Darwin Natural Selection http www wuhsd orgsitehandlersfiledownload ashx

Darwin & Natural Selection http: //www. wuhsd. org/site/handlers/filedownload. ashx? moduleinstanceid=3044&dataid=22517&File. Name=Darwin. Natural%20 Selection 11. ppt

Learning Goals 1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection, giving an example of each. 3. Explain the importance of "Variation". 4. Does Natural Selection act on an organism phenotype or genotype? Explain! 5. List the 5 evidences that support the Theory of Evolution.

Theory of Evolution ▪ Evolution: The process of change over time • Specifically, a change in the frequency of a gene or allele in a population over time

Charles Darwin ▪ Father of Evolution ▪ Proposed a mechanism for evolution, natural selection ▪ Darwin went on a 5 -year trip around the world on the ship, the HMS Beagle • As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands • Wrote a book, “Origin of the Species”

Darwin’s Finches

Natural Selection ▪ Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others

▪ Darwin’s Theory of Natural Selection occurs in four steps: • • Overproduction Variation Competition Selection

1. Overproduction ▪ Each species produces more offspring that can survive

2. Variation ▪ Each individual has a unique combination of inherited traits. ▪ Adaptation: an inherited trait that increases an organism’s chances of survival

What adaptations do you see? http: //www. eveboo. com/wp-content/uploads/2013/05/snow-wolf-wallpaper. jpg

What adaptations do you see? http: //i. imgur. com/HZTh 8 ZG. jpg

Why is Variation Important? ▪ Because the environment changes. ▪ The more variation within a species, species the more likely it will survive • EX: If everyone is the same, they are all vulnerable to the same environmental changes or diseases ▪ The more variation of types of species in an habitat, the more likely at least some will survive • EX: Dinosaurs replaced by mammals

3. Competition ▪ Individuals COMPETE for limited resources: • Food, water, space, mates ▪ Natural selection occurs through “Survival of the fittest” fittest ▪ Fitness: the ability to survive and reproduce ▪ Not all individuals survive to adulthood

4. Selection ▪ The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring. • Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup) • Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

▪ Individuals with traits that are not well suited to their environment either die or leave few offspring. ▪ Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals

Peppered Moth A ▪ Which moth will the bird catch? B

Descent with Modification ▪ Descent with Modification – each living species has descended, with changes, from other species over time. ▪ Common Descent – all living organisms are related to one another

Evidence for Evolution: ▪ ▪ ▪ Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence

The Fossil Record ▪ Fossils: a record of the history of life on Earth

Archaeopteryx ▪ Missing link between reptiles and birds

Homologous Body Structures ▪ Homologous Body Structures: similar anatomy in different types of animals because of common ancestor

Vestigial Organs • Vestigial Organs: “leftover” traces of evolution that serve no purpose

Embryology ▪ Embryology: embryos of all vertebrates are very similar early on

Biochemical Evidence ▪ Biochemistry: DNA with more similar sequences suggest species are more closely related • EX: Humans and chimpanzees share more than 98% of identical DNA sequences

Coral Snake (Poisonous) Milk Snake (Not poisonous)

Stick Mantid

Flower Mantid