Warm UpWith your partner, write a sentence (20

words or less) using two of the following terms to show your knowledge of genetic engineering:

* Transgenic Organisms, Recombinant DNA, Recombinant Bacteria, Selective Breeding, PCR, Gel Electrophoresis, Genetically Modified

Changes Over Time SOL: BIO 8 a-e

Theory of Evolution• Science is made up of many ideas, theories, and laws. Many of

these ideas have gone through many changes throughout the years.

• Our job as life-long learners is to examine all the evidence concerning a particular topic.

• Evolution is part of the Core Knowledge curriculum for Biology.• The origin of life is a sensitive subject for many people. There

are many theories concerning the change in things over time. • You may hold a different view than what will be presented as

part of the Core Knowledge curriculum. • Out goal is to explore the theory of evolution from a scientific

standpoint, not to discount any other theories on the origin of life.

Charles Darwin The Father of Evolution

History• During Darwin’s Time(1809 -

1875) most people believed the Earth was only a few thousand years old.

• They also believed that neither the planet nor it’s living species had changed over that thousand years

• Darwin’s ideas were shocking and radical

HISTORY• Darwin was influenced by many

explorers and great thinkers who were starting to challenge views about the world

• Some new ideas that were influential to Darwin’s discoveries were:– Taxonomy of Carolus

Linnaeus– Lyell’s “Principles of

Geology”

Carolus Linnaeus

(1707 – 1778)Believed in the “Fixity of Species” or that all species have remained unchanged throughout the history of the Earth.

Binomial System of Nomenclature

Charles Lyell • Father of Geology• Suggested that

layers of rock form slowly and are moved up by the forces beneath Earth

• His theories suggested that the Earth is millions of years old.

• Suggests that sedimentary rock is very old – therefore the species that are represented in this rock must also be old.

• Most fossils are found in sedimentary rock.

• Older fossils will be found below younger fossils.

Charles Lyell

• How did his ideas influence Darwin?– If the Earth could change over time, might

life change as well?– The changes (evolution) Darwin would

later suggest would have been possible only if the Earth were extremely old

Knowledge CheckWho was Linnaeus?

Who was Lyell?

If Lyell looked at fossils in a cross section of sediment, would the fossils more towards the surface be older or younger than those below? Why?

Charles DarwinAt the age of 22, he joined a 5 year expedition aboard the HMS Beagle to map the coast of South America

The voyage of the Beagle

Darwin’s Voyage

• Darwin explored and collected specimens whenever The Beagle landed ashore

• He noticed the diversity of organisms as he traveled and noticed how animals and plants seemed remarkably suited for their environment

• One stop that was important to the development of Darwin’s theories was the Galapagos Islands

• These islands are just west of South America and were particularly interesting because although they are very close together, they have dramatically different climates

• Because they were formed by volcanoes, they range from barely at sea level to 1500m above sea level

Darwin’s ObservationsLand Tortoises

• Shell shape varied from one island to another • Hood Island Tortoise: Long neck and curved

shell allows this tortoise to reach the high vegetation

• Isabela Island Tortoise: Dome shaped shell and short neck as vegetation is closer to the ground

• Through his observations made in the Galapagos Islands, Charles Darwin formulated a theory of how species change over time, called natural selection.

Knowledge Check• What was the name of the boat on

which Darwin traveled?• What unique observation did Darwin

make about the landscape of the Galapagos Islands?

• What observations did Darwin make regarding the organisms living on the island?

Charles Darwin’s Theory of

Evolution by Natural Selection

1. Heritable Variation: Members of a population have heritable variations.(Inheritance of traits)

2. Overpopulation: In a population, more individuals are produced than the environment can support. They compete for food and shelter. (overpopulation- struggle for survival).

3. Survival of the Fittest: Some individuals have adaptive characteristics that enable them to survive and reproduce better than other individuals (survival of the fittest).Fitness: Ability of an organism to survive and reproduce

4. Adaptation: An increasing number of individuals in succeeding generations have these adaptive characteristics

Darwin described his theory in the form of a long essay which he called

“On the Origin of Species”.

Concerned about the public’s response to his ideas(remember what happened to Galileo)

Arranged to publish his work …AFTER HIS DEATH !!

He finally decided to publish his essay, “On The Origin of Species” in 1859

Charles Darwin

At age 50 (1859)

At age 65 (1874)

Charles Darwin

Before publication After publication

Knowledge CheckWhat was the name of Darwin’s book?

On what islands did Darwin make observations that lead him to develop his ideas about natural selection?

Explain how natural selection can be observed in a population.

How does Evolution work?• Evolution is governed by

the principles of genetics

• It is a change in successive generations of organisms, due to:1. random mutation2. Adaptation3. Natural selection4. Extinction

MUTATIONS• Genetic mutations and variety

produced by sexual reproduction allow for diversity within a given population.

• Mutations are inheritable changes because a mutation is a change in the DNA code

Mutation• Mutations are

important in how populations change over time because they result in genetic changes to the gene pool.

A mutation may result in change that is:1. Favorable;

improves a species’ ability to exist in its environment

2. Unfavorable; does not improve a species’ ability to exist in its environment.

3. Neutral; neither harms nor helps the species.

Adaptation• Adaptations are structures,

functions, or behaviors that enable a species to survive.

Adaptation• Depending on the rate

of adaptation, the rate of reproduction, and the environmental factors present, structural adaptations may take millions of years to develop.

Knowledge Check

• What are the 3 types of changes that mutations can result in?

• What is an adaptation? (HINT: It is a NOUN)

Natural Selection• the survival and reproduction of

the individuals in a population that exhibit the traits that best enable them to survive in their environment.

• The Survival of the Fittest

Natural Selection• Populations produce more

offspring than the environment can support.

Natural Selection• This leads to

competition for resources and individuals with certain genetic variations will be favored to survive and pass their variations on to the next generation.

• These five canine species evolved from a common ancestor through natural selection

African wilddog

CoyoteFox WolfJackal

Thousands tomillions of years

of natural selection

Ancestral canine

When humans choose organisms with specific characteristics as breeding

stock, they are performing the role of the environment

• This is called “artificial selection”

Example of artificial selection in plants: five vegetables derived from wild mustard

Artificial Selection in Animals: Dog Breeding

German shepherd

Yorkshire terrier English springerspaniel

Mini-dachshund Golden retriever

Hundreds tothousands of years

of breeding(artificial selection)

Ancestral dog

Extinction• If a species does

not include traits that enable it to survive in its environment or to survive changes in the environment, then the species may become extinct.

Individuals die, and eventually the species becomes extinct.

Knowledge Check

• What is another name for natural selection?

• What is artificial selection?• What can lead to extinction in a

population?

WARM UP

• Explain how each process below can lead to evolutionary change.– Heritable Variation– Overpopulation– Survival of the Fittest– Adaptation

EVIDENCE FOR

EVOLUTION

• Darwin argued that living things have been evolving on earth for millions of years, and evidence could be found in:– the fossil record, – the geographical distribution of

species – homologous structures of living

organisms– Similarities in early development

(embryology)

Fossil Record• Darwin saw fossils as a record of

the history of life on Earth• By comparing fossils from older

rock layers with fossils from younger layers, scientists could document the fact that life on Earth has changed over time.

• The study of fossils provides strong evidence for evolution.

Hominid skulls

Petrified Trees

Scorpion in amber

“Ice Man”

Distribution of species• On his voyage, Darwin discovered

many species of finches, all similar but distinctly different from one another based on where they were found

• He eventually concluded that these finches had descended with modification from a common ancestor as populations adapted to different environments (adaptive radiation)

Allopatric SpeciationGeographic isolation/separation can lead

to speciation (emergence of a new species)

Homologous Structures • Structures that have different mature forms but

develop from the same embryonic tissues are called homologous structures; these structures provide support to Darwin’s theory of evolution

• Darwin noted striking anatomical similarities among the body parts of animals with backbones; the limbs of reptiles, birds and mammals vary in form and function, yet they are all constructed from the same basic bones

Homologous StructuresHuman Cat Whale Bat

…Not to be confused with Analagous Structures

• Structures in different species that have the same appearance, structure, or function but have evolved separately, thus do not share a common ancestor.

• For example, birds and some insects have wings and both species use these for the same function, to fly. However, birds and insects evolved separately; they do not share a common ancestor.

Vestigial Structures• Homologous structures that apparently

serve no function in an organism and are allegedly holdovers from an evolutionary past. Such features, though no longer useful, are presumed to have been useful in ancestral species.

• They are vestiges, or traces of homologous structures in ancestral species

EX.: Wings in flightless birds

EX.: appendix in humans, whale pelvis, tiny snake pelvic and limb bones, and the eyes in cave-dwelling salamanders and fish that are completely blind.

Why do these structures hang around ?

• Although they serve no purpose, one argument states that since these organs do not affect an organisms ability to survive and reproduce, natural selection would not cause their elimination.

Similarities in Embryology• Many species have very similar

embryonic development. • The embryo of a chicken, a pig,

and a fish are almost identical at certain points in their development.

Summary of Darwin’s Theory• Individual organisms differ, and some of this

variation is heritable• Organisms produce more offspring than can

survive, which leads to competition for limited resources

• Organisms best suited to their environment survive and reproduce most successfully (and pass their traits on) causing a species to change over time (natural selection)

• Species alive today are descended with modification from ancestral species