NOTES – EvolutionNOTES – Evolution

Charles Darwin – the “Father of Evolution”Charles Darwin – the “Father of Evolution”

The Diversity of LifeThe Diversity of Life

Millions of different types of organisms Millions of different types of organisms live on the earth todaylive on the earth today

They differ in structures, behaviors, and They differ in structures, behaviors, and genes but are also alike in many waysgenes but are also alike in many ways

Where did all of these organisms come Where did all of these organisms come from?from?

How do scientists explain the How do scientists explain the differences and similarities in living differences and similarities in living things?things?

The Work of The Work of DarwinDarwin

From 1831 to 1836, British scientist Charles From 1831 to 1836, British scientist Charles Darwin sailed around the world as a ship’s Darwin sailed around the world as a ship’s naturalistnaturalist

He observed many living things and formed He observed many living things and formed ideas about evolutionideas about evolution

In 1859, Darwin published On the Origin of In 1859, Darwin published On the Origin of Species, a book in which he explained his Species, a book in which he explained his ideas about evolution and natural selectionideas about evolution and natural selection

Darwin’s work formed the basis for the study Darwin’s work formed the basis for the study of evolution and his ideas are still influential of evolution and his ideas are still influential todaytoday

What is a species?What is a species? SpeciesSpecies – a group of organisms that are – a group of organisms that are

physically similar and can produce offspring physically similar and can produce offspring that are then able to reproduce themselvesthat are then able to reproduce themselves EX. The Eastern EX. The Eastern

Grey Squirrel (1 Grey Squirrel (1 of about 280 of about 280 squirrel squirrel species)species)

What is a species?What is a species? The goal of a species is to survive The goal of a species is to survive

long enough to reproduce a lotlong enough to reproduce a lot

A species that does not reproduce A species that does not reproduce enough is in danger of going extinct enough is in danger of going extinct (disappearing from the Earth forever)(disappearing from the Earth forever)

The traits of a particular species are The traits of a particular species are determined by the genes of that determined by the genes of that speciesspecies

What is a species?What is a species? PopulationPopulation – a group of organisms of the – a group of organisms of the

same species living in an areasame species living in an area

Gene PoolGene Pool – the combination of all the – the combination of all the versions (alleles) of all the genes in a versions (alleles) of all the genes in a population of any speciespopulation of any species

Many versions of genes = larger gene Many versions of genes = larger gene pool = more difference between pool = more difference between individualsindividuals

Few versions of genes = smaller gene Few versions of genes = smaller gene pool = less difference between individualspool = less difference between individuals

A Population of SquirrelsA Population of Squirrels

Where did all the species Where did all the species on the Earth today come on the Earth today come from?from? Remember 2 important statements from Remember 2 important statements from

the cell theory:the cell theory:

1.1. All living things are made of one or more cellsAll living things are made of one or more cells

2.2. All cells come from other cellsAll cells come from other cells

This means that all cells must have come from This means that all cells must have come from some group of original cells in the distant pastsome group of original cells in the distant past

How can different species How can different species come from the same cells?come from the same cells? The simple answer: since the The simple answer: since the

appearance of the first prokaryotic appearance of the first prokaryotic cells about 3.5 billion years ago, cells about 3.5 billion years ago, some of those cells have changed in some of those cells have changed in enough different ways that they now enough different ways that they now form all the different living species form all the different living species

The branch of biology known as The branch of biology known as evolutionevolution deals with this question deals with this question

What is evolution?What is evolution? EvolutionEvolution – Change in species over – Change in species over

time (changes in the gene pool of a time (changes in the gene pool of a species lead to changes in the overall species lead to changes in the overall traits of the species)traits of the species)

This sometimes leads to the formation This sometimes leads to the formation of new species (speciation)of new species (speciation)

Evolution says that species can Evolution says that species can change over many generations of change over many generations of reproductionreproduction

Evolution happens to a species NOT to Evolution happens to a species NOT to individual organismsindividual organisms

What is the main idea of What is the main idea of evolution?evolution? The main idea of evolution is that all The main idea of evolution is that all

species are descended from the first species are descended from the first living organisms, which were living organisms, which were prokaryotic bacteriaprokaryotic bacteria

Species alive today share common Species alive today share common ancestors some time in the pastancestors some time in the past

The more closely related 2 species The more closely related 2 species are, the more recent their common are, the more recent their common ancestor existedancestor existed

Common ancestorCommon ancestor – a species that – a species that existed in the past that split into 2 existed in the past that split into 2 groups which eventually became 2 groups which eventually became 2 different speciesdifferent species

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

What is the main idea of What is the main idea of evolution?evolution?

A few steps in the history of A few steps in the history of species…species…

mya = million years ago mya = million years ago (1,000,000)(1,000,000)

1.1. 5 mya – common ancestor of 5 mya – common ancestor of humans and chimpanzeeshumans and chimpanzees

2.2. 70 mya – common ancestor 70 mya – common ancestor of primates (humans, apes, of primates (humans, apes, monkeys) and grazing monkeys) and grazing animals (horses, etc.)animals (horses, etc.)

3.3. 250 mya – common ancestor 250 mya – common ancestor of mammals and reptilesof mammals and reptiles

4.4. 450 mya – common ancestor 450 mya – common ancestor of vertebrates (animals with of vertebrates (animals with a backbone) and a backbone) and invertebrates (animals invertebrates (animals without a backbone)without a backbone)

5.5. 1,000 mya – common 1,000 mya – common ancestor of animals and ancestor of animals and plants plants 3,500 mya – common 3,500 mya – common ancestor of all life, the first ancestor of all life, the first prokaryotic cells prokaryotic cells

A few steps in the history of A few steps in the history of species…species…

4,500 mya – the formation of the 4,500 mya – the formation of the EarthEarth

13,000 mya – the formation of 13,000 mya – the formation of the Universethe Universe

If you compare the history of life If you compare the history of life on Earth to one year, the first on Earth to one year, the first bacteria arrive at 12:00 AM on bacteria arrive at 12:00 AM on January 1st and the first humans January 1st and the first humans appear at 11:59 PM on December appear at 11:59 PM on December 31st – 364 days, 23 hours and 59 31st – 364 days, 23 hours and 59 minutes later – We haven’t been minutes later – We haven’t been here very long!here very long!