Evolution

Sections 15-1 & 15-2

Life’s Diversity

On Earth there are millions of different types of organisms = biological diversity

What is a Theory?

In science, the word theory takes on a new and very different meaning.

A scientific theory is…

• Testable

• Well-supported

• Based on facts, observations, and hypotheses

Evolution Why is there so much biological diversity?

evolution = change over time Process of by which modern organisms have

descended from ancient organisms

Lamarck

First person to propose a theory of evolution.

Law of use and disuseAn organism can lose or change a body

feature during its life time and passes it on to their children

1. Using it -improves2. Not using it - disappear

•short-neck giraffes stretched their necks to reach higher into trees for food = acquired longer necks

•this acquired characteristic was passed on to (inherited by) their off-spring

Lamarck

evolution affects individuals the individuals evolve

environmental changes cause evolution Area with short flowers and hummingbirds with short beaks , now

starts to grow long flowers instead

organisms change in response to the environment

Hummingbirds with short beaks start to develop long beaks all organisms survive

those with short beaks will develop long beaks in time to be able to survive

Charles Darwin

Disproved Lamarck’s theory of evolution

Darwin’s new theory was based on …

natural selection

Charles Darwin sailed on the Beagle around the world.

Voyage of the Beagle made observations, collected fossils, living

organisms, and studied the Earth

Some fossils looked like living organisms while others looked foreign

The Importance of Fossils Darwin asked important questions as he

collected the fossils.

Why had so many species disappeared?

Are these fossilized species related to living species?

What other important info do fossils hold?

The Galapagos Islands Islands were close together but had very

different climates Darwin studied the animals on the islands

Darwin

evolution affects populations Not just individual

environmental changes cause evolution Same as Lamarck

organisms with certain features are naturally selected

hummingbirds with slightly longer beaks are naturally selected for

certain organisms survive hummingbirds with the longer beaks will survive.

Darwin explained evolution by

NATURAL

SELECTION

Mutations

A change in the DNA code, that forms a new trait

Can be good = increase survival Can be bad = decrease survival

Darwin’s Findings

Adaptation A beneficial trait (good mutation) that helps an

organism survive and reproduce

Adaptations evolve (develop or change over time) (1000’s years)

Anatomical - Teeth, body covering Physiological - movement, camouflage, mimicry

Adaptation?

My partially webbed hind feet help me to swim.

My flattened tail acts as a rudder.

My teeth help me to shred cattails and other plants to build my lodge. Sea otter

Adaptation?

My hard outer shell helps to protect my soft body from predators.

I can make my own cement to attach myself to stationary objects.

I have feathery legs for trapping plankton and other food.

Barnacles

Adaptation?

My long beak helps me to drink the nectar from plants.

My wings help me to hover in one place.

My small body is lightweight.

Hummingbird

Behavior adaptations can be learned or instinctive.

1. Social behavior - some animals live by themselves,

while other live in groups.  2. Behavior for protection -  can help to protect the

animal.  For instance the opossum plays dead.  A rabbit freezes when it thinks it has been seen. 

• Migration (birds, whales) • Hibernation (bats, snakes, bears)

Artificial Selection

Aka selective breeding

humans choose attractive matescattle ranchers choose biggest and

healthiest cowsFarmers choose biggest tomatoes

Natural Selection

Nature selects the best traits best traits survive Survive and reproduce = fitness “survival of the fittest”

4 points of Natural Selection "survival of the fittest"

1. Variations exist among members of a population

2. Many more individuals are produced than will survive

3. Members of a population compete for food, space, mates...

4. Individuals that are better adapted survive & reproduce

Evidence of Evolution

1. Fossils2. Bio-geographical 3. Anatomical 4. Embryological 5. Biochemical

1. Fossils

2. Biogeographical

Geographic Distribution of Living Species

? why similar species lived in different locations?

3. Anatomical

Homologous Body Structures

• (definition) different mature forms, but develop from the same embryonic tissues.

• means they all had a common ancestor.

4. Embryology

In the early stages of development, the embryos of many different species look very similar.

Means = a common ancestor!

5. Biochemical

same basic biochemical moleculesDNA, ATP, enzymes ...

Similarities in amino acid sequences (DNA codes) means = a common ancestor