Speciation Chapter 15

Vocabulary Ch 15 Adaptive radiation Vestigial Structure Homologous structure Gene pool Mimicry Camouflage Natural Selection 8. Stabilizing Selection 9. Disruptive Selection 10. Directional Selection 11. Artificial Selection 12. Polyploid 13. Punctuated Equilibrium 14. Allelic Frequency 15. Genetic drift

The two populations no longer interbreed since the two populations can’t get together. They evolve different traits due to natural selection.

Reproductive Isolation Two populations cease interbreeding due to behavior changes or differences in genes. Different mating seasons. Genes become so different that an embryo fails to form.

Reproductive Isolation Happens between two polyploids, except for wheat, cotton, apples, and bananas. Two species will not breed anymore because their genes are too different.

Genetic Drift A change in allele frequency in a population.

Stabilizing Selection Average trait species are favored to survive Trait types (beak type) Population

Average-size spiders survive predators Birds catch the big spiders Average-size spiders survive predators Birds catch the big spiders. Small spiders die from competition.

Directional Selection Species with extreme traits are favored to survive. Woodpecker with long beak gets the worm in the tree, those with short beaks die off.

Directional Selection One extreme of the trait is favored to survive in a population Due to environment and predator pressure.

Long beaked birds get food from a deep lake, while short beaked birds can’t reach the bottom of the lake and perish.

Disruptive Selection Two Extreme traits (either short or long) favored for survival over the average trait Light and Dark limpets (type of snail) survive because they can camouflage themselves on light and dark rocks.

limpets

Geotaxis Preference of flies to fly up straight, or down to get to food.

Founder Effect

Sexual Selection Peacocks have long feathers to show peafowl they can produce healthy offspring. Longest feathered males will be chosen to mate. Short feathered males will die off.

Adaptive Radiation A common ancestor develops into different species. Different species fill different niches. Galapagos finches change beak size depending on food types. Different types of honeycreeper birds in Hawaii

Divergent Evolution Species that once were similar to an ancestral species diverge and become distinct in appearance

Divergent Evolution Hummingbird species beaks have shown an increase in size, depending on the flowers they get nectar from. Larger beak hummingbirds no longer mate with short beak birds

Convergent Evolution Different organisms living in different places on earth, but in similar environments, evolve similar traits due to similar natural selection pressures. They fill similar niches but are different species

Pika and groundhog

Similar Plant on different continents Organ Pipe Cactus and the Euphorbia African Cactus

Sharp Teeth/ Predators Shark in oceans & tiger in Asia

Browsers, Long Ears Deer from North America and kangaroos from Australia

Scavengers Coyote & Golden Eagle

Speciation

Sympatric speciation Evolves into new species without barriers to reproduce

Allopatric speciation A barrier separates two populations and they don’t interbreed.

Gradualism Hypothesis that species gradually evolve over time.

Punctuated Equilibrium Hypothesis that species change when a disaster strikes, like Dinosaur Extinction at the Mesozoic Era.