Evolution

Evolution

TIME

13-1 Evolution and Life’s Diversity

• Evolution is a theory, like many other scientific theories

• Scientists have accumulated significant evidence that modern organisms were produced by change over time.

• Evolution: the process by which a species changes over time resulting from environmental pressure.

Who was Darwin?• Lived 1809-1882• Well educated in biology and

natural history• Traveled the world by sea• The plant and animal life he saw

on many of the remote islands he visited, peaked his curiosity.

• Darwin: “Why is it that way?” –famous for the theory of Natural Selection:•Survival and reproduction by individual organisms based on their respective fitness in changing environments.•“Survival of the Fittest”

Diversity of Life• Diversity – a variety of living

things• Estimates for # of species on

Earth range from 3 to 20 million.• More than 99.9% of the species

that have inhabited Earth are now extinct.

What is Fitness?• Fitness- An organism’s ability to

survive and reproduce in a given environment based on its physical traits and behaviors.

• An organism with favorable traits and behaviors is more likely to survive, and pass those traits on to subsequent generations

Principle of Common Descent

• Darwin’s theory that species have shared or common ancestors.

• Just as each individual organisms comes from previous organisms, each species has developed from previous species.

Adaptation• Adaptation: any inherited

characteristic that allows an individual to better survive and reproduce in a given environment–Tiger’s camouflage stripes–Polar bear’s thick fur and fat–Eagle’s talons and beak

Evidence in Living Organisms

• Similarities in Early Development–Embryology

• Similarities in Body Structure–Homologous Structures

• Similarities in Biochemistry

Early Development

• Embryology- study of organisms at early stages of development

• Vertebrates (for example) show significant similarities during early development

Which one is human?

Which one is human?

• Homologous Structures - structures that develop from the same body parts

Ex: Human arm, dolphin fin, bat wing,

bird wing….

Body Structures

• Analogous Structures - Structures that are not homologous, but serve similar purposes:• Ex: trachea tubes vs lungs• Ex: bird wings vs dragonfly wings

• Vestigial Structures - organs or structures that serve no purpose–wisdom teeth, appendix, snake legs–whale pelvis

Biochemistry• DNA/RNA structure identical

throughout all organisms• ATP found in all living systems• Complex proteins (cytochrome c)• Closely related organisms have

almost identical biochemistry

6.5 EvolutionHow Change Occurs

14-1 Evolutionary Theory• A collection of

carefully reasoned and tested hypotheses about how evolutionary change occurs.

Early Explanationsof Evolutionary Change

• Lamarck (1744-1829)–Natural urge to better themselves

–Use and disuse–Passing on acquired traits

Shaping Darwin’s Thinking:• Charles Lyell- Understood that Earth was very old.

Shaping Darwin’s Thinking• Malthus- Babies are being born faster than people are dying.

• Population must be limited• Darwin realized that plant and animal populations must be controlled against growth.

14-2 Evolution by Natural Selection

•Natural Selection- Survival and reproduction by individual organisms based on their respective fitness in changing environments.

14-2 Evolution by Natural Selection

Four Main Parts1. Overpopulation- more individuals born than can survive

2. Variation- Each individual is genetically different.

3. Competition- Individuals compete for resources:

Food, water, space, mates

“Survival of the fittest”

Natural selection- Individual with best traits (adaptations) to the environment will survive and reproduce.

Kettlewell and the

Peppered Moths

Kettlewell and the

Peppered Moths

14-3 Genetics and Evolution

Evolution happens through changes in genes

The environment dictates which adaptations (phenotypes) are favorable.

An individual’s phenotype is controlled by it’s genes (genotype)

The total amount of genes found in a population is the GENE POOL

Changes in the Gene Pool can cause the population to evolve

Changes in the gene pool are caused in many ways

Causes of Change1. Mutations in the genes (DNA) of individuals allowing new adaptations2. Geographic Isolation- population is split by some physical barrier: river, mountain, ocean

3. Reproductive Isolation: individuals unable to breed together: behavior or physical characteristics

4. Temporal Isolation:

changes in mating cycles

The formation of a new species from a preexisting population is SPECIATION.

Some species evolve to new environments with new adaptations-

divergent evolution

The environment also causes different creatures to become similar looking-

Convergent Evolution

4-5 Evolutionary Theory Evolves

Genetic Drift is because of evolution by random chance

No Natural Selection

Happens by accident

2 types of Genetic Drift

1. Bottleneck Effect- Competition is killed and is a random act2. Founders Effect- No competition in new environment – the evolution of a new Island.

Rates of evolution

1. Gradualism- Slow steady evolution of species

2. Punctuated Equilibrium- long periods of no evolution, then brief periods of change

End Here

13-2 The Age of the Earth

• Earth’s age is estimated at 4.6 billion years.

• James Hutton in 1788- proposed that features of the earth were influenced by volcanoes, erosion, etc.. These things all act very slowly

• In 1830, Charles Lyell agreed that the earth had been shaped over a long period of time…but also stressed the importance of explaining theory in terms of scientific method.

Geologic Time Scale• Relative Dating- the age of

some rocks “relative” to others based on their position.

NEWER: RECENTLY DEPOSITED

OLDER: DEPOSITED EARLIER

• Absolute Dating: using scientific techniques to find the approximate actual age of artifacts.

• Radioactive Dating: using the known rate of decay to calculate the age of artifacts. (14C)

Element Half Life

Rubidium-87 50 billion years

Thorium-232 13.9 billion years

Uranium-238 4.5 billion years

Potassium-40 1.3 billion yearsUranium-235 713 million years

Carbon-14 5770 years

13-3 The Fossil Record• Fossils- preserved remains of

ancient organisms• Formation of fossils- when

animals are buried in some medium that prevents decay–mud, sand, silt, tar pits–Sedimentary Rock

• Specific conditions are required for fossils to form –mountains vs. rivers and streams–many organisms never fossilize

• Not all fossils have been found

Problems with the Fossil Record:

• The quality of fossils varies greatly

• As a result, the fossil record is not as complete as paleontologists would like

Cabrian: 500 million

Triassic:

250 million

Jurassic: 200 million

Trilobite

The Fossil Record• Collectively, the millions of

fossils that have been collected make up The Fossil Record

• Many pieces are missing• Scientists have been able to

construct detailed paths of change through time for many species

• Evidence indicates that Earth’s climate has changed significantly over time

• Evidence also shows that species of plants and animals changed to fit those environments, or perished.