Darwin & Natural Selection Unit 6: Evolution Chapter 15

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 genotoype? 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 Evolution occurs in four steps: Overproduction (overpopulation) Competition Variation Survival

1. Overproduction:Potential for a species to increase in number Each species produces more offspring that can survive

Overpopulation Negative: having a population so dense as to cause environmental deterioration, an impaired quality of life, or a population crash. Positive: still large enough population and genetic diversity (variation).

2. Variation: New genetic variation within a species Each individual has a unique combination of inherited traits. Adaptation: an inherited trait that increases an organism’s chances of survival

Inheritance - The process of genetic transmission of characteristics from parent or ancestor to offspring. Ex. Traits such as eye color, height, hair color, etc.

What adaptations do you see?

What adaptations do you see?

What causes members of the same species to be different from one another? GENETIC VARIATION!

Causes of Variation

Why is Variation Important? Because the environment changes. The more variation within a 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

Artificial Selection Nature provides the variations, humans select those they find useful “Selective Breeding” ex. Cow milk Plant and animal breeders

Speciation Speciation - Evolutionary process by which new biological species arise Species - Similar characteristics and can breed and produce fertile offspring Can occur as a result of natural or artificial selection

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

4. Survival: Proliferation of those organisms that are better able to survive and reproduce in the environment 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.

Fitness - the genetic contribution of an individual to the next generation's gene pool relative to the average for the population, usually measured by the number of offspring that survive to reproductive age.

Peppered Moth A Which moth will the bird catch? B

Stop Point – Natural Selection http://www.hhmi.org/biointeractive/making-fittest-natural-selection-and-adaptation

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

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 genotoype? Explain! 5. List the 5 evidences that support the Theory of Evolution.

Coral Snake (Poisonous) Milk Snake (Not poisonous)

Stick Mantid

Flower Mantid