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!
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!
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
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
The fossil record shows how modern species evolved from extinct ancestors.
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?
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
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
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 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
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)
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...
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?
Similar patterns of embryological development provide further evidence that organisms have descended from totally separate and different ancestors.
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
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?"