Darwin & Natural Selection

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. 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  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 natural selection  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  Father of Evolution natural selection  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”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  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  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?

What adaptations do you see?

Why is Variation Important?  Because the environment changes. variation within a species survive  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 variation of types of species some will survive  The more variation of types of species in an habitat, the more likely at least some will survive  EX: Dinosaurs replaced by mammals  Because the environment changes. variation within a species survive  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 variation of types of species some will survive  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 Survival of the fittest  Natural selection occurs through “Survival of the fittest”  Fitness: the ability to survive and reproduce  Not all individuals survive to adulthood  Individuals COMPETE for limited resources:  Food, water, space, mates Survival of the fittest  Natural selection occurs through “Survival of the fittest”  Fitness: the ability to survive and reproduce  Not all individuals survive to adulthood

4. Selection best traits / adaptations will survive and have the opportunity to pass on it’s traits  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) best traits / adaptations will survive and have the opportunity to pass on it’s traits  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. good traits build up in a population bad traits are eliminated by the death of the individuals  Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.  Individuals with traits that are not well suited to their environment either die or leave few offspring. good traits build up in a population bad traits are eliminated by the death of the individuals  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  Which moth will the bird catch? A 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  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  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

EmbryologyEmbryology  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  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