The Theory Evolution via natural selectionThe Theory Evolution via natural selection

How did different organisms arise? How are they related?

Voyage of the Voyage of the BeagleBeagle

1831, ship sets sail for a 1831, ship sets sail for a voyage around the voyage around the worldworld

Aboard is Charles Aboard is Charles Darwin, a 21 yr old Darwin, a 21 yr old college graduate, college graduate, serving as ships’ serving as ships’ naturalist (unpaid)naturalist (unpaid)

Observations and Observations and evidence collected on evidence collected on this voyage changed this voyage changed biology forever.biology forever.

The voyage of the HMS Beagle

Darwin’s observationsDarwin’s observations

FossilsFossils: he finds evidence of extinct animals: he finds evidence of extinct animals DiversityDiversity: animals and plants vary widely in similar : animals and plants vary widely in similar

habitatshabitats Why are some species widely found, others live only Why are some species widely found, others live only

in one place?in one place?

Giant sloth claw Land and marine iguanas

Ideas that shaped Darwin’s thinkingIdeas that shaped Darwin’s thinking

LyellLyell: Geology shows evidence of an ancient : Geology shows evidence of an ancient earth with geologic processes happening over earth with geologic processes happening over extended periods of timeextended periods of time

LamarckLamarck: traits of a parent can be passed on to : traits of a parent can be passed on to the offspringthe offspring

MalthusMalthus: population size is determined by : population size is determined by limiting factors: food, living spacelimiting factors: food, living space

Publication of “On the Origin of the Publication of “On the Origin of the Species”Species”

In 1859 Darwin proposes In 1859 Darwin proposes a a mechanism to explainmechanism to explain the complexity of lifethe complexity of life

Theory: evolution has Theory: evolution has been going on for billions been going on for billions of years, and continues of years, and continues today.today.

Evolutionary theoryEvolutionary theory

Inherited variationInherited variation: all species have individuals that are : all species have individuals that are slightly different from each otherslightly different from each other

Over reproduction: Over reproduction: species produce excess offspringspecies produce excess offspring Struggle for existenceStruggle for existence: there is competition to survive : there is competition to survive Natural selectionNatural selection: the weak will die off: the weak will die off Survival of the fittestSurvival of the fittest: the members best adapted to : the members best adapted to

their environment will their environment will live to reproducelive to reproduce, and their traits , and their traits will be passed on to their offspringwill be passed on to their offspring

How Does Natural Selection How Does Natural Selection Work?Work?

Survival of the fittest?Survival of the fittest? What is fitness?What is fitness?

Being: big? fast? Strong? beautiful?Being: big? fast? Strong? beautiful?

Blue Whale

Cheetah

Rhinoceros beetle

Then why do small, slow, weak, Then why do small, slow, weak, and ugly animals exist?and ugly animals exist?

• Because fitness is simply the ability to live long enough to pass on as many genes as possible.• A variety of qualities can be adaptive (fit) depending upon an organism’s environment. That environment includes other living things, including members of the same species.

                              

Are these insects easy to see?

If you were a bird would you try to eat one of these insects?

Why?

What’s for Dinner?  

How do obvious, yet harmless insects

survive?  

Robber flyBumblebee

Flower fly

Conopid fly

Honey fly

Wasp

Harmless mimics need unpleasant models.

I’ll have a taste

The models must out number the mimics so the negative reinforcement is more common than the reward.

Better not take the chance

Do the math

The signal must be consistent Looks like trouble

Crazy, beautiful birdsCrazy, beautiful birdsHave you ever wondered why there are so Have you ever wondered why there are so

many colorful birds and why they sing?many colorful birds and why they sing?Did you know that some birds dance?Did you know that some birds dance?

Does this mean you have to be bold to mate?Does this mean you have to be bold to mate?

Rock – Orange throat, aggressive w/ large territory & many females in harem

Paper – Blue throat, defends small territory, 1-2 females

Scissors - Yellow throat, no territory, sneaks around and mates with females from the harems of other males

Meet the side-blotched lizard – AKA the “rock, paper, scissors” lizards

Competition & deception is not the whole story cooperation Competition & deception is not the whole story cooperation

can be a very successful strategy as well. can be a very successful strategy as well. Do you remember how mitochondria & chloroplast became part of Do you remember how mitochondria & chloroplast became part of

the eukaryotic cell? the eukaryotic cell?

                              

To Summarize natural selection Natural selection is more complex than a simple competition for food resources.

There are different aspects to selections:

Sexual selection - because mates are resources necessary to pass on genes

Kin selection – helping a closely related individual survive & breed is equivalent to breeding yourself.

Co-evolution –Some survival strategies are dependent on others – the mimic needs the model

Ecosystems - are complex, there are many successful survival strategies in nature.

Evolution is Descent Evolution is Descent with modificationwith modification

Each species alive today Each species alive today descended, with descended, with changes, from other changes, from other speciesspecies

All species, living and All species, living and extinct, were derived extinct, were derived from from common ancestorscommon ancestors

A single “tree of life”A single “tree of life”

links us all togetherlinks us all together