natural selection

Natural SelectionNatural Selection

Darwin’s Big IdeaDarwin’s Big Idea

Charles Darwin (born February 12, 1809) was a British scientist. He

sailed around the world as a naturalist,

recording what he saw. He made important observations and

connections that no scientist had figured out

before. You will read more about his

discoveries tomorrow.

Natural SelectionNatural Selection

The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)

Charles Darwin (1809-1882) saw three problems in need of a solution. Darwin was not the only one to notice

these problems. Other scientists, including Alfred Russel

Wallace, shared ideas with Darwin and contributed to figuring out the solution.

The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)

Charles Darwin (1809-1882) saw three problems in need of a solution. Darwin was not the only one to notice

these problems. Other scientists, including Alfred Russel

Wallace, shared ideas with Darwin and contributed to figuring out the solution.

Problem #1Problem #1

Living things on Earth change over time. The fossil record

shows that in the past there were a lot of plants and animals that are now extinct.

Living things on Earth change over time. The fossil record

shows that in the past there were a lot of plants and animals that are now extinct.

Problem #2Problem #2 Living things could be

classified into different categories. People were big into

classifying stuff. It was pretty obvious that

there was a relationship between different species. Different birds, different

grasses, different cats etc

Living things could be classified into different categories. People were big into

classifying stuff. It was pretty obvious that

there was a relationship between different species. Different birds, different

grasses, different cats etc

Problem #3Problem #3

Living things have adaptations. Different kinds of teeth

for different animals, say carnivore ripping teeth and herbivore grinding teeth

Different tissues within species Heart vs. eye etc.

Living things have adaptations. Different kinds of teeth

for different animals, say carnivore ripping teeth and herbivore grinding teeth

Different tissues within species Heart vs. eye etc.

The Solution!The Solution!

Darwin figured out a theory that made sense of all of these problems.

He called it Natural Selection.

Darwin figured out a theory that made sense of all of these problems.

He called it Natural Selection.

Darwin’s LogicDarwin’s Logic

Fact 1: Species reproduce exponentially. Fact 2: Populations stay constant. Fact 3: Resources are limited.

Inference 1: There must be competition to survive.

Fact 1: Species reproduce exponentially. Fact 2: Populations stay constant. Fact 3: Resources are limited.

Inference 1: There must be competition to survive.

Darwin’s LogicDarwin’s Logic

Fact 4: Individuals in a population vary. Fact 5: Variations are inherited genetically.

Inference 2: Some individuals have traits that help them survive better than others (natural selection).

Inference 3: Over time adaptations accumulate in a populations, creating different species (evolution).

Fact 4: Individuals in a population vary. Fact 5: Variations are inherited genetically.

Inference 2: Some individuals have traits that help them survive better than others (natural selection).

Inference 3: Over time adaptations accumulate in a populations, creating different species (evolution).

How does it work?How does it work?

Selection determines which individuals grow up and have babies. This selection is done by the environment. The individuals who are best fit to their

environment survive and reproduce. They pass these fit traits on to their offspring.

Selection determines which individuals grow up and have babies. This selection is done by the environment. The individuals who are best fit to their

environment survive and reproduce. They pass these fit traits on to their offspring.

The SolutionThe Solution

MisconceptionsMisconceptions

Lamarckism Traits that you develop during

your lifetime can be passed on. Giraffes really wanted leaves, so

they stretched their necks and…..

Correction:Individuals cannot evolve.

Lamarckism Traits that you develop during

your lifetime can be passed on. Giraffes really wanted leaves, so

they stretched their necks and…..

Correction:Individuals cannot evolve.

MisconceptionsMisconceptions

There is a plan or goal to evolution. Organisms can change because the want to.

Correction: Traits change because of genetics mutations that happen by chance.

There is a plan or goal to evolution. Organisms can change because the want to.

Correction: Traits change because of genetics mutations that happen by chance.