Darwin & Natural Selection Unit 3: Evolution

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. Any change in the heritable traits Specifically, a change in the frequency of a gene or allele in a population over time https://www.youtube.com/watch?v=Cs1uud8HiCQ https://www.youtube.com/watch?v=GhHOjC4oxh8

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”

Voyage of the Beagle

Voyage of Beagle Dates: February 12th, 1831 Captain: Charles Darwin Ship: H.M.S. Beagle Destination: Voyage around the world. Findings: evidence to propose a revolutionary hypothesis about how life changes over time

Patterns of Diversity Darwin visited Argentina and Australia which had similar grassland ecosystems. those grasslands were inhabited by very different animals. neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.

Patterns of Diversity Darwin posed challenging questions. Why were there no rabbits in Australia, despite the presence of habitats that seemed perfect for them? Why were there no kangaroos in England?

Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, called fossils. Some of those fossils resembled organisms that were still alive today.

Living Organisms and Fossils   Others looked completely unlike any creature he had ever seen. As Darwin studied fossils, new questions arose. Why had so many of these species disappeared? How were they related to living species?

Fossils

The Galapagos Island The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation.

The Galapagos Island Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos. Giant tortoises varied in predictable ways from one island to another. The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

Animals found in the Galapagos Land Tortoises Darwin Finches Blue-Footed Booby Marine Iguanas

Animals

The Journey Home Darwin Observed that characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor

Lamarck

Lamarck’s Theory of Evolution He came up with the theory of Inheritance of Acquired Traits in 1809 His theory was that if an organism continually used a structure to carry out a certain task, the structure used would become physically modified over time to make the task easier. This modified structure would then be passed on to any offspring.

Lamarck’s Theory of Evolution Lamarck also believed that when body parts were not being used, such as the human appendix, they gradually disappear. Eventually, people will be born without these parts. Lamarck believed that evolution happens according to a prearranged plan and that the results have already been decided.

Darwin’s Finches

Natural Selection Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others “Survival of the fittest”

Natural 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

What adaptations do you see?

What adaptations do you see?

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

Which community has a better chance of surviving a natural disaster? Community A Community B

3. Competition 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. 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

Evidence for Evolution Vestigial organs-organs that serve no useful function in an organism i.e.) appendix, hip bones in whales

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