Basic Life ScienceUnit 4 Lecture

Pages 98-99 and 102-111Chapter 4

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

Species

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

Adaptations

• An adaptation is a trait that makes the organism better suited to live in its environment

• Ex: camouflage• Ex: Thick skin in reptiles

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

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

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

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.

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

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

Explaining Evolution

• The fossil record shows that living things change over time

Lamarck’s Theory

• Lamarck thought that species develop new characteristics to help them adapt to their surroundings

• Giraffes and their long necks

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

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

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

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

Modern Humans

• We belong to the genus and species Homo sapiens

• Our earlier Homo sapien ancestors were Neanderthals and Cro-Magnons

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