how did we get here? it all started with a big bang!

How did we get here?

It all started with a big BANG!

Between 10 and 20 billion years ago…

• All the material and energy in the universe was condensed into one singularity a few millimeters wide.

• Then, it exploded.

All that matter was expanding

• Different elements collided– Some made planets– Other made stars

• About 4.6 billion years ago the Earth was made

Our solar system…

• The closest star, our sun, had a gravitational force that pulled several new planets into orbit around it.

Then the Earth began to cool…

• The molten surface cooled and formed a rocky surface, which we know as the crust.

• The atmosphere was dense and filled with toxic elements.

Early Earth• Constant volcanic

eruptions• Toxic atmosphere (little

to no free Oxygen)• Brown Oceans from

dissolved iron• Lightning storms

• This is the environment in which life evolved

The building blocks of Life

• Lightning struck the elements swirling around on the young Earth and created amino acids, the building blocks of proteins.

• Stanley Miller and Harold Urey

Organic Stew

• The Earth was now filled with these organic molecules.

• About 3.8 billion years ago the first cell is believed to have been formed.– Prokaryotes

Cells became diversified

• Photosynthetic cells (used sunlight to get energy gave off Oxygen)

• This new oxygen was toxic to many early life forms

• Others adapted to use the oxygen

Endosymbiotic Theory• About 2.2 billion years ago cells began joining together

to survive.• Anaerobic cells incorporated aerobic cells in order to

survive in the new oxygen rich environment.– Eukaryotes – Eventually photosynthetic cells joined the club

Multicellular Organisms

• About 1.2 billion years ago simple multicellular organisms evolved

Marine Life

• 555 million years ago multicellular organisms are abundant in the oceans

• 500 million years ago fish-like vertebrates evolved

Land Ho!

• About 450 million years ago (MYA), arthropods moved onto land (scorpions, spiders, mites, etc)

• 420 MYA land plants evolved

• 360 MYA four limbed animals moved onto land and seed plants and forests evolved

DINOSAURS!

• 225 MYA dinosaurs and mammals evolve• 65 million years ago a massive asteroid hit the Earth

which caused the dinosaurs to go extinct

Humans• The first Human

ancestor evolved about 4 million years ago– Lucy – Astralopithecus – Bipedal

Modern Humans

• Modern humans emerged about 130,000 years ago

Let’s get a visual here…• Stretch out both arms

– The tip of your left hand is the beginning of the Earth

Let’s squeeze all of Life into 24 hours

Click on the picture for a video!

The environment needed to be just right for life to evolve…

• The environment is the driving force behind evolution

What is evolution?

• Evolution is gradual change over time.

• The Theory of Evolution is thought to explain how life on Earth has come to what it is today. – Theory: a well-tested

explanation for a set of observations; can be used to make predictions

Evolution by Natural Selection

• Certain organisms are better suited for a particular environment; those who are better suited will survive, and pass on their genes.

• This theory was suggested by Charles Darwin– Set in motion by his

voyage on the HMS Beagle

HMS Beagle 1831

Darwin’s Observations

• Noticed that similar animals existed in different environments– Emus/Ostriches/ Rhea– Kangaroos only in

Australia

• Species varied locally– Tortoises– Finches

• Fossils that resembled living organisms

Darwin’s Conclusions

• The struggle to survive– More individuals are

produced than can survive; need to compete for resources

• Variation and Adaptation– Individuals vary based on

inherited traits; some traits are better suited for survival in that environment

• Survival of the fittest

Survival of the…sexiest?• Fitness is an organisms ability to survive and

reproduce.• Those who are able to reproduce more and produce

more offspring are more fit• It’s all about passing on those genes!

Remember Genetics??

• Genetics creates variation among sexually reproducing organisms.

• The different traits are crucial to evolution by natural selection!

Natural Selection

• Remember artificial selection? What was that?

• Natural Selection is on way evolution works– Organisms with traits

that are beneficial in their particular environment will survive and reproduce

Click on a the picture for an interactive example.

How does the environment determine who survives?

• If the environment is mostly orange, and an organism is bright green, it will easily be seen by predators.– The green prey will get

eaten more, reducing the amount of green organisms that can pass on their genes.

The Environment

• The environment is where an organism lives. • In order to reproduce, the organism needs to be

able to survive in its environment.

Which one is better suited to survive in the Arctic?

Who will better survive if there is only tiny insects in holes to eat?

What traits would be beneficial in an environment like this?

Think about the predators…

Adaptation

• Adaptations are characteristics that can be inherited and that increase an organisms fitness or chance of survival.

Adaptations

• When the environment changes, organisms that have a particular trait that’s beneficial are better adapted to the new environment.– Opposable thumbs– Coloring

But what about…

• Traits that don’t increase or decrease one’s fitness or survival?– Then natural

selection does not work for or against those traits

But what about…?

• Why are there so many different organisms? Isn’t the goal one perfect being?

• NO! There are so many different ways to survive, that no one way is best. It’s just important to survive and pass on genes.

THE BIG PICTURE!

• The environment dictates which organisms will survive and pass on their genes

• Certain traits will increase an organisms survival

• Those traits will be passed on

Shaping a Population

• A population is a group of the same species living in the same area.

• Natural selection can determine the dynamics of a population

Types of Natural Selection

• Disruptive/Diversifying– When individuals with either

extreme of the trait survive better. (The average is selected against)

• Stabilizing– When individuals with average

traits survive better. (The extremes are selected against)

• Directional– When individuals with one

extreme of a trait survive better. (One extreme is selected against).

Directional Natural Selection

Stabilizing Natural Selection

Disruptive Natural Selection

Shaping a Population

• Natural selection greatly alters a population over time and can create some very different looking animals that are of the same species.

Same species??

What is a Species?

• A group of similar organisms that can produce viable offspring– Viable: able to produce

offspring (fertile)

A population

• A population has a specific gene pool– All the genes available in

a population

• Allele frequency is the number of times an allele occurs in a gene pool

Creating a Species• New species can occur

when members of a population become isolated from the others.

• Gene flow: when new genes enter a population– Migration– Geographical changes

Creating a Species

• Founder Effect: when some members of a population go to a new area and reproduce – Islands– Migration

What alters a species?

• Genetic Drift can alter an existing species or create a new species– Random change that

alters the gene pool in a population

Altering a Species

• Bottleneck: a change in allele frequency after a dramatic drop in population size– Disease– Natural Disaster

Altering a Species

• Mutations can alter a population.– Beneficial mutations can

help certain individuals survive better

– Need to happen in gametic cells to be passed on

BIG PICTURE!!!

• Some things other than natural selection can change the genes in a population

Can animals of different species mate and produce offspring?

• They’re not supposed to be able to…– Modern science has

allowed some crazy combinations of species.

– Nature has its own method of birth control• Zygotic Barriers

Evidence of Evolution

Evidence of Evolution

• Fossils• Homologous Structures• Analogous Structures• Embryology

Fossils

• Imprints of organisms found in rocks

• Sometimes whole bodies; usually just parts

• Used to see the change in an organism over different time periods– Dinosaurs– Tiktaalik– Early Humans

Homologous Structures

• The same structures found in different organisms– Bones– Parts of plants

Homologous structures are believed to be inherited from a common ancestor

Analogous Structures

• Similar structures among different organisms

• Not the same structure, but used for similar functions or reasons– Wings

Different structure, but similar function

Vestigial Structures

• Structures that are inherited from ancestors but are not used in the modern organism– Original function was

selected against in natural selection

Why keep them?• If the remaining structure does not affect the ability to

survive or reproduce, it can not be selected for or against– Remains neutral

Embryology

• Animals with backbones (vertebrates) go through very similar developmental stages– Gill slits– Tails

REMEMBER DNA??!!!

• All living cells use DNA and RNA to carry out protein synthesis.

• DNA unites every living organism– This genetic code is

nearly identical in almost all organisms

– A T C G and U!

Common Ancestor

BIG PICTURE!!!• All living organisms evolved from one common

ancestor– Several examples of evidence

Modern Evolution

• Drug resistant bacteria– Antibiotics kill off the

bacteria (medicines, sanitizers)

– Those who are able to survive it will pass on those genes

– Superbugs

How it works

THE BIG BIG PICTURE

• Evolution is the gradual change over time

• The Earth provides an environment in which organisms need to survive

• Some traits help an organism survive better in their environment