The EvidenceThe Evidencefor Evolutionfor Evolution

Evidence for EvolutionEvidence for Evolution• Every idea that is put forth in science needs

evidence to back it up before it is accepted by those who work in the field.

• Evolution has many pieces of evidence that support it. These include:– The Fossil Record– Homologous Structures– Embryology – Geographic Distribution– Molecular Biology– Chromosomal Action– Protective Resemblance– Artificial Selection

The Fossil RecordThe Fossil Record• The study of fossils and the fossil record is called

paleontology.• Fossils provide some of the strongest pieces of

evidence for the theory of evolution. The fossil record includes many items such as fossilized bones, preserved specimens (in amber), imprints, petrified remains and microfossils.

• It is generally accepted that the deeper the layer of rock, the older the materials of the rock and of those things found in the rock. Fossils that are deeper are older while those that are closer to the surface are newer/more recent.

• Throughout the fossil record, one can plainly see a flow of form as you go back in geologic time.

The Fossil RecordThe Fossil Record

Homologous StructuresHomologous Structures• Homologous structures are parts of the

body (found on sometimes, very different species) that have a similar structure even though they may have entirely different functions.

• Again, traits come from DNA…DNA from parents…So similar traits…similar DNA…similar ancestral parents.

• The forelimb of many mammals is a great example of homologous structures.

Homologous StructuresHomologous Structures

Vestigial & Analogous StructuresVestigial & Analogous Structures• Vestigial structures are structures that are not

used by and organism but hint at its evolutionary past.

• Vestigial structures are used as evidence for evolution along the same lines as homologous structures.– The human appendix or the hind digits on dogs are an

example of vestigial structures.• Analogous structures are structures that have a

common function but not in origin or anatomical structure.

• Analogous structures are not an example of evolution.– A birds wing and a butterflies wing may both aid in flight

and look pretty but they are constructed quite differently.

Vestigial & AnalogousVestigial & AnalogousVestigial Structures• Femur in Whale• Human Structures

Analogous Structures• Insect wing vs. Bird

or Bat Wings• Shark vs. Dolphin

EmbryologyEmbryology• Embryology is the study of the embryonic

development of seemingly unrelated species.• You will see many similar structures between

“unrelated” species if you compare the earlier stages of embryonic structure. These structures include the gill slits (even on terrestrial species) and the elongated tail (even on those without tails at birth).

• As the embryos develop, you see the divergences that have occurred between the species as they all adapt to their future environments. It’s like evolution on fast-forward.

EmbryologyEmbryology

Molecular BiologyMolecular Biology

• The molecules that make up living things are called biomolecules. (Carbs, Lipids, Proteins and Nucleic Acids)

• All living things use these molecules in their structure and function in much the same way.

• A great example of this is the cell membrane (phospholipid bilayer) and protein structure (amino acids).

Chromosomal ActionChromosomal Action• The chemical composition of chromosomes in all

living things is similar (as you just saw).

• To go along with this, the actions chromosomes perform during cell division are repetitive in many different, seemingly unrelated, species.

• Think of mitosis…Coil, pair, middle, separate!

Geographic DistributionGeographic Distribution

Using the Past…• Fossils of related species have been found on

land masses that were once very close to each other but now reside thousands of miles away from each other.

• South America and Africa were once beside each other as part of the super continent of Pangaea but now they are far apart, yet, fossils that are remarkably similar have been found on once neighbouring coastline of each continent.

PangaeaPangaea

Geographic DistributionGeographic DistributionUsing the Present…• If you look at species that live in a specific

environment, like a mountain example, those species will have more in common with species that live in other mountains – even if the mountains are thousands of miles apart.

• Many times, a species will have more in common with something that resides in a similar environment that is very far away, than it does with something that lives in a neighbouring environment.

• This shows the impact of environmental selection pressure on the structures a species will possess.

Same But Different!Same But Different!

Protective ResemblanceProtective Resemblance• The peppered moth resides in England in large

stands of birch trees and other lightly-coloured flora.

• The moth has a light and dark form (in terms of the colouration of its wings and body).

• The light ones dominated the forest as they were able to hide better from predators – the dark ones showed up more easily and their numbers were kept smaller.

• The industrial revolution began in the 1800’s and the factories began to spew smoke and soot onto the nearby forests. What do you think happened between the two peppered moth variants?

Protective ResemblanceProtective Resemblance

Artificial SelectionArtificial Selection

• AKA: Domestication• Artificial selection

occurs when humans chose the desired traits within a species and select which individuals shall be bred and give rise to the next generation.

• The humans select the fit individuals instead of the environment – hence the name artificial selection.

• The dogs below are the result of people choosing their traits – not nature.

That’s All I Got…Oh…And This…That’s All I Got…Oh…And This…