15-3 Darwin Presents His Case

I. Inherited Variation & Artificial Selection

Desired traits are selected for human use. Artificial Selection- humans take advantage of the genetic variation that already exists in plants & animals. Desired traits are selected for human use. From a single ancestral plant breeders selected for different traits

II. Evolution Happens As A Result of Natural Selection

Evolution happens because organisms: Struggle for Existence- members of species (plants, animals, bacteria, etc.) compete for food, water, shelter, & mates These bears fight for food, mates, and territory

Adaptation- An inherited trait that helps an organism survive & reproduce.

Survival of the fittest- Fitness is the ability of an organism to survive in its environment that results from inherit traits (adaptations) Cheetahs that are the faster runners catch more food and survive to reproduce and pass their genes to the next generation

The traits are inherited which slowly changes a population over time Natural Selection- nature selects traits that are best suited for survival. The traits are inherited which slowly changes a population over time In this cartoon, darker colored birds are more successful at surviving and reproducing than lighter colored birds, and so they increase their proportion in the population in later generations.

Natural selection can’t be seen directly, it can only be observed as a population slowly changes over many generations.

Descent w/ Modification- All living species have descended from a common ancestor w/ changes (modification) over time Evolution of the Camel

III. Evidence For Evolution These bones that are similar in all of these animals is evidence that they have a common ancestor

Prehistoric “Ice Man” in Andes Mountains The fossil record- All of fossilized artifacts & how they are placed w/i the earth's rock layers or sedimentary rocks. provides information about the history of life on earth Strata of rock w/ fossils

Biogeography- the way species are spread around the world Darwin used this to explain how species evolved from common ancestors Lizards on different islands of the Galapagos

Homologous Structures- structures that have different mature forms but develop from the same embryonic tissues

Discuss w/ Partner: Discuss w/ partner: What do you have in common w/ the cat, whale, & bat.

Whales evolved from mammals that Vestigial Organ- organ that has no useful function in an organism. Left-overs of homologous organs in other species Whales evolved from mammals that lived on land

Ex: legs of skinks, a type of lizard Coccyx (tailbone) in humans

Similarities in Embryology- the study of structures that appear during the development of different organisms Tortoise Pig Lizard Human

What do these embryos have in common? Discuss w/ Partner: What do these embryos have in common?

Molecular Biology- the study of the molecular basis of genes and gene expression

Discuss w/ Partner: Which two organisms have the most amino acids in common? Which two organisms have the least amino acids in common?

Answers: Which two organisms have the most amino acids in common? Humans and the Rhesus monkey Which two organisms have the least amino acids in common? Humans and the lamprey

The genetic code is nearly universal in all organisms on earth All organisms use the same 20 amino acids to make proteins The Genetic Code is the 20 amino acids that makes proteins