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Darwin & Natural Darwin & Natural SelectionSelection
Darwin & Natural Darwin & Natural SelectionSelection
Evolution Unit NotesEvolution Unit Notes
Learning GoalsLearning 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 6 bodies of 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 6 bodies of evidences that
support the Theory of Evolution.
Theory of EvolutionTheory of EvolutionTheory of EvolutionTheory 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
Or… “Change of genetic information 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
Or… “Change of genetic information in a population over time.”
Charles DarwinCharles DarwinCharles DarwinCharles Darwin
Father of Evolution Proposed a mechanism for
evolution, natural selectionnatural 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 Proposed a mechanism for
evolution, natural selectionnatural 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, Wrote a book, ““On The On The Origin of the SpeciesOrigin of the Species””
Darwin’s FinchesDarwin’s Finches
Natural SelectionNatural SelectionNatural SelectionNatural Selection
Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others
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. Overproduction1. Overproduction1. Overproduction1. Overproduction
Each species produces more offspring that can survive
Each species produces more offspring that can survive
2. Variation2. Variation2. Variation2. Variation
Each individual has a unique combination of inherited traits. Adaptation:Adaptation: an inherited
trait that increases an organism’s chances of survival
Each individual has a unique combination of inherited traits. Adaptation: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?Why is Variation Important? Because the environment changes. The more variation variation withinwithin a species a species, the
more likely it will survivesurvive EX: If everyone is the same, they are all
vulnerable to the same environmental changes or diseases
The more variation of variation of types of types of speciesspecies in an habitat, the more likely at least some some will survivewill survive EX: Dinosaurs replaced by mammals
Because the environment changes. The more variation variation withinwithin a species a species, the
more likely it will survivesurvive EX: If everyone is the same, they are all
vulnerable to the same environmental changes or diseases
The more variation of variation of types of types of speciesspecies in an habitat, the more likely at least some some will survivewill survive EX: Dinosaurs replaced by mammals
Which community has a better Which community has a better chance of surviving a natural chance of surviving a natural disaster?disaster?
Which community has a better Which community has a better chance of surviving a natural chance of surviving a natural disaster?disaster?
Community ACommunity A Community BCommunity B
3. Competition3. Competition3. Competition3. Competition
Individuals COMPETE for limited resources: Food, water, space, mates
Natural selection occurs through “Survival of the fittestSurvival of the fittest” FitnessFitness: the ability to survive and
reproduce
Not all individuals survive to adulthood
Individuals COMPETE for limited resources: Food, water, space, mates
Natural selection occurs through “Survival of the fittestSurvival of the fittest” FitnessFitness: the ability to survive and
reproduce
Not all individuals survive to adulthood
4. Selection4. Selection4. Selection4. Selection The individuals with the best traits / best traits /
adaptations will survive and have the adaptations will survive and have the opportunity to pass on itopportunity to pass on it’’s traitss 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)
The individuals with the best traits / best traits / adaptations will survive and have the adaptations will survive and have the opportunity to pass on itopportunity to pass on it’’s traitss 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 good traits build up in a populationbuild up in a population over many generations and bad traits are bad traits are eliminated by the death of the eliminated by the death of the individualsindividuals.
Individuals with traits that are not well suited to their environment either die or leave few offspring.
Evolution occurs when good traits good traits build up in a populationbuild up in a population over many generations and bad traits are bad traits are eliminated by the death of the eliminated by the death of the individualsindividuals.
Peppered MothPeppered Moth
Which moth will the bird catch? Which moth will the bird catch?
A
B
Descent with Descent with ModificationModificationDescent with Descent with ModificationModification Descent with Modification Descent with Modification – each
living species has descended, with changes, from other species over time.
Common Descent Common Descent – all living organisms are related to one another
Descent with Modification Descent with Modification – each living species has descended, with changes, from other species over time.
Common Descent Common Descent – all living organisms are related to one another
Evidence for Evolution:Evidence for Evolution:
Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence Radiometric Dating
Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence Radiometric Dating
The Fossil RecordThe Fossil RecordThe Fossil RecordThe Fossil Record
FossilsFossils: a record of the history of life on Earth
FossilsFossils: a record of the history of life on Earth
Archaeopteryx Archaeopteryx
Missing link between reptiles and birds
Missing link between reptiles and birds
Homologous Body Homologous Body StructuresStructuresHomologous Body Homologous Body StructuresStructures Homologous Homologous
Body StructuresBody Structures: similar anatomy in different types of animals because of common ancestor
Homologous Homologous Body StructuresBody Structures: similar anatomy in different types of animals because of common ancestor
Vestigial OrgansVestigial OrgansVestigial OrgansVestigial Organs
Vestigial Organs: “leftover” traces of evolution that serve no purpose
Vestigial Organs: “leftover” traces of evolution that serve no purpose
EmbryologyEmbryologyEmbryologyEmbryology
EmbryologyEmbryology: embryos of all vertebrates are very similar early on
EmbryologyEmbryology: embryos of all vertebrates are very similar early on
Biochemical EvidenceBiochemical EvidenceBiochemical EvidenceBiochemical Evidence
BiochemistryBiochemistry: DNA with more similar sequences suggest species are more closely related EX: Humans and chimpanzees share
more than 98% of identical DNA sequences
BiochemistryBiochemistry: DNA with more similar sequences suggest species are more closely related EX: Humans and chimpanzees share
more than 98% of identical DNA sequences
Radiometric DatingRadiometric Dating
https://www.youtube.com/watch?v=udkQwW6aLik
Watch to 2:10
https://www.youtube.com/watch?v=-EYQPcGvx4c
https://www.youtube.com/watch?v=udkQwW6aLik
Watch to 2:10
https://www.youtube.com/watch?v=-EYQPcGvx4c
Learning GoalsLearning 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 6 bodies of 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 6 bodies of evidences that
support the Theory of Evolution.
Coral Snake (Poisonous)
Milk Snake (Not poisonous)
Stick Mantid
Flower Mantid