Evolution

Not necessarily a scary word…

DISCLAIMER!1. My job as a science teacher is to teach you science. This

includes scientific theories, laws and discoveries over time. These are theories that have been tested repeatedly, analyzed and peer- reviewed.

2. I am teaching you the scientific theories behind Earth’s history. I am NOT teaching you religious theories (because that is not my job).

3. You do not have to agree with or believe all or anything I teach you.

4. If you are curious about other beliefs and theories on Earth’s history I recommend asking a parent, religious leader, other community member or reading about the topic.

5. Remember, I am not telling what to believe. I am merely giving you information so that you will be better educated on the topic. You choose what to believe and how to think

When you think of evolution, what do you think?

Did you think of these?

To evolve is to change

The Earth and its life have changed over the past 4.6 billion years.

How do we know about past life on Earth?

From the rocks! The fossil record. People have found fossils and developed ways to date the Earth.

These are used to study past life on Earth.

Where did it all begin??

Charles Darwin, a naturalist, read a book and went on a trip.

He read Charles Lyell’s Theory of Uniformitarianism….

He sailed to the Galapagos Islands

As he traveled between islands

Darwin collected animals (esp. finches) and he noticed something…

Members of a certain species were slightly different on different islands.

Why?

The finches at each island had adapted, or changed, over thousands of years to be able to survive.

Finches adapted, or changed, to eat the food on their islands. The seeds, plants and bugs on each island were different…

Some seeds were big and in hard shells and some bugs were hidden deep in narrow flowers… So over time the finches that had the best adaptations for getting food survived and had little babies with their same genes.

Natural Selection:The theory that the organisms best suited to the

environment will be most likely to survive and produce offspring.

What would artificial selection be?Processes such as breeding choose what traits

are passed onto future generations.

This ability to survive due to your adaptations is called

Survival of the Fittest

Meaning the most fit, or the ones who can find the food, survive and reproduce will be able to successfully pass on their genes to their children and their children and their children.

The same evolutionary processes work for all plants and animals

Say thousands of years ago there was a weird giraffe. This giraffe had a mutation on his gene for neck length causing his neck to be longer than all the other giraffes. They made fun of him. But one day he realized he could reach all of the nice green leaves on the tops of trees while the other giraffes had to compete for the lower down leaves.

When a volcano erupted shading the land, only the tall plants with big leaves on top were able to get enough sunlight for photosynthesis. All of the giraffes with shorter necks competed over the few lower leaves until they were all gone. The weird long-necked giraffe, however, survived because he could reach the high-up leaves.

When he met another lovely giraffe and had children most of them got his long-neck gene as did their children. The other giraffes had either died of starvation, were too hungry to reproduce or their children and grandchildren did not get enough food. Over thousands of years the long neck giraffes eventually out-competed the short neck giraffes and the short-neck giraffes became extinct. The log-necked giraffes were the “fittest” and therefore they and their offspring survived.

Now… what will happen if one day tree stop growing leaves on their higher branches?

Now…

Say one of the short-neck giraffes had stretched and stretched until his own neck became a little longer due to his lengthening of his muscles. Would his offspring have longer necks?

No! Because only the GENES in an organism’s DNA can be passed down.They are naturally selected.

If your have an unfortunate accident with a saw and lose your thumb, does that mean your children will be born without thumbs??

No! Because you still have the gene for a thumb which you will pass onto your children.

Will this lady’s children have long necks like hers? (Hint: she has stretched her neck with rings over time)

Every organism on Earth has evolved, or changed, over time. Including humans.

Over millions of years evolution caused extinctions (the loss of every member of that species) and caused new species to emerge.

Does that mean humans used to be monkeys??

Not really… Humans are a different species from other primates (chimps, gorillas, baboons etc..) We have a different genetic make up.

So where do the rumors come from?

Scientific evidence. Scientists have discovered that the gene sequence (remember genes give us our traits) of humans is very close to that of chimpanzees.

Why? Are we related to Chimps?Your relatives are your mother, father, aunts, uncles

cousins and so forth…

So chimps aren’t really our relatives. But our DNA sequence is so similar to theirs because

we share a common ancestor.

Many different species of living organisms, that look and act very differently, share common ancestors.

How do scientists know??

The fossils in the rocks and dating techniques

Scientists and Anthropologists have been studying fossils, Ice Cores and other core samples for hundreds of years.

Now that they have figured out dating techniques such as Carbon-14 and radiometric dating they are able to place fossils on a timeline.

Ice cores

Carbon 14 Dating

Homologous- same original structure from a common ancestor but the use has evolved.

Analagous- similar use, but structures come from different ancestors.

Some of the homology between humans and other primates is due to their common ancestor millions of years ago. Humans and other primates each split off to have specialized traits. For example, humans evolved a large skull to fit a large brain which has allowed us to become such sophisticated intelligent organisms. Other primates evolved or retained specialized structures such as long arms and thick jaws to help them move through trees and eat.

Why does everything change?

Environmental pressures or changes in the environment.

What are some possible examples??What role does competition play??

Also gene mutation and inheritance of genes…

Today’s biotechnology

Has led to an increase in intentional gene sequencing and mutations.

This is done either to create genetically modified organisms for a specific purpose, or to treat disease.

What are some upside and downsides to genetically modified organisms?

If they begin to genetically modify everything how could this become a problem in the future?

To sum it up…An acrostic poem, in sentences using the

following terms… evolution (or evolve), ancestor, gene, mutation, trait, survival of the fittest, Charles Darwin and Galapagos.

CHANGE