Unit 9: Evolution

UNIT XI – EVOLUTION

Test Friday 2-24THE THEORY OF EVOLUTION

The theory of evolution is one of the most

fundamental concepts in Biology. Evolution

Is defined as _________ in a

__________________over time. The

scientist considered to be the founder of

modern evolutionary theory is

______________.

changes

population of organisms

Charles Darwin

A. History of Evolutionary

Theory

During the 1700s, several scientists

began challenging the idea of a

world in which changes did not

occur. These scientists and their

hypotheses were very important to

Darwin’s work.

A. History of Evolutionary

Theory

1. Gradualism - __________________ first

suggested that the planet was much ______

than previously thought; began to find

evidence that _______ were slowly, but

constantly taking place.

Geologists (Hutton & Lyell)

older

changes

A. History of Evolutionary

Theory

2. Malthus – Published an essay that had a

huge impact on Darwin. Proposed that

organisms ____ - reproduce; in other words,

reproduce at a _____ rate than resources

can supply

over

greater

A. History of Evolutionary

Theory

3. Lamarck

Lamarck was one of the first scientists to propose

a mechanism for evolution; that is, the _______ in

a _________ of organisms over _____. His major

hypotheses included:

changes

population time

3. Lamarck

Cont.

Tendency Toward Perfection – Stated that

organisms were continually changing in

order to ________________.live more successfully

3. Lamarck

Cont.

Use and Disuse – Changes in ____

and/or ______ of a structure in an

organism was a response to use or disuse.

Structures used extensively ________

and structures used less frequently

__________.

Inheritance of ________ Traits

size

shape

grew bigger

got smaller

Acquired

Acquired Traits

B. Charles Darwin

(1809 – 1882)1. Darwin’s History

Darwin’s data was collected on a 5-year

journey around the world on the HMS

______. He made observations and

collected data throughout the journey.

He used this data to propose a

________ to explain the diversity he saw.

Beagle

hypothesis

1. Darwin’s History

Cont.

The area that had the greatest impact on

Darwin was the _________ Islands due

to the differences he saw in the same

animals living on different islands.

Galapagos

Galapagos

• He began to suspect that populations from

the mainland changed after reaching the

Galapagos.

• Upon his return he talked to animal

breeders & called what they did to direct

breeding to produce offspring with the

desired traits __________________,

which is the same as what we called

selective breeding last unit.

Artificial selection

2. Darwin’s Observations

• Members of a population often vary greatly in

their _____.

• Traits are inherited from __________________.

• All species are capable of producing _____

offspring than _____________________

• Variations that increase reproductive success

will have greater change of being passed on

than those that do not

increase repro. success

traits

parents to offspring

more

environment can support

3. Darwin’s TheoriesBased on his observations and the

hypotheses of other scientists Darwin

proposed evolution occurred by a process

called Natural Selection:

1. Organisms with favorable ____ tend to

survive and _________; thereby leaving

more descendants than other individuals

• Fitness = ability to ______ and ________

traits

reproduce

survive reproduce

3. Darwin’s Theories2. This will result in an accumulation of

these traits in the ________ if they are

heritable, changing the original

_______make-up of the population

• Adaptations = traits enriched in a

population that increase the _____ of an

organisms having them

fitness

population

genetic

III. THE PRINCIPLES OF

EVOLUTIONARY THEORY

Examples of adaptations are ____________

___________________________________

thorns on a cactus,

camouflage, antibiotic resistance in bacteria

4. Darwin’s Legacy

• Did not publish his findings for years

• Alfred Wallace – formed identical ___________ based on his research. Sent his manuscript to Darwin, and finally Darwin was persuaded to publish his own conclusions

• Released “______________”, still considered one of the greatest scientific works ever written

hypotheses

Origin of Species

• Darwin’s two major contributions:

– Darwin ___________ (but did not originate)

the idea that species evolve over time and

share ________________

• This became widely accepted quickly in the

scientific community

– Darwin proposed how this happened with his

original theory of _______________

• It wasn’t widely accepted until the early 20th

century

4. Darwin’s Legacy

popularized

common ancestry

natural selection

III. EVIDENCE FOR EVOLUTION

A. Fossils – Fossils are

______________________________________

Fossils provide a record of earlier life and evidence

that evolution has occurred.

Types: Imprints, molds (impressions), casts (filled impression), tracks, hard parts, actual remains.

preserved bones and traces of organisms

Evidence of EvolutionA. Evidence from Fossils

1. Dating Fossils

a) Absolute Dating-

1) Radioactive _____________ used to find

the age of rocks. Uranium-Lead,

Potassium-Argon dating

b) Relative Dating

1) Sediments are laid down in strata

2) ___________ layers are oldest

3) A fossil’s __________ in

undisturbed rock gives its _______

relative to other fossils.

isotopes

lowest

positionage

III. EVIDENCE FOR

EVOLUTION

• Fossils can be used to deduce the

__________________ that occurred in a

species or group of organisms over time.

• _________________ are remains of

organisms with characteristics that are

____________ between those of an

ancestral and descendent group.

sequence of changes

intermediate

Transitional fossils

Copyright Pearson Prentice Hall

III. EVIDENCE FOR

EVOLUTION

• There are two major classes of traits when

studying transitional fossils:

1. derived traits- ____________ features

such as feathers, that do not appear in

the fossils of common ancestors

2. ancestral traits- more ________ features

such as teeth & tails, that do appear in

ancestral ones

primitive

newly evolved

Tiktaalik

III. EVIDENCE FOR

EVOLUTION

B. Biogeography- The geographic

__________ of species can be explained

by ________________ and the limits

geography imposes on migration.

(common descent = shared ancestors)

distribution

common descent

III. EVIDENCE FOR

EVOLUTION

• Distantly related species living in different

parts of the world with similar

____________ have similar ___________

• Closer inspection shows these species are

often more closely related to

geographically _______ species with

different adaptations

environments adaptations

closer

III. EVIDENCE FOR EVOLUTION

C. Comparative anatomy– Scientists use

anatomical studies of different organisms for

evidence of evolutionary relationships.

1. Homologous structures-For example, appendages that are very ___________ in

structure, but differ in ____________ are known as

____________ structures. Examples of

homologous structures are _____________________________________.

homologous

arm of human, flipper of dolphin, wing of bat

similar

function

III. EVIDENCE FOR EVOLUTION

2. Vestigial Structures - A structure that is

_________ in function in a living organism, but

may have been used by an ancestor is known as a

_______ structure. A structure may become

vestigial when an organism changes in form or

behavior. Examples are ______________

_______________________________.

vestigial

wings of ostrich

eyes on cave fish,human appendix

reduced

III. EVIDENCE FOR

EVOLUTION

3. Analogous structures- Not all similar

features are evidence of common

ancestry. Analogous structures ca be

used for the _____________ & can be

superficially similar in construction but are

______________ from a common

ancestor. They show that functionally

similar features can evolve independently

in similar environments. Ex wings birds

vs. insects

same purpose

not inherited

III. EVIDENCE FOR EVOLUTION

D. Embryology – Similarities in the

structures of developing ________ of

different organisms are considered to

be proof of a close evolutionary

relationship.

embryo

III. EVIDENCE FOR EVOLUTION

E. Comparative biochemistry–

Scientists use DNA studies to

determine the evolutionary relationship

between organisms. The more similar

the DNA (or protein AA sequence) ,

_______________________________the closer the evolutionary relationship

IV. MECHANISMS FOR

EVOLUTION

A. Evolution occurs because of natural

selection - a mechanism for change that

occurs when organisms with _________

characteristics for a particular environment

______ and ________ to pass these

characteristics on to ________.

favorable

survive reproduce

offspring

IV. MECHANSIMS FOR

EVOLUTION

• Evolution does not occur in an

individual; instead it refers to

________________ that occur in a

__________ over time.

• In other words, evolution is a change in

______________ for any gene in a

population.

heritable changes

population

allele frequency

IV. MECHANSIMS FOR

EVOLUTION

• Other mechanisms work with natural

selection to produce ________ changes

in populations:

genetic

V. MECHANSIMS FOR

EVOLUTION Cont.

A. Mutation – A mutation is a

______________. Although mutations

are often _______, sometimes

the resulting change in _________ may

be beneficial to an organism under

certain conditions.

change in DNA

harmful

phenotype

In jaguars, the mutation is dominant hence

black jaguars can produce both black and

spotted cubs, but spotted jaguars only produce

spotted cubs when bred together.

V. MECHANSIMS FOR

EVOLUTION Cont.

• If the change occurs in the ________,

this change will be passed onto the

offspring of that organism.

gametes

V. MECHANSIMS FOR

EVOLUTION Cont.

• A mutation is the ultimate source of

__________ in a species.

• Without a variety of alleles for genes

in population, ______________ has

nothing to “choose”

• Low variation = low _______ of

population to adapt

new alleles

natural selection

ability

V. MECHANSIMS FOR

EVOLUTION Cont.

• A ___________ is a collection of all the alleles

for every gene in a population. Large gene pool

= high variation. Small gene pool = low variation.

gene pool

V. MECHANSIMS FOR

EVOLUTION Cont.

1. ________ mutations alone cannot

cause adaptation. ___________

natural selection is required for

forming adaptations.

2. Organisms do not ___________ in

response to challenge. Variation

must be already present for

_________ to operate.

RandomNon-random

try to mutate

selection

Clarifications about common misconceptions:

V. MECHANSIMS FOR

EVOLUTION Cont.

B. Diploidy – Most organisms are diploid, which means _______________________.

This allows for increased genetic variation in a population.

Heterozygote Advantage – Seen in _______________ and _________.

Recombination – Leads to increased genetic variation as a result of _____________ during __________ of _______.

double set of chromosomes

sickle cell allele malaria

crossing over prophase Imeiosis

V. MECHANSIMS FOR

EVOLUTION Cont.

C. Gene Flow – Gene flow occurs when

organisms from one community migrate to

another. This introduces new _________

into the gene pool of another _________,

changing its genetic makeup.

alleles

population

V. MECHANSIMS FOR

EVOLUTION Cont.

D. Genetic Drift – This describes a

situation in which ________ change in

allele frequency in gene pool is

magnified because the population size

is very ______.

Causes of genetic drift include

random

small

V. MECHANSIMS FOR

EVOLUTION Cont.

Bottleneck effect – large portion of

population ______________________

Founder effect – segment of

population moves to new ________

destroyed in disaster

habitatSimple

illustration

of founder

effect. The

original

population

is on the

left with

three

possible

founder

populations

on the right

Add to notes:

• Genetic drift ultimately results in the loss

of alleles from the genepool.

• Only mutations and gene flow can

introduce new alleles and increase

diversity

IX. MECHANSIMS FOR

EVOLUTION Cont.

• E. Single Gene Traits-Natural selection

on __________ traits can lead to changes

in ______ frequencies and therefore to

evolution. EX. _____________________

single gene

allele

Color change in a lizard poplution

IX. MECHANSIMS FOR

EVOLUTION Cont.

F. Selection of Polygenic Traits-Natural

selection can affect the distributions of

phenotypes in 3 ways:

• Directional Selection-Individuals at ___

end of the bell curve have higher fitness

than those in the middle or other end.

EX:_______________________________

_________________________________

one

Birds with bigger beaks are selected for over

Medium & small beaks.

IX. MECHANSIMS FOR

EVOLUTION Cont.• Stabilizing Selection-Individuals in the ________

have the highest fitness causing the curve to

narrow.

• EX:___________________________________

______________________________________

• Disruptive Selection-when individuals at both ends of the

curve have the higher fitness. If lasts long enough can

cause the curve to split in two and create _____ distinct

phenotypes. EX.

_____________________________

middle

Birth weight, babies in the middle weight range are more

likely to survive than smaller or larger babies

two

Finches beak sizes, large & small beaks are selected for &the medium beaks

Struggle to survive.

IX. MECHANSIMS FOR

EVOLUTION Cont.

III. Macroevolution

D. As organisms ________ and adapt,

_________ may occur. Speciation is

the formation of new species - a group of

similar organisms that _______ with one

another and produce ___________

___________________________.

survive

speciation

breed

fertile offspring….

that is, babies that can make babies

• For speciation to occur population must

diverge & then be reproductively isolated.

Abert & Kaibab squirrels of the Grand Canyon

F. Isolating Mechanisms: allow for the gene

pools to become ____________ so they

can form a new __________. (No gene

flow)

Reproductive isolation- as new ______

evolves, populations become

_________________ isolated from

each other.

separate

species

species

reproductively

• Prezygotic- prevents reproduction by making

______________________ because of

geographic, ecological, behavioral, temporal or

other differences.

• Ex: _________________________ have

overlapping ranges & are similar in appearance

but use different mating songs & do not

interbreed.

• Ex: Fireflies- similar species but mate at different

_____________________

fertilization unlikely

Eastern & Western Meadowlark

times of night

• Postzygotic- when fertilization has

occurred but a ___________ offspring

_________________or reproduce;

prevents offspring survival or reproduction

• Ex. Mule, liger

hybrid

Cannot develop

V. Macroevolution

G. The failure of an

organism to _____

to changes in its

environment will

ultimately lead to its

_________

because of

_______________.

adapt

extinction

natural selection

V. MACROEVOLUTION

• A. Extinction-More than ____% of all

species that have ever lived are now

______, which means the species has

died out. Darwin proposed possible

reasons with competition for

___________________________

99

extinct

resources & environmental change

Fig. 1: Number of assessed taxa in each species group in Volume 1. For

each species group, the pie chart shows the absolute number of taxa and

that number as a percentage of all taxa (n = 478). By agreement, neobiota

are not included in the analysis.

V. MACROEVOLUTION

• ______ extinction has occurred several times,

wiping out entire __________.

• _______ , volcanic action, and ___________

movement has been blamed.

• Mass extinctions clear the way for __________

of other species. EX: _________

Mass

ecosystems

Meteorites Tectonic plate

evolution

Mammals

V. MACROEVOLUTION

B. Adaptive radiation or divergent evolution -

the process where a _____ species has evolved

through ________________ into diverse forms

that live in short period of time that live in different

ways. Often follows mass extinctions EX:

__________________________

C. _____________________ when unrelated

species evolve similar traits even though they live

in different parts of the world because of similar

ecology & climate. EX:__________________

single

natural selection

Finches & tortoises of the Galapagos

Convergent evolution

Mara of South

America & rabbit

of England

X. MACROEVOLUTION

D. ______________ is when a change in one organism

leads to a ____________ change in another organism.

EX: _______________

E. ____________________ Equilibrium is another pattern

of evolution. Unlike __________ punctuated equilibrium is

characterized with long periods of __________ interrupted

by brief periods of ______ change. It is controversial but

known that evolution does occur at different rates.

Co-evolutioncorresponding

Orchid/moth bee with other flowers

Punctuated Equilibriumgradualism

stability

rapid