Understanding Evolution: The Theory of Natural Selection, Slides of Biology

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Evolution – How Change Occurs

Some things to keep in mind BEFORE we study

evolution... the nature of SCIENCE.

• What is SCIENCE?
  • A process that seeks to find natural explanations for observations of the natural world
  • Science cannot comment on anything that is outside the realm of the physical/natural. - Philosophy - Ethics / morality - Religion
  • Nor do philosophy, etc. operate in the terms of science. Religion, philosophy, etc. are valuable tools designed to help people answer MANY important (perhaps THE MOST important) questions, but NOT scientific questions. - Questions like - why is the sky blue , - how do bacteria cause disease, - How do cells become cancerous? - How can we kill cancer cells?... are answerable by science…

questions like: “What’s the meaning of life?” are NOT. Docsity.com

What are the rules of science?

• Rule 1:
  • We rely on observations of the natural world to explain phenomena we see.

What are the of rules of science?

• Rule 2: Science is TESTABLE
  • Scientific questions must be TESTABLE and that means the you can make observations either through experimentation or some other means to test whether a hypothesis is wrong.
  • Ideas of religion, morality, philosophy CANNOT be “tested” with experiments or observations and are not meant to be.
  • For example, The whole point of religion is that it is based on faith, NOT whether a hypothesis was “accepted” or “rejected” based on “evidence”.

Other Things to Keep in Mind before

we study Evolution...

Theory vs. Hypothesis

• It’s called the THEORY of Evolution – what

does this mean??

• THEORY vs. HYPOTHESIS

What’s a hypothesis?

• A possible explanation for an observation

• It’s NOT been tested a lot
• It’s NOT been supported by a lot of evidence.
• Often in everyday usage, people say “I have a

theory about…” when what they really mean is

“hypothesis”.

So, what exactly IS evolution?

• Evolution = the kinds of organisms on Earth have

changed over time

• This is observable. It is not hypothesis or theory, but fact.
• Best evidence is fossil record , which we will talk about later…
• Natural Selection is the theory part…
• This is the WAY (mechanism) by which evolution occurs
• Fact: Fossil record shows that over time life on Earth has changed
• Theory: Natural selection explains how life on Earth has changed.

Note that neither evolution nor

natural selection is a…

• Guess
• Opinion
• Hypothesis
• The vast majority of scientists agree that the evidence points to

natural selection as the mechanism that causes evolution to happen.

• This is well supported by lots of research, over long periods of time, by lots of people ---- that is, it’s a THEORY.
• In science a theory is a BIG DEAL
  • Other theories:
    • Cell theory
    • Newton’s theory of gravitation
    • Copernicus – Earth moves around the sun

Ideas before Darwin

• Lamarck
  • Said organisms evolved by passing on traits acquired during their lifetime
  • Wrong
  • Example :
    • Said giraffes stretched their necks to reach leaves
    • Passed on their stretched necks to their offspring - “Inheritance of Acquired Characteristics”

Who is Charles Darwin?

• British
• Born 1809
• Tried many careers
  • Minister
  • Doctor
• Became ship’s naturalist

aboard the HMS Beagle

• 1831-
• Focus of ship was to map coast of S. America and collect specimens of life forms there

Voyage of the HMS Beagle

• Stopped in Galapagos Islands
  • 500 miles off coast of Ecuador

Galapagos Islands

Ph o to - JPE G d e co m p re s s o rQ u ickTi m e ™ a n d a a re n e e d e d to s e e th i s p ictu re.

Finch? Sparrow?

Woodpecker? Warbler?

Darwin found… birds

Collected many

different birds on the

Galapagos Islands.

Sparrow?

Woodpecker? Warbler?

Thought he had found

many, very different

kinds of birds…

Finch?

But what he found was many different

kinds of finches

Darwin was amazed

to find out:

All 13 species of birds

were finches…

Sparrow?

But there is only one

species of finch on

the mainland!

Warbler Finch

Small Ground Finch

Large Ground Finch

Did one species of finches become many different species? If so, how?

Woodpecker Finch Docsity.com