Chapter 15

Fossils Evidence of organisms that lived in

past times. Because there are many methods of

formation, there are many types of fossils. See pg 382 & 418

Fossil types1. Trace – marking left by animal; such as a

footprint.2. Casts – minerals fill a space left by a

decayed organism.3. Petrified – minerals penetrate and replace

parts of an organism.4. Imprint – thin object imprint preserved in

hardened sediment.5. Molds – organism buried in sediment

decays, leaving empty space.6. Amber – entire organism trapped in

hardened tree sap.7. Frozen – entire organism trapped and

quickly frozen in ice.

Paleontology: the scientific study of ancient life using fossil evidence.

Geologic Time ScaleFormation of earth, estimated to be 4.6 billion years ago.

Era Period # of years ago eventsPrecambrian 3.5 billion unicellular prok/eukPaleozoic cambrian 540 million invertebrates

Ordovician 510 million vertebratesSilurian 439 million jawed fish/land plantsDevonian 408 million amphibiansCarboniferous 362 million seed plants/ reptilePermian 290 million conifers dominant

Mesozoic Triassic 245 million dinosaurs/mammalJurassic 208 million flowering plants/birdsCretaceous 146 million flowering plants dom

Cenozoic Tertiary 66 million placental mammalsQuaternary 1.6 million humans@200,000yrs

determining age of rocks

1. Relative dating Geologic law: if rock layers have not

been disturbed… The layers at the surface are younger

than the deeper layers. Fossils in the top layers are younger than

those fossils in deeper layers. Relative dating cannot be used to

determine actual age.

2. Radiometric dating Utilizes radioactive isotopes to determine

specific age. Radioactive isotopes decay over time

giving off radiation. As radioactive decay continues, these

isotopes form new elements. Radioactive isotopes have decay rates,

this rate can be used as a type of clock called half-life.

Rock/fossil age can be estimated by comparing the amount of radioactive isotope present to the amount of new element present in the sample item.

Examples of Radaiometeric dating Radioactive half-life=1 million years If a

rock contains equal amounts of the radioactive isotope and the new element to which it decays, the rock must be 1 million years old.

Fact: For very old rocks/fossils potassium 40 is used; it decays to argon 40. Half-life=1.3 billion years.

For rocks/fossils less than 50,000 years old carbon 14 is used; it decays to nitrogen 14. Half-life=5,730 years.

EvolutionEvolution

Simply stated evolution is the change in Simply stated evolution is the change in living things, or populations, over time.living things, or populations, over time.

A change in the gene pool of a population.A change in the gene pool of a population.

Theories of evolutionTheories of evolution In 1809 Jean Baptiste de In 1809 Jean Baptiste de

Lamark was one of the Lamark was one of the first to present a theory first to present a theory of evolution.of evolution.

It was based on two It was based on two principles :principles :

The use and disuse of The use and disuse of organs organs

Inheritance of acquired Inheritance of acquired traitstraits

His ideas are flawed and His ideas are flawed and later his hypothesis is later his hypothesis is rejectedrejected

Others Who Influenced Others Who Influenced Evolutionary ThoughtEvolutionary Thought

Earth is ancient and changingEarth is ancient and changing James Hutton James Hutton – 1785, – 1785,

proposed that Earth is proposed that Earth is shaped by geological shaped by geological forces. forces.

Charles LyellCharles Lyell – 1833, wrote – 1833, wrote principles of Geology and principles of Geology and stressed that scientists stressed that scientists must explain past events in must explain past events in terms of processes that terms of processes that they can actually observe, they can actually observe, like geological forces.like geological forces.

Thomas MalthusThomas Malthus – 1798, an – 1798, an economist who predicted economist who predicted that the human population that the human population will grow faster than the will grow faster than the space and food supplies space and food supplies needed to sustain it.needed to sustain it.

James Hutton

Thomas Malthus

Charles Lyell

Theories of EvolutionTheories of Evolution Charles Darwin (1809-1882) Charles Darwin (1809-1882)

he published his book he published his book Origin of Species, on how Origin of Species, on how species change over time…species change over time…after 22 years of reading, after 22 years of reading, study, specimen collection, study, specimen collection, observation and observation and experimentation.experimentation.

In it he presented his In it he presented his revolutionary new theory of revolutionary new theory of evolution which remains evolution which remains the cornerstone of modern the cornerstone of modern evolutionary thought today. evolutionary thought today.

Darwin's travels on the HMS Beagle took Darwin's travels on the HMS Beagle took him to the Galapagos Islands where he him to the Galapagos Islands where he noted similar animals to those on the noted similar animals to those on the South American continent, but they were South American continent, but they were not exactly alike. One example were the not exactly alike. One example were the finches he found on the different islands.finches he found on the different islands.

Darwin’s PrinciplesDarwin’s Principles Variation exists within species, and Variation exists within species, and

some of this variation is heritable. some of this variation is heritable. All organisms compete for limited All organisms compete for limited

resources.resources. Organisms produce more offspring Organisms produce more offspring

than can survive, and many that do than can survive, and many that do survive do not reproduce.survive do not reproduce.

The environment selects organisms The environment selects organisms with beneficial traits with beneficial traits Natural Natural Selection Selection ( survival of the fittest)( survival of the fittest)

Evidence of EvolutionEvidence of Evolution1. 1. Fossils:Fossils: The fossil record gives us lots of evidence The fossil record gives us lots of evidence

that species have changed over timethat species have changed over time

Examples of extinct plants and animals Examples of extinct plants and animals comes in many forms such as comes in many forms such as imprints ,molds ,casts, petrified fossils and imprints ,molds ,casts, petrified fossils and even insects trapped in amber .even insects trapped in amber .

2. Geographic Distribution of Living Species.2. Geographic Distribution of Living Species. The existence of similar The existence of similar

but unrelated species. but unrelated species. Example: Darwin found Example: Darwin found

entirely different species entirely different species of animals on South of animals on South America and Australia, America and Australia, yet when he looked at yet when he looked at similar environments on similar environments on those continents, he those continents, he sometimes saw different sometimes saw different animals that had similar animals that had similar anatomies and anatomies and behaviors. This led to his behaviors. This led to his theory of descent with theory of descent with modification. P 383modification. P 383

3. Anatomical Evidence3. Anatomical Evidence Homologous structuresHomologous structures are are

body parts found in different body parts found in different organisms with the same organisms with the same basic structure. Vary in form, basic structure. Vary in form, or function not structure. or function not structure. These suggest a common These suggest a common ancestryancestry

Vestigial structuresVestigial structures organs organs that are so reduced in size that are so reduced in size that they are just vestiges, that they are just vestiges, or traces, of homologous or traces, of homologous organs in other species. organs in other species. Suggest evolution from Suggest evolution from organisms that used them. organisms that used them. Ex: shortened legs, toes, Ex: shortened legs, toes, appendixes in humans.appendixes in humans.

4. Embryological Evidence4. Embryological Evidence Embryonic cells Embryonic cells

develop in the same develop in the same order and patterns order and patterns to produce the to produce the tissues.tissues.

Similarities in Similarities in development of development of embryos suggest a embryos suggest a common common evolutionary evolutionary relationshiprelationship

Analogous Structures Analogous Structures

Wings of birds and Wings of birds and wings of insects have wings of insects have the same the same functionfunction but but not not the same the same structurestructure and are said to be and are said to be analogous . They have analogous . They have no evolutionary no evolutionary relationship.relationship.

Ch. 16 Origins of VariationCh. 16 Origins of Variation Only genetic variations are passed from generation to Only genetic variations are passed from generation to

generationgeneration Genetic recombination during meiosis is one source of variation Genetic recombination during meiosis is one source of variation

(gene shuffling can produce 8.4 million gene combinations)(gene shuffling can produce 8.4 million gene combinations) Mutation is another important source Mutation is another important source Artificial selectionArtificial selection – breeding organisms with specific traits in – breeding organisms with specific traits in

order to produce offspring with identical traits, used to improve order to produce offspring with identical traits, used to improve crops, livestock and pets.crops, livestock and pets.

Darwin hypothesized that if it happens artificially then it should Darwin hypothesized that if it happens artificially then it should be happening naturally.be happening naturally.

Mechanisms of EvolutionMechanisms of Evolution Natural selectionNatural selection – occurs when organisms – occurs when organisms

having particular positive variations survive, having particular positive variations survive, reproduce, and pass on the variations to the reproduce, and pass on the variations to the next generation. next generation.

These adaptations can be structural, These adaptations can be structural, anatomical, physiological processes and anatomical, physiological processes and behavior.behavior.

Structural adaptation example: mimicry – Structural adaptation example: mimicry – enables one species to resemble another.enables one species to resemble another.

Physiological adaptations (can develop Physiological adaptations (can develop rapidly) Example: antibiotic resistance – rapidly) Example: antibiotic resistance – bacteria bacteria

Members of a species that live in the same Members of a species that live in the same area are members of a area are members of a populationpopulation..

Evolution occurs when there is a change in Evolution occurs when there is a change in the genetic makeup of a population.the genetic makeup of a population.

Mechanisms of EvolutionMechanisms of Evolution A A gene poolgene pool is all the alleles of all genes in all the is all the alleles of all genes in all the

individuals in a population.individuals in a population. The gene pool in a population will stay in The gene pool in a population will stay in

equilibriumequilibrium unless something happens to make it unless something happens to make it change. (Hardy-Weinberg Principle)change. (Hardy-Weinberg Principle)

Relative frequencyRelative frequency – of an allele is the number of – of an allele is the number of times that the allele occurs in a gene pool, times that the allele occurs in a gene pool, compared with the number of times other alleles compared with the number of times other alleles for the same gene occur.for the same gene occur.

For evolution to take place For evolution to take place something must upsetsomething must upset the genetic equilibrium of a population the genetic equilibrium of a population

These processes include : These processes include : natural selection, natural selection, migration, genetic drift, isolation, and mutation.migration, genetic drift, isolation, and mutation.

The classic example of The classic example of Natural selection in Natural selection in action was the change in action was the change in population densities of population densities of light colored moths light colored moths during the industrial during the industrial revolution in England.revolution in England.

Before industrial revolution

After industrial revolution

Darwin’s Hypotheses Descent with Modification – Darwin proposed that

over long periods of time natural selection produces organisms that have different structures, establish different niches, or occupy different habitats.

Each generation is modified due to which individuals reproduce.

Darwin also suggests that all living organisms are related to one another called common descent.

Looking back over time, one will find: Tigers, panthers, and cheetahs share common

ancestors Felines, horses, dogs, and bats share common

ancestors Mammals, birds, reptiles, and fish share common

ancestors All species—living and extinct—share common

ancestors.

Natural Selection on Polygenic traitNatural Selection on Polygenic traitThree types of natural selection occurThree types of natural selection occur1.1. Directional selectionDirectional selection is gradual is gradual

environmental pressure to change.environmental pressure to change.2.2. Stabilizing selectionStabilizing selection eliminates the eliminates the

extremes and reduces variationextremes and reduces variation3.3. Disruptive selectionDisruptive selection selects against the selects against the

average and favors the extremesaverage and favors the extremes

Directional selection

Stabilizing selection

disruptive selection

Mechanism for Change:Mechanism for Change:1. Migration1. Migration

Migration is the movement of Migration is the movement of organisms into (organisms into (immigration) immigration) and and out of (out of (emigrationemigration) a population.) a population.

This either increases or decreases This either increases or decreases the genes in a gene poolthe genes in a gene pool

2. Genetic Drift2. Genetic Drift Genetic drift is the change in gene Genetic drift is the change in gene

frequency of a very small frequency of a very small population due to chance.population due to chance.

Individuals that carry a particular Individuals that carry a particular allele may leave more descendants allele may leave more descendants than others, over time a series of than others, over time a series of chance occurrences of this type chance occurrences of this type can cause an allele to become can cause an allele to become common in a populationcommon in a population

Founder Affect – when the Founder Affect – when the population that moved into a new population that moved into a new environment have particular alleles environment have particular alleles that then start to present that then start to present themselves due to the environment themselves due to the environment (chance not natural selection)(chance not natural selection)

The mutations seen in this Amish child occur at The mutations seen in this Amish child occur at

the rate of 1 in 14 as opposed to 1 in 1000 in the rate of 1 in 14 as opposed to 1 in 1000 in the general population due to chance the general population due to chance introduction in a small isolated populationintroduction in a small isolated population

3. Isolation3. Isolation

Geographic isolationGeographic isolation occurs when occurs when a physical barrier separates a physical barrier separates populations. Ex: Mountain, River,etcpopulations. Ex: Mountain, River,etc

Genetic isolationGenetic isolation results when two results when two populations are unable to interbreed. populations are unable to interbreed. Ex: they reproduce at different times, Ex: they reproduce at different times, have differences in courtship rituals have differences in courtship rituals or other reproductive stategies.or other reproductive stategies.

4. Mutation4. Mutation

Many mutations are harmful (lethal) Many mutations are harmful (lethal) but when a mutation gives an but when a mutation gives an organism an advantage it is retained organism an advantage it is retained (phenotype changed) in the gene (phenotype changed) in the gene pool and changes the frequency of pool and changes the frequency of alleles in the population.alleles in the population.

SpeciationSpeciation

SpeciationSpeciation is the evolution of an is the evolution of an organism into a new species.organism into a new species.

A A nicheniche is the place and “profession” is the place and “profession” of a species (its job in its habitat)of a species (its job in its habitat)

It is difficult for two species to It is difficult for two species to occupy the same niche, competition occupy the same niche, competition is bound to favor one over the other.is bound to favor one over the other.

Speciation from Isolating Speciation from Isolating MechanismsMechanisms

Geographic isolationGeographic isolation: occurs when : occurs when a physical barrier separates populationsa physical barrier separates populations

Behavioral isolations: occurs whentwo population of organism have differentcourtship or mating rituals.

Temporal isolation: occurs when two populations have two different mating seasons

Patterns of EvolutionPatterns of Evolution1. Divergent Evolution1. Divergent Evolution

Divergent evolutionDivergent evolution is the process by is the process by which organisms become less alikewhich organisms become less alike

This can result in speciation.This can result in speciation.1.5 It can also lead to 1.5 It can also lead to adaptive radiationadaptive radiation,, where species adapt to a variety of where species adapt to a variety of

habitats and evolve into diverse forms habitats and evolve into diverse forms occupying different niches.occupying different niches.

2. Convergent Evolution2. Convergent Evolution Convergent evolutionConvergent evolution occurs when distantly occurs when distantly

related organisms develop similar characteristics related organisms develop similar characteristics due to influence of similar environments and due to influence of similar environments and natural selection.natural selection.

A good example of convergent evolution is A good example of convergent evolution is marine mammals and fish marine mammals and fish

Convergent evolution can Convergent evolution can often lead to often lead to mimicrymimicry-when -when one organism evolves to one organism evolves to resemble another.resemble another.

These animals have a selective These animals have a selective advantageadvantage

3. Coevolution

Two different species evolve in response to changes in each other over time.

Example: flowers that attract a specific type of pollinator.

Biochemical Evidence of Biochemical Evidence of EvolutionEvolution

The more closely The more closely related organisms related organisms are, the more are, the more similar their similar their biochemical biochemical makeup is. makeup is.

Similar chemistry Similar chemistry and structure of and structure of chromosomes in chromosomes in EukaryotesEukaryotes

Cytochrome c is an example of a protein that can be used to check if an organism is closely related to another organism.

Ch.17 Models for Rate of Evolution

Gradualism – a slow gradual change in a species over a long period of time. (Think millions into billions of years)

Punctuated Equilibrium – patterns of long, stable periods interrupted by brief periods of more rapid change. (Think hundreds of thousands even millions of years)

Speciation ratesSpeciation ratesLoxodonta africana

Elephas maximus

Mammuthusprimigenius

Mammuthus

Elephas

Loxodonta

Primelephas

about 55 million years agoAncestral species

6

5

4

3

2

1

0

Mil

lion

s of

Yea

rs A

go

Related Topics Extinction – disappearance of a species

from all portions of its geographical range. Causes: natural selection, abiotic change and /or food web collapse.

Microevolution – change of allele frequency; genetic variation due to processes such as selection, mutation, genetic drift or migration.

Macroevolution – evolutionary change at or greater than the species level; formation of new species, new genera and so on.

Earth’s Early History (Hypothesis)a. Early Earth’s atmosphere had hydrogen

cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water, very caustic environment.

b. 4 billion years ago first solid rocks and volcanic activity, no oceans still too hot.

c. 3.8 billion years ago cooled enough for water to remain liquid, this is when early life appeared.

d. First organic molecules – Miller, Urey –experiments produced organic compounds even cytosine and uracil.

e. Evolution of RNA and DNA – science is still working on this puzzle but have made surprising discoveries (viruses could be source of nucleus, choloroplasts and mitochondrion from bacteria – Margulis) RNA before DNA.

f. Free Oxygen – photosynthetic bacteria became common in shallow seas of the Precambrian Era, they produced oxygen which combined with Iron causing the oceans to rust. This O2 accumulated and caused the formation of the ozone layer.

Origin of Eukaryotic Cells

Endosymbiotic theory- smaller prokaryotes began living inside larger cells causing a symbiotic relation such as the mitochondria and the chloroplast. (lynn Margulis)

Nucleic Acid Nucleic Acid comparisons (DNA comparisons (DNA fingerprinting) - the fingerprinting) - the more closely related more closely related two organisms are, two organisms are, the more similar is the more similar is their DNA, e.g. their DNA, e.g. identical twinsidentical twins

Chlorophyll is the Chlorophyll is the same basic molecule same basic molecule in all photosynthetic in all photosynthetic organismsorganisms