15.1 Evidence of Evolution 15.6 Domains & Kingdoms

15.8 Origin of Life 15.13 Natural Selection

Evolution

Origins of Life on Earth

Very little to

No Oxygen!!!

Evolution is studied using concepts about earth history. The earth is between 4.3 and 4.5 billion years old.

Approximately 3.9 billion years ago, the surface was likely cool enough for water vapor to condense and form oceans

Geological evidence suggests that cells similar to modern bacteria were common 3.8 billion years ago.

Earth History

Until the 1700’s people believed that living things could come from nonliving substances, spontaneous generation.

How did life on Earth begin?

Spontaneous generation: Pasteur’s experiment

• Experiment: Pasteur filled a flask with broth with a long S shaped neck. He boiled it to kill all life. It was open and exposed to air, but anything in the air got stuck on the curves of the neck.

• Conclusion: Spontaneous generation was disproved and biogenesis theory was substantiated. Contamination came from other microorganisms, not “air”.

Original Conditions on Primitive Earth to make life….Presence of liquid waterModerate temperature rangeFree oxygen in the atmosphere (contributed by cyanobacteria)

Adequate sunlightAbsence of toxic substances in atmosphere

Absence of lethal radiation

Volcanoes Play a BIG RoleWater vapor (eventually condensed and fell as RAIN)MethaneHydrogen NitrogenAmmoniaCarbon Dioxide (we now have oxygen b/c of

photosynthetic bacteria) Carbon Monoxide

Cyanobacteria!

ADDED OXYGEN TO EARTH!

OXYGEN ATMOSPHERERemember the atmosphere of

early Earth was made up of nitrogen, carbon dioxide, water vapor, but no free oxygen

Oxygen comes from photosynthesis when leaving oxygen gas.

About 2 billion years ago, the oxygen level in the atmosphere started to rise.

Aerobic metabolism, much more efficient than anaerobic, became possible.

QuestionWhat are the reactants in

photosynthesis?The products?

The evidence of oxygen gas formation can be seen in rocks when layers of iron oxide on the bottoms of oceans stopped forming when oxygen appeared.

Cyanobacteria created the oxygen in the atmosphere.

“Primordial Soup Theory” Conditions on the early Earth were

very different.

The atmosphere had no oxygen Energy sources, such as lightning, volcanic activity, and ultraviolet

sunlight (no ozone layer)

Theory of Chemical Evolution

Earth’s early atmosphere: HCN, CO2, CO, N, H, S, H2O“Life arose from the oceans”He believed that energy from lightning and the sun

can spark chemical reactions to create AMINO ACIDS that made proteins.

Chemical Evolution

Urey and Miller Created in the laboratory,

the conditions of early Earth.

They discharged sparks in an “atmosphere” of the Miller-Urey model consisted of H2O, H2, CH4, and NH3 gases.

produced a variety of amino acids and other organic molecules.

Chemical Evolution

Chemical Evolution• Alternate sites proposed for the synthesis of

organic molecules include • submerged volcanoes and deep-sea vents

where hot water and minerals gush into the deep ocean.

• Prokaryotes were the earliest organisms on Earth and evolved alone for 1.5 billion years.

• two prokaryotic domains: Bacteria and Archaea

Prokaryotes

• have a cell wall external to the cell membrane

• Lack membrane bound nuclues and organelles

• Double-stranded DNA molecule is in a single ring shaped

Prokaryotes

EvolutionProcess by which species of organisms change

over timeThing evolve around us all the timeBased on scientific evidence such as…

◦Fossils◦Comparative morphology/anatomy of organisms◦Embryology◦Analysis of genetic material (DNA analysis…DNA

fingerprinting!)

Terms to KnowSpecies

◦ a group of organisms that share similar characteristics and can interbreed to produce fertile offspring

◦As species EVOLVE, they produce new traits and lose other traits….

Adaptation◦Any physical or behavioral trait that improves an organisms chance for survival and reproduction

Fossil Evidence for EvolutionFossils:

◦Remains or evidence of organisms that have lived in the past

◦Provided clues of when different species livedLaw of Superposition

◦States that in undisturbed sedimentary rock, older rock layers lie beneath younger rock layers

◦By Identifying the fossils indifferent layers of rock and applying the law of superposition, scientists can determine: when the certain organisms lived The order in which things evolved

Law of Superposition

Biogeography

Study of the distribution of Earth’s organismsContinental Drift Hypothesis

◦States that the continents were once joined in a single, large landmass called PANGAEA

◦Pangaea broke up over millions of years and continents ended up where they are today

◦Fossil evidence shows that in addition to changing Earth’s surface, continental drift also changed the distribution of organisms on Earth

Comparative Anatomy/Morphology

Do other organisms have arms like us?Many species share similar structures..Do flamingos and blue jays have

feathers?◦Yes…the presence of feathers suggest that both groups of birds descended from an animal with feathers

◦Flamingos and blue jays are more closely related than either one is to an animal without feathers (like us)

Homologous StructuresBody parts of different

organisms that have similar structure but NOT similar FUNCTION

Homologous structures DO indicate shared ancestor

Analogous StructuresBody parts that have a SIMIALR FUNCTION but NOT

similar structureBody parts with Different structure, same functionDo NOT indicate shared ancestry An analogous structure found in two different species

Homologous vs. Analogous StructuresHomologous= Same structure, DIFFERENT Function

Analogous= Different Structure, SAME Function

Anatomical features that are similar in structure are called homologous structures, and they

indicate common ancestry.

Comparative Anatomy

Vestigial StructuresStructures that do not seem to play a role in the

body functions of the organism◦Appendix

Rats digestion Humans no use…appendix is a vestigial structure It can be concluded that the common ancestor of the human

and rat had an appendix

Embryology

Study of embryosEmbryo early stage in the development

of an organismScientists compare the development of

the embryos of different speciesSimilarities in development =shared

ancestorMore traits in common=more closely

related

Modern Organisms EVOLVED from

COMMON Ancestors in an Evolutionary Chain

Chemical Evidence of EvolutionChemicals found in living things also

provide clues to ancestry..what chemical?◦ DNA!!!

Comparisons of the sequences of the nucleotides in DNA and the amino acids in certain proteins can also be used to show more common ancestry

More similarities in two DNA sequences or amino acid sequences = the more closely related the organisms are ◦ DNA fingerprinting

ALL organisms have DNA made up of the same Amino Acids…

The only thing that’s different is the ARRANGEMENT/sequence of amino acids…

The More similar AA sequences= the

more closely related the organisms are!

Similarities in Molecular BiologyCommon amino acid sequences suggest an evolutionary relationships between various

species of organisms.

Darwin’s Theory of Evolution by Natural Selection

◦Before Darwin people believed Earth was less than 10,000 years old and also relatively unchanged Buffon- Studied the fossil record which showed that the Earth might be much

older.(4.3 and 4.5 billion years old)

Hutton - Layers of rock are moved by forces beneath Earth’s surface. Most geological processes operate extremely slowly.

Lyell - geologic process that shaped the Earth in the past still continue today.

Ideas that shaped Darwin

Before Darwin people believed that species were fixed, plants and animals had always been the way they are today

Cuvier – based fossils from different rock layers gave evidence that organisms from the past differed greatly from living species

Ideas that shaped Darwin

Lamark’s Use or disuse1st to suggest that species change or evolve over time. But his explanation was flawed.

He thought characteristics acquired through your life could be passeddown from parent to offspring.

Ideas that shaped Darwin

Darwin made a voyage around the word collecting thousands of plant and animal specimens.

His observations and collected evidence led him to propose hypothesis that living things change over time

Theory of Evolution through Natural Selection.

Voyage of the Beagle

Darwin noticed that plants and animals on the Galapagos islands of the coast of Ecuador were different from those on the mainland and also from island to island.

Voyage of the Beagle

Neck-size vs. Vegetation height

Galapagos’ Finches

Galapagos’ Finches

In 1859, Darwin published a book titled, “On the Origin of Species” In this book he presented all the evidence he had gathered

over the past several years supporting his theory that evolution has been taking place for millions of years—and continues in all living things.

Darwin’s Theory

• In his book he also proposed a mechanism for evolution called

• Natural Selection

Observed Evolutionary

Change

Speciation◦ Evolution of a new species from an

existing species◦ Due to Types of isolation…more on next slide

Occurs when a population is separated into groups that cannot reach each other to interbreed◦ Due to :

Behavioral barriers Anatomical barriers Genetic barriers

Once groups are separated, environmental conditions in each area influence which traits are helpful or harmful to members of each population◦ Less helpful traits disappear◦ Helpful traits become more popular

Overtime, these changes can produce 2 distinct species that can no longer interbreed

How We Get New SpeciesReproductive isolation

◦When organisms of the same species become genetically split and STOP breeding with each other

◦Gene pool split, two different groups can no longer interbreedBehavioral isolation

◦Groups of organisms of the same species develop different courtship rituals (or behaviors) over time and will not be attracted to others

Geographic isolation◦When two populations are separated by geographic barriers◦Mountains, rivers, etc.◦Doesn't always separate all species…river and birds vs. squirrels

Temporal isolation◦When two or more species reproduce at different times◦Specific day/season when that species is able reproduce

Sympatric speciation means that one population of one species became two species while in the same geographic region with no physical separation.

Allopatric speciation means that speciation occurred in different regions. The key with allopatric speciation is geographical separation.

Geographic Isolation Reproductive Isolation

Adaptive RadiationWhere species all

deriving from a common ancestor have over time successfully adapted to their environment via natural selection

NicheDerived from Latin word meaning

“nest”The role an organism plays in

its community or ecosystemNo two species can occupy

the same niche in the same area at the same time

Think of a sports team…everyone has a specific role on the field◦ You can’t have two people playing

short stop at the same time

Terms to Know

Two Ways Evolution is believed to have OccurredGradualism

◦Evolution occurring over a long period of time

◦Slow and constant change◦Small difference between generations◦This is how Darwin believed NATURAL

SELECTION workedPunctuated Equilibrium

◦Evolution occurs in spurts ◦Changes occur rapidly followed by long period without change

◦Causes: random mutations in DNA Sudden Major changes in environment

organisms that descended from different ancestors

Evolve similar anatomies and/ or behaviors if they live in similar environments

Convergent Evolution

Divergent EvolutionOrganisms from the same ancestor have developed different anatomies/behaviors (and eventually form new species)

Environment influences their new anatomy/behaviors

MicroevolutionWhen evolution occurs quickly enough for

scientists to observeBacteria

◦Reproduce rapidly◦Trait for Resistance to antibiotics is passed down to

offspring◦This is how bacteria become resistant to certain

medicines…NOT GOOD

The ability of an organism to survive and

reproduce in its specific environment is

called fitness.

• Individuals with characteristics that are

not well suited to their environment either

die or leave few offspring

• Individuals that are better suited to their

environment survive and reproduce most

successfully.

• Darwin called this process Survival of

the Fittest, or Natural Selection.

NATURAL SELECTION

4 Principles of Natural SelectionVariationCompetitionExcess offspringSurvival of the Fittest

4 Main Principles of Natural Selection

1. Variation exists within a population

2. Organisms compete for limited resources

3. Organisms produce more offspring than can actually survive

4. Individuals with variations suitable for their habitat are the ones that SURVIVE and REPRODUCE

Three species of lizard. B- The ones at the bottom live in the shrubland, and are colored to blend in.

•The top pictures show the same species of lizard, but the variety that lives in the White Sands•They all evolved to become white (camouflage)

•The DNA on the bottom shows the location of the mutation that gives the white color

Individual organisms within the population differ. Most of this variation is determined by genetic

inheritance (recombination), but sometimes it is the result of genetic mutations.

1. Inherited Variation

More on Variation

What is a gene?◦Section of DNA on your chromosome that codes for a particular

protein=traitGenes determine a particular trait an organism expressesMany times organisms can have duplicate copies of a gene

◦ think of these copies as back up files◦Sometimes the back up files get mutated by they are not expressed◦ If an environment changes, that mutated copy of the original gene

MAY be useful if it helps the organisms survive◦The mutated copy may then be passed onto offspring

2. Struggle for Existence Because so many offspring are produced, many

will die due to a lack of resources, predation, disease, or other unfavorable conditions.

3. Overproduction of OffspringOrganisms produce more offspring than can survive. Many of the offspring do not survive to reproductive age.

4. Differential Reproduction Individuals best suited to their environment survive and reproduce

most successfully. Therefore these organisms pass their advantageous traits to their

offspring while offspring with disadvantageous traits die or produce fewer offspring.

Descent with ModificationNatural

selection causes species to change over time.

Species alive today descended with modification from ancestral species.

Diving Into The Gene Pool!

Different forms of genes Genes

◦ Sections of DNA that code for a specific protein that give you a specific trait

◦ “factors” that determine an individuals characteristics; passed down from parents to offspring

Gene Pool◦ All the genes (including different

alleles) in a population◦ Gene Pool: the combined genetic

information of ALL members of a population

Allele frequency is the # of times a specific allele occurs in a gene pool Evolution involves changes in

ALLELE FREQUENCY in a population over time

“Alleles”

• Allele: One gene of a gene pair for a trait. • In the gene pair Bb for hair color, both

B & b are alleles • Genotype: The 2 alleles an organism

possesses for a trait. (Its genetic makeup.)

• Phenotype: The external appearance of the organism for a trait. (blue eyes, black hair, hitchhiker's thumb, etc...)

• Dominant Allele: An allele that masks the presence of another allele for the same characteristic. Usually shown as a capital letter (Ex......A, B, G, T, etc....)

• Recessive Allele: An allele that is hidden by the presence of a dominant allele for the same characteristic. Usually shown as a lower case letter (Ex......a, b, c, t, etc....)

How to calculate the ALLELE Frequency in a Gene Pool

Allele X or Allele x for certain TRAIT

Allele frequency X = # of allele X in population (gene pool)

total # of alleles (X + x) in population (gene pool)

Allele frequencies measure genetic variation.– how common allele is in population

– can be calculated for each allele in gene pool

1. Calculate the allele frequency for G(Green frogs) in the population

2. Calculate the allele frequency for g (brown frogs) in the population

1. Genetic Drift2. Gene Flow3. Non-Random Mating

Mechanisms for Evolution

OTHER than Natural Selection:

Genetic Diversity Is Important in Evolution

Within a population there MUST be genetic diversity to INCREASE chances of surviving and reproducing

Genetic variation is caused by:◦Gene flow◦Genetic drift◦Non-random mating

changes in the allele frequency within a population that occur by chance

genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals

Some individual may have more offspring than others, although both groups are equally fit◦ Bird A and Bird B lay eggs◦ Predator steals Bird A’s eggs◦ Who’s gene will be passed on?

No guarantee that the new population will be better suited to its environment than the original population

Genetic drift is more likely to effect small populations

Genetic Drift

Before After

Gene Flow genes from one population are introduced into the gene pool of another population◦Biggest Factor that Effects Gene Flow: MOBILITY For example:

The immigration and emigration of organisms. The dispersal of seeds or spores.

Hardy-Weinberg Equilibrium principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors

Cannot exist in real life; a way to see how alleles change in a population

NO EVOLUTION WILL OCCUR WHEN THESE 5 CONDITIONS ARE MET—GENETIC EQUILIBRIUM

Hardy Weinberg Equationp2 + 2pq + q2 = 1 and p + q = 1

5 CONDITIONS:1. No mutations must occur so that new

alleles do not enter the population. 2. No gene flow can occur (i.e. no migration

of individuals into, or out of, the population).

3. Random mating must occur (i.e. individuals must pair by chance)

4. The population must be large so that no genetic drift (random chance) can cause the allele frequencies to change.

5. No selection can occur so that certain alleles are not selected for, or against.

Non-Random MatingSome individuals in a population have more opportunity to mate and produce offspring than others

Genes of individuals with less chances to mate are eliminated from population

Common in animals b/c animals choose their mates

Another source of genetic variation…

MUTATIONS!

Genetic variation comes from several sources. Can you think of some?

Mutation is a random change in the DNA of a gene.

• Recombination forms new combinations of alleles.

– can form new allele– How can mutations be passed on to offspring?

– usually occurs during meiosis, What is the process called?

–CROSSING OVER –parents’ alleles

arranged in new ways in gametes

Sources of Genetic VariationMutation

◦Somatic mutations (to your regular cells with 46 chromosomes)

◦Germ mutations (to your gamete cells with 23 chromosomes)

Recombination◦Rearrangement of genes◦Gives offspring combinations of genes different from

those combinations in parents◦Sources of recombination:

Sexual reproduction Chromosomal changes during gamete formation

MutationsChange to an organisms genetic material (DNA)

Change the NUCLEIC ACIDS that make up one or more genes

Changes can produce new traits that can either HELP or HURT the survival of an organism◦BENEFICIAL Mutations help organism◦NEUTRAL Mutations have no effect on organism

◦NEGATIVE Mutations hurt organisms chances for survival

Germ MutationMutation in a gameteCAN BE passed off to offspring and AFFECT

survival of those offspring and their descendants

Helpful mutations persist (stay around) in population

Helpful mutations contribute to evolution and speciation

Reasons for MutationsSpontaneousNatural factors◦Ultraviolet radiation from the sun

Exposure to chemicalsExposure to radiation

DNA is the blue-print for building ALL living things on planet Earth. DNA sequences are changed by:

random mutations Radiation Viruses Chemicals sexual reproduction Migration geological events

As a result there is variation within populations of a species. Those individuals of a particular species with a phenotype (as a result

of their genotype) that is more fit to survive in a given environment has a better chance to reproduce.

Those individuals who reproduce more pass-on their genes at a higher frequency than those who do not.

EVERYTHING is trying to SURVIVE and REPRODUCE

Summary of Evolution