Evolution: Evidence

The Saga Continues…

More Evolution Humour…

What does the picture show?

• The concept of evolution was conceived piece by piece

• It was not something that developed overnight!

• There are still pieces to be discovered

Evolution is a Unifying Concept that has many “Puzzle Pieces”

It has taken 100’s of years for Evolution to become a strong Scientific concept

Copernicus and Galileo were shunned for their Scientific proposals that are currently understood as fact and truth

Just as Copernicus cast the earth out from the center of the universe, evolution has displaced humans as the epicenter of the natural world

Keep an open mind!

Early Ideas About Evolution

Early thinkers could not ignore their observations of the life around them

Lamarck was the first Biologist to recognize the key role of the environment in evolution

Lamarck theorized that species can be self-sustaining as long as they are able to adapt to the changing environmental conditions

Let’s look at a couple of examples in the animal world

Lamarck: If you want something badly enough…While Lamarck was on the

right track, he also was a little off!

He took the example of a giraffe

What is their main adaptation?

He believed that if a giraffe tried stretching their neck long and hard enough, it would lead to its elongation; this trait would then be passed on to its offspring

He tried

Charles Darwin: He’s da Man!

Went on a boat called HMS Beagle in 1831 and developed one of the most influential theories in human history

The boat took him to the Galapagos Islands where he made his most famous discoveries

Darwin’s Journey

Darwin and his Finches

Evidence #1: Biogeography

Darwin noticed that geographically close environments are more likely to be populated by related species

Animals found on islands resemble those found on the closest continent

Darwin and his Finches

Looking at the diagram, what do you think caught Darwin’s attention?

Darwin noticed that Finch species differed in beak size

He tried to devise a theory that would explain the diversity of the finches

Structure fits Function!

Evidence #2: Anatomy Homologous features are shared by two species that

is similar because of common ancestry For example, forelimbs of the following organisms are

adapted to carry out very different functions but have very similar bone structure

Analogous FeaturesA feature/structure that serves the same function in

two species, but is NOT derived from a common ancestral structure is said to be analogous

For example, the wings of bats, insects, and birds allow these animals to fly but they do not share a common ancestor

Vestigial Features and Anatomical Oddities

Ever wonder why people get their appendix removed?

Tonsils?Why do you think this is possible?

We do not need all the structures in our bodyThey do not serve any useful function These are called vestigial features:

rudimentary and nonfunctioning structures that are homologous to fully functioning structures in closely related species

Examples?

Vestigial Features

Actually, now it’s believed that the appendix is part of the immune system, strategically located at the entrance of the almost sterile ileum from the colon with its normally high bacterial content

Originally, scientists believed they were evolutionary “left-overs”

Hmmm…

What about the tonsils?

The tonsils have a similar function in the entrance to the pharynx (possible immune function)

Doctors have found higher occurrences of respiratory issues in patients who have had their tonsils removed

Vestigial Structures in Whales

Hipbones are used to transfer body weight to the hind legs

What use do whales have for these?Whales are also mammals - perhaps they

are descendents of ancestral mammals that possessed hind legs

More Vestigial Organs

Pelvic elements in pythonid snakes and cetaceans

Vestigial Toes

Dogs, pigs, and horses have a digit that serves no present purpose

Goosebumps – vestigial?

What is the purpose of goosebumps?

Why would they be vestigial?

The function in human ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators

Raising the hair is also used to trap an extra layer of air, keeping an animal warm (this function is not vestigial of course) but the reflex to form them under stress is

Anatomical Oddity

Why does the spermatic cord go all the way around and not directly?

Evidence #3: EmbryologyMatch the Animal with its Embryo!

Your choices:

• Human

• Chicken

• Pig

• Cow

• Rabbit

• Fish

• Salamander

• Tortoise

Evolution has been Constructed with a lot of Help!

It was NOT only Biologists that contributed to the current understanding of Evolution

Paleontologists and Geologists have provided what some consider as the best evidence

This evidence is referred to as the fossil record

What are fossils?Any preserved remains or traces of an organisms or

its activity

Evidence #4: Fossils

Most easily recognized by hard body parts like shells, bones, and teeth

Can include footprints, impressions of burrows, and chemical remains

How do they form?Remains of dead organisms become trapped in

sediments (particles of dirt and soil) which become compressed by gravity and pressure from layers above

These layers eventually become sedimentary rock which preserves many specimens from our past

Archaeopteryx – A prime example!

Based on its Fossil…

Dangerous Ideas…

Evidence from the Fossil Record

Fossils appear in chronological order in the rock layers

Paleontologists can trace back ancestry based on the physical similarities and age of the fossils

Horse toe evolution based on fossils

How do we know the age of fossils then?

Absolute age of fossils can be determined through a technique called radiometric dating

This theory is based on radioactive decay (elements break down over time and release radioactive energy that can be measured) and the half-life of radioisotopes

How old is the Earth? About 4.6 billion years old!

Evidence #5: DNA

Two closely related species will share similar DNA sequences

All living things undergo protein synthesis using RNA

Junk DNA?

Much of our DNA does not code for anything – why is that?

95% is “junk!”

It all comes down to Survival

Those organisms better suited to their environment will live to reproduce and leave offspring behind

Therefore, favourable variations are preserved and unfavourable ones are lost

What is the basis for variation? GENES! (Genetics &

DNA) & mutations