What is EVOLUTION?. Biologists consider evolution the UNIFYING THEORY OF BIOLOGY because it helps us explain and understand the DIVERSITY of life on the.

What is EVOLUTION?

Biologists consider evolution the UNIFYING THEORY OF BIOLOGY because it helps us explain and understand the DIVERSITY of life on the planet.

In your own words: define diversity:

Here is a clue!

Consider the following observations:

Lions live in Africa

Tigers live in India.How are they similar?How are they different?

If you put a lion and a tiger together in a zoo, they can have babies. We call them ligers.

How does evolution explain this?

"nothing in biology makes sense

except in the light of evolution”

~Theodosius Dobzhansky (1900-

1975)

Photo by “davemee”

flickr creative commons

In science, theories are

statements or models that

have been tested and

confirmed many times.

In science, the term "Theory" does

not express doubt.

•They explain a wide variety of data

and observations

•They can be used to make

predictions

•They are not absolute, can be

changed as new evidence is found

•Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale?

•Why is the sequence of DNA very similar in some groups of organisms but not in others?

•Why do the embryos of animals look very similar at an early stage?

Photo courtesy of Swamibu, Flickr Creative Commons

Charles Darwin developed

the Theory of Evolution by

NATURAL SELECTION 

... which explained how

organisms changed over

time  (ADAPTED)

Where did the Theory of Evolution come from?

1. Variation exists among individuals in a

species.

2. Individuals will compete for resources.

3. Competition would lead to the death of some,

while others would survive.

4. Individuals that had advantageous variations

are more likely to survive and reproduce.

Key Points to the Theory of Evolution by Natural Selection

This process came to be known as Natural

Selection

The favorable variations are called Adaptations

Photo courtesy of digitalART2, flickr creative commons

What adaptations do tigers have?

Humans?

Snakes?

What is an adaptation?

An adaptation is a genetic feature that is common in a population because it provides some improved function that helps members of the population survive and reproduce.

Examples:• Physical characteristics—giraffe’s long neck• Behavioral characteristics—lions stalking prey• Internal characteristics—cheetah’s extra large heart that helps

them run fast

What an adaptation is not

• Adaptations are not acquired through practice or use.

Organisms only pass on what is in their genes. If you practice basketball and become excellent at it, you cannot pass that on to your offspring!

• Adaptations do not arise because they are needed.

Adaptations arise from chance mutations that are passed on when their helpful function helps organisms survive.

Lamarke's Theory of Acquired Characteristics

Some thought that you would gain or lose features if you overused or didn't use them

  !! INCORRECT !!

Adaptations arise by chance. They are passed on if they help a species survive and reproduce.

Photo courtesy of ucumari,

creative commons, flickr

Say in a species of blob….there exists blobs

of all shapes and sizes (variation)

Blobs eat the little purple organisms that live

underground and on the surface.

During a particularly hot year, food became less

abundant (competition), blobs that had the ability

to dig into the soil to get food had a better chance

of survival.

Many blobs died that year…….

The ones that survived mated and passed their

genes to the next generation. (reproduction)

The next generation had more blobs with the pointed

noses. That is NATURAL SELECTION.

1.Variation

2.Competition

3.Survival

4.Reproduction

In 1-2 sentences, explain this image. What can you predict will happen?

Checkpoint

1. The theory states that

a) individuals of a species have differences, called_________ b) these individuals ________________ for resources c) some will die, others will ____________________ d) survivors will _________________________ and pass traits to offspring

2. Any trait that helps an organism survive is called an _______________________________

Theory of Evolution -- evidence

1. Artificial Selection2. Fossils

3. Homologous structures

4. Vestigial organs

5. DNA

6. Embryos

7. Direct Observation

Artificial Selection - humans selected variations they found useful and bred animals and plants for those traits.

Much of our agriculture (food, animals, clothing) is a result of artificial selection that has occurred over many generations.

We can influence the EVOLUTION of a species

Fossil Evidence shows…..

● similarities between extinct animals and animals that are

alive

● earth’s layers, and species that lived at each time

Dinosaurs have always fascinated us, movies such

as Jurassic Park capitalize on that fascination.

How do we know what dinosaurs looked

like?

We create a picture based on the bones

we find (fossils) and use modern reptiles

to guess at their texture and skin color.

•Homologous structures – these are parts of the

body that are similar, but have different functions

ex. The flippers of

whales, and the wings

of birds

All forelimbs of

vertebrates have the

same pattern of bones

• Common ancestry

•Vestigial Organs – these are organs or parts that

seem to have no function

Whales have pelvic bones that do not attach to legs

Watch a short video clip on whale evolution at PBS

•Biochemistry and DNA: When comparing the DNA of

one species to another, more similarities are found in

species that are more closely related.

Lion photo credit: ucumari Tiger photo credit: digitalART2

Embryological Development

Embryos of different species develop in almost

identical ways.

Human fetus at 8 weeks

Direct observation of species change

1.Bacteria become resistant to antibiotics

2.Peppered moth in response to pollution

Checkpoint:

1. When humans choose which organisms to breed, this is called _____________________________.

2. ____________ evidence shows when organisms lived on the earth

3. Species that are closely related will have similar _____

3. A _______________ organ is one that has no function.

4. _________________ structures look the same but have different functions, like the arm of a human and the flipper of a whale.

5. ____________ of different animals develop in the same way.

6. As humans change environments everywhere, it is possible to see evolution happen through __________________.