835• Traveled on the Beagle• Studied life forms at each port• Wrote Origin of Species

http://www.youtube.com/watch?v=vmphlbRhLu8

Finches• Darwin's finches are an

excellent example of the way in which species' gene pools have adapted in order for long term survival via their offspring.

• The Darwin's Finches diagram below illustrates the way the finch has adapted to take advantage of feeding in different ecological niche's.

http://www.youtube.com/watch?v=lDX4gIUv9kI

Mutation

• Genetic• DNA mistake• Leads to a new trait• Trait can be passed to offspring• Not always bad

Adaptation

• Good genetic mutation

• New trait• Inherited by

offspring• Helps it to survive

Katydid

• Mimicry of leaves by insects is an adaptation for evading predators.

creosote bush

• Desert-dwelling plant• Produces toxins that prevent other plants

from growing nearby, thus reducing competition for nutrients and water

Penguins

• Dense layer of tiny, waterproof feathers that protect them in the water.

http://www.youtube.com/watch?v=ciu9xFTvELQ

Natural Selection

• Nature• Selects the organisms with the best traits to

survive

• Organisms with bad traits will not have offspring and will die

• Bad traits eventually are removed from a population http://www.youtube.com/results?search_filter=1&search_categ

ory=27&search_query=natural+selection&search_duration=short&search_type=videos&suggested_categories=24%2C27%2C10%2C20%2C28&uni=3

Selective Breeding

• Plants for food• Animals for food, pets, or competition• Breeders of animals and plants in today's

world are looking to produce organisms that will possess desirable characteristics

• high crop yields, resistance to disease, high growth rate and best looking

http://www.youtube.com/watch?v=LyRA807djLc

Speciation

• Process when one species becomes 2• Species separates into 2 groups• 2 groups mutate over time• Genes get lost

Speciation

1. Allopatric2. Sympatric3. Parapatric

Allopatric•Speciation by geographic isolation•Something extrinsic to the organisms•Prevents two or more groups from mating with each other regularly•Great distance or a physical barrier, such as a desert or river

•Exhibit regional “varieties” •Genetically and in appearance•Live in different geographic locations

Northern Spotted Owl and the Mexican Spotted Owl

Sympatric Speciation

• Does not require large-scale geographic distance to reduce gene flow between parts of a population.

• Exploiting a new niche may automatically reduce gene flow with individuals exploiting the other niche.

• This may occasionally happen when, for example, herbivorous insects try out a new host plant

grass species Anthoxanthum odoratum

• Some of these plants live near mines where the soil has become contaminated with heavy metals.

• The plants around the mines have experienced natural selection for genotypes that are tolerant of heavy metals.

• Meanwhile, neighboring plants that don’t live in polluted soil have not undergone selection for this trait.

• The two types of plants are close enough that tolerant and non-tolerant individuals could potentially fertilize each other—so they seem to meet the first requirement of parapatric speciation, that of a continuous population.

• However, the two types of plants have evolved different flowering times. This change could be the first step in cutting off gene flow entirely between the two groups.

Parapatric speciation

• Barrier to gene flow• The population does not mate randomly• Individuals are more likely to mate with their

geographic neighbors

apple maggot flies• For example, 200 years ago, the ancestors of apple maggot flies laid their eggs only on

hawthorns—but today, these flies lay eggs on hawthorns and domestic apples • Females generally choose to lay their eggs on the type of fruit they grew up in, and

males tend to look for mates on the type of fruit they grew up in. • So hawthorn flies generally end up mating with other hawthorn flies and apple flies

generally end up mating with other apple flies. • This means that gene flow between parts of the population that mate on different types

of fruit is reduced. • This host shift from hawthorns to apples may be the first step toward sympatric

speciation—in fewer than 200 years, some genetic differences between these two groups of flies have evolved.

Interbreed

• Speciation• Species separated for thousands of years will

not be able to interbreed if reacquainted