Overview Insights to Darwin’s Theory Natural Selection & its principles 4 Means of Evolutionary Evidence
LETS REVIEW! Define Evolution Give me an example of a catastrophic event. How do fossils help scientists link species? What are examples of variations and adaptations?
Developing Darwin’s Natural Selection 20+ Years of Research & Investigation Studied Animals & Plants Examined the process of artificial selection in breeders. Humans change a species by breeding it for certain traits. Breed pigeons
Heritability In order for artificial/natural selection to occur a trait must be heritable. Heritability: ability of a trait to be passed down from one generation to the next. Examples in pigeons: Tail feathers, neck feathers, crop. Quick Question! What kind of traits are not passed down?
Struggle for Survival Idea Developed by Thomas Malthus Populations are limited in growth by the abundance of resources (food, water, shelter, etc.) Darwin expanded: Variation & adaptation resulted in “descent with modification” Supply Offspring Demand
Natural Selection Defined: A mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. Expand: Advantageous characteristics result in survival and reproduction. Analyze: How long could this process take?
On the Origin of Species… Darwin wrote a book depicting the four main principles of natural selection: Variation Overproduction Adaptation Descent with modification
Variation The basis for natural selection. Differences in individuals results from differences in genetic material. Inherited or mutations
Overproduction Increased offspring = Increased chance for some to survive Results in competition for resources
Adaptation Certain variations increase chances of survival over others in its environment.
Descent with Modification Over time, adaptations found beneficial to survival and reproduction become more abundant in the population. Leads to future generations having that trait. As long as environmental conditions remain, trait will remain beneficial.
Adaptations as Compromise Misconception: Natural selection means that individuals become perfection suited for their environment. Reality: Some structures never change but do change in their role. Panda bears wrist bone acts as a “thumb” Never physically changed the bones function, just its size.
Fast Brain Break Researchers recently found a new species of spider and named it “Darwin bark spider” This spider spins web 10 times stronger than Kevlar that are the width of some rivers. Scientists are still studying how it can possibly make webs this large.
Evidence of Evolution Darwin found multiple different forms of evidence: Fossils Geography Embryology Anatomy
Fossils Earlier scientists noticed changes in rock stratum had changes in the types of fossils. Later studies proved that the age of fossils was different in these layers. Supports descent with modification.
Geography Galapagos Island’s Migration Differing ecosystems on the islands leads to different traits in the same species. Finches All share same ancestor from mainland South America
Embryology Similar features in embryos in very different organisms suggests evolution from a distant common ancestor. Crab vs. Barnacle larvae
Anatomy Evidence based on comparing body parts of different species. Homologous structures: Features similar in structure but appear in different organisms and have different functions. Why would different groups of animals share similar structures? Similar structures does not prove close relationship. Some structures found in different species evolved from different ancestors.