The Theory of Evolution

Evolutionary biology addresses fundamental questions Why are there so many different kinds of organisms? Why are organisms so proficient at life tasks: finding food, acquiring mates, fighting disease, and avoiding predators?

OVERVIEW: Four Main Points to the Theory of Evolution. Variation exists within populations. Some individuals of a population are better suited to their environment. Over time, traits that make certain individuals of a population able to survive and reproduce tend to spread in that population. There is clear proof from fossils and many other sources that living species evolved from organisms that are now extinct.

Does Variation Exist Within the Genes of every population or species (the result of random mutations)?

Is this variation Heritable?

Natural Selection Acts on These Heritable Variations of Traits. Working definition of Natural Selection: Natural Selection is the process by which populations change in response to their environment. Individuals better adapted to the environment leave more offspring than those individuals not suited to the environment.

HOW ABOUT A REAL LIFE EXAMPLE, BEYOND THE CARTOONS. Do individuals who are better suited to their environment really leave more offspring than others? HOW ABOUT A REAL LIFE EXAMPLE, BEYOND THE CARTOONS. Day Day Day

Real Life Examples of Evolution Natural Selection in Action

Industrial Melanism

A hypothesis for the explaining the increase in dark moths was formed using Darwin’s theory of evolution by natural selection. Hypothesis: The dark variety was camouflaged on the soot-darkened bark and so are not eaten by birds.

The Experiment Populations of light and dark peppered moths were raised in the laboratory. Moths were marked so they could be identified later Moths were released into two separate wooded areas. Birmingham= Heavily polluted Dorset = unpolluted

Results

Overcoming Misconceptions The darkened trees did not cause the darker variant of moth to appear. The darker characteristic was already present in the population. The “new” environment merely favored the survival of the darker moths.

Beyond the Fossil Record Evidence of Evolution Beyond the Fossil Record

How Does Anatomy and Structure Show Evidence of Ancestry? Comparing the anatomy of different types of organisms often reveals basic similarities in body structures, even though their functions may be very different.

Common Ancestor A Species from which two or more species have diverged.

Homologous Structures Structures that share common ancestry.

Analogous Structures Analogous structures have similar forms, but they are not due to common ancestry.

Vestigial Structures Vestigial structures are anatomical structures of organisms in a species, which have lost much or all of their original function. Structures that are considered to be evidence for an organisms evolutionary past.

Flightless Cormorant of the Galapagos

Vestigial Pelvis of the Whale

Femur and Pelvis of Whale

How is Embryonic Development Evidence for Evolution? The evolutionary history of organisms is seen in the development of embryos.

What are some common structures that vertebrate embryos share? Tail bud Pharyngeal pouches Buds that become limbs

How are Biological Molecules a Record of Evolution? Species that share common ancestry more closely, have more amino acid sequence in common. Species that have diverged from a distant common ancestor have more differences in amino acid sequences.

The Hemoglobin Protein shows common ancestry.

Hemoglobin Comparison Species Amino acid differences Gorilla 1 Rhesus monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125

Great Moments in Evolution

What is the Fossil Record? Working definition: All the fossils known to science. Provides snapshots of the past Illustrate a panorama of evolutionary change over time

Nice Striations!

What’s a Fossil, You Ask? The remains or traces of once-living things. shells, teeth, bones, footprints, leaf impressions, and petrified wood.

“Endless forms most beautiful and most wonderful” – Charles D.

Is the Fossil Record Complete? No, it most certainly isn’t.

The probability that any particular organism that once existed, is part of the fossil record today is rare. For Three Good Reasons. . . Fossil formation is a rare event Fossils survival is a rare event An exceedingly small fraction of surviving fossils will ever be found

John Day Fossil Beds

Transitional Forms in Horse Evolution

Lahars: Pyroclastic Mud Flows