1. Basic Life Science Unit 4 Lecture
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Chapter 4

2. Evolution The earth is 4 billion years old
We have found evidence that creatures that lived long ago were more simple than those living today
This gradual change over time is call evolution

3. Species
A species is a group of organisms that look alike and can reproduce with each other and make fertile offspring

4. Adaptations
An adaptation is a trait that makes the organism better suited to live in its environment
Ex: camouflage
Ex: Thick skin in reptiles

5. Mutations A mutation is the random change in a gene
Usually mutations are hidden
Sometimes mutations can be helpful or deadly
A white python has a mutation in its gene for skin pigment

6. The Fossil Record
By investigating the fossil record, scientists can see that animals have changed over time
They have also found evidence of past climate changes
Scientists have found fossils of extinct organisms

7. The Changing Horse
The most complete fossil record of an animal that has changed over time is the horse
The earliest horse lived 60 million years ago and was ¼ of today’s size

8. Similar Body Structures
A lion’s foreleg, a bat’s wing, and a dolphin’s flipper all contain similar bones
Homologous structures are bones that were inherited from a common ancestor.

9. Vestigial Structures
Some homologous structures that were inherited from an ancestor long ago no longer have a function
A whale hip bone
A human tail bone

10. DNA Evidence
The more DNA organisms share with each other, the more closely they are related
This means they evolved from a common ancestor
We share 80% of our DNA with mice
We share 99% of our DNA with chimpanzees

11. Explaining Evolution
The fossil record shows that living things change over time

12. Lamarck’s Theory
Lamarck thought that species develop new characteristics to help them adapt to their surroundings
Giraffes and their long necks

13. The Voyage of the Beagle
Darwin sailed on a ship called the Beagle to the Galapagos Islands
Every island had a different species of tortoise
He also found different species of finches
Each had a beak adapted for eating a certain type of food

14. Natural Selection
Natural selection is the mechanism that drives evolution
In order for evolution to occur, the following four criteria must be met:
1. more offspring than can survive
2. competition for resources
3. variation in traits
4. survival of the most fit

15. Natural Selection
Remember from last unit that all animals need food, water, and shelter
They compete for these resources
Humans cause changes in population due to pollution and other changes in the environment
This has led to the extinction of many species

16. Early Human-like Species
The human fossil record is still being pieced together each time new skeletons are found
Lucy, an Australopithecus afarensis, lived 4.5 million years ago
She was 3 feet tall and walked upright
We have found human like fossils as old as 6 million years old

17. Modern Humans We belong to the genus and species Homo sapiens
Our earlier Homo sapien ancestors were Neanderthals and Cro-Magnons

18. Comparing our ancestors
Neanderthals
Short, stalky build
Hunted big game
No body art
No jewelry
Limited tool usage
Lived near caves
Cro-Magnons
Taller, leaner
Had a more diversified diet
Wore body art
Jewelry
Had a variety of tools
Moved across various terrain