Evolution and Darwin. Evolution is surrounded by controversy Why? People have religious beliefs People don’t like the idea that “Human’s came from monkeys”

Evolution and Darwin

Evolution is surrounded by controversy

• Why?

• People have religious beliefs

• People don’t like the idea that “Human’s came from monkeys”

• There is a lot more to evolutionary theory than monkeys.

The Camps surrounding Evolutionary Theory

• Creationists- believe a supreme being (God, Allah, Great Spirit etc.) created everything as it is today

• Intelligent Design-followers believe the living world is too complex for it to just happen. Some intelligent form had to be behind making the blue prints.

• Evolutionists- believe organisms changed over time to their present forms.

What do you need to do to be successful with Unit #4?

• You do not have to believe Evolutionary Theory.

• You only have to understand its principals and concepts that we learn in our future lessons

Old Theories of EvolutionOld Theories of Evolution

• Jean Baptiste LamarckJean Baptiste Lamarck (early 1800’s) proposed:

““The inheritance of acquired characteristicsThe inheritance of acquired characteristics””

• He proposed that by using or not using its body parts, an individual tends to developdevelop certain characteristicscharacteristics, which it passespasses on to its offspringoffspring.

““The Inheritance of Acquired The Inheritance of Acquired CharacteristicsCharacteristics””

• Example:Example:

A giraffe acquired its long neck

because its ancestor stretched

higher and higher into the trees

to reach leaves, and that the

animal’s increasingly lengthened

neck was passed on to its offspring.

Would these acquired characteristics get passed on to their offspring?

Of course not. The acquired characteristics did not cause changes in the sex cells

Larmarck’s Theory

• Use and Disuse

-Fish in caves don’t use their eyes so they disappear

-Elephants use their trunks a lot so they get longer

• Although false, his theory was the first attempt to explain how organisms adapted to their environment over time

Charles DarwinCharles Darwin

• Influenced by Charles LyellInfluenced by Charles Lyell who published ““Principles of GeologyPrinciples of Geology””..

• This publication led DarwinDarwin to realize that natural forces gradually change the Earth’s surface and that the forces of the past are still operating in modern times.

Charles DarwinCharles Darwin• Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831-1836)

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

• On the Galapagos Islands, Galapagos Islands,

Darwin observed species

that lived nowhere else in

the world.

• These observations led

Darwin to write a book.

HMS Beagle and its route

California Academy of Sciences in San Francisco

• Mr. Down’s spent the day there on a summer trip to visit my son and daughter

• The CAS had an incredible Darwin Exhibit

You will use this chart for Beaks of Finches Lab

Darwin’s Finches

Charles DarwinCharles Darwin

• Wrote in 1859Wrote in 1859: ““On the Origin of Species by On the Origin of Species by Means of Natural SelectionMeans of Natural Selection””

• Two main points:Two main points:

1.1. Species were not created in their present Species were not created in their present form, but evolved from ancestral species.form, but evolved from ancestral species.

2.2. Proposed a mechanism for evolution:Proposed a mechanism for evolution: NATURAL SELECTIONNATURAL SELECTION

Natural SelectionNatural Selection• IndividualsIndividuals with favorablefavorable traitstraits are more

likely to leave more offspring better suited for their environmentenvironment.

• Also known as ““Differential ReproductionDifferential Reproduction””• Example:Example:

English peppered moth (English peppered moth (Biston betularia))

- light and - light and

dark phasesdark phases

http://tidepool.st.usm.edu/crswr/peppermoths.html

Artificial SelectionArtificial Selection• The selective breedingselective breeding of domesticated

plants and animals by man.• Selective Breeding is also called

Artificial selection

• Question:Question:

What’s the ancestor of the domesticated dog?

(Canis familiaris)• Answer:Answer: WOLF (WOLF (Canis lupus)

Mr. Downs’ dog Clancy at 6 weeks old

Both of these trees are in my yard and are the same species (Thuja occidentalis)

Which one looks better? Why?

They are both in the same environment (water, sun, nutrients are the same). Why do they look so different?

Different Traits in their DNA

Which one do you think humans selected desirable traits in deliberate plant crosses?

A B

Darwin is the founder of Modern Darwin is the founder of Modern Evolutionary TheoryEvolutionary Theory

• Science attempts to:

-Describe events based on phenomena we

can observe

-Explain events of the past in terms of

events we can observe today

-Make predictions about future events

• A Theory such as Evolution Theory is

supported by a lot of data collected by

thousands of Scientists

• Theories can be discarded (i.e.Lamarck) or revised as scientist get new information

• Theories can’t be proven with absolute certainty (i.e.-Gravitational Theory, Cell Theory, Contagious Disease, Genetics)

Darwin is the founder of Darwin is the founder of Modern Evolutionary TheoryModern Evolutionary Theory

• Evolution is the processesprocesses that have transformed life on earth from it’s earliest earliest formsforms to the vast diversitydiversity that characterizes it today.

• Evolution results in

A changechange in the

genes!!!!!!!!genes!!!!!!!!

• Darwin never did claim that humans originated from monkeys.

• Darwin claimed that humans and monkeys (well, apes really) have a COMMON ancestor. That is, they originated from the same species many years ago

• Evolution is the process (mutation, adaptation, natural selection and extinction) of change in a population through generations

• Existing life forms have evolved from earlier life forms.

• Evolutionary theory is a unifying principle for the biological sciences. ( Genetics, Biochemistry, Anatomy, Physiology etc.)

• Evolution Theory provides

an explanation for the

differences/ similarities in

structure, function, and

behavior among life forms.

Evidence of EvolutionEvidence of Evolution

Cladograms or

phylogenetic trees are

graphic representations

of species relationships.

Common Ancestor


1.1. Geographical distribution of species. Geographical distribution of species. Alfred Russell Wallace was also known as the "father of biogeography.

• Biogeography -the study of the past and present geographical distribution of organisms.

Reproductive Isolation- prevents mating with birds on the other islands. Two populations develop independently

2. Fossil Record:2. Fossil Record:

Fossils and the order in which they appear in Fossils and the order in which they appear in layers of sedimentary rock layers of sedimentary rock (strongest (strongest evidence).evidence).

Younger Fossils

Older Fossils

Evolution of the horse

What changes do you notice in moving from the bottom to the top?

Increase in size

Changes in the leg bones

• Relative Dating-In relative dating, something is determined to be older or younger than something else by using the laws of superposition.

-Layers (strata) close to the surface are younger

-Deeper Layers contain the oldest strata• Absolute Dating-dating determines the actual age of

artifacts

-One of the most widely used

and well-known absolute dating

techniques is carbon-14

dating, which is used to date

organic remains.


3. 3. Taxonomy-Taxonomy-classification of organisms into different categories based on their physical characteristics and presumed natural relationships (remember Did King Philip Come Over………..?)

• In 1735, Carolus Linnaeus

published a book in which he

outlined his scheme for classifying

organisms and is still in use today

The Linnaean system uses two Latin name categories, genus and species , to designate each type of organism.

4. 4. Homologous structuresHomologous structures::Structures that are similar because Structures that are similar because

of of common ancestry (comparative common ancestry (comparative anatomy)anatomy)

• Homologous Structures- structures shared by related species because they have been inherited from a common ancestor.

(flipper of a whale and hand of a human)

• Analogous Structures- Analogous structures serve the same function in different species but is not a result of sharing a common ancestor. (wing of a butterfly and wing of a bird)

• Vestigial Structures- organ or structure that once was useful in an animal’s evolutionary past, but that now is useless or very close to useless. (wing of an ostrich)

My favorite Vestigial Structures

Snake Whale

Plica Semilunaris -it is the “crusty” factory. It secretes a sticky mass that collects any foreign materials. All this trash is surrounded by the sticky gook so that it does not scratch the sensitive cornea.

Darwin’s point is found in the majority of mammals, and humans are no exception. It is most likely used to help focus sounds in animals, but it no longer has a function in humans.Wisdom Teeth - Early humans ate a lot of plants – and they needed to eat them quickly enough and eat a sufficient amount in one day to get all of the nutrients they needed.


5. 5. Comparative embryologyComparative embryology::

Study of structures that Study of structures that

appear during embryonic appear during embryonic

development.development.

Any ideas on why theAny ideas on why the

embryos are so similar?embryos are so similar?

Scientist believe thatScientist believe that

mutations at early stages mutations at early stages

result in death orresult in death or

spontaneous abortion.spontaneous abortion.

6. Molecular biology: DNA and proteins 6. Molecular biology: DNA and proteins (amino acids)(amino acids)

• Diagram shows chromosome

1 next to the human chromosome 1.

• The A-T bases are black and

the G-C bases white.

Blue areas in the rendered chromosomes identify

bases not known yet.

• DNA Analysis can show us

how closely related different

organisms are.

-There is no thought involved in Natural selection

-There are no choices in Natural Selection

-It is all about the genes an organism is born with

Concepts of Natural Selection

• 1. Overproduction -- Within a population,

more offspring are born than can possibly survive.

These are tadpoles that hatched from one female toad. Do you think many will survive?

• 2. Competition – Over production results in struggle for space, water, food, light, mates or other limited resources

• 3. Variations-Members of populations show variations (differences in traits) that make certain individuals better adapted to survive

• 4. Natural Selection-Some variations are more

helpful than others, there is a natural selection against organisms that can’t adapt.

• 5. Organisms that can’t adapt DIE and

some populations may become extinct

• 6. Survival of the Fittest -- The individuals who

survive are the ones best adapted. • 7. Inheritance of variations-Organisms with helpful

variations survive and live long enough to

REPRODUCE. • 8. The best adapted individuals survive and

reproduce, passing on the favorable variations to their offspring (& population ). These changes improve the fitness of a species (population) in its environment

• 9. If an organism does not live long enough to reproduce it has NO EFFECT ON THE EVOLUTION OF THE POPULATION.

• 10. Individuals can’t evolve, only populations can evolve. (make sense because genes have to be passed on to offspring for evolution to take place.

• 11. Evolution of New Species-Over long periods of time, so many variations may accumulate that a population may become a new species. This process is called Speciation

Some Sources of Variation in Modern Natural Selection Theory• 1. The genetic basis for variation within a species is

provided by mutations and

sexual reproduction. (crossing over

and recombination)

• 2. Mutations are spontaneous

and provide the raw material for

evolution.

Modern Natural Selection Theory

• 1.) All species have the potential to increase in numbers.

• 2.) There is a finite amount of resources for any species. Species tend to make too many

organisms for these resources. • 3.) Species will show genetic variability due to

mutation, crossing over, and genetic recombination (during fertilization) of genes.

• 4.) The scarce finite resources of the environment will select those offspring better able to survive and less fit offspring may die.

• 5.) Variations within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions.

-Traits which are beneficial to the survival of an organism in a particular environment tend to be

retained and passed on, and therefore, increase in frequency within a population.

-Traits which have a low survival value to organisms tend to diminish in frequency from generation to generation.

-If environmental conditions change, traits that were formerly associated with a low survival value may, in

a changed environment, have greater survival value and increase accordingly.

Population GeneticsPopulation Genetics

• The sciencescience of genetic changegenetic change in population.

• Hardy-Weinberg equation is important and will be discussed shortly.

VocabularyVocabulary

• Population- Population- A localized group of individuals belonging to the same speciessame species.

• Species- Species- A group of populationspopulations whose individualsindividuals have the potential to interbreedinterbreed and produce viableviable offspring.

• Gene Pool-Gene Pool-The total collection of genescollection of genes in a population at any one time.

Hardy-Weinberg PrincipleHardy-Weinberg Principle

• The conceptconcept that the shuffling of genesshuffling of genes that occur during sexual reproduction, by itself, cannot changecannot change the overall genetic makeup of a population.


• This principleprinciple will be maintained in nature only if all fivefive of the following conditions are met:

1.1. Very large populationVery large population

2.2. Isolation from other populationsIsolation from other populations

3.3. No net mutationsNo net mutations

4.4. Random matingRandom mating

5.5. No natural selectionNo natural selection


• Remember:Remember:

If these conditions are met, the population is at equilibriumequilibrium.

• This means ““No ChangeNo Change”” or or ““No evolutionNo evolution””..

• The Hardy–Weinberg equilibrium is impossible in nature. Genetic equilibrium is an ideal state that provides a baseline to measure genetic change against.

MacroevolutionMacroevolution

• The origin of taxonomic groups higher than higher than the species levelthe species level.

• Involves very long periods of time

• Grand scale changes in organism

• Scientists can see changes in fossils of Intermediate species

• Sea cow (manatee)

ancestor with legs

MicroevolutionMicroevolution

• A change in a populationpopulation’’s gene pools gene pool over a secession of generations.

• Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.

Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution

1. Genetic drift:1. Genetic drift:

Change in the gene pool of a Change in the gene pool of a small small population due to chance.population due to chance.

• Two examples:Two examples:

a. Bottleneck effecta. Bottleneck effect

b. Founder effectb. Founder effect

a. Bottleneck Effecta. Bottleneck Effect

• Genetic driftGenetic drift (reduction of alleles in a population) resulting from a disasterdisaster that drastically reduces reduces population sizepopulation size. (result are similar to inbreeding)

• Examples of disasters:Examples of disasters:

1.1. EarthquakesEarthquakes

2.2. VolcanoVolcano’’ss

3. Droughts 3. Droughts

b. Founder Effectb. Founder Effect• Genetic driftGenetic drift resulting from the colonizationcolonization of a new

location by a small number of individuals.• Founder populations are

often found on islands• Results in random changerandom change

of the gene pool.

• Mutiny on the Bounty (1789): Population of 9 mutineers, 8-9 Tahitian females and 6 Tahitian males to uninhabited Pitcairn Island.


2. Gene Flow:2. Gene Flow:

TThe gain or loss of allelesgain or loss of alleles from a population by the movementmovement of individuals or gametes.

– Immigration- Immigration- movement out/away–EmigrationEmigration- movement in


3. Mutation:3. Mutation:

Change in an organismChange in an organism’’s DNA thats DNA thatcreates a new allele.creates a new allele.

4. Non-random mating:4. Non-random mating:

The selection of mates The selection of mates

other thanother than by chance.by chance.

5. Natural selection: 5. Natural selection: Differential reproduction- competition for mates, those best adapted competition for mates, those best adapted survive and produce more offspring.survive and produce more offspring.

Modes of ActionModes of Action

• Natural selectionNatural selection has three modesthree modes of action:

1.1. Stabilizing selectionStabilizing selection

2.2. Directional selectionDirectional selection

3.3. Diversifying selectionDiversifying selection

Number ofIndividuals

Size of individualsSmall Large

1.1. Stabilizing SelectionStabilizing Selection

• ActsActs upon extremesextremes and favorsfavors the intermediateintermediate.



2.2. Directional SelectionDirectional Selection

• FavorsFavors variants of one extremeone extreme.



3.3. Diversifying SelectionDiversifying Selection

• FavorsFavors variants of opposite extremesopposite extremes.



SpeciationSpeciation

• The evolutionevolution of new species.

Reproductive BarriersReproductive Barriers

• Any mechanismmechanism that impedesimpedes two species from producing fertile and/or viable hybrid fertile and/or viable hybrid offspringoffspring.

• Different species most likely have different number of chromosomes

• Two barriers:Two barriers:

1.1. Pre-zygotic barriersPre-zygotic barriers

2.2. Post-zygotic barriersPost-zygotic barriers

1.1. Pre-zygotic BarriersPre-zygotic Barriers

a. Temporal isolation:a. Temporal isolation:

Breeding occurs at different times for different species.

b. Habitat isolation:b. Habitat isolation:

Species breed in different habitats.

c. Behavioral isolation:c. Behavioral isolation:

Little or no sexual attraction between species.

1.1. Pre-zygotic BarriersPre-zygotic Barriers

d. Mechanical isolation:d. Mechanical isolation:

Structural differences prevent gamete exchange.

e. Gametic isolation:e. Gametic isolation:

Gametes die before uniting with gametes of other species, or gametes fail to unite.

2.2. Post-zygotic BarriersPost-zygotic Barriers

a. Hybrid inviability:a. Hybrid inviability:

Hybrid zygotes fail to develop or fail to reach sexual maturity.

b. Hybrid sterility:b. Hybrid sterility:

Hybrid fails to produce functional gametes.

c. Hybrid breakdown:c. Hybrid breakdown:

Offspring of hybrids are weak or infertile.

Interesting but not Fertile

Horse- 64Donkey- 62Mule- 63

Lion- 38Tiger- 38

Human - 46Chimpanzees- 48Gorilla- 48

Allopatric SpeciationAllopatric Speciation

• Induced when the ancestralancestral population becomes separatedseparated by a geographical geographical barrier.barrier.


Grand Canyon and ground squirrels

Adaptive RadiationAdaptive Radiation

• Emergence of numerous speciesEmergence of numerous species from a common ancestorcommon ancestor introduced to new and diverse environments.


DarwinDarwin’’s Finchess Finches

Sympatric SpeciationSympatric Speciation

• Result of a radical change in the genome that produces a reproductively isolated sub-reproductively isolated sub-populationpopulation within the parent population (rare).

• Example: Plant evolution - polyploidExample: Plant evolution - polyploid

A species doubles it’s chromosome #chromosome # to become tetraploid.

reproductive sub-population

Parent population

Interpretations of SpeciationInterpretations of Speciation

• Two theories:Two theories:

1.1. Gradualist Model (Neo-Darwinian):Gradualist Model (Neo-Darwinian):

Slow changes in species overtime.

2.2. Punctuated Equilibrium:Punctuated Equilibrium:

Evolution occurs in spurts of relatively rapid change.

Convergent EvolutionConvergent Evolution

• SpeciesSpecies from different evolutionary branchesevolutionary branches may come to resemble one another if they live in very similar environments.very similar environments.


1.1. Ostrich (Africa) and Emu (Australia).Ostrich (Africa) and Emu (Australia).

2.2. Sidewinder (Mojave Desert) andSidewinder (Mojave Desert) and

Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)

CoevolutionCoevolution

• Evolutionary changeEvolutionary change, in which one species act as a selective forceselective force on a secondsecond species, inducing adaptations that in turn act as selective force on the firstfirst species.


1.1. Acacia ants and acacia treesAcacia ants and acacia trees

2.2. Humming birds and plants with Humming birds and plants with flowers flowers with long tubeswith long tubes

• Speciation-creation of new species• Morphology-study of structure• Geographic Isolation (Reproductive

Isolation)-• Divergent Evolution-• Convergent Evolution• Coevolution-• Adaptive Radiation-• Genetic Drift-

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Evolution and Darwin. Evolution is surrounded by controversy Why? People have religious beliefs People don’t like the idea that “Human’s came from monkeys”