Evolution Chapter 16. Misconception Evolution is “just a theory” Scientific theories are explanations that are based on supporting evidence, valid predictions,

EvolutionEvolution

Chapter 16Chapter 16

MisconceptionEvolution 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 TheoryScientific Theory

Well-tested explanation that makes Well-tested explanation that makes sense of a great variety of sense of a great variety of scientific observationsscientific observations

Examples:Examples:– Theory of Evolution. Theory of Evolution.

– Cell TheoryCell Theory

ObjectivesObjectives

Describe what evolution explains.Describe what evolution explains. Identify key observations from Darwin's Identify key observations from Darwin's

voyage that led to his theory of Natural voyage that led to his theory of Natural Selection. Selection.

Summarize ideas from other Scientists that Summarize ideas from other Scientists that influenced Darwininfluenced Darwin’’s work. s work.

Describe the two main points of Darwin's Describe the two main points of Darwin's theory of Evolution. theory of Evolution.

Previous Ideas about Previous Ideas about Organisms/Earth (that were wrong)Organisms/Earth (that were wrong)

Life, Species, & Earth is Life, Species, & Earth is unchanging!unchanging!

Earth itself is less than 10,000 Earth itself is less than 10,000 years old years old

What is Evolution?What is Evolution?

Evolution = The process of Evolution = The process of changing/transforming life over time.changing/transforming life over time.

Explains: Explains: –how species have changed. how species have changed. –how new species replace extinct ones.how new species replace extinct ones.

Claims that all organisms originated Claims that all organisms originated from a common ancestor.from a common ancestor.

What is Evolution? - YouTube Isn't Evolution Just a Theory? - YouTube

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

• 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

1. Organisms varied around the world

2. Organisms vary locally

1. The Tortoises on each island of the

Galapagos had a different type of shell

2. The Finches on each island of the

Galapagos had differently (uniquely)

shaped beaks

3. Organisms vary over time (fossil

evidence)

1. Example – Glyptodonts

Scientists that Influenced Charles DarwinScientists that Influenced Charles Darwin

Georges BuffonGeorges Buffon (French Naturalist, 1750)(French Naturalist, 1750)– Earth is much older than we thought!Earth is much older than we thought!– Found that fossils are similar to living Found that fossils are similar to living

species! species!

Charles LyellCharles Lyell (Geologist)• Said Earth changes

through geological processes such as:

• Canyon / River• Mountain /Earthquake

Thomas MalthusThomas Malthus (1838) (1838) Stated that populations grow Stated that populations grow fasterfaster than the than the

environment can support them. environment can support them. Therefore, it is almost impossible for all Therefore, it is almost impossible for all

offspring survive!offspring survive! Leads to a Leads to a ““struggle for existencestruggle for existence””

Alfred WallaceAlfred Wallace (British Naturalist, 1858)

•Came up with the same conclusions as Darwin!! But didn’t get credit

Lamarck Lamarck (French Naturalist, 1800)(French Naturalist, 1800)– Stated that life changes over time Stated that life changes over time (he (he

was correct)was correct)– Came up with the wrong mechanism for Came up with the wrong mechanism for

evolutionevolution Life changes/evolves by Life changes/evolves by adaptations adaptations (correct) Inheritance of Inheritance of Acquired CharacteristicsAcquired Characteristics

(wrong)

Adaptation (def.)Adaptation (def.) – inherited characteristic that – inherited characteristic that improves an organism's ability to survive and improves an organism's ability to survive and reproduce in a particular environmentreproduce in a particular environment

EXAMPLES??EXAMPLES??

LamarckLamarck’’s Mistakes Mistake Came up with Came up with WRONGWRONG mechanism mechanism

for evolution (acquired for evolution (acquired characteristics)characteristics)

Did not account for genetics!Did not account for genetics! Acquired characteristics is NOT Acquired characteristics is NOT

how a species changes over time!how a species changes over time!

AdaptationsAdaptationsBefore we can understand DarwinBefore we can understand Darwin’’s Theory of Evolution through NATURAL s Theory of Evolution through NATURAL

SELECTION…we must first understand adaptations.SELECTION…we must first understand adaptations.

Explain what features these organisms have and how it helps them…

DarwinDarwin’’s Two Main Points in s Two Main Points in his book:his book:

On the Origin of SpeciesOn the Origin of Species1. Descent with modification1. 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

2. 2. Natural SelectionNatural Selection is the mechanism is the mechanism for evolutionfor evolution

Process by which individuals with inherited characteristics well-suited to the environment leave more offspring than others

DarwinDarwin’’s Two Main Points in s Two Main Points in his book:his book:

On the Origin of SpeciesOn the Origin of Species

What is Natural Selection? - YouTube

Natural SelectionNatural Selection

MisconceptionMisconceptionEvolution involves organisms Evolution involves organisms ““tryingtrying”” to adapt and Natural Selection gives to adapt and Natural Selection gives organisms what they organisms what they needneed to survive. to survive.

There is no There is no ““tryingtrying”” involved in evolution!!! involved in evolution!!! Organisms have no Organisms have no control over their traits control over their traits or adaptations. or adaptations. Natural selection does Natural selection does not have intentions, and not have intentions, and can not sense what can not sense what organisms need to organisms need to survive. It does not survive. It does not ““grantgrant”” adaptations. adaptations.

Natural Selection1.In nature, populations (of organisms) contain many individuals with variations (genetic mutations) which make them slightly different from each other.

2.All those individuals deal with the struggle for existance (getting enough food, water, shelter, etc.) to stay alive.

3.Survival of the Fittest – individuals with the helpful adaptations will live longer than others and be able to reproduce.

4.Those beneficial adaptations will be passed on to offspring & future generations!

Evolution: How does Evolution: How does Evolution Actually Work? Evolution Actually Work?

(Natural Selection!)(Natural Selection!)

Evolution: Videos for Students: Evolution: Videos for Students: Evolving IdeasEvolving Ideas

Do you Do you REALLYREALLY understand Natural understand Natural Selection???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 Evolution

Evolution Has Left Much Evidence

Fossil EvidenceFossil 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 Homologous Structures

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

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

Similarities in Development

Embryos of related Embryos of related species have similar species have similar stages of embryo stages of embryo developmentdevelopment

Ex. Throat pouchesEx. Throat pouches

Supports that all Supports that all vertebrates evolved vertebrates evolved from a common from a common ancestor.ancestor.

Molecular BiologyMolecular 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 DistributionGeographic 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