Darwin’s Theory of Evolution Chapter 15. 15-1 Warm Up A Trip Around the World While on his voyage...

Darwin’s Theory of Evolution

Chapter 15

15-1 Warm Up A Trip Around the World

While on his voyage around the world aboard the H.M.S. Beagle,Charles Darwin spent about one month observing life on theGalápagos Islands. There, he encountered some unique animals,such as finches and tortoises.

1.On a sheet of paper, list five animals that you have encountered in the past two days.

2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in your textbook.)

3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.

The Puzzle of Life’s Diversity Biological Diversity – the variety of living

things

- describes the millions of different shapes, sizes & habitats on Earth

Evolutionary Theory – a possible answer to explain the diversity of living things

- a collection of scientific facts, observations, and hypotheses.

Evolution Change over time

The process by which modern organisms have descended from ancient organism

Theory

A well supported testable explanation of phenomena that have occurred in the natural world

Charles Darwin Born in England on Feb. 12, 1809

(same day as A. Lincoln) In 1831, he set sailed on the H.M.S Beagle for a

trip around the world

Darwin’s Observations Patterns of Diversity:

1. plants and animals seem remarkably well adapted to whatever environment they inhabit (live)

2. organisms have many different ways to survive & produce offspring

3. certain animals were only found on specific continents, even though other continents had similar environments .

Darwin’s Observations Living Organisms and Fossils:

1. Darwin collected many fossils:

- preserved remains of ancient organisms

2. he realized that some resembled living organisms and others looked completely unlike any other creature.

3. These fossils made Darwin wonder how so many species disappeared & if they

were related to living things now

Charles Darwin

Warm Up Timeline – Origins of Evolutionary Thought pp. 374-375 Construct a timeline using the information on

the timeline in your book Do not copy pictures, just the written

information and dates

Galapagos Islands

Small group of islands located off S. America Very different climates even though there are

close together Darwin used his observations from these islands

to create his Theory of Evolution He studied land tortoises & marine iguanas and

observed differences between each island Most importantly he studied birds called a Finch

and observed and analyzed their differences in their beaks

Land Tortoises of the Galapagos Islands

.

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shellHoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Land Tortoises

Land Iguana

Marine Iguanas

Marine Iguanas

Galapagos Islands from Space

H.M.S. Beagle

Finches

Finches

Finches

The Journey Home Upon returning to England, Darwin thought about

his observations & asked himself 3 very important questions:

1. Were the animals living on the different islands once members of the same species?

2. If they were, how did these species evolve after being separated onto the different islands?

3. If they did evolve (change) how did they do it?

Warm - UpMy, How You’ve Changed!

Prior to the 1800s, life scientists knew that living things changed overgenerations. They just didn’t know how these changes were broughtabout.

1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.

2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument.

3. Which of the items in your lists do you think you might pass on to your children? Explain your answer.

Inherited Acquired

Eye color

Hair color

Skin color

Type of muscle

Genetic diseases

Nose shape

Eye shape

Ear shape

ANYTHING ANATOMICAL

Language

Ability to read and write

How to play a sport

How to play a musical instrument

What music you like

What type of person you like

ANYTHING MENTAL

Ideas that Shaped Darwin’s Thinking

Before Darwin’s time, most Europeans believed that Earth and all life forms:

1. were created only a few 1000 years ago

2. had not changed since creation During Darwin’s life, a lot of evidence was

discovered to change this way of thought This made Darwin dramatically change his way

of thinking.

An Ancient, Changing Earth During the 18th and 19th centuries, scientists

recognize:1. Earth is millions of years old2. processes that changed Earth in the past are the same processes that are happening today

James Hutton Charles Lyell Jean Baptiste Lamarck Thomas Malthus

Scientists Who Influenced Darwin In your notebook, create a table to show the

scientists and their findings that influenced Darwin.

Use pages 374-377 to find the information

Hutton

-list beliefs

1.

2.

3.

4.

Lyell

list beliefs

1.

2.

3.

4.

Lamarck

list beliefs

1.

2.

3.

4.

Malthus

list beliefs

1.

2.

3.

4.

CLASS ACTIVITY

Read “Hutton and Geological Change” on page 374. (1 paragraph)

List at least 4 beliefs of Hutton in your notebook. 1. geological forces shaped the Earth. 2. 3. 4. 5. You will have 5 minutes to finish!

James Hutton - 1795 He believed:

1. geological forces have shaped Earth

2. Earth was made of layers of rocks that form very slowly

3. rocks move up by forces beneath the surface & others are buried & others are pushed up to make mountains

4. outer layer is shaped by natural forces – rain, wind, heat & cold temperatures

5. All of these processes operate extremely slow – over millions of years

6. Concluded that Earth is millions of years old

Movement of Earth’s Crust.

Sea level

Sedimentary rocks form in horizontal layers.

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Sea level

Scientists Who Influenced Darwin

In your notebook, create your own notes on the scientists and their findings that influenced Darwin.

Lyell – 5 main points (describe each one) Lamarck – 3 main points (describe each one) Malthus – 2 main points (describe each one)

Use pages 375-377 to find the information

Charles Lyell Wrote book called “Principles of Ecology” Darwin read it when on the Beagle He stressed that scientists must study past events

to understand the events they are observing now His work explained how geological features could

be build up & broken down over long periods of time

It also helped Darwin understand how important geological phenomena is on the location and findings of fossils

Jean Baptiste Lamarck French scientist who was one of the first to:

1. recognize that living things have changed over time2. all species were descended from

other species3. organisms somehow adapted to

their environments Lamarck’s work was published in 1809, the

same year Darwin was born

Lamarck’s Evolution Hypothesis He proposed that by:

1. use or disuse of organs, organisms gained or lose certain traits during

their lifetime.2. These traits could then be passed on to their offspring3. Over time, this process led to change in a

species

Tendency Toward Perfection Lamarck proposed that all organisms have an

innate tendency toward complexity & perfection.

As a result, living things are always changing & acquiring new traits to help to adapt & survive

Use and Disuse Lamarck proposed that organisms could

change the shape and size of certain organs by using their bodies in new ways

If the organism used a new part of body, it would develop into a new structure

If the organism disused the part of body, it would decrease in size and over many generations disappear.

Inheritance of Acquired Traits Lamarck thought that acquired

characteristics could be inherited Acquired Characteristics – traits you gain

from your own experiences and training Example – if you spent your life lifting

weights to build your muscles, then your children would inherit big muscles too!

Evaluating Lamarck’s Hypothesis Incorrect in many ways:

1. He did not know how traits are inherited

2. He did not know that an organism’s behavior has no effect on its inheritable characteristics

** Lamarck was the 1st to develop a hypothesis of evolution & to realize that organisms can adapt to their environment.**

Thomas Malthus Important influence on Darwin In 1798, Malthus published a book that stated:

“If the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone”

He felt that the only forces that could fight against this were: war, famine, & disease

Darwin’s Thoughts on Malthus He realized Malthus’ ideas applied to plants and animals

even more Because animals & plants can reproduce much faster &

more numbers than humans What Darwin did not realize at this time was:

1. majority of offspring die2. only a few survive long enough to reproduce themselves

** Trying to figure out why the above occurs was the central idea behind his explanation of evolutionary change.**

Warm Up

When Is a Flipper a Wing?All living things are related. Some relationships are easy to see—your pet cat may not roar like a lion, but it clearly resembles one. Other relationships are less obvious.

Warm Up 1. In your notebook, construct a table that has 5 columns & 6 rows.

In the columns, write the following headings: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect.

2. Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many?

3. Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer.

Mammal

Bird

Fish

Amphibian

Reptile

Insect

Animal Example Legs Fins Tail

Mammal elephant 4 No Yes

Bird Seagull 2 No Yes

Fish Shark No Yes Yes

Amphibian Frog 4 No Yes/no

Reptile Turtle 4 No Yes

Insect Ant 6 No No

Animal Example Legs Fins Tail

Darwin Presents His Case It took 25 years for Darwin to present his

Theory of Evolution 1859 – “On the Origin of Species” This book proposed:

1. a mechanism for Evolution called

Natural Selection

2. Evolution has been taking place for millions of years & continues today

Details of the Origin of Species Inherited Variations – differences that are

passed from parents to offspring

- Darwin had no idea how it happened

- We now know it is caused by variations in genes

- variations are found in both wild and domesticated living things

Artificial Selection When nature provides the variations and

humans select specific variations that they find useful

Produces many diverse domestic animals & plants

Example – breeding only the fastest horses

The Struggle for Existence Darwin was convinced that Artificial Selection worked in

nature. He knew that:↑ birth rates & ↓ of basic needs = competition of resources

Struggle For Existence:Members of each species regularly compete for the necessities of life

Ex. Faster, bigger predators catch more prey Faster, camouflaged, & protected prey will not be eaten

The Struggle for Existence (cont.)

Key Factor – how well suited an organism to its environment

Fitness – ability of an individual to survive & reproduce in its own environment

**the ability to ADAPT = ↑ FITNESS**

Adaptations Any inherited characteristics that increases an

organisms chance of survival 3 types:

1. Anatomical – porcupine develops sharp quills

2. Physiological – plants being able to make own food

3. Behavioral – living in groups & hunting

Survival of the Fittest Individuals with traits that are not well suited to

their environment (low levels of fitness) will die or leave few offspring

Individuals with traits that are well suited to their environment (adaptations that enable fitness) will survive & reproduce successfully

Darwin referred to Survival of the Fittest as

NATURAL SELECTION because it has similarities to Artificial Selection.

Natural Selection Traits being selected increase over time Contribute to an organism’s fitness in its

environment Over time, it results in changes in the

inherited traits of a population Can only be observed as changes in a

population over many successive generations Cannot be seen directly

Descent with Modification Each living thing has descended with changes from other

species over time Species today look different from their ancestors Natural selection over long periods of time, produce

organisms with:1. different structures2. occupy different habitats3. establish different niches

(place on the food web) Also implies that all living organisms are related to one

another

Common Descent All species – living and extinct – are from

common ancestors

A single “Tree of Life” links all living things

Evidence of Evolution Darwin argued that living things have been

evolving on Earth for millions of years. Evidence for this process could be found in the:

1. fossil record

2. the geographical distribution of living species

3. homologous structures of living organisms

4. similarities in early development, or embryology

Evidence of Evolution Activity Create a concept chart for the evidence that supports

evolution in your notebook. It will include the four types of evidence:

1. fossil record2. the geographical distribution of living species3. homologous structures of living organisms4. similarities in early development, or embryology

Use supporting facts of each one to complete the concept chart.

Use the chart on the next slide to help you get started.

Evidence of Evolution Concept Map

includes

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development

Fossils Record Darwin saw fossils as a record of the history of

life By comparing fossils in older layers with ones

from younger layers, we can document the indeed life has changed over time

Transitional Fossils (between modern & ancient species) have shorten the gap between the two

Gaps in the fossil record point out uncertainties in our understanding of exactly how some species evolved.

Geographical Distribution of Living Things

Similar animals in different locations were the product of different lines of evolutionary descent

However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of natural selection

Because of this, different animals ended up evolving certain common features.

Beaver

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Coypu

Figure 15–14Geographic Distributionof Living Species

Section 15-3

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Homologous Body Structures Structures that have different mature forms but

develop from the same embryonic tissue Evidence of evolution can also be found in living

animals This provides strong evidence that all 4-limbed

vertebrates (has a backbone) have descended, with modifications, from common ancestors

Vestigial Organs – homologous organs that have been reduced in size – resemble miniature legs, tails, or other structures. Does not effect the organisms ability to survive or reproduce.

Turtle Alligator Bird Mammals

Typical primitive fish

Figure 15–15 Homologous Body Structures

Similarities in Embryology Embryos of many animals with backbones are

very similar Embryos look especially similar during early

stages of development The same group of embryonic cells develop in the

same order and in similar patterns to produce tissues and organs

These common cells & tissues, growing in similar ways, produce the Homologous Structures

Strengths & Weaknesses of Evolutionary Theory

Scientific advances in biology, geology and physics, have confirmed and expanded most of Darwin’s hypotheses.

Today, evolutionary theory offers great information to all biological and biomedical science.

Evolution is known as the “great unifying theory of the life sciences”

Strengths & Weaknesses of Evolutionary Theory

Like any theory, it continues to change as new data is gathered & new ways of thinking come about.

Researchers still debate:

1. how new species arise

2. why species become extinct

3. how life began

Summary of Darwin’s Theory Page 386 – copy the 5 main points into your

notebook.