Natural Selection and Evolution

Darwin’s Journey Around the Globe

A little bit about Darwin Naturalist on the ship the Beagle. Developed the theory of evolution based on observation, fossils, and specimens he collected. His most famous observations were from the Galapagos islands.

Other fun facts Avid Fan of Backgammon. Darwin ate a lot of animals Giant Tortoise Rhea Puma Owl – Which gave him horrible food poisoning Afraid of Blood. Probably why he stopped trying to be a doctor. Overall considered a slacker in school and college

Darwin’s Observations

Darwin’s Influences Hutton Earth had to be more than a few thousand years old Malthus Populations grow faster than the food supply Lamarck Use or disuse of traits; passed on to offspring Lyell Explained that geologic features could be built up or torn down. Wallace Produced similar ideas to Darwin; caused him to publish

Observations + Influences = Natural Selection Natural Selection: reproductive success over the long run - the genes that are passed on are best suited for the environment.

Ingredients of Natural Selection What must exist for Natural Selection to happen Individuals within species vary Some of these differences are genetic More offspring are produced than can survive The organisms that survive are the ones with the variations best suited for the environment Natural Selection almost always happens WITHIN species.

Variation among species This graph shows that the Penguins are all different sizes, 18 lbs is the most common. Yet The range is lbs. Man, I could totally take a coolness break to chow down on some of those 9 lb. penguins. A Narwhal can dream, man.

This is Genetic Variation!

Same Species and Variation

What is the major source of genetic variation??? Sex! Recombination Crossover Mutations

EXCESS REPRODUCTION (# of offspring [eggs or seeds] per reproductive season) Starlings4 – 6 Bull frog6,000 – 20,000 Trout200 – 6,000 Eastern OysterUp to 1,000,000 RagweedUp to 3,000 Lamb’s Quarters90 – 50,000

After 3 months Brood size # of broods # of young #% BROOD SIZE AND SURVIVAL IN STARLINGS

Questions Survival of the Fittest? Is it always the strongest that survives?

Coho Salmon!

Fittest Fittest ≠ Strongest Fittest = Most Children to survive to breeding age.

Darwin’s Theory of Natural Selection Species change over time. Natural selection causes changes in characteristics, as a result, new species form and others disappear. “Descent with modification”: species alive today descended with modification from past species. *** Only groups of organisms can evolve (populations or species); individuals NEVER evolve