Biology Chapter 15

Evolution Unit:

Darwin’s Theory of Evolution

15-1 The Puzzle of Life’s Diversity

I. Background: Evolution and Its Core Principles

A. Evolution is a

T. Zobzhansky: “Nothing in biology makes sense except in the light of evolution.”

Central theme in biology

B. Core principles of evolution:

1. All life is linked through a ___________________

2. Populations of living things ___________________ (evolve).

3. The _______________________

this change (natural selection) so

that advantageous traits are selected over less advantageous traits.

4. The _________________________________ ____________________________________ (descent with modification).

Common ancestor

Change over timeEnvironment influences

advantageous traits become morecommon in the population

Peppered Moth

Example of

natural selection

II. Voyage of the BeagleA. A sea voyage helped

____________________

1. Darwin was born in England on February 12, 1809.

2. Set sail on the HMS Beagle from England in 1831 for a ____________ around the world.

Darwin frame his theory of evolution.

5 year voyage

Darwin’s Journey

Marine Iguana

Tortoise

3. Darwin’s Observations:a. ___________________: plants and

animals seemed remarkably well suited to whatever environment they inhabited.

Patterns of Diversity

b. ____________________________: Many of the fossils that Darwin discovered resembled living organisms but were not identical to them.

For example, glyptodon, an extinct animal, is an ancient relative of the armadillo of South America. (page 370)

Living Organisms and Fossils

c. The Galapagos Islands: 1.) Located 1000 km west of South America.

2.) Islands were close together but had _________________

3.) Hood Island had __________________. Tortoises on this island had _____________ to reach the sparse vegetation.

4.) Isabel Island had _________________.

Tortoises on this island had _____________.

different climatessparse vegetation

long necks

rich vegetation

shorter necks

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shellHoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Giant Tortoises of the Galápagos Islands

Section 15-1

5.) Galapagos Finches: striking correlation between form of finches and the environment they inhabit;

similarities and differences with mainland species

Beak AdaptationsBeak Adaptations

Large Ground Finch Small Tree Finch

WoodpeckerFinch

15-2 Ideas That Shaped Darwin’s Thinking

I. Evolutionary Thinking before Darwin

A. ________ believed that species were fixed and did not evolve.

B. All species were created in a single act of creation about 6,000 years ago.

C. Buffon (mid-1700’s) suggested that _______________________ and raised the possibility that different species ______________________________

Aristotle

Earth was much older

arose from common ancestors.

II. An Ancient Changing Earth

A. Hutton (1785)

1. ________________

________________

________________

2. Earth is much older than a few thousand years.

Geological processesoperate extremely slowly.

B. Lyell (1833)

1. Wrote Principles of Geology.

2. Promoted the idea ofcontinual, gradual, consistent geological changes.

C. Lamarck (1809) was the

1. Believed organisms acquired or lost certain traits during their lifetime.

Example: giraffe

2.

therefore, this led to a change in a species.

first to support the idea of evolution.

Traits could be passed to offspring

Example: Giraffe

D. Malthus (1798)

1. If human populations _______________, it would lead to competition for scarce resources, and

2.

increase too fast

only some individuals would survive.

Limits to population growth.

E. Wallace (1858)

1. Conceived of essentially the same theory as Darwin.

2. Speculates on evolution by natural selection.

15-3 Darwin Presents His Case

I. Publication of

On the Origin of Species

A. Wallace’s letter outlining basic principles of natural selection spurs Darwin into taking his ideas public.

B. After much fierce debate,

1. Contains a well-constructed

2. Backed by

3. He used the phrase

4. The book is “sold out” in one day.

Darwin publishes his theory in 1859.

argument for natural selection.

considerable evidence.

“descent with modification.”

C. Advances in genetics in the twentieth century yield the mechanism through which natural selection operates, vindicating Darwin’s ideas.

DNA Fingerprinting

II. Inherited Variation and Artificial Selection

A. Nature provided the variation,

B. Variation existed both in nature and in farms. This variation was inherited.

1. Cows that __________________________ were selected by breeders.

2. Plants that __________________________ were selected.

selected those variations that they found useful.

and humans

produced the most milk

produced the largest and mostflavorful fruit

Artificial Selection: Dogs

Artificial Selection: Plants

III. Evolution by Natural Selection A. The Struggle for Existence

1. High birth rates and a shortage of life’s basic needs would force organisms to compete.2. Result:

or better protected, such as a porcupine can avoid being caught. Those predators that are faster or have a better mechanism to catch prey survive.

Those prey that are better camouflaged,

B. Survival of the Fittest

1. Fitness –

2. Darwin proposed that

3. Adaptation – any _________________ characteristic that increases an organism’s chance of survival.

ability of an organism to survive and reproduce.

fitness is a result of adaptation.

inherited

Examples of Adaptationsa. Waxy coating on the

surface of leaves

prevents against water loss

b. Ability to climb trees - spider monkey

- Tree boa

c. Coloration

- Octopus

Look closely: It’s an Insect!

4. Those individuals best suited to their environment survive and reproduce most successfully. Darwin called this process “survival of the fittest” or natural selection.

Mantids exhibit camouflage.

C. Descent with Modification

1.

2. Common descent: all species –__________________– were derived from common ancestors.

3.

All living organisms are related to one another.

A single “tree of life” links all living things.

living and extinct

The “Tree of Life”

IV. Evidence of Evolution

Evidence Example

1. Fossil Record

Fossils – the bones, shells, teeth, and other remains of organisms.

Fossils of simpler organisms are found in older rocks.

Newer strata contain more complex organisms.

Strata of sedimentary rock at the Grand Canyon.

Water carries small rock particles to lakes and seas.

Dead organisms are buried by layers of sediment, which forms new rock.

The preserved remains may later be discovered and studied.

Section 17-1

Figure 17-2 Formation of a Fossil

Go to Section:

Formation of sedimentary rock and deposition of fossils from different time periods.

Ammonites

Leaf Fossil

Dinosaur Fossil

Insect in Amber

IV. Evidence of EvolutionEvidence Example

2. Geographic Distribution of Animals

1. All 13 species of Galapagos finches descended with modification from a common mainland ancestor.

2. Similar ecological conditions cause different animals to end up evolving striking features in common.

Darwin’s Finches

The continent of Australia is home to unique animals, such as these marsupials, that evolved in isolation.

IV. Evidence of Evolution

Evidence Example

3. Current Evolution

Experimental evidence can demonstrate natural selection at work.

Example: Peppered moths, antibiotic resistance of bacteria.

Overuse of Antibiotics has lead to Antibiotic Resistance in bacteria.

Evolution of Pesticide Resistance in insect populations.

IV. Evidence of Evolution

Evidence Example

4. Artificial Selection

Humans select from among the naturally occurring genetic variations in species.

Example: Wheat, corn, cows, race horses, domestic breeding of dogs – poodles.

Evidence Example

5. Comparative Anatomy

Similarities in form and structure between otherwise different-appearing structures.

Homologous structures: Same structure but different function. (organization of bones in fins of whales, wings of bat, paws of cat and gorilla point to their common evolutionary origin)

Vestigial Structures: Useless structures. (in humans – appendix, wisdom teeth, muscles that move the ears and nose.)

Evolution Evidence: Comparative Anatomy

• Homologous structures (homology)

• Descent from a common ancestor

• Vestigial organs Ex: whale/snake hindlimbs; wings on flightless birds

Comparative Anatomy: Whale hind limbFossilized leg bones of Basilosaurus, an ancient whale.

A transitional fossil linking past and present.

Whales are mammals that evolved from land dwellers.

Evidence Example

6. Comparative Embryology

Early embryo development in all animals goes through similar stages, to the extent of producing structures not seen in adults.

Example: The fish, bird, rabbit, and human embryos are similar in appearance and all have a two-chambered heart, pharyngeal slits, and a tail with muscles to move it.

Evolution Evidence: Comparative Embryology

Evolution Evidence: Comparative Embryology

• Pharyngeal pouches, ‘tails’ as embryos

IV. Evidence of Evolution

Evidence Example

7. Comparative Biochemistry

Similarity in genes that control cellular function in very different organisms.

Example: Same set of genes controls many early events in the development of the fruit fly and mouse.

*All living things contain DNA.

Evolution Evidence: Molecular Biology

• Similarities in DNA, proteins, genes, and gene products

• Common genetic code

V. Summary of Darwin’s Theory

A. Individual organisms

B. More organisms

C. Individual organisms

for limited resources.

differ from one another in a population.

are produced than can survive.

must compete

Overproduction of offspring.

A few of the color variationsin a population of Asian lady beetles.

D. Individuals best suited to their environment survive and reproduce most successfully. These “best fit” individuals pass their heritable traits to their offspring.

E. Natural selection, the environment selecting the best traits (phenotype) under the current conditions, causes species to change over time.

THE END!

Homologous Structures