Changes over time

Life originated from a single-celled organism.

Finding a fossils age helps scientists to construct an evolutionary timeline.

Three types of Structures

Homologous Vestigial Analogous

Homologous Structures

Traits are similar in different species because they share a common ancestor.

The Theory of Evolution

Variation, Adaptation, and Evolution

Evolution Learning Goals: Relate variation and adaptation Describe how fossils are used to study

ancient-life Analyze Darwin’s theory of evolution Explain how scientists reconstruct history

using fossils Identify characteristics defining a species Describe the principles of population genetics Explain the effect of environmental change on

populations

A species consists of organisms that mate with each other and that can produce healthy offspring.

Differences between individuals in a population is called variation.

Ex. Fur color in foxes.• Two things can cause variation:

mutation and recombination• Mutations can be harmful, neutral or

beneficial.

Variation in a Species

Causes of Variation*Two things can cause variation: mutation

and recombination

• Mutations can be harmful, neutral or beneficial

• Beneficial mutations increase the chances of an organism’s survival.

Adaptation

An adaptation is an inherited trait that increases a population’s chances of survival and reproduction in an environment.

Adaptations= advantages that help an organism survive.

Biodiversity

The many different types of organisms that make up a biologically diverse community.

During times of change, populations that are better able to adapt will survive.

Natural Selection’s 4 points: Variation within populations- inherited

through traits. Some variations are favored- improves

chances of survival Not all young survive- few live to

reproduce Individuals that survive and

reproduce are those with favorable traits

Fossils, a peek into the past

Fossils, or the remains of ancient organisms, help scientists learn about Earth’s history.

Changes in the Past

All life originated from a common single-celled organism.

Finding the age of fossils allows scientists to construct an evolutionary timeline.

3 Types of structuresHomologous Vestigial Analogous

Similar structures in different species

Unused structures that are reduced in size

Similar characteristics in different species

Share common ancestor

Share common ancestor

No common ancestor. Independent evolution!!!

Homologous Structures

Causes of Speciation

Geographic isolation- members become separated from the original population due to geographic barrier.

Examples: mountain range, river

** Reproductive isolation- populations cannot or will not be able to produce offspring.

Embryology

Animals at the developmental stage of life look similar, but they grow up looking different.

Page 385 dragonfly book picture

Origin of Species

Speciation- is the evolution of one or more species from a single ancestor species.

Mechanisms of Evolution

There are 3 types of evolution:• Divergent evolution• Convergent evolution• Coevolution

Divergent Evolution Once related populations evolve

independently Often happens because of geographic

isolation Ex. Polar Bear and Brown Bear

Convergent Evolution

Unrelated species have produced (analogous) similar adaptations to help these organisms live in similar environments.

Ex. African Serval cat and S.American Maned wolf (pg.242)

Coevolution

When two or more populations closely interact for a long period of time, they begin to adapt together.

Ex. Hummingbirds and flowers. (pg. 243)

Adaptive Radiation

Evolution of many different, diversely adapted, species from one ancestral species.

Ex. Galapagos finch (13 different species)

Speciation in Darwin’s Finches

1. Founders Arrive – birds arrive2. Separation of Populations- isolated one

bird type onto 2 island3. Changes in Gene Pool – through natural

selection, mutation, etc.4. Reproductive Isolation – new birds don’t

cross-breed5. Ecological Competition – may lead to new

bird6. Continued Evolution – process continues