History History ofof Life Life onon Earth Earth

It Started with the SunIt Started with the Sun

From a ball of swirling gas a centre point From a ball of swirling gas a centre point emerged. emerged.

This centre mass became the Sun.This centre mass became the Sun.99.8% of the entire mass of our solar 99.8% of the entire mass of our solar

system is contained in the Sun. system is contained in the Sun. Nuclear fusion powers the Sun. Nuclear fusion powers the Sun.

Essentially 4 H Essentially 4 H He + energy +2 neutrinos He + energy +2 neutrinos

This reaction began about five billion years This reaction began about five billion years ago. ago.

We estimate that the Sun is about halfway We estimate that the Sun is about halfway through its life cycle, so we only have through its life cycle, so we only have about five billion years to go before the about five billion years to go before the Sun burns out.Sun burns out.

No Sun no life.No Sun no life.

Some of the gas at the centre as it was Some of the gas at the centre as it was cooling was ejected outwards.cooling was ejected outwards.

This gas further cooled and collected to This gas further cooled and collected to form the planets, and some other debris.form the planets, and some other debris.

Remember that all the masses of the Remember that all the masses of the planets and debris only account for about planets and debris only account for about 0.2% of the entire mass of our Solar 0.2% of the entire mass of our Solar System. System.

Luckily at about 1.5 x10Luckily at about 1.5 x1088 km from the Sun km from the Sun a little speck formed.a little speck formed.

This is just the right distance from a star This is just the right distance from a star for life, as we know it, to form. for life, as we know it, to form.

This little speck became known as the This little speck became known as the Earth.Earth.

Once Upon a Time on Earth Once Upon a Time on Earth

The history of life on Earth began approx. The history of life on Earth began approx. 3.5 billion years ago.3.5 billion years ago.

How this occurred has been and will How this occurred has been and will continue to be a topic for inquiry.continue to be a topic for inquiry.Remember people often just thought that life Remember people often just thought that life

was life and little questioning occurred.was life and little questioning occurred.Until science came along.Until science came along.

Scientific evidence indicates that since Scientific evidence indicates that since life’s beginning, each organism that has life’s beginning, each organism that has inhabited this planet has been the product inhabited this planet has been the product of evolution.of evolution.

Evolution is the change of an organism Evolution is the change of an organism over time.over time.

Let’s Visualize Let’s Visualize

Could you physically carry $1 billion Could you physically carry $1 billion dollars?dollars?

Let’s VisualizeLet’s Visualize

One One millionmillion dollars would be a stack of dollars would be a stack of $1000 bills approx. 1 metre high. (1000 $1000 bills approx. 1 metre high. (1000 bills high)bills high)

AA billion billion dollars would be 1000 metres dollars would be 1000 metres high. (1 million bills)high. (1 million bills)

The Earth was over 1 billion years old The Earth was over 1 billion years old beforebefore any kind of life was present. any kind of life was present.

We can use Radiometric dating, looking at We can use Radiometric dating, looking at the amount of radioactive isotopes present the amount of radioactive isotopes present in a sample, to determine the age of in a sample, to determine the age of something, including the Earthsomething, including the Earth

Isotopes are different forms of an element Isotopes are different forms of an element that have differing atomic masses. that have differing atomic masses.

Half-life is associated with this.Half-life is associated with this.How long half of a substance will exist as it How long half of a substance will exist as it

decays.decays.Carbon-14 is a common one isotope used for Carbon-14 is a common one isotope used for

things up to about 50 000 years old.things up to about 50 000 years old.

Most scientist believe that life on Earth Most scientist believe that life on Earth developed through natural chemical and developed through natural chemical and physical processes. (p.253 text)physical processes. (p.253 text)

Essentially nonliving matter reacted to Essentially nonliving matter reacted to produce life, due to the presence of the produce life, due to the presence of the Sun, and volcanoes. Sun, and volcanoes.

These molecules combined to form more These molecules combined to form more complex molecules and then eventually complex molecules and then eventually life.life.

This process of nothing to something is This process of nothing to something is known as spontaneous origin.known as spontaneous origin.

There are two main models to help explain There are two main models to help explain this spontaneous origin.this spontaneous origin.

Primordial Soup Model, andPrimordial Soup Model, andthe Bubble modelthe Bubble model

Explain the Primordial Soup Model.Explain the Primordial Soup Model.

This model states that there were many This model states that there were many different types of organic molecules different types of organic molecules present in the ocean, like a soup. present in the ocean, like a soup.

These organic molecules were formed These organic molecules were formed when energy from the sun, volcanoes and when energy from the sun, volcanoes and lightning were added to the oceans.lightning were added to the oceans.

Due to high levels of energy these Due to high levels of energy these molecules could freely interact. molecules could freely interact. (More energy (More energy led to electron interactions between molecules.)led to electron interactions between molecules.)

Explain the Bubble Model.Explain the Bubble Model.

This model states that the key process to This model states that the key process to form chemicals for life took place within form chemicals for life took place within tiny bubbles on the surface of the oceans.tiny bubbles on the surface of the oceans.

Underwater volcanic activity released Underwater volcanic activity released gases, gases in a liquid form bubbles.gases, gases in a liquid form bubbles.

The bubbles may have protected these The bubbles may have protected these gases from harmful UV rays. (Reactions in gases from harmful UV rays. (Reactions in bubbles would happen quicker, which was bubbles would happen quicker, which was a flaw of the primordial soup model”.)a flaw of the primordial soup model”.)

Bubble cont.Bubble cont.

Most gases are lighter than liquids so they Most gases are lighter than liquids so they rose to the surface of the oceans, which rose to the surface of the oceans, which then released these organic molecules then released these organic molecules into the air. (Not Ointo the air. (Not O22 rich yet.) rich yet.)

Still able to rise further chemical reactions Still able to rise further chemical reactions were able to occur.were able to occur.

Some of the more complex molecules Some of the more complex molecules returned to the oceans for more reactions returned to the oceans for more reactions to take place.to take place.

According to TheoryAccording to Theory

What was the importance of oxygen?What was the importance of oxygen?

Oxygen was essentially “tied up” with Oxygen was essentially “tied up” with hydrogen and minerals. This did not allow it hydrogen and minerals. This did not allow it to freely be present in our atmosphere. UV to freely be present in our atmosphere. UV radiation helped release some oxygen which radiation helped release some oxygen which eventually formed ozone (Oeventually formed ozone (O33). Remember ). Remember

that ozone helps filter UV, too much UV is that ozone helps filter UV, too much UV is bad, it may lead to mutations.bad, it may lead to mutations.

According to Theory According to Theory

What was the first step that led toward What was the first step that led toward cellular organization?cellular organization?Microspheres might have led to cellular Microspheres might have led to cellular

organization.organization.Microspheres are short chains of amino acids Microspheres are short chains of amino acids

that gather into tiny vesicles.that gather into tiny vesicles.Microspheres that survived for a long time Microspheres that survived for a long time

may gathered more molecules that led to an may gathered more molecules that led to an organization. organization.

According to TheoryAccording to Theory

How did the development of heredity How did the development of heredity contribute to the successful formation of contribute to the successful formation of life?life?Heredity is a necessary feature of living Heredity is a necessary feature of living

things. Microspheres that contained things. Microspheres that contained replicating RNA might have transferred both replicating RNA might have transferred both their structure and their RNA to offspring. their structure and their RNA to offspring.

Models can change, when might a model Models can change, when might a model change?change?Models may change as our understanding Models may change as our understanding

increases. increases.

More information usually changes peoples More information usually changes peoples thinking.thinking.

The AtmosphereThe Atmosphere

Is the Atmosphere an infinite resource? Is the Atmosphere an infinite resource?

Will it always be present in its current Will it always be present in its current form?form?

So long ago the atmosphere was a hostile So long ago the atmosphere was a hostile place for life as we know it.place for life as we know it.

Ammonia, Methane, Carbon Dioxide were Ammonia, Methane, Carbon Dioxide were some of the main constituents of our some of the main constituents of our atmosphere.atmosphere.

It took an oxygen rich atmosphere for life It took an oxygen rich atmosphere for life to really exist. to really exist.

Is there a problem now? Is there a problem now?

Complex Organisms DevelopmentComplex Organisms Development

See Graphic Organizer on BoardSee Graphic Organizer on Board

Write down the definitions for the Write down the definitions for the following.following. fossilfossilcyanobacteriacyanobacteriaeubacteriaeubacteriaarchaebacteriaarchaebacteriaendosymbiosisendosymbiosisProtistsProtistsmass extinctionmass extinction

Compare and ContrastCompare and Contrast

Use a Venn Diagram to show similarities Use a Venn Diagram to show similarities between prokaryotes and eukaryotes.between prokaryotes and eukaryotes.

Why might mass extinctions be important?Why might mass extinctions be important?

ProjectProject

Create an interesting Time Line of life on Create an interesting Time Line of life on Earth.Earth.

Start at about 3.5 billion years ago and go Start at about 3.5 billion years ago and go to present day.to present day.

Show at least 25 biological events that Show at least 25 biological events that have occurred during this time.have occurred during this time.

Due Tuesday 15.01.08 Due Tuesday 15.01.08