Evolution Chapter 16

Misconception Evolution is “just a theory” Scientific theories are explanations that are based on supporting evidence, valid predictions, and have been tested over and over! The “everyday” definition of a theory can be confusing! Like the Cell Theory (another scientific theory), it can be changed, modified or disproved if scientific evidence supports that action!

Scientific Theory Well-tested explanation that makes sense of a great variety of scientific observations Examples: Theory of Evolution. Cell Theory

Objectives Describe what evolution explains. Identify key observations from Darwin's voyage that led to his theory of Natural Selection. Summarize ideas from other Scientists that influenced Darwin’s work. Describe the two main points of Darwin's theory of Evolution.

Previous Ideas about Organisms/Earth (that were wrong) Life, Species, & Earth is unchanging! Earth itself is less than 10,000 years old

What is Evolution? Evolution = The process of changing/transforming life over time. Explains: how species have changed. how new species replace extinct ones. Claims that all organisms originated from a common ancestor. Isn't Evolution Just a Theory? - YouTube What is Evolution? - YouTube

What do you think you will be doing when you are 22???

Charles Darwin & the HMS Beagle 22 yr old scientist Set sail for 5 yrs on the HMS Beagle Studied Nature on Galapagos Islands Darwin collected a lot of data: Plant & animal specimens (birds, bugs, etc.) Took meticulous notes about what he observed

Darwin’s Notes from the Galapagos Islands (off coast of S. America) Organisms varied around the world Organisms vary locally The Tortoises on each island of the Galapagos had a different type of shell The Finches on each island of the Galapagos had differently (uniquely) shaped beaks Organisms vary over time (fossil evidence) Example – Glyptodonts

Glyptodont (extinct) & Armadillos

Scientists that Influenced Charles Darwin Georges Buffon (French Naturalist, 1750) Earth is much older than we thought! Found that fossils are similar to living species! Charles Lyell (Geologist) Said Earth changes through geological processes such as: Canyon / River Mountain /Earthquake

Thomas Malthus (1838) Alfred Wallace (British Naturalist, 1858) Stated that populations grow faster than the environment can support them. Therefore, it is almost impossible for all offspring survive! Leads to a “struggle for existence” Alfred Wallace (British Naturalist, 1858) Came up with the same conclusions as Darwin!! But didn’t get credit 

Lamarck (French Naturalist, 1800) Stated that life changes over time (he was correct) Came up with the wrong mechanism for evolution Life changes/evolves by adaptations (correct) Inheritance of Acquired Characteristics (wrong) Adaptation (def.) – inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment EXAMPLES??

Lamarck’s Mistake Came up with WRONG mechanism for evolution (acquired characteristics) Did not account for genetics! Acquired characteristics is NOT how a species changes over time!

Adaptations Before we can understand Darwin’s Theory of Evolution through NATURAL SELECTION…we must first understand adaptations. Explain what features these organisms have and how it helps them…

Darwin’s Two Main Points in his book: On the Origin of Species 1. Descent with modification Process by which descendants of organisms spread into various habitats and accumulate adaptations to diverse ways of life Example: Snowshoe Hare and Jackrabbit

Darwin’s Two Main Points in his book: On the Origin of Species 2. Natural Selection is the mechanism for evolution Process by which individuals with inherited characteristics well-suited to the environment leave more offspring than others What is Natural Selection? - YouTube

Natural Selection

Misconception Evolution involves organisms “trying” to adapt and Natural Selection gives organisms what they need to survive. There is no “trying” involved in evolution!!! Organisms have no control over their traits or adaptations. Natural selection does not have intentions, and can not sense what organisms need to survive. It does not “grant” adaptations.

Natural Selection In nature, populations (of organisms) contain many individuals with variations (genetic mutations) which make them slightly different from each other. All those individuals deal with the struggle for existance (getting enough food, water, shelter, etc.) to stay alive. Survival of the Fittest – individuals with the helpful adaptations will live longer than others and be able to reproduce. Those beneficial adaptations will be passed on to offspring & future generations!

Evolution: How does Evolution Actually Work? (Natural Selection!) Evolution: Videos for Students: Evolving Ideas

Do you REALLY understand Natural Selection??? You will write a paragraph explaining why giraffes have long necks today….Using Darwin’s theory of natural selection correctly!! Use the diagram to help you if necessary!

Evolution Has Left Much Evidence

Fossil Evidence Fossil – any preserved remains left by organisms that lived in the past As ground “strata” go deeper, older fossils are found. This shows how life’s organisms change in form over time.

Homologous Structures (Def.) Similar structure found in more than one species that share a common ancestor

Vestigial Structures (Def.) Remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species. Shows that species with these structures must have all come from a common ancestor and simply changed over time! “Remodeling Process” Example: Hind legs on Whales

Evolution Primer #3: How Do We Know Evolution Happens? - YouTube

Similarities in Development Embryos of related species have similar stages of embryo development Ex. Throat pouches Supports that all vertebrates evolved from a common ancestor.

Molecular Biology Organisms that are more closely related have more similar DNA base pair sequences. Supports idea that similar sequences (genes) are come from a common ancestor.

Geographic Distribution Certain species evolved from ancestors that lived in a specific place, which is why related species are found mainly in those specific regions today! Ex. Australia & Marsupials