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Theory of Evolution

Mr. Saenz

Biology Dept

North Pitt High School

FYI…Charles DarwinCharles Darwin came from a family of doctors, and he

almost became one, too. Both his father and grandfather were doctors, and they urged him to follow in their footsteps. Charles started out in medical school but soon found that he did not like it. He then went to theological school to study to become a minister. Darwin had always been interested in nature, so he also took courses in biology and geology. These courses were the extent of his formal training as a naturalist when he accepted a job on the HMS Beagle. Darwin was not the most qualified applicant, but he was hired anyway because the captain, Robert Fitz Roy, thought Darwin would make a good companion for the five-year voyage.

Theory of Evolution

• Before Darwin came up with his theory he

had some ideas from earlier scientists.

Theory of Evolution

James Hutton and Charles Lyell:

• They proposed that the Earth has changed

gradually over time.

Darwin took this idea and expanded on it…

“Life has changed gradually over time”!!!

Theory of Evolution

Jean-Baptiste Lamarck (1809):

• French naturalist, who first recognized that living

things have changed over time and that all species

were descended from other species.

• He proposed that by selective use or disuse of

organs, organisms acquired or lost certain traits

during their lifetime. These traits could then be

passed on to their offspring. Over time, this

process led to change in a species

• Theory Status: Disproven

Lamarck’s Theory

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Theory of Evolution

Thomas Malthus (1798):

• He reasoned that if the human population

continued to grow unchecked, sooner or

later there would be insufficient basic needs

for everyone.

• Main reason why populations cannot grow

exponentially forever (J-curve)

Theory of Evolution

What scientific explanation can account for the diversity of life?

Evolution

Who was Charles Darwin?

The founder of the modern theory of evolution was born on February 12, 1809

What was his job?

Naturalist (collect, study and label specimens)

Where did he do a lot of his onsite research?

Galapagos Island (South America)

What was the name of the boat?

HMS Beagle

Theory of EvolutionWhat happened during his travels?

• He saw lots of biological diversity

• Ex. In a forest in Brazil he collected 68 different species of beetles-despite the fact he was not even looking for them.

• He noticed that even though Argentina and Australia have similar grassland ecosystems, the animals inhabiting those lands were different from each other.

• He collected fossil remains of ancient organisms which resembled organisms of today.

• Found several brown birds w/ different shaped beaks

• Found some mockingbirds which were different from each other

Theory of Evolution

What did he later learn from his travels?

• The brown birds w/ different shaped beaks were

actually the same species

• The mockingbirds were actually different species

What did he envision?

• a theory about the origin of adaptation,

complexity, and diversity among Earth’s living

creatures

• Many found his idea brilliant, while others

strongly opposed it…WHY?

Back in those days…

• People believed that the Earth and all its

forms of life had been created only a few

thousand years ago. Since that original

creation, they concluded, neither the planet

nor its living species had changed.

• Many religions still do this day.

Theory of Evolution

Who was this theory?

The theory of evolution by natural selection

What is natural selection?

• Remember, since growth does not occur exponentially forever species will struggle to exist!

• small, random, heritable differences among individuals result in different chances of survival and reproduction

– This is called fitness

• success for some, death without offspring for others

• this leads to changes in shape, size, strength, color, biochemistry and behavior among the descendants

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Theory of Evolution

How does it work?

• since less successful competitors produce fewer

offspring, those weaker traits disappear

• the stronger/better traits tend to increase gradually

throughout the population

What is another phrase for this?

“Survival of the Fittest”

What is artificial selection then?

• Same as natural selection, just instead of nature picking

the strong traits, man does

Theory of Evolution

What is the name of the book he wrote?

The Origin of the Species by Natural Selection

What evidence does he have for this?

1- Biogeography

2- Paleontology

3- Embryology

4- Morphology

Biogeography

The study of the geographical distribution of living creatures

• Species now living on different continents had each descended from different ancestors.

• Since some animals on each continent were living under similar conditions, they were exposed to similar pressures of natural selection.

• Because of these similar selection pressures, different animals ended up evolving certain striking features

Biogeography

• If you put two different animals in similar environments, then the strong traits in one area for an animal will be the same strong traits for the other area for the other animal.

• This can lead to two different looking animals evolving to look the same…but they are still different species.

Beaver

NORTH

AMERICAMuskrat

Capybara SOUTH

AMERICA

Coypu

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Paleontology

• Hundreds of transitional fossils that document

various intermediate stages in the evolution of

modern species from organisms that are now

extinct.

• Fossils sometimes can tell what was alive at one

time and how long ago it was

• Gaps remain

• a.k.a. “The Fossil Record”

Embryology

• That many different organisms have many

similarities when comparing their early stages of

life.

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Morphology

• The number of shared characteristics between

any one species and another indicates how

recently those two species have diverged from a

shared lineage

• In other words…

• The more different species look alike (or have in

common) indicates how closely related they are.

Morphology

Homologous Structures

• Structures in different species which

superficially look different but are quite similar

in their foundation.

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Morphology

Analogous Structures

• no similarity in structure, but similarity in fxn

Vestigial Structures

• structures which now have no fxn, but once did

• vestigial structures stand as left behind evidence

of the evolutionary history of a lineage

Variations in Natural Selection

• Traits have variation.

• Some variations of a trait increase or decrease an organism’s chance of survival in an area.

• Variations of a trait are controlled by alleles (genes) and can be inherited.

• Therefore, the frequency of an allele (gene) for a trait in a populations gene pool can change due to natural selection.

• Significant changes in the gene pool can lead to the evolution of a new species over time.

Variation in Traits

These butterfly live

in different areas of

North America

Despite their slight

variations, they can

interbreed to produce

fertile offspring

Variations in Natural Selection

Stabilizing Selection

• average organisms have the survival advantage

in an environment

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Variations in Natural Selection

Directional Selection

• one extreme trait for a species has the advantage

for survival but another extreme does not

Variations in Natural Selection

Disruptive Selection

• either extreme trait for a species has the

advantage for survival

Patterns of Evolution

Types:

1. Macroevolution

a. Extinction

b. Divergent Evolution

c. Convergent Evolution

d. Coevolution

e. Punctuated Equilibrium

f. Changes in Developmental Genes

2. Microevolution

Macroevolution

• Large scale evolutionary patterns that occur

over a long period of time.

Extinction

• Usually, it occurs due to reasons of natural

selection (Darwin).

• Sometimes events cause wipe outs of entire

ecosystems leading to mass extinctions.

– Ex. dinosaurs

• Mass extinctions can result in a burst of

evolution that produces many new species.

Divergent Evolution

• When an ancestral species evolves into an array of species to fit a variety of habits.

• If you place 2 similar looking species in different environments over time they will become more different in their appearance due to the differences in the traits needed to survive.

• This is how one species can evolve into many different species.

• Another name for this is ADAPTIVE RADIATION

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Divergent EvolutionConvergent Evolution

• When different looking species evolve similar

traits due to living in similar environments.

• If you place 2 different looking species in similar

environments over time they will become more

similar in their appearance due to the similarity in

the traits needed to survive.

• Ex. Beaver, Muskrat, Cupybara

• Ex. Shark, penguin, dolphin

Coevolution

• How two species evolve

to each others needs

over time

• Ex. The moth with the

long tongue due to the

flowers petals

Punctuated Equilibrium

• Rapid evolution in a species

after long periods of no

change (equilibrium)

• Could indicate that evolution

is not always slow and

steady like Darwin said

• Gradualism – evolution at a

slow and steady rate.

Changes in Developmental Genes

• Changes in the activation of certain genes can lead to major evolutionary transformations.

• Ex. Ancient insect wings compared to modern insect wings. Due to “wingless” gene being turned on at an insects body segment.

• Ex. Long legs/short legs; same for fingers

Microevolution

• Evolution within a single population or

species.

• Tends to happen quicker

• Ex. Bacteria becoming resistant to

antibiotics.

• Ex. Insects and weeds becoming

resistant to insecticides and herbicides.

• Ex. HIV becomes resistant to AZT