Lesson 6.1Objectives How scientists use fossils to learn about the history

of life How organisms evolved more complex forms over

time About mass extinctions

Fossil Record – information provided by fossil records and their location.

Fossil record lets scientists identify periods during which different species existed.

Cyanobacteria – earliest known organisms in the fossil record

◦ Contained chlorophyll and used photosynthesis to make sugars from carbon dioxide

◦ The bacteria produced oxygen as a by-product of photosynthesis

The first eukaryotes were single-celled

The oldest eukaryotes are from algae that lived 2 billion years ago.

600 mya the first multicellular animals (jelly-fish like) evolved.

Bacteria and algae – first life forms on land

Primitive insects – first land-dwelling animals

The loss of all the members of a species

Mass extinctions – several periods of huge numbers of species have become extinct in a very short time

Permian extinction – the largest mass extinction in Earth’s history.

Cretaceous Extinction – dinosaurs extinction

Lesson 6.2Objectives•About early ideas and observations on evolution•How Darwin developed his theory of natural selection•How new species arise

Refers to the process through which species change over time

French naturalist Proposed that during the

organism’s lifetime, they change in response to their environment

Example – giraffes long neck

British naturalist He published a book about a voyage in

Galapagos island Beagle – the name of a British navy ship

The book described his observations about how evolution works

Galapagos Island

Darwin observe several types of: Tortoises Finches

According to Darwin: Individuals that are best suited to their

environment survive and reproduce at a higher rate than other members of species in that environment

Overproduction

Variation

Adaptation

Selection

Population – is a group of similar species

In nature, organisms reproduce a lot but not many can survive.

Variation or differences among individuals

Genetic variation happens when offspring get a mix of chromosomes from both parents

An inherited trait that gives an organism’s an advantage in its particular environment

Individuals that adapted in their environment have a good chance of survival.

The adaptive trait will be passed on to their offspring.

Overtime, the useful trait will become more common in the population

The evolution of a new species from an existing species.

Isolation is the key factor that leads to speciation

Lesson 6.3Objectives•How populations increase and decrease in size•What factors affect population size and survival•How species can become extinct

All populations have the ability to grow rapidly over time

Populations tend to remain about the same size

Population increase through births and immigration

Immigration – the movement of individuals into a population

Emigration – the movement of individuals out of the population

Limiting factors:RESOURCESCOMPETITIONPREDATORSDISEASECATASTROPHIC EVENTS

Lesson 6.4Objectives•How scientists develop theories•About the evidence Darwin used to support the theory of natural selection•About additional evidence most scientists use today

Theory – is an explanation of natural phenomena based on a wide range of scientific evidence

Ancestor – is an early form of an organism from which later forms descend

Vestigial Organs – are structures that were fully developed in ancestral organisms but are reduced and unused in later species

Fossils provided evidence that species in the past were very similar to species living in Darwin’s time

Vestigial Organs - similar structures with different functions

Similarities in Development

DNA contains the information that organisms need to grow and to maintain themselves.

When organisms reproduce, they pass on their genetic material to their offspring