Changes

in

Organism

s Over

Time11

Unit Learning Goalsa. Trace the history of the theory.

b. Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution.

c. Explain

how

fossil &

biochemi

cal

evidence

support

the

theory.

d. Relate natural selection to changes in organisms.

e. Recognize the role of evolution to

biological resistance (pesticide & antibiotic resistance).

22

Cosmos: Some things

that Molecules do

Age of EarthAge of Earth

Scientist believe that the Earth is 4.6 billion 4.6 billion

years old.years old.•Evidence:

-Rock data,

-Environmental changes

33

CLIP

Where do I live?• What type of

environment am I best “fit” for?– Hot/cold????– Wet/dry???

• Why

• Organisms have traits (GENES) that help them to survive in different environments.

44

A variation is a small change in a trait that makes an individual slightly different from other members

of its species.• All organisms in a

population are not the same. Variation/diversity exist.

• What causes this variation??

What is Fitness?• Fitness is a measure of

reproductive reproductive successsuccess. (survive long enough to reproduce)

• Reproductive Reproductive success:success: Having traits so that an organism is able to pass on genes onto the next generation (and in a way so that the next generation can also pass those genes on)

• Any trait that promotes promotes survivalsurvival — at least until one's reproductive years are over — increases fitness.

• Such traits are called adaptations.

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GAME

What if an organism has a trait. that makes it impossible to live in

its environment?• The organism

will not survive.• If it does not

survive—it CANNOT reproduce.

• If it does not reproduce—its genes are not passed to the next generation.

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What if the environment What if the environment changes?changes?•If they do not have the traits (genes)

that enable them to survive…they die, and DO NOT reproduce.

• If they do have the traits, then they survive…and reproduce. – SO… the next generation has more of the

“fit” traits for THAT environment.• The population then CHANGES!

– This is a very slow process….does not occur over night…many generations must past before any change in the population can be seen.

Natural Selection

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Current Theory …

Natural Selection•Also know as “survival of the

fittest.”•Only certain members of the

population will survive and reproduce.

•Ones that survive are most suited to the environment—they

are the most fit!!.

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survival of the fittest

•Artificial selection provides a model that helps us understand natural selection.People have been artificially selecting domesticated plants and animals for thousands of years. •Broccoli and brussels sprouts bear little superficial resemblance to their wild mustard relatives (left).

99Humans have been doing this for 1000s of years!

HumansHumans select and breed for certain traits.

Examples: The largest hog, the cow that gives the most milk, fastest horse, or cutest dog.

Dog Breeds Corn

Pigs

Where do NEW traits

come from?

1010

How do new traits arise?a) Mutations.

b) Sexual Reproduction.– Mixing of genes makes new

combinations– A combo of traits may be necessary

for survival……so… sexual reproduction and crossing over can create new combination of traits.

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Decent with modificationsOvertime

natural selection

produces

organisms

that have

different

structures,

established

different

niches, or occupy

different

habitats.

Organisms that were once the same have now grown “apart” and have become different organisms.

These changes increase a species’

fitness in their environment.

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•ADAPTATIONS (traits) that are that are favorablefavorable become more prevalent within that population.

•These traits will be passed onpassed on to the next generation.

•The GENE POOLGENE POOL of a population CHANGES in favor of the “FITTEST” phenotype & genotype!!!

THE BASICS: A review1313

Environment selecting “good” traits for THAT environment.1414

Example: Peppered MothExample: Peppered Moth

Two

versions of

the moth-

Black

and

peppered

During the

industrial

revolution

on England

Population

of moths

changed

1515

1616

Sampling the birds that died as well as those that survived

showed that •the larger birds were

favored over the smaller ones

•those with larger beaks were favored over those with smaller

ones.  

Beak length (mm)

Beak depth (mm)

Dead birds 10.68 9.42

Survivors 11.07 9.96

From 1976 through 1977, a severe drought struck an island in the Galapagos.

of

Sm

all

bea

ks

Some phenotypes are more fitmore fit than others when it comes to competing for resources. The more “FIT” phenotype will survivesurvive and have the possibility of passing its alleles to the next generation.

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1818

1919

2020

Review Clip

• James HuttonJames Hutton -1785-Proposed that the Earth is millions of years old.

• Many land formations took millions of years to form.

• Known as the founder of modern geology.

History 2121

• Thomas Malthus -1798-• Proposed that populations outgrew

their food supplies, causing competition between organisms and a struggle for one species to survive against another

• This "struggle for existence" drives population change.

HistoryHistory 2222

Jean-Baptiste Lamark -18091809-

• Believed that all life forms evolved and that the driving force of evolution was the inheritance of acquired acquired characteristicscharacteristics.

• He believed that organisms changed due to the demands of their environment.

HistoryHistory 2323

What we What we understaunderstand now:nd now:

2424

•Charles Lyell -1830-proposed that plant and animal species had arisen, developed variations, and then became extinct over time. •He believed that every animal or plant, including humankind, was adapted to the niche in which it was created.

15.115.1

•He also believed that the Earth’s physical landscape changed over a long period of time.

the present is the key to

understanding the past

2525

•Alfred Russel Wallace -1858

• Emphasis was based on the idea of competition for resources as the main force in natural selection.

15.215.2

Best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish on his own theory

2626

• Charles Darwin -1859- Publishes “On the Origin of Species”

• Believed that Natural Natural SelectionSelection is the driving force for evolution.

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Charles Darwin

British Naturalist

1809 -1882

“I have called this principle, by

which each slight variation, if

useful, is preserved, by the

term Natural Selection.”

—Charles Darwin from "The Origin

of Species"

2828

•From 1831 to 1836

Darwin served as a

naturalist aboard the

H.M.S. Beagle on a British

science expedition

around the world.

•In South America Darwin

found fossils of extinct

animals that were similar

to modern species.

•On the Galapagos

Islands in the Pacific

Ocean he noticed many

variations among plants

and animals of the same

general type as those in

South America.

CLIP

2929

Summary of Darwin’s Summary of Darwin’s IdeasIdeas

1. Individual organisms differ, and some of this variation is heritable.

2. Organisms produce more offspring than can survive, and many that do survive do not reproduce.

3. Because more organisms are produced than can survive, they compete for limited resources.

4. Individuals best suited to their environment survive and reproduce most successfully.

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5. These organisms pass their heritable traits to their offspring. Other individuals die or leave fewer offspring.

6. This process of natural selection causescauses species to change over time.

7. Species alive today are descended with modification from ancestral species that lived in the distant past.

8. This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life.

Summary of Darwin’s IdeasSummary of Darwin’s Ideas

Review Clip

3131

3232

Whale Video Clip- Intro to evidence ( Questions in packet)

Review Clip: 10min

Evidence for Change Over TimeFossil Record

–Fossils that show how the same organism looked millions of years ago.

–Paleontology –Use rock layers–1) Isotope dating

3333

Clip

3434Fossil Record

2) Relative Dating 3535

3636

Structures

that have

different

mature

forms in

different

organisms

but have

developed

from the

same type

of tissue.

Homologous structures 3737

Homologous structures3838

Analogous versus Homologous Structures

•Embryology–Early development of the organism

3939

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Vestigial organsVestigial organs–Organs or Organs or structures that structures that do not seem to do not seem to be used by the be used by the organism any organism any longer. longer.

–They are They are usually usually reduced in reduced in size.size.

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Vestigial Organs

c

4242

GeneticsGenetics

DNA sequences in

organisms are close

Sources of genetic

variation in species:

1.Mutations

2.Gene Shuffling

3.Crossing over

during meiosis

4.Sexual Reproduction

•Things that cause

change.•Why we are all a little bit

different…

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Genetic Comparison4444

• The numbers represent the number of amino acid differences between the beta chain of humans and the hemoglobins of the other species.

• In general, the number is inversely proportional to the closeness of kinship.

GEOGRAPHIC DISTRIBUTION • Organisms that are related change/adapt

according to their environment.

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• The evolution of many The evolution of many diversely adapted speciesdiversely adapted species from a common ancestorfrom a common ancestor– Relatively rapid

• Usually occurs when a population colonizes an area of diverse geographic or ecological conditions.– New niches

Adaptive Radiation

•Each species becomes specialized for a different set of conditions

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Macroevolution

SpeciationSpeciation

Evolution: change in the allelic frequencies in a population

Species: population whose members can interbreed in nature and produce viable,

fertile offspring

Macroevolution

How do we get new species?

Where do new species come from?

5151

Speciation

In the physical world, natural barriers form and cause the breakup of populations to

form smaller populations.

Volcanoes, sea-level changes, and earthquakes are a few examples of

natural occurrences that affect populations

5252

•Overtime they can change so much that they become unable to breed as they adapt to their environment.

Speciation Mechanisms• Geographic Isolation

– Separated by bodies of water or mountains.

• Temporal Isolation– Reproduction takes place at different times of the year– Different Mating seasons

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•Behavioral Isolation–Populations are capable of interbreeding, but have different courtship rituals or other type of behavior.–Do not recognizes another species as a mating partner.

–Sexual Selection–Brightly colored male- drab female

– video clip: Dressing fro desire

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VOCAB CHECKVOCAB CHECK

5555

Gene Pool•Combined genetic

information of a

particular population.

•All the genes present

with in a population

•Can change

•A population is a localized group of individuals that belong to the same species.

5656

Changes in allele frequency with in a population

Genetic drift

•Random changesRandom changes in allele frequency

that occurs in small populations

•“Lucky” individuals leave more

offspring.

•Also known as the “Founder Effect”

Genetic driftGenetic drift— along with natural selection, mutation, and migration—is one of the basic mechanisms of evolution. 5757

Gene Flow

• Immigration• Emigration

Start Packet #2

• Review Clip

5858

Divergent Evolution•Divergent evolution is the process of two or more related species becoming more and more dissimilar.•The red fox and the kit fox provide and example of two species that have undergone divergent evolution. •As they adapted to different environments, the appearance of the two species diverged.

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Two or more related species becoming more and more dissimilar

Divergent Evolution 6060

Convergent Convergent EvolutionEvolution

•Convergent evolution is

the emergence of

biological structures or

species that exhibit

similar function and

appearance but that

evolved through widely

different evolutionary

pathways.•examples include the

multiple origins of wings

(bats, birds) and eyes.

Independent development of similar structures

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Convergent Convergent EvolutionEvolution

Independent development of similar structures

6262

Coevolution •Predators and their prey •Parasites and their hosts•Plant-eating animals and the plants upon which they feed •One example of coevolution is between plants and the animals that pollinate them.

CoevolutioCoevolutio

n is the n is the

joint joint

change of change of

two or two or

more more

species in species in

close close

interactioninteraction

..

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• Some Central American Acacia species have hollow thorns and pores at the bases of their leaves that secrete nectar. These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores.

Bumblebees & the flowers they pollinate have coevolved so that both have become dependent on each other for survival.

Coevolution 6464

Evolution at the species level is called microevolution.

It results from genetic variation and natural selection within a population of organisms.

Small Changes Macroevolution is evolution

that occurs between different species.

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Evolution is the change in

a species over time.

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7070

Rates of Evolution

7171

Gradualism Gradualism && Punctuated Equilibrium Punctuated Equilibrium• Two ways in

which the evolution of a species can occur.

• A species can evolve by only one of these, or by both.

CLIP

•Species with a shorter evolution evolved mostly by punctuated equilibrium, and those with a longer evolution evolved mostly by gradualism.

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GradualismGradualism•Very gradually, over a long time... Over a short period of time it is hard to notice. •Slow Changes•Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die.•Change is slow, constant, and consistent.

Punctuated equilibriumPunctuated equilibrium•change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals.

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• STOP HERE>>>>>>>>>>>>>

Biological Resistance• When organisms are no longer

affected by a drug.• First documented around

1952 • Causes: Natural consequence

of selective pressures in the environment.

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Resistance in Bacteria

Read page p403.

7676

• Bacteria- Antibiotic resistance

• Many insects have developed a resistance to insecticides. (simple point mutations)

7777

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The Effects of Selection

on Populations

7979

Types of Selective Processes in Types of Selective Processes in Natural SelectionNatural Selection

•Stabilizing Selection•Directional Selection•Diversifying Selection•Balancing Selection

–Heterozygote Advantage

–Frequency-dependent

8080

Stabilizing SelectionStabilizing Selection Intermediate forms of Intermediate forms of

a trait are favored and a trait are favored and alleles that specify alleles that specify extreme forms are extreme forms are eliminated from a pop. eliminated from a pop.

Ex: Human birth weight Ex: Human birth weight stay between 6-8 lbs. stay between 6-8 lbs. Lower or higher has Lower or higher has higher mortality.higher mortality.

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Directional Directional SelectionSelection

Changing environmental conditionsChanging environmental conditions give rise give rise to directional selection, where to directional selection, where one phenotype one phenotype replaces anotherreplaces another in the gene pool. in the gene pool.

Can produce rapid shift in allelic frequencies.Can produce rapid shift in allelic frequencies. Ex: Peppered mothEx: Peppered moth

– – peppered moths, pesticide resistance, peppered moths, pesticide resistance, antibiotic resistanceantibiotic resistance Occur in response to:Occur in response to:

* directional change in the environment * directional change in the environment * one or more new environmental conditions* one or more new environmental conditions* a mutation that appears and proves to be * a mutation that appears and proves to be

adaptiveadaptive

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Diversifying Diversifying (Disruptive)(Disruptive) SelectionSelection Increases the Increases the

extreme typesextreme types in in a population at a population at the expense of the expense of the intermediate the intermediate forms.forms.

One population One population divided into two.divided into two.(bill size in seedcrackers)(bill size in seedcrackers)

8383

• Diversifying selectionDiversifying selection can result in balanced polymorphism.• For example, two distinct bill types are present in

black-bellied seedcrackers in which larger-billed birds are more efficient when feeding on hard seeds and smaller-billed birds are more efficient when feeding on soft seeds.

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Heterozygote AdvantageHeterozygote Advantage• Exists when a heterozygote heterozygote

(Aa) has a higher fitness(Aa) has a higher fitness than either homozygote (AA, aa).

•ex: Sickle Cell

8585

• The term given to an evolutionary process where the fitness of a the fitness of a phenotype is dependent on its phenotype is dependent on its frequencyfrequency

• Can arise in systems of mimicry– ex: Butterflies

• ex: Maintenance of a 50:50 sex ratio: If one sex becomes more common, some of its members will not be able to mate

Frequency dependent

8686

•Adaptation is a key concept in natural selection.

•Natural selection can change the inherited characteristics in a population and possibly even result in a new species.

8787

Two main sources of Two main sources of genetic variationgenetic variation

1.1.MutationsMutations2.2.Genetic Shuffling Genetic Shuffling

(by sexual (by sexual reproduction)reproduction)

8888

EOCT- It is important that you are able to explain how the concepts of genetics provide the basis for explaining natural selection and evolution. This will help you answer questions

like this:

What is the end result of natural selection?

A increased number of offspring of a given phenotype that survive

B changes in the frequency of alleles in a population

C fossil formation through extinctionD environmental changes of a habitat

8989

Although the Arctic fox and the kit fox are closely related, they look very different because the individualsA acquired traits during their lifetimes that contributed to survivalB with traits most suited to their environments reproduced most successfullyC migrated long distances to environments that most suited their traitsD passed on to their offspring acquired behaviors that were helpful

9090

Fossils of Fossils of ArcheopteryxArcheopteryx show that this show that this animal had feathers, like a bird. It animal had feathers, like a bird. It also had a bony tail, teeth, and also had a bony tail, teeth, and claws on its wings, like a claws on its wings, like a reptile. This fossil is evidence reptile. This fossil is evidence that supports the idea thatthat supports the idea that

A. birds and reptiles have a common ancestorB. birds have changed very little over 150 million yearsC. reptile species are more advanced than bird speciesD. reptiles are warm-blooded like birds

9191

Horses and tapirs have a common ancestor, but Horses and tapirs have a common ancestor, but now look very different. Horses now are grassland now look very different. Horses now are grassland animals adapted for grazing on grass and shrubs. animals adapted for grazing on grass and shrubs. Tapirs are jungle animals that live in dense forests Tapirs are jungle animals that live in dense forests and eat fruit, leaves and aquatic vegetation. Which and eat fruit, leaves and aquatic vegetation. Which of the following led to the development of such of the following led to the development of such differences in the two species?differences in the two species?

9292

A selective breedingA selective breedingB convergent evolutionB convergent evolutionC DNA hybridizationC DNA hybridizationD natural selectionD natural selection

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Review CLIPAdaptation is the key concept in natural selection.

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