Darwin & Natural Darwin & Natural SelectionSelection
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 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
Charles 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
•Wrote a book, “Wrote a book, “Origin of the SpeciesOrigin of the Species””
Darwin’s Finches
Natural SelectionNatural 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 parts: Overproduction Variation Selection Adaptation
1. Overproduction1. Overproduction Each species produces more
offspring than can survive
2. Variation2. Variation Each individual has a
unique combination of inherited traits.
These natural differences are called variations
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
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. Selection3. Selection Individuals COMPETE for limited resources:
Food, water, space, mates Natural selection occurs through “Survival Survival
of the fittestof the fittest” FitnessFitness: the ability to survive and reproduce-the
advantageous trait will be passed to the next generations
Not all individuals survive to adulthood
4. Adaptation4. Adaptation
The individuals with the best traits / best traits / adaptations will survive and have the adaptations will survive and have the opportunity to pass on it’s traitsopportunity to pass on it’s traits to offspring.
Adaptation:Adaptation: an inherited trait that increases an organism’s chances of survival
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.
What adaptations do you see?
What adaptations do you see?
Peppered Moth Which moth will the bird catch?
A
B
Evidence for Evolution: Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence
The Fossil RecordThe Fossil Record FossilsFossils: a record of the history of life
on Earth
Archaeopteryx Missing link between
reptiles and birds
Homologous Homologous (Common) (Common) Body Body StructuresStructures Homologous Homologous
Body StructuresBody Structures: similar anatomy in different types of animals because of common ancestor
Vestigial OrgansVestigial Organs Vestigial Organs: “leftover” traces of
evolution that serve no purpose
EmbryologyEmbryology EmbryologyEmbryology: embryos of all
vertebrates are very similar early on
Biochemical 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
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