PowerPoint Presentation - EVOLUTION · 2019. 1. 29. · Darwin’s Theory of Evolution Evolution,...

EVOLUTION

Chapter 13.1

Charles Darwin

Darwin’s Theory of Evolution

◼ Evolution, or change over time, is the process by

which modern organisms have descended from

ancient organisms.

◼ A scientific theory is a well-supported testable

explanation of phenomena that have occurred in

the natural world.

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Who was Charles Darwin?

◼ Son of Robert Darwin (physician); grandson of

Erasmus Darwin (physician)

◼ Was to study medicine, stomach not strong

enough

◼ Studied theology, loved natural science

Not testable

Voyage of the Beagle

Voyage of the Beagle

◼ Dates: February 12th, 1831

◼ Captain: Charles Darwin

◼ Ship: H.M.S. Beagle

◼ Destination: Voyage around the world

◼ Original purpose: Collect evidence to support

biblical account of creation

Not testable

Patterns of Diversity

◼ Darwin visited Argentina (left pic) and Australia

(right) which had similar grassland ecosystems

◆ Grasslands were inhabited by very different animals

◆ Neither Argentina nor Australia was home to the

sorts of animals that lived in European grasslands

Patterns of Diversity

◼ Darwin posed challenging

questions.

◆ Why were there no rabbits in

Australia, despite the presence

of habitats that seemed perfect

for them?

◆ Why were there no kangaroos

in England?

Living Organisms and Fossils

◼ Darwin collected the preserved remains of ancient

organisms, called fossils

◼ Some of those fossils resembled organisms that were

still alive today

◼ Others looked completely unlike any creature he had

ever seen

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Living Organisms and Fossils

◼ As Darwin studied fossils, new questions arose.

◆ Why had so many of these species disappeared?

◆ How were they related to living species?

Fossils

For more info, see ch 13-3. Not testable (review from science 10).

The Galapagos Islands


◼ The smallest, lowest islands

were hot, dry, and nearly

barren (e.g. Hood Island-

sparse vegetation

◼ The higher islands had

greater rainfall and a different

assortment of plants and

animals (e.g. Isabela Island

had rich vegetation)


◼ Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galapagos

◼ Giant tortoises varied in predictable ways from one island to another

◼ The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited

Animals found in the GalapagosLand Tortoises Darwin’s Finches

Blue-Footed Booby Marine Iguanas

The Journey Home

◼ Darwin analysed the specimens he had collected

and observations he had made

◼ Darwin observed that characteristics of many

plants and animals vary greatly among the islands

◆ Many observations contradicted creationism

◼ Hypothesis (based on his evidence): Separate

species may have arisen from an original ancestor

◆ Wrote an essay with his findings but did not publish for

20 years for fear of being discredited as a scientist

Key Notes from “Fitness: To

Survive and Reproduce” (13-1)

◼ Fitness: the physical traits and behaviours

that enabled organisms to survive and

reproduce in their environment



Discuss:

◼ Broadly, what might affect an organism’s

fitness? (e.g. ability to ______?)◆ Attract mates, look after offspring, fertility

◆ Find/extract/digest food

◆ Work together with social group or symbiotic partner

◆ Hide from predators (camouflage, running, etc)

◆ Regulate body temperature

◆ Use resources efficiently

◆ And more!!



Discuss:

◼ What is one trait that affects the fitness of

humans? Maple trees? Domestic dogs?

◼ What would happen to an organism’s

fitness if the environment changes? Think

of specific examples.



◼ Darwin’s argument: new organisms come

from pre-existing organisms, and each

species has descended from other species

over time

◼ Principle of common descent:

◆All species have shared/common

ancestors

Common misconception: Humans are not

descended from apes. We are simply relatives

descended from a common ancestor.

What the common

ancestor of

chimpanzees &

humans may have

looked like



◼ Adaptation: process of changes that allow

an organism to be:

◆Better suited to its environment

◆Better able to survive and reproduce

◆= inherited characteristics that increases

an organism’s fitness for survival



Discuss:

◼ How are fitness and adaptations similar?

Different? Add to your notes.

◆ Similar: both linked to ability to survive and

reproduce in environment; can be inherited; can

refer to individual organisms or larger groups

(e.g. species)

◆ Different: fitness is the overall ability to survive

and reproduce; adaptations are the traits that

increase fitness.

James Hutton:

◼ 1795 Theory of Geological change

◆ Geological changes occur slowly over time through natural processes

◆ Earth is very old: much older than thousands of years

Darwin’s Inspirations/Influences

Charles Lyell:

◼ Book: Principles of Geography

◼ Geographical features can be built up or torn down

◼ Darwin: if earth changed over time, what about life?


Jean Baptiste Lamarck

(1744-1829)

◼ French naturalist

◼ First to come up with a theory of evolution

◆ Organisms change during their lifetimes to

‘adapt’ to environment

⧫ Desire to change

⧫ Use and disuse

◆ Changes are inherited by offspring; change takes

place gradually and constantly


Lamarck: Use and disuse

Further reading:

https://www.sparknotes.com/biology/evolution/lamarck/section2/

◼ Parts of organism that are used most often

will become more developed, specialized

for environment

◆ (Similar to everyday use of “adaptations”)

◼ Parts of organism that are not used will be

underdeveloped or disappear

◆ (Similar to “vestigial structures”…stay tuned!)



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