e v o l u t i o n i s : c h a n g e s i n o r g a n i s m s o v e r t i m e

Evolution

is:

Changes in

Organisms

Over Time

Age of EarthAge of Earth

Scientist believe that the Earth is 4.6

Billion years old.

•Evidence:

Rock data, environmental changes

“Isn’t Evolution Just A Theory? Clip

How did the theory of Evolution come about?

• James Hutton -1785-Earth is millions of years old.

• Thomas Malthus -1798- populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another

• Jean-Baptiste Lamarck -1809-believed that all life forms evolved and that the driving force of evolution was the inheritance of acquired characteristics. He believed that organisms changed due to the demands of their environment.

•1831: Charles Darwin – voyage to the Galapagos Islands•Lyell -1833- plant and animal species had arisen, developed variations, and then became extinct over time. He also believed that the Earth’s physical landscape changed over a long period of time. •Alfred Russel Wallace -1858-competition for resources is the main force in natural selection •Charles Darwin -1859- Publishes “On the Origin of Species”

Charles Darwin

British Naturalist

1809 -1882

“I have called this principle, by

which each slight variation, if

useful, is preserved, by the

term Natural Selection.”

—Charles Darwin from "The Origin

of Species"

CHARLES DARWIN

*served as a

naturalist on the

HMS Beagle from

1831 to 1836

*found fossils of

extinct animals that

looked like modern

animals

*did most of his

work on the

Galapagos Islands

CLIP

On the Galapagos Islands Darwin noticed many variations among plants and animals of the same general type as those in South America. clip

Finches- noticed different shapes and sizes of beaks which fit the type of food each bird eats

Tortoises- noticed different shaped shells which allowed for different neck movement based on the environment

Natural Selection

•Only the ones that are most suited for the environment will survive and reproduce and pass on their genes.

Video Clip

If an organism reproduces, then the traits of that organism are passed to

the next generation.Traits that are favorable for a

certain environment become more prevalent within that population.

What if the environment What if the environment changes?changes?

The organisms must adapt to the environment.

Those that don’t adapt-die.

This is a very slow process….does not occur over night…many generations must past before any change in the

population can be seen.

Example: Peppered MothExample: Peppered Moth

*Two versions of

the moth-

1.Black

2.Peppere

dDuring the

Industrial

Revolution

pollution

covered

treesPopulation

ofmothschanged

When the trees were normal, the black moths were easily seen by the birds, so there were more peppered moths that survived.

When the trees were black, the peppered moths were easily seen by the birds, so there were more black moths that survived.

Decent with modifications

Overtime natural

selection

produces

organisms

that have

different

structures,

different

niches, or

different

habitats.

Organisms that were once the same have now grown “apart” and have become different organisms.

These changes increase a

species’ fitness in their

environment.

Examples: The largest hog, the cow that gives the most milk, fastest horse, domesticated dogs.

Darwin compared the processes of nature to …Artificial selection –aka- selective breedingHumans select and breed for most desirable traits.

WOLFHUSKY

Crab ClipCrab Clip

Evidence for Change Over Time

1. Fossil Record– Fossils that show how

an organism looked millions of years ago.

2. Geographic Distribution

3. Comparative Anatomy and Embryology

4. Genetics & Molecular Biology

How do we know evolution is happening? Clip

Relative Dating of fossils helps us to know how old organisms are and when they lived…

Homologous

structures

Structures

that have

different

mature

forms in

different

organisms

but have

developed

from the

same type

of tissue.

Embryology-study of

early stages of

development

This may show that organisms

had a common ancestor.

Vestigial organsVestigial organs–Organs or structures Organs or structures that are no longer that are no longer used by an organism. used by an organism.

–They are usually They are usually reduced in size.reduced in size.

Vestigial Organs

c

Sources of Genetic Sources of Genetic

DiversityDiversity

DNA sequences in

organisms are close

Sources of genetic

variation in species:

1.Mutations

2.Gene Shuffling (Ex.immigration

& emigration)

3.Crossing over during

meiosis

Speciation

•the evolution of a new species when the genes in a population changes

•Overtime they can change so much that they become unable to breed as they adapt to their environment.

Speciation Mechanisms• Behavioral Isolation

– Populations are capable of interbreeding, but have different courtship rituals or other type of behavior.

• Geographic Isolation– Separated by bodies of water or mountains.

• Temporal Isolation– Reproduction takes place at different times of the year

Gene Pool•Combined

genetic

information

of a particular

population.

•All the

genes present with

in a population

•Can change!

Changes in allele frequency with in a population

Genetic drift

•Random changes in allele frequency

that occurs in small populations

•Also know as the “founder effect”

•Populations may move into a new area

and the alleles that carry with them will

be passed on to their offspring.

Divergent Evolution•when two or more related species become more and more dissimilar.•The red fox and the kit fox provide and example of two species that have undergone divergent evolution. •As they adapted to different environments, the appearance of the two species diverged.

Example…Adaptive Radiation

Convergent Convergent EvolutionEvolution

•Convergent evolution is when

organisms have similar functions

and appearance but

that evolved through widely different evolutionary paths.

•EX: multiple origins

of wings (bats, birds) and eyes.

Coevolution•Predators and their prey •Parasites and their hosts•One example of coevolution is between plants and the animals that pollinate them.

Coevoluti

on is the

joint

change of

two or

more

species in

close

interactio

n.

Evolution is the ______ in a species over

_____.

REMEMBER!!!!!!!

StructuralAdaptation

• Change in physical structure or anatomy

• EX: wings of a seagull

TYPES OF ADAPTATIONS

PhysiologicalAdaptation

• Change in internal function or chemistry

• EX: having the proper enzyme to digest carbs

BehavioralAdaptation

• Change in behavior that responds to environment

• EX: lay eggs in nests

Rates of Evolution

GradualismGradualism• Very gradually change, over a long time...

• Change is slow, constant, and consistent.

• Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die.

CLIP

3388

•change comes in spurts.

•There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals.

Punctuated Punctuated EquilibriumEquilibrium

LABEL each as gradualism or punctuated equilibrium

GRADUALISM PUNCTUATED EQ

PUNCTUATED EQ GRADUALISM

Resistance in Bacteria

3939 Read page p403.

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