1. Name ________________________ Date ______________ Pd _____
Evolution Notes
Name ________________________
Date ______________
Pd _____

2. The History of Life on Earth
Earth has been home to living things for about 3.8 billion years
Fossils provide evidence of earlier life
Fossils – the remains of organisms preserved in the Earth
Types of Fossils:
Hard body parts, such as bone
Minerals replace parts of organism
Prints made by organisms
Original remains of entire organism
Fossilized Bone
Imprint Fossil
Woolly Mammoth
Insect in Amber

3. History of Life Continued…
Relative Dating
Absolute Dating
The age of fossils can be used to determine the history of life on Earth
Relative Dating – by comparing one fossil with another fossil, it can be determined if one fossil was formed before or after another
Absolute Dating – by measuring radioactivity, the exact age of a fossil can be determined

4. History of Life Continued…
Once the age of fossils is determined, the fossil record can be established
Fossil Record – the information about the fossils found in a particular location
The fossil record can be used to determine when a species lived or died

5. The History of Life Continued…
The fossil record indicates that more complex organisms developed on Earth over time
At first, all living things lived in the oceans
First came unicellular organisms (3.8 billion years ago)
These are organisms made of a single cell.
Over time, different types of unicellular organisms developed – bacteria, archaea, protists, etc.
Then came multicellular organisms (1.2 billion years ago)
These are organisms made of many cells
Then came life on land (500 million years ago)
500 million years ago the first multicellular organisms moved from water to land
First came plants, fungi, and insects, then came amphibians and reptiles, finally came birds and mammals

6. The History of Life Continued…
Although organisms were constantly developing, Earth’s history also includes mass extinctions
Mass Extinction – when huge numbers of species have died or become extinct in a very short time
Permian Extinction (250 million years ago)
In this extinction, 90% of the species living in the oceans became extinct
Occurred when Earth’s land masses joined together
Cretaceous Extinction (65 million years ago)
In this extinction, more than half of the species on Earth (including dinosaurs) became extinct
This was caused by a meteorite collision – the evidence of this is the Chicxulub Crater

7. The History of Life Continued…

8. Life Changes Over Time
Because of the fossil record, in the past 200 years scientists have explored the idea of evolution
Evolution – the process through which species change over time
Evolution results from a change in DNA (a mutation)
Jean Baptiste de Lamarck (early 1800s) – he was the first scientist to propose an idea of how life evolved
He proposed that an organism can acquire a trait during its lifetime and pass that trait on to its offspring
This idea could not be supported by evidence so it was not accepted as scientific fact
Jean Baptiste de Lamarck
Lamarck’s Giraffes

9. Life Changes Over Time Continued…
Charles Darwin – A British Naturalist who spent 5 years on the H.M.S. Beagle
He observed animals, especially on the Galapagos Islands
For example, when observing finches, he saw a variety of beak shapes that were adapted to what they ate and where they lived
Charles Darwin

10. Life Changes Over Time Continued…
Darwin proposed the idea of evolution through the process of natural selection
Natural Selection – members of a species that are best suited to their environment survive and reproduce at a higher rate than other members of the species
Natural selection occurs through the continuous cycle of genetic mutation and reproduction
Key Principles of Natural Selection:
Overproduction
Variation
Adaptation
Selection

11. Natural Selection Overproduction: Variation:
When a plant or animal reproduces, it usually makes more organisms than can survive
Variation:
Within a species there are natural differences in traits caused by differences in DNA
These natural differences are passed from one generation to the next
Sometimes there is a change in DNA, a mutation, that is also passed on
Variation
Overproduction

12. Natural Selection Continued…
Adaptation:
Sometimes a mutation occurs that makes an organism better able to survive than others
Adaptation – any inherited trait that gives an organism an advantage in its particular environment
Selection:
Species with an adaptation are more likely to survive and reproduce
This adaptation becomes more common with each generation
The environment is selecting for this trait
Adaptation
Selection

13. Evolution
Through the process of natural selection, new species develop from earlier species
In 1859, Darwin’s observations resulted in the publication of On the Origin of the Species, a book about evolution through natural selection
Speciation: evolution of new species from an existing species
May occur when the environment changes
Isolation is essential to speciation
Speciation of Salamanders
Isolation:
For a species to develop into two new species, two populations must be prevented from reproducing with each other
When separate, they each develop different mutations, which, over time, result in different species

14. Evidence for Evolution
Observations provide evidence for theories
In order to understand the importance of Darwin’s work, it is important to understand the term scientific theory
Scientific Theory:
A statement based on fact and observation
A theory that has been widely accepted is used to explain and predict natural phenomena
Examples of Scientific Theories:
Theory of Gravity
The Big Bang Theory
Evolution through Natural Selection
A scientific theory is NOT a guess or an opinion!!!

15. Evidence for Evolution
Fossil evidence for the evolution of the horse
Fossil evidence supports evolution
Geographic evidence about fossils shows that two species with a common ancestor can develop differently in different locations
Ancestor – an early form of an organism from which later forms descend
Scientists can determine modern plants and algae have a common ancestor in fossil algae

16. Evidence for Evolution Continued
Biological evidence supports evolution
The structure of living things:
Vestigial organs – physical structures that were fully developed and functional in an earlier group of organisms but are reduced and unused in later species
Example – hip and femur bones in whales
Homologous Structures – similar structures with different functions:
Many different species share similar structures, but they are used differently by each species
This indicates a common ancestor
Example – arms and wings
Homologous Structures
Vestigial Organ

17. Evidence for Evolution Continued…
Biological Evidence Continued…
Development of living things:
Similarities in development – scientists have seen that many organisms are very similar during early stages of development, when an embryo
Similarities in Development
genetic
Genetic evidence supports evolution
Scientists can tell how closely related organisms are by comparing their DNA
Example – clock gene

18. Cladograms
Cladogram – a visual representation of the evolutionary relationship among species based on the evidence collected
Show how closely (or distantly) related two species are
Show which species evolved before or after other species
Show the similarities between more closely related species

19. Evolution of Humans Early humanlike species:
Ardipithecus – one of the oldest hominid fossils found
Australopithecus afarensis – Lucy – 3.5 million years old, 1 meter tall
Fossils are 500,000 to 6 million years old
Each species is more humanlike than the one before
Over time, some hominids went extinct and others evolved. Eventually, the only one left was us, Homo sapiens.

20. Evolution of Humans Continued…
Neanderthals and Cro Magnons lived at the same time as modern humans, but went extinct
Neanderthals – Homo neanderthalensis
Lived 130,000 to 35,000 years ago
Larger skulls with sloping foreheads, but shorter than modern humans
Cro Magnons - Homo sapiens sapiens
Lived 35,000 to 10,000 years ago
Tall with large and round skulls
Skilled hunters and toolmakers
Modern humans:
Modern humans are Homo sapiens (“wise human”)
First fossil evidence of modern humans is about 100,000 years old
Cro Magnon Skull