Charles Darwin, Evolution - PowerPoint Presentation

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Charles Darwin, Evolution

&

Natural Selection

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studied medicine at Edinburgh University (1825-1827) where the sight of blood and surgery without anesthetics repulsed him

studied to become a clergyman at Cambridge University (1827-1831)

born in Shrewsbury, England, in 1809

Charles Darwin

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After Cambridge, Charles was recommended for a surveying trip on the HMS Beagle.

He sailed aboard the

Beagle

for 5 years, working as a

naturalist.

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This voyage lasted from 1831 to 1836.

The

Beagle

sailed around the world.

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At the time Darwin made his trip, the majority of people believed the Earth and all of its forms of life had been created only a few thousand years in the past.

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People also believed in

fixity of species

;

in other words, species never changed

.

After careful observation

and study of new scientific discoveries, Darwin began to think otherwise.

People also believed that the Earth had not

changed

during those few thousand years.

The first dinosaur to be described scientifically was

Megalosaurus

by William Buckland in 1824.

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Darwin was influenced by geologist James Hutton’s writings that described

geologic

forces he thought had

changed and were still

changing the

earth.

Hutton proposed that the Earth had to be

much more than a few thousand years old.

The Father of Geology

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Darwin was also influenced by geologist Charles Lyell who wrote

Principia

Geologica

.

Lyell’s book proposed that tremendous

geologic processes

had shaped the Earth such as seen in volcanoes

active in the present.

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On the voyage, Darwin noticed that everywhere he went, the

animals

and

plants

differed vastly.

Patterns in the species suggested that the species had

changed

over time and had given

rise

to

new

and

different

species.

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The Galapagos Islands lie

500

miles west of Ecuador in the Pacific Ocean, directly on the

equator

.

Many of Darwin’s conclusions were based on observations of wildlife in the

Galapagos

Islands.

“Galapagos” means turtle.

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What it must have been like to be Darwin…

Darwin noticed on these islands, there were several types of finches.

Galapagos finches

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In particular, Darwin observed something

odd

about the finches: they all

looked like a bird he had seen on the

South American continent.

Galapagos finches

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Darwin wondered if the birds and other animals had been

created

to

match their environment, why didn’t these birds look like the birds of the

African continent, since the environments of both the

Galapagos and Africa were

similar.

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Darwin guessed that some of the birds from South America

migrated

to the Galapagos.

Once on the islands, the birds must have

changed

over the years.

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This would explain the

numerous

species of birds present.

woodpecker finch

cactus finch

large ground finch

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Darwin called this…

or

evolution

(change in species over time)

Darwin concluded:

Each species has descended, with changes, from other species over time.

Descent With Modifications

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EVOLUTION IS

GENETIC CHANGE IN A POPULATION THROUGH TIME

.

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EVIDENCE

OF EVOLUTION

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Charles Darwin

On his journey around the world, Darwin found evidence of

gradual

change (evolution).Darwin cited evidences he found in fossil records, geographic distribution and

homologous structures.

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Evidences of Evolution

Today most evidences for evolution are grouped into five main categories:

Fossil Record

BiochemicalComparative AnatomyBiogeographyObservable Events

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FOSSIL RECORD

Paleontology

Fossil – remains or traces of an

organism that lived long agoRemains: ex. bones, teeth, or shellTraces: ex. burrow,

footprint, or imprint

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FOSSIL RECORD

Most fossils are found in layered

sedimentary rock

Oldest fossils are on the lowest layer

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FOSSIL RECORD

Comparing fossils from different layers shows:

Life on Earth has

changedIncreased number of life forms

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FOSSIL RECORD

When Whales Had Legs

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BIOCHEMICAL

THE GENETIC CODE

Triplets of DNA nitrogen-base sequences that

code for specific amino acidsThe amino acid triplet is the same in almost all organisms.

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BIOCHEMICAL

The similarity of triplet

DNA codes making-up amino acids shows

:A probable common ancestor for all life on Earth

Amino Acid Sequencing is probably the STRONGEST evidence for relationships among organisms

.

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COMPARATIVE ANATOMY

HOMOLOGOUS STRUCTURES

structures with

similar structure but different function(ex: turtle, alligator, bird, mammal)

Turtle

Alligator

Bird

Mammal

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COMPARATIVE ANATOMY

Homologous structures show

Similar genes

Descent from a common ancestor

Turtle

Alligator

Bird

Mammal

Ancient lobe-finned fish

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COMPARATIVE ANATOMY

VESTIGIAL STRUCTURES

organs so

reduced in size that they are nonfunctioning remnants of similar organs in other species

ex: human tailbone, appendix, whale pelvis

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COMPARATIVE ANATOMY

Vestigial structures show:

an organism’s

evolutionary pasta common ancestor with species that have similar

structures that are still functioning

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COMPARATIVE ANATOMY

When Whales Had Legs

Vestigial Structures

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COMPARATIVE ANATOMY

EMBRYOLOGY

Embryos of different species

may appear similar in early stages of development ex:

vertebrate development

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COMPARATIVE ANATOMY

Comparison of similarities in embryos can show:

Relationship to a

common ancestor

Human embryo

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BIOGEOGRAPHY

GEOGRAPHIC DISTRIBUTION OF ORGANISMS

organisms living

widely apart (even different continents) may be similar because they share a common ancestor

Beaver

Muskrat

Beaver andMuskrat

Coypu CapybaraCoypu andCapybara

Shows common ancestor

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OBSERVABLE EVENTS

Some changes in species have been observed and studied:

Peter

&

Rosemary Grant’s

Study of Beak Size Shift in Darwin’s Finches

H.

Kettlewell’s

Study of

Peppered Moth

Color Shifts

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OBSERVABLE EVENTS

Observable events show that

evolution

is an ongoing process

Peter & Rosemary Grant’s Study of Beak Size Shift in Darwin’s Finches

H. Kettlewell’s Study of Peppered Moth Color Shifts

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Malthus was a British social scientist who made these observations about humans:

People have more

children

than are able to

survive

.

There are built-in population checks:

disease

,

famine

, and

war

.

Darwin based his theory on his own observations and the writings of Thomas Malthus.

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Darwin extended these principles to biology, which helped him form his theory of…

Natural Selection

…or

Survival of the Fittest

.

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Five basic components of

Natural Selection

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1. All species have

genetic

variation.

Every species is

different

, even within itself.

Look around you…are you all the same?

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2.

Organisms produce more

offspring

than can survive

. Many that survive do not produce offspring

.

The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches.

It is likely that less than 1%

of the hatchlings will ever reach sexual maturity.

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3. Since

more organisms are produced than can survive, there is

competition

(struggle for existence).

Competition exists WITHIN and AMONG species.

food

Within and Among Species for

And Within a Species for

water

mates

shelter

space

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The constant struggle for survival is affected by short-term natural disasters. (

drought

, fires, floods,

snowstorms, hurricanes, and tornadoes)

The constant struggle for survival is also affected by long-term changes in the environment. (

ice ages, biome shifts, etc)

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4.

Survival of the fittest

Some organisms are more suited to their environment as a result of variations in the species.

Fitness: the ability of an individual to

survive and reproduce

in its specific environment. Fitness is a result of adaptations

.

He who spreads the most genes wins!

1st

Individuals that are fit to their environment

survive

and leave more

offspring

than those who aren’t.

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5.

Decent

with

modification: Living species today are descended with modifications from common ancestral species that lived in the past.

Over time, genes for

less favored characteristics will be eliminated

from the gene pool.

Example:

giraffes

and their increasingly

longer necks

.

Characteristics of fit individuals

increase

in a population over time.

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Natural Selection: Survival of the Fittest

the variation exists first.

An

adaptation

is any inherited characteristic (a

genetic variation

) that can increase an organism’s chance of survival.

the environment changes.

a variation may give an advantage to survive environmental change.

An organism does not change because of

need

or

desire

to survive. The organism either already has the

variation

that enables it to survive or it

dies

.

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