Lesson 2 | Theory of Evolution by Natural Selection



Name Date Class

Theory of Evolution by Natural Selection

A. Charles Darwin

1. Charles Darwin was a(n) naturalist, a person who studies plants and animals by observing them.

2. Darwin was not the first to develop a theory of evolution, but his theory is the one best supported by evidence today.

3. The type of tortoise, mockingbird, and finch that live on each of the Galápagos Islands

was slightly different; Darwin later figured out that some varieties were different enough to be classified as different species.

B. Darwin’s Theory

1. Darwin noticed that there was a relationship between each species and the food sources of the island it lived on.

2. Darwin thought all the Galápagos tortoises shared a common ancestor that came to one of the islands millions of years ago.

3. Darwin knew that in any species, members of the same species each have slight

differences, called variation.

4. Darwin didn’t know about genes , but he realized that variations in populations could help explain how the different species of Galápagos tortoises and other organisms evolved.

6. Natural Selection is the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than populations that do not have the variations.

a. AKA- Survival of the Fittest

TEST DATES:

Tuesday 11/15- Block G

Wednesday 11/16- Blocks A, D, E, F, & H

Remember to use

ID # 21445

Name Date Class

Study Guide continued

C. Adaptations

1. A(n) adaptation is a characteristic of a species that enables the species to survive in its environment.

2. Scientists classify adaptations into 3 categories.

a. Structural adaptations involve shape, size, color, and other

physical features; the length of a Galápagos tortoise species’ neck is an example

of this type of adaptation.

b. Behavioral adaptations involve the way organisms act; hunting

at night is an example of this type of adaptation.

c. Functional adaptations involve internal body systems that affect

organisms’ biochemistry; expanding blood vessels that cool a jackrabbit’s blood is

an example of this type of adaptation.

3. A structural adaptation that aids members of a species in blending in with their environment is called camouflage.

4. An adaptation in which one species resembles another species is

called mimicry.

5. The living and the nonliving parts of the environment are always

changing; species that cannot adapt to such changes will

become extinct.

D. Artificial Selection

1. Artificial Selection is the breeding of organisms for desired characteristics.

3. Darwin realized that Natural Selection and Artificial Selection are similar processes.

a. In Natural Selection, nature causes the changes in the species; in

Artificial Selection, humans cause the changes in the species.

E. Acquired Characteristics

1. Lamarck’s theory of Acquired Characteristics states desired changes that occurred during a parent’s lifetime were passed onto offspring.

Review your notes!!

(Power Point can be found on ConnectEd as well!)

Review of Important Terms to Know

← Traits-characteristics of a species that are passed from parent to offspring.

← Offspring- the scientific name for “babies” of an organism

← Species- a group similar organisms that can mate with each other and produce fertile offspring

← Fertile- the ability to reproduce

Variation

← Variation- any inherited difference between members of the same species

← Ex: albino squirrel, the ability for baby turtles to swim faster, a longer neck, wider nostrils, thicker fur…

← What Causes Variation?

← SEXUAL REPRODUCTION

← Variations result from permanent changes in an organism’s genes.

← The permanent changes in the genes are called MUTATIONS.

← Mutations…Good or Bad???

← Mutations can be either beneficial, harmful or neutral.

← Some gene changes produce LARGE variations.

← Ex: Albino squirrel

← Some gene changes produce small variations

← Ex: shape of human hairlines

4 Principals of Natural Selection

← 1) Overproduction- producing more offspring than can survive

← 2) Competition- individuals compete for food, nesting sites, territory, & other resources that affect their ability to reproduce

← 3) Variations- a difference between members of same species that may help it survive and reproduce

← 4) Selection- over time, the environment “selects” organisms w/ helpful traits to be parents of next generation

Name Date Class

LESSON 2

Theory of Evolution by Natural Selection

Directions: On each line write the letter of the term from the word bank that matches the definition correctly.

Some terms will not be used.

A. adaptations

B. behavioral adaptation

C. mimicry

D. selective breeding

E. ancestor

F. camouflage

G. naturalist

H. structural adaptation

I. artificial selection

J. functional adaptation

K. natural selection

L. variations

D 1. the breeding of organisms for desired characteristics

A 2. characteristics of a species that enable it to survive

K 3. explains how populations change as their environment changes

L 4. slight differences in the appearance of individual members of a species

B 5. an adaptation that involves the way an organism behaves

F 6. an adaptation that enables a species to blend in with its environment

J 7. an adaptation that involves internal body systems that affect biochemistry

H 8. an adaptation that involves color, shape, and other physical characteristics

C 9. the resemblance of one species to another species

I 10. the results of selective breeding

The Environment and Change Over Time

Name Date

LESSON 2

The Theory of Evolution by Natural Selection

Key Concept How does Darwin’s theory of evolution by natural selection explain how

species change over time?

Directions: On each line, write V if the statement is about variations or A if the statement is about adaptations.

A 1. There are three categories of these: structural, behavioral, and functional.

V 2. If this is helpful to one individual, it can spread to all members of a

population.

A 3. Every species has many of these.

A 4. An example is a jackrabbit’s powerful legs.

V 5. These are slight differences in the appearance of individual members

of a species.

V 6. These arise naturally in populations.

V 7. These are a result of random mutations in an animal’s phenotype.

A 8. Moving in herds for protection is an example of this.

A 9. A drop in body temperature as characteristic of a species is an example of this.

V 10. More of these occur as time passes, so they eventually accumulate.

A 11. This is characteristic of a species and enables the species to survive in an

environment.

A 12. These involve color and shape seen in an entire species.

V 13. As a result of natural selection, these spread from one individual to other

members of a population.

A 14. All members of the saddleback tortoise have these.

V 15. These might help a few members of a population compete for food.

The Environment and Change Over Time

Name Date Class

LESSON 2

Theory of Evolution by Natural Selection

True or False

Directions: On the line before each statement, write T if the statement is true or F if the statement is false. If the

statement is false, change the underlined word(s) to make it true. Write your changes on the lines provided.

T 1. Charles Darwin was a naturalist.

F 2. The breeding of organisms for desired characteristics is called natural selection.

Selective breeding or artificial selection

F 3. Camouflage is the resemblance of one species to another species.

mimicry

Multiple Choice

Directions: On the line before each question or statement, write the letter of the correct answer.

C 4. How did Charles Darwin study plants and animals?

A. by making scientific models

B. by experimenting in the laboratory

C. by observing them in their habitats

A 5. A jackrabbit’s powerful legs are an example of a

A. structural adaptation.

B. functional adaptation.

C. behavioral adaptation.

A 6. Mutations in genes cause

A. variation.

B. competition.

C. reproduction.

A 7. According to Darwin’s theory, what process causes populations to change as

their environment changes?

A. natural selection

B. artificial selection

C. selective breeding

The Environment and Change Over Time

The theory of evolution emerges from different lines of evidence, such as fossil records, modification by descent, and the evidence from biogeography, genetics and other forms of evidence.

Jean-Baptiste Lamarck (1744-1829) and Charles Darwin (1809-1882) had different theories about how life on earth got to be the way it is now.

Jean-Baptiste Lamarck (1744-1829)

Lamarck was a French biologist who is best known for his Theory of Inheritance of Acquired Characteristics, first presented in 1801. He believed that evolution was the “acquired traits” of a species that is inherited by its offspring. His theory was that if an organism continually used a structure to carry out a certain task, the structure used would become physically modified over time to make the task easier. This modified structure would then be passed on to any offspring. For example, if a short-nosed elephant was continually stretching out its trunk to try to reach the leaves high up in trees, it’s trunk would stretch and become longer over time, and any babies that it had would be born with longer trunks. Lamarck also believed that when body parts were not being used, such as the human appendix, they gradually disappear. Eventually, people will be born without these parts. Lamarck believed that evolution happens according to a prearranged plan and that the results have already been decided.

Charles Darwin (1809 -1882)

Charles Darwin is famous for the theory of evolution and Natural Selection, or ‘Survival of the Fittest’. He dedicated his life to studying plants and animals and believed that the desires of animals have nothing to do with how they evolve. He said that organisms, even of the same species, are different in some ways, and over time those creatures which are adaptable, survive, while those that do not adapt to changing conditions, such as climatic and environmental change, do not live to breed and pass on their genes. He came to the conclusion that there was a variation of physical and behavioral features within a species. Organisms which had features that helped them to adapt to their environment and circumstances had a better chance of survival than individuals who lacked these features. These adaptable organisms survived to breed and produce offspring which generally inherited the ‘successful’ features of their parents. He called this process ‘natural selection’. Darwin knew that organisms evolved and changed from generation to generation, but did not know how traits were passed on from one generation to another. Only after more was understood about genetics, was this explained. Darwin also suggested that each species evolves over time and adapts to the environment in which they live. Thus, the same species living in different environments will evolve differently and become more and more differentiated (different) over time. He believed that all species of life on Earth are interrelated and have a common ancestor.

Questions Study: Answer the questions that follow.

1. What is natural selection?

Natural Selection is the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than populations that do not have the variations.

2. Is it a fact or a theory? Explain your answer.

This is a theory that is supported by evidence.

3. What science was developed later which was found to support Darwin’s theory?

Genetic theory or the study of genes was found to support Darwin’s theory.

4. Which theory sounds like an explanation that Lamarck might give? Explain your answer.

An animal wanted to change his body so he did. Later he passed that change on to his children.

5. Which theory sounds like an explanation that Darwin might give? Explain your answer.

Animal with long neck were able to reach food and survive. Since these animal survived they were able to pass on their genes.

6. What are the specific clues that most clearly distinguish a Darwinian explanation from a Lamarckian explanation?

The choice to change and believe in extinction.

7. What term did Lamarck use to explain how new species emerged?

Acquired Traits/ Characteristics

8. What term did Darwin use to explain how new species emerged?

Variation among species

9. Do you think there is any similarity in the theories proposed by the two scientists? Explain.

Your thoughts!

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Study Guide

Content Practice B

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adaptations

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