Evidence for Evolution

Evidence

• Ever since Darwin introduced his ideas of natural selection, scientists have been looking for evidence

• There are many different areas of science that contributed to the evidence for natural selection

Evidence

• Previous scientists have found evidence for natural selection in the fields of biology, geology, chemistry and physics

• Modern day scientists have found evidence for evolution in the field of genetics

Fossils

• A fossil is the remains or traces of an organism that died long ago

• Fossils most often form when a trace of an organism is buried

• Traces of an organism can be a footprint, droppings, eggs, a corpse, etc.

Fossils

• Fossils provide us small snapshots of the past that can be used gain knowledge of the past

• With the right amount of fossils, we can build a complete picture of the looks, actions and patterns of ancient organisms

Fossils

• We can tell how old fossils are in two ways

• Superposition is the idea that the deeper a rock formation is, the older it is

• If we know that age of a rock formation, we can approximate the age of the fossils in it

Fossils

• Carbon dating is a measurement of how old an element is

• This allows modern day scientists to see how old the carbon in a particular fossil is

• It give a good approximate of the age of fossils

Video

• http://www.youtube.com/watch?v=SEDfRy6DQns

Fossil Record

• With these fossils we can draw conclusions about the organisms on the earth during different time periods

• We can line up the fossils and make a timeline of what organisms looked like and how they changed

Fossil Record

• What we see most often in organisms is that they have adapted over time

• Species do not randomly appear

• Different species come from different adaptations

• http://www.youtube.com/watch?v=bYMVNYARBqU

• http://www.youtube.com/watch?v=GOKW_7KajCU

Anatomy

• Anatomy is the study of structures in the body

• Anatomy also provides very compelling evidence for natural selection

• Some of the structures of animals are very similar

Anatomy

• Compare the two structures that you see here

• What is similar about them?

• What is different about them?

Anatomy

• The structures of both the human hand and the bat hand are very similar

• The bones, the joints and the placement of the bones are all similar

• This goes across other animals as well

Anatomy

• Homologous structures are anatomical structures that originated by heredity– They have a related

structure and function

• This means they are similar because they were passed down from a common ancestor

Anatomy

• Analogous structures have closely related functions but do not derive from similar ancestors

• A good example of this would be a bird and a butterfly

• They both have wings, but they are built nothing alike

• This is because they came from a different ancestor

Anatomy

• Sometimes there are structures that are left in organisms long after they have ceased to be useful

• These are remains of structures that from ancestors long past

• We call these vestigial structures

Anatomy

Biogeography

• Darwin noticed something on his voyage that is evidence for natural selection

• Darwin noticed that in different parts of the world there are organisms that are closely related but are geographically far apart

Biogeography

• These organisms were at one time the same species

• When land masses began moving, the species was separated

• When the species separated, there were different adaptations

• This created the different species we see today

Genetics

• With the advent of modern technology we can start to study evolution and natural selection at a genetic level

• Modern genetics allows us to make comparisons in DNA to other organisms

Genetics

• When we look at DNA and how it is expressed we can see the relationships between organisms

• It gives us a better idea of what organisms are closely related, even if they don’t look like each other

Embryo Evidence

• Think about all the ways of producing offspring

• Are they similar or different?

• What is an embryo?• An embryo is an unborn

or unhatched organism that is developing

Embryo Evidence

• The process of development is similar across many organisms

• Many organisms have structures when they develop that are not seen in their final form

• For example humans have tails when they develop

Embryo Evidence

• Why would these embryos have structures that are not seen in their final forms?

• It is because they share common ancestry

• The common ancestor had a feature that is not present in the current organism

Video

• http://www.youtube.com/watch?v=h3Lkac890c0