Ch.12-14 Evolution Change in the inherited traits of a population of organisms from one generation to the next. The unifying principle for all biological.

Ch.12-14

EvolutionChange in the inherited

traits of a population of organisms from one generation to the next.

The unifying principle for all biological sciences.

Provides explanation for differences in structure, function, and behavior among life forms.

Who is this man and why are people still talking about him?

3

Charles Darwin

Before Darwin During and After Darwin

People believed that species were divine creations that were unchanging.

Found evidence on his voyage on the Beagle he that challenged the traditional belief that species are unchanging.

Darwin’s theory was that all species descended from earlier species . He called this Descent with Modification.

Published his evidence in his book On The Origin of Species.

Galapagos IslandsDarwin noticed many of

the plants and animals of the Galapagos Islands resembled those of the nearby coast of South America 620 miles away.He concluded that they

migrated there and changed after they arrived. See photo on p. 278.

Natural SelectionOrganisms best suited

for the environment are most likely to survive and reproduce; survival of the fittest, only the strong survive.

Mutations – random changes in DNA can result in favorable trait variations that are then passed on to generations.

Factors of Natural Selection1. All populations have genetic variation.2. Environment presents challenges to

successful reproduction.3. Individuals tend to produce more offspring

than the environment can support.4. Individuals that are better able to cope with

the challenges presented by their environment tend to leave more offspring than those that are less suited.

PopulationIndividuals of a

species that live in a specific geographical area and that can interbreed.In a population you

can have variation, where members of the same species have differences.

AdaptationFeature that has

become common in a population because the feature provides a selective advantage.

Species and SpeciationSpecies

A group of organisms that are closely related and can mate to produce fertile offspring.Subspecies – populations

of same species that differ genetically due to adaptation to their environments.

Speciation Process by which new

species form.

How Populations EvolveGene pool – all the alleles

(different versions of genes) in all the individuals of a population.

Gene flow – exchange of genes with another population.

Genetic drift – change in gene pool due to chance.

Artificial selection – intentional reproduction of individuals in a population that has desirable traits.

Geographic IsolationPhysical barrier divides a population and they can no

longer reproduce. May become separate species over time.Gene frequency changes more likely to occur in small

populationDifferent initial gene frequencies than main population.Different mutations occur within main pop and isolate

them.Different environmental factors have different selection

pressures on each population.

Reproductive IsolationTwo populations of

same species do not breed with one another because of a geographic separation.Ex. Darwin’s

Finches and Australia’s marsupials

Phylogeny

The evolutionary history of a species.Cladogram –

diagram that shows ancestral relations between organisms.

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GradualismModel of

evolution in which gradual change over time leads to new species.

Punctuated EquilibriumPeriods of rapid

change in species are separated by periods of little or no change.

Questions 1. The process by which a species becomes better adapted

to its environment is called. A. Gradualism B. Adaptation C. Natural selection D. Reproductive isolation2. The process by which isolated populations of the same

species becomes new species is called. A. Speciation B. Reproductive isolation C. Genetic variation D. Natural selection

Questions 3. How does gradualism differ from

punctuated equilibrium?

Evolutionhttp://www.pbs.org/wgbh/evolution/library/11/2/real/e_s_1.

htmlhttp://www.pbs.org/wgbh/evolution/library/04/2/real/

l_042_02.html (whale)http://www.pbs.org/wgbh/evolution/library/11/2/real/e_s_5.

html (human)

Evidence of EvolutionScientists agree that:1. Earth is about 4.6

billion years old.2. Organisms have

inhabited Earth for most of its history.

3. All organisms living today share common ancestry with earlier, simpler life-forms.

EvidenceFossil RecordHomologous and Analogous structures (Comparative

Anatomy)Comparative Biochemistry Comparative CytologyComparative Embryology

Geologic RecordsFossils – preserved

remains of organisms that lived in past.

Fossil record – collection of fossils recorded in rock layers over time.

Extinct – species that no longer exist.

PaleontologistsScientist who study

fossils.Age of fossils determined

fairly accurately using radiometric dating. Have found intermediate

fossils . Fishes and amphibians Reptiles and birds Reptiles and mammals. http://www.pbs.org/wgbh/evol

ution/library/03/4/real/l_034_49.html

Vestigial StructuresOrgans inherited but not

used by modern organisms

Present but greatly reduced in modern organismsEx. Hip bone in pythonAppendix in humanTail bone (cocyx) in

human

Figure 2.2.3. X-ray image of an atavistic tail found in a six-year old girl

Homologous StructuresSimilar parts of different organisms

that developed from the same ancestral body parts.

Phalange

Metacarpals

Carpals

Radius

Ulna

Humerus

Human Cat Whale Bat

Analogous StructuresSimilar in purpose, but not inherited from a

recent common ancestorEnvironment selected for trait

Wings of birds and insectsConvergent evolution

Convergent Vs. Divergent EvolutionConvergent evolution – Unrelated species

become similar due to same type of environment.Analogous structures

Divergent evolution – Group from a specific population develops into a new species due to environmental conditions.Homologous structures

Comparative BiochemistryAll life is based on organic chemistry

Carbon based compoundsAll life uses same molecule as blueprint

DNASimilar chemical processes

Bacteria, algae, and plants all do photosynthesisCellular Respiration

Similar organisms have similar genetic codeHumans and chimpanzees share nearly identical

genes (98.4% identical gene sequences)

Comparative CytologyOrganelles are structurally and functionally similar in all living

thingsEndosymbiosis

Theory that mitochondria are descendants of symbiotic, aerobic eubacteria and chlor0plasts are descendants of symbiotic, photosynthetic eubacteria.

Comparing EmbryosAll vertebrate embryos, including humans,

share featuresEye spot Gill pouchesNotochord

Shows similar genetic ancestryVideo

http://www.pbs.org/wgbh/evolution/library/04/2/real/l_042_02.html

Why do we care about evolution?Understanding where we came from.BacteriaViruseshttp://www.pbs.org/wgbh/evolution/library/

11/2/real/e_s_6.html (antibiotic resistance)http://www.pbs.org/wgbh/evolution/library/

01/1/real/l_011_20.html (AIDS)

Questions1. Anatomical structures that share a common ancestry are called

____________ structures. A. Vestigial B. Homologous C. Analogous D. Evolutionary

2. The process by which isolated populations of the same species become new species is called.

A. SpeciationB. Reproductive isolationC. Genetic variationD. Natural Selection

The Peppered Moth StudyAn Example of Natural Selection!

What are similarities and differences between these two organisms!

Both have the Scientific Name:Biston betulariaBoth are the same moth, commonly called peppered moths. There is a story behind these two different color variations. Click to find out what happened!

During the early 1800’s in Birmingham, England there were dark and cream colored moths. However, almost all peppered moths were cream colored because the tree trunks were light colored.

Can you find the moth on the tree trunk?

Would it be an advantage or disadvantage for the moth to be light?

•A greater number of factories were being created, which meant more pollution!Think/Pair /Share:•What do you think was happening to the peppered moths as a result of industrialism?

Something was happening in the cities of England at this time,

What could that have been?

WHAT’S HAPPENING!Around 1850, black- colored peppered moths started to become more common than cream, usually in heavily industrialized areas.

Why did the frequency of black moths increase

with the growing industries?

Darwin’s Theory of evolution by natural selection suggests a hypothesis.

White tree trunks were blackened by heavy pollution from factories.

Which Moth is better adapted to its environment? Explain why?

•Perhaps dark moths sitting on soot-darkened bark escaped being eaten by birds because it was too hard for the birds to see the dark moths against the dark background.

•Light-colored moths would have stood out against a dark background and would have been easy prey for hungry birds. Therefore, more dark moths survived.

This is an example of Natural Selection!

Natural Selection- is a gradual change in a species in response to the demands of its environment.

Do Now:Write how the peppered moth during the 1800’s was an example of natural selection in action!