Life on Earth: The Life on Earth: The Theory of EvolutionTheory of Evolution

What is a TheoryWhat is a Theory Video Segment 1Video Segment 1 https://www.youtube.com/watch?https://www.youtube.com/watch?

v=85diEXbJBIk&list=PL5270149AB732v=85diEXbJBIk&list=PL5270149AB732F0FB&index=1F0FB&index=1

Origin of LifeOrigin of Life Before the 17Before the 17thth century people believed century people believed

in a process called spontaneous in a process called spontaneous generation. generation. Living things could arise from non-living Living things could arise from non-living

things.things. Why did they think that?Why did they think that?

If they would leave rotting meat out then If they would leave rotting meat out then maggot seem to appear so the meat must maggot seem to appear so the meat must give rise to maggots. (NOT Exactly)give rise to maggots. (NOT Exactly)

ExperimentsExperiments In 1668, Redi proved spontaneous generation In 1668, Redi proved spontaneous generation

to be falseto be false Meat and FliesMeat and Flies

Spallanzani also preformed an experimentSpallanzani also preformed an experiment 2 broth flasks (boiled)2 broth flasks (boiled) Problem: what happens to bacteria when you Problem: what happens to bacteria when you

cook them?cook them? 1800’s, Louis Pasteur modified Spallanzani’s 1800’s, Louis Pasteur modified Spallanzani’s

experimentexperiment Used curved necked flaskUsed curved necked flask

Earth’s HistoryEarth’s History Earth is about 4.6 billion years oldEarth is about 4.6 billion years old No usable oxygen. No usable oxygen. Anaerobic organisms.Anaerobic organisms. The fossil evidence says they were most The fossil evidence says they were most

likely prokaryoteslikely prokaryotes Probably heterotrophsProbably heterotrophs Some may have also been autotrophsSome may have also been autotrophs

Archaebacteria bacteria that uses chemosynthesis Archaebacteria bacteria that uses chemosynthesis instead of photosynthesisinstead of photosynthesis

We need More OxygenWe need More Oxygen Some relatives to cyanobacteria used Some relatives to cyanobacteria used

photosynthesis photosynthesis more oxygen is more oxygen is formed.formed.

Some of this oxygen went into the upper Some of this oxygen went into the upper atmosphere where it formed the ozone atmosphere where it formed the ozone layer.layer. The ozone layer helps protect the earth The ozone layer helps protect the earth

from ultraviolet radiation that can damage from ultraviolet radiation that can damage DNADNA

More complex cells More complex cells formform So we have prokaryotes that are So we have prokaryotes that are

aerobic and are not to complexaerobic and are not to complex EndosymbiosisEndosymbiosis

The small invaders would give rise to The small invaders would give rise to mitochondria and chloroplastsmitochondria and chloroplasts Mitochondria and chloroplast have their own Mitochondria and chloroplast have their own

circular DNA that is different from the cells DNAcircular DNA that is different from the cells DNA

Possible Possible explanations for explanations for the things that the things that

have been have been observed.observed.

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Lamarck’s explanationLamarck’s explanation His hypothesisHis hypothesis

Similar species descended from a common Similar species descended from a common ancestorancestor

His evidenceHis evidence Fossil recordsFossil records

His reasoningHis reasoning Acquired trait are passed on to offspringAcquired trait are passed on to offspring

Things passed on due to Things passed on due to experienceexperience not not geneticgenetic

““The Inheritance of The Inheritance of Acquired Acquired

Characteristics”Characteristics”

Example:Example:A giraffe acquired its long neck because its A giraffe acquired its long neck because its ancestor stretched higher and higher into the ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on increasingly lengthened neck was passed on to its offspring.to its offspring.

Darwin and WallaceDarwin and Wallace About 50 years later, two scientists, About 50 years later, two scientists,

Charles Darwin and Alfred Wallace, Charles Darwin and Alfred Wallace, both came up with the same idea: both came up with the same idea: natural selectionnatural selection

Natural selection: organisms that are Natural selection: organisms that are best suited for their environment are best suited for their environment are able to reproduce hence passing on the able to reproduce hence passing on the favorable traits.favorable traits.

Charles DarwinCharles Darwin Darwin set sail on the Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831- (1831-

1836) to survey the south seas 1836) to survey the south seas (mainly (mainly South America and the Galapagos Islands)South America and the Galapagos Islands) to collect plants and animals.to collect plants and animals.

On the On the Galapagos IslandsGalapagos Islands,, Darwin observed Darwin observed species that lived no where else in the world.species that lived no where else in the world.

These observations led Darwin to write a These observations led Darwin to write a book. book.

Video Segment 2 “Who is Charles Darwin”Video Segment 2 “Who is Charles Darwin” https://www.youtube.com/watch?https://www.youtube.com/watch?

v=vmphlbRhLu8&list=PL5270149AB732F0v=vmphlbRhLu8&list=PL5270149AB732F0FB&index=2FB&index=2

Darwin’s Two TheoriesDarwin’s Two Theories Descent with modificationDescent with modification

Newer forms appearing in the fossil record are Newer forms appearing in the fossil record are really modified descendants of older speciesreally modified descendants of older species

Modification by natural selectionModification by natural selection Describes how evolution occursDescribes how evolution occurs Environment affects populations, some organisms Environment affects populations, some organisms

can cope and others cannot.can cope and others cannot. Adapting results in a change in the genetic make-up of Adapting results in a change in the genetic make-up of

the population the population (selective advantage)(selective advantage) Fitness is a single organisms contribution to changeFitness is a single organisms contribution to change

Natural SelectionNatural Selection IndividualsIndividuals with with favorablefavorable traitstraits are are

more likely to leave more offspring more likely to leave more offspring better suited for their better suited for their environmentenvironment..

Example:Example:English peppered mothEnglish peppered moth ( (Biston Biston betulariabetularia))

- light and dark phases- light and dark phases

Natural SelectionNatural Selection1.1. All species produce offspring at a All species produce offspring at a

faster rate than food supplies can faster rate than food supplies can increase.increase.

2.2. Except for identical twins, no two Except for identical twins, no two individuals are exactly alike.individuals are exactly alike.

3.3. In each generation, more individuals In each generation, more individuals are produced than can survive.are produced than can survive.

4.4. Individuals that possess certain traits Individuals that possess certain traits have an advantage over those that do have an advantage over those that do not.not.

Natural SelectionNatural Selection5.5. Geographical isolation may lead to the Geographical isolation may lead to the

formation of a new species.formation of a new species.6.6. The environment determines whether The environment determines whether

a trait is beneficial.a trait is beneficial.7.7. Traits are inherited and passed on to Traits are inherited and passed on to

the next generation. the next generation. 8.8. Over time, successful variations Over time, successful variations

accumulate in a population, and a new accumulate in a population, and a new species may appear.species may appear.

https://www.youtube.com/watch?v=ewtw_nZUIDQ&list=PL5270149AB732F0FB&index=3

Darwin’s key idea: Natural SelectionDarwin’s key idea: Natural Selection****Four tenants of natural selection**Four tenants of natural selection**

1.1. Genetic VariationGenetic Variation: Variety of traits exist. These variations are : Variety of traits exist. These variations are called alleles. Example: blue eyes, brown eyes. called alleles. Example: blue eyes, brown eyes.

2.2. Overproduction of offspringOverproduction of offspring: Organisms produce more : Organisms produce more offspring than can survive offspring than can survive

3.3. Struggle for existence (Survival of the fittest)Struggle for existence (Survival of the fittest): Organisms : Organisms compete over resources to survive and reproduce. compete over resources to survive and reproduce. Organisms best suit for environment survive to pass on Organisms best suit for environment survive to pass on genes. genes.

4.4. Differential survival & reproduction:Differential survival & reproduction: over time, traits of over time, traits of successful reproducers become more commonsuccessful reproducers become more common

Evidence of EvolutionEvidence of Evolution1.1. Biogeography – Plate TectonicsBiogeography – Plate Tectonics2.2. Fossil Record Fossil Record 3.3. AdaptationsAdaptations4.4. Comparative AnatomyComparative Anatomy

• Vestigial StructuresVestigial Structures• Homologous/Analogous structuresHomologous/Analogous structures

5.5. Comparative embryologyComparative embryology6.6. Molecular biologyMolecular biology

How does it workHow does it work Video Segment #4: How Does Video Segment #4: How Does

Evolution Really Work?Evolution Really Work? https://www.youtube.com/watch?https://www.youtube.com/watch?

v=xkwRTIKXaxg&index=4&list=PL5270v=xkwRTIKXaxg&index=4&list=PL5270149AB732F0FB149AB732F0FB

BiogeographyBiogeographyGeographical Geographical distribution of species.distribution of species.

Organisms tend to Organisms tend to arise in areas where arise in areas where similar organisms similar organisms lived in the pastlived in the past

Comparative Anatomy:Comparative Anatomy: Structural similarities link Structural similarities link related speciesrelated species

Vestigial StructuresVestigial Structures Features that are not used by the organism Features that are not used by the organism

but may have been useful to ancestorsbut may have been useful to ancestors Example: Example:

In humans: tailbone, appendixIn humans: tailbone, appendix In whales: pelvic bone and four chambered In whales: pelvic bone and four chambered

stomachstomach In snakes: pelvic bone, limb bonesIn snakes: pelvic bone, limb bones

Homologous Homologous structuresstructures

Homologous: structures that are similar because of common ancestry and develop similarly

Homologous and embryoHomologous and embryo Complete the homologous and embryo Complete the homologous and embryo

color sheet following the teacher color sheet following the teacher directions. directions.

Comparative Comparative embryologyembryology

Study of Study of structures that structures that appear during appear during embryonic embryonic development.development.

Molecular biologyMolecular biology DNA and proteins (amino acids)DNA and proteins (amino acids) Mutations are changes in the DNA. Mutations are changes in the DNA. Gene flow is any movement of genes from Gene flow is any movement of genes from

one population to another.one population to another. Sexual ReproductionSexual Reproduction

Convergent EvolutionConvergent Evolution Species from different evolutionary branches Species from different evolutionary branches

may come to resemble each other even may come to resemble each other even though they are not closely relatedthough they are not closely related

Example:Example:1.1. Ostrich (Africa) & Emus (Australia).Ostrich (Africa) & Emus (Australia).2.2. Sidewinder (Mojave Desert) &Sidewinder (Mojave Desert) &

Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)3. Sharks and Dolphins 3. Sharks and Dolphins

Divergent EvolutionDivergent Evolution 2 or more species or related population 2 or more species or related population

become more and more dissimilarbecome more and more dissimilar Can result in a new speciesCan result in a new species

Types:Types: Adaptive radiation: related species evolve Adaptive radiation: related species evolve

from a single ancestral species (Galapagos from a single ancestral species (Galapagos finches)finches)

Artificial selection: breeding organisms for Artificial selection: breeding organisms for specific trait (dogs)specific trait (dogs)

WritingWriting Under your notesUnder your notes Write me a paragraph in detail describing Write me a paragraph in detail describing

what you have learned so far about what you have learned so far about evolution. evolution. We have done dot lab, checks lab, evidence We have done dot lab, checks lab, evidence

of evolution, theory of evolution, lamark of evolution, theory of evolution, lamark versus Darwin. versus Darwin.

Mechanisms of ChangeMechanisms of Change1.1. MutationMutation

A change in the DNA sequence.A change in the DNA sequence. (1 in 100,000) leads to new traits.(1 in 100,000) leads to new traits.Some traits will be advantageous to the Some traits will be advantageous to the

species.species.2.2. MigrationMigration

Movement of individuals form Movement of individuals form one population into another. one population into another. Can alter the genetic Can alter the genetic characteristics of a population. characteristics of a population.

Mechanisms of ChangeMechanisms of Change3.3. Nonrandom Mating- controls the genesNonrandom Mating- controls the genes

When individuals mate with one another more or When individuals mate with one another more or less frequently: less frequently: example inbreedingexample inbreeding. .

4.4. SelectionSelection Artificial Selection – Artificial Selection – individuals breed individuals breed organisms for specific organisms for specific traits. traits. Natural Selection -Natural Selection -environment dictates environment dictates Which traits are neededWhich traits are needed to survive. to survive.

Mechanisms of ChangeMechanisms of Change5.5. Genetic DriftGenetic Drift

Random loss of alleles. Small population Random loss of alleles. Small population a person does not reproduce. a person does not reproduce. Founder effect – one or a few individuals Founder effect – one or a few individuals

migrate and become an isolated population migrate and become an isolated population with distinct genotypes.with distinct genotypes. The population splits due to migration eventsThe population splits due to migration events

Bottle neck – restrictions in genetic variability Bottle neck – restrictions in genetic variability due to flooding or natural disasters. due to flooding or natural disasters. The population splits due to natural disastersThe population splits due to natural disasters

Speciation Speciation (How do we get a new species?)(How do we get a new species?)

Usually involves successive changeUsually involves successive change Local populations of a species become isolated Local populations of a species become isolated

and more specialized (adapted)and more specialized (adapted) Natural selection acts to keep them specialized Natural selection acts to keep them specialized

(different from the larger population)(different from the larger population)

Populations of a species Populations of a species mustmust become become reproductively isolatedreproductively isolated in order to develop in order to develop into new species.into new species.

Mechanisms of ChangeMechanisms of Change Complete the coloring sheet Gene FlowComplete the coloring sheet Gene Flow

Be sure to read and highlightBe sure to read and highlight Color neatlyColor neatly

Complete the coloring sheet Genetic Complete the coloring sheet Genetic DriftDrift Be sure to read and highlightBe sure to read and highlight Color neatlyColor neatly