Evidence of Evolution

Evidence of Evolution

Since Darwin's time...

During the 160+ years since Darwin published On the Origin of Species, research in many fields (biology, geology, physics, paleontology, chemistry, embryology, genetics, and molecular biology) has provided independent tests of hypotheses related to Darwinian theory and repeatedly support what Darwin explained about Natural Selection.

Let's Explore Some of the Evidence for Evolution!

Biogeography

• Looks at patterns between fossils and living organisms, where they are found/live - Tells us how modern organisms descended from ancient ones

• Very distantly related species can evolve similar adaptations if they live in similar environments or face similar challenges in the struggle for existence

• Natural selection in similar habitats led to similar adaptations

Geographical Distribution of Living Species

• As organisms changed over time, they adapted to different habitats and spread to new ecological areas

• Descent with Modification is involved here!

Multiple Select

Which 2 statements describe how biogeography is useful for identifying evolutionary relationships?

• Shows distantly related species can evolve similar adaptations if they live in similar environments

• Natural selection in similar habitats led to similar adaptations

• Shows how various structures across different species have the same function but have evolved separately

Age of the Earth + Fossils

• Radioactive dating --> Earth ~ 4.5 billion years old, plenty of time for evolution to lead to diversity of life

• Many recently discovered fossils now show clearly how modern species evolved from extinct ancestors

• So many intermediate forms have been found that it is often hard to tell where one group begins and another ends

*

Multiple Choice

The fossil record shows how modern species evolved from extinct ancestors.

• True

• False

Comparing Anatomy

Why do limbs of different organisms have different functions, but similar internal structures?

Think about the function of human arms, whale fins, and bat wings - what do they do?

What's similar about the bone structures of these appendages?

Why do you think this is?

Homologous Structures

• Similar structures that are shared by related species and have been inherited from a common ancestor

• Homologous Structures show that organisms descended from a common ancestor

• Increased similarities --> more closely related

Multiple Choice

What do Homologous Structures show us about the evolutionary relationships between organisms?

• Shows that structures have lost much or all of their original size and function and have changed over time

• Shows that totally different structures across species must have been inherited from a common ancestor

• Shows that similar structures that are shared by related species must have been inherited from a common ancestor

Analogous Structures

• These are NOT the same as Homologous Structures...

• Body parts that serve similar functions, but do not share similar structure and development

• Various structures across different species have the same function but have evolved separately (not from a recent common ancestors

• Analogous Structures grow and develop from different embryonic tissues

Convergent Evolution

• Convergent Evolution is the process in which organisms that are not closely related independently evolve similar features. Adaptations may take the form of similar body forms, colors, organs and other adaptations which make up the organism’s phenotype.

• “Like bats and birds are not closely related BUT they did converge on flight by flapping bits of their bodies around - possibly as a way to get around quickly while avoiding predators” - Hank Green

Multiple Choice

Which type of body parts/structures serve similar functions, but do not share similar structure and development (example: bat wings and butterfly wings both used for flight)

• Homologous Structures

• Vestigial Structures

• Analogous Structures

Vestigial Structures

• A structure "left over" from evolution, was used by ancestors but useless now

• These are homologous structures, inherited from ancestors, that have lost much or all of its original size and function over time

• Example: hip bones of dolphins...they don’t have legs!

• We have a bunch of vestigial structures...

Multiple Choice

How do vestigial structures provide evidence for evolution?

• Shows that organisms have new and unique structures show up over time, which has no relation to the organisms they descended from

• Shows that organisms inherited structures from ancestors, since the structure has lost much or all of its original size and function over time

Development + Similarities in Embryology

• Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor

• Common cells grow/develop in similar ways

• Observations make clear that the same groups of embryonic cells develop in the same order and in similar patterns to produce many homologous tissues and organs

Notice the embryological similarities?

Multiple Choice

Similar patterns of embryological development provide further evidence that organisms have descended from totally separate and different ancestors.

• True

• False

Genetics + Molecular Biology

• Just look at the DNA!

• Overwhelming similarities in genetic code of all organisms provide evidence of common descent

• Genetics provides some of the strongest evidence for how organisms evolved

• DNA provides powerful evidence that all organisms evolved from common ancestors that shared this genetic code

• Some functions found in all living things so must've been in a common ancestor

Multiple Select

Which 2 statemnets are accurate about what DNA can show us about the relationship between different organisms or species?

• That all organisms evolved from common ancestors

• That all organisms are separate and evolved independently of one another

• Some functions found in all living things so it must've been in a common ancestor and was passed on

Let's recap what we learned with a video!

"What is the Evidence for Evolution?"