CHAPTER 15

EVOLUTION IS CHANGE IN EVOLUTION IS CHANGE IN SPECIES OVER TIMESPECIES OVER TIME

Orderly succession of changes.

Change of populations of organisms over generations.

Fossil record shows a modification process at work.

EVIDENCE SUPPORTING THE EVIDENCE SUPPORTING THE THEORY OF EVOLUTION:THEORY OF EVOLUTION:

1. The FOSSIL 1. The FOSSIL record record

Traces of long-dead organisms (10,000 years old at the least 2B fossil).

Found in sedimentary rock.

Examples: cast, mold, or petrified.

Robert Hooke 1668 says they’re not rocks- smarty pants, not just microscope dude.

STRATAsuccessivelayers of rockdeposited over geologictime.

Geologic History of EarthGeologic History of EarthThe Fossil RecordThe Fossil Record

LAW OF SUPERPOSITION

1. Successive layers of rock or soil were deposited by wind or water.

2. Lowest STRATUM is the oldest.

3. Top STRATUM is the most recent.

4. Relative or absolute age can be determined.

5. Patterns of mass extinctions.

5 so far (we are in the 6th)

GEOLOGIC GEOLOGIC HISTORY OF EARTHHISTORY OF EARTH

ARCHEAN- prokaryotes arise

PROTEROZOIC- eukaryotes arise

PALEOZOIC- marine invertebrates, fish, amphibians, reptiles, plants arise

MESOZOIC- dinosaurs rule

CENOZOIC- mammals diversify

DISCOVERIES FROM DISCOVERIES FROM THE FOSSIL RECORDTHE FOSSIL RECORD

Earth’s history is more than 100,000 times longer than recorded human history (4.5 billion NOT 6K years).

Pattern: species appear-exist-disappear-new arise etc.

Mass extinctions due to drastic environmental change.

5 so far and we are currently in the 6th one

Biogeography (studying the global distribution of fossils and living organisms) shows a logical pattern.

ie. kangaroos only live (Australia) where kangaroo ancestor fossils are found- Australia.

PANGEA = ALL LAND

ARCHAEOPTERYXARCHAEOPTERYX

Bird-

Dinosaur

link

2. COMPARATIVE ANATOMY2. COMPARATIVE ANATOMYcompare anatomy of species to infer (figure out)

evolutionary relationships.

1. Homologous Structures reveal the pattern of divergent evolution.

2. Analogous Structures reveal a pattern called convergent evolution.

3. Vestigial Structures show divergence from an ancestor.

Are similar features that originated in a common ancestor that are adapted and modified for different functions.

HOMOLOGOUS STRUCTURES

HOMOLOGOUS STRUCTURES reveal common ancestry and a pattern of evolution called DIVERGENT EVOLUTION.

ANALAGOUS STRUCTURESLook-alike structures in unrelated species form as a response to similar “selection pressures” ex. The fat insulated, streamlinedbodies of penguins (bird), sharks (fish) and dolphins (mammal).

HUMMINGBIRD wings- endoskeleton (bones)

HUMMINGBIRD MOTH wings- exoskeleton… not arms

Analogous structures reveal a pattern of evolution called convergent evolution.

Similar environments selected for superficially similar adaptations.

Hedgehog, porcupine, echidna all evolved the quills independently.

are features that serve no useful purpose but show relationships to ancestors in which the structure WAS useful.

VESTIGIAL STRUCTURES

examples of vestigial examples of vestigial structures:structures:

Tailbone in humans no longer useful because we don’t have a tail/muscles attached to it. Shows our primate heritage.

Blind mole rat eyes (non functional) covered by layer of skin.

Human body hair- goose bumps… (hair fluffs up for insulation or to make the organism look bigger).

Penguins and dodo birds have hollow bones (adaptation for flight) even though they don’t fly.

Embryological development reveals evolutionary history

3.EMBRYOLOGY

Von Baer- correct simple observation

Embryos of different vertebrate species could not be as easily distinguished as adults of that species.

Earnest Haeckel- WRONG theory “biogenetic law”

- “ontogeny recapitulates phylogeny”

- development retraces evolutionary history (time machine)

- sketches exaggerated/ time machine idea crazy.

Genes that are “common” are expressed (turned on) early in development.

Genes that differ (mutations that accumulated in the different species) are expressed later.

Modern evidence- Hox genes / developmental pathways.

From Campbell BiologyFrom Campbell Biology

Closely related organisms go through similar stages of development.

The theory of recapitulation is an overstatement.

Although vertebrates share many features of embryonic development- it is not as though a mammal first goes through a ‘fish stage’, then an ‘amphibian stage’, and so on.

Ontogeny can provide clues to phylogeny but it is important to remember that all stages of development may become modified over the course of evolution.

4. BIOCHEMISTRY 4. BIOCHEMISTRY COMPARE DNA OR

AMINO ACID SEQUENCES

MORE SIMILAR = MORE RECENT COMMON ANCESTOR

DNA mutations occur at a steady rate. The number of differences are used to create a “MOLECULAR CLOCK” to better estimate divergence from common ancestors.

COMPARISON OF DNA SEQUENCES CONFIRM THE EVOLUTIONARY HISTORIES SUGGESTED BY FOSSILS AND ANATOMY. Ex. chimps and humans share 98-99% DNA

5. EXAMPLES5. EXAMPLESof evolutionof evolution

… post industrial revolution England changed the moth’s environment. Lichen on tree bark turned black from factory-released soot & smoke.

The Peppered Moth

•The “right stuff” (phenotype) used to be the light coloration.•The “right stuff” became the dark coloration phenotype.•Black moths were hidden from predators.

Industrial melanismBlack colored moths became more abundant in the population = microevolution.

Insecticide resistanceInsecticide resistanceex. Raid Bug spray on ex. Raid Bug spray on

cockroachescockroaches

Few insecticide Few insecticide resistant mutants resistant mutants

survive and reproduce survive and reproduce (preadaptation)(preadaptation)

population made mostly population made mostly of “resistant” mutants… of “resistant” mutants…

spray insecticidespray insecticide

Insecticide ineffectual Insecticide ineffectual at killing insects !at killing insects !

Antibiotic resistant Antibiotic resistant microbes!microbes!

TB

Gonorrhea

Staph MRSA

pneumonia

PATTERNS OF PATTERNS OF EVOLUTIONEVOLUTION

1. Co-evolution

2. Convergent evolution

3. Divergent evolution

4. Adaptive Radiation

5. Parallel Evolution

PATTERNS OF PATTERNS OF EVOLUTIONEVOLUTION

1. Co-evolution (arms race) organisms “drive” each other’s evolution

Predator-prey, parasites-hosts, plants-pollinators

2. Convergent evolution (come together) same environment selects similar phenotypes

(analogous structures) Insect & Bird wings

1. Divergent evolution (go apart) different environments selects different phenotypes

(homologous structures) your hand and bat wing

4. Adaptive Radiation

divergent evolution of many species from one common ancestor.

Ex. Galapagos finches, mammals

5. Parallel Evolution

The convergent evolution of species adapted tot he same way of life after a divergence occurred.

Ex. Marsupial & Placental mammals… ex. sugar glider & flying squirrel.

COEVOLUTION is the change of two or more species due to their close interactions.

•Predator-preyEx. cheetah-gazelle

•Parasites-hostEx. viruses-cells

•Herbivore-plantEx. tortoise-cactus

•Plants-pollinatorsEx.flowers-moths

CARRION FLOWER SMELLS LIKE ROTTING MEAT TO ATTRACT IT’S INSECT POLLINATORS- FLIES

CONVERGENT CONVERGENT EVOLUTIONEVOLUTION

Occurs when the environment selects similar phenotypes (forms) even though the ancestors are quite different.

Bird/fish/mammal all have fat insulated, stream lined bodies with flippers.

Analogous Traits

Divergent Evolution occurs when two or more related populations become more and more dissimilar- due to differing habitats… this RESULTS in NEW SPECIES & Homologous Traits

DIVERGENT

ADAPTIVE RADIATION OF DARWIN’S FINCHES… much divergent evolution from a single ancestral species.

Punctuated Equilibrium Gradualism

Two ideas aboutthe rate of speciation…

Either long periodsOf “stasis” Followed by Rapid periods of Evolution

Or Gradual consistentChange.

Parallel Evolution… The Placental vs. Marsupial split occurredLong ago. Nature selected “for” similar adaptations in both Lineages to fulfill the same niche on separate continents.

EVOLUTIONARY EVOLUTIONARY THEORY:THEORY:LAMARCK

“inheritance of acquired characteristics”

DARWIN“natural selection”

LAMARCK’S EXPLANATION

•Similar species descended from a common ancestor.•ACQUIRED TRAITS were passed to offspring.•Acquired traits- determined by behavior NOT genetics.•Duck’s webbed feet come from “stretching” their toes.•Human’s lost tail because they “don’t use it”.•Girraffe’s long neck ‘cause they “stretched” to reach leaves.•WRONG & EASILY DISPROVED

CHARLES DARWINCHARLES DARWIN“NATURAL SELECTION”

Organisms best suited to their environment reproduce more than those who aren’t.

Favorable traits increase in populations over time.

1. Differences exist between members of the same species.

2. Competition for resources.

DARWIN’S INFLUENCESDARWIN’S INFLUENCES UNIFORMITARIANISM

earth undergoes processes like earthquakes, volcanoes, erosion, sedimentation repeatedly.

Modification of environments is slow, but inevitable.

Earth is old! 4.5 billion years not 6 thousand.Charles Lyell

Principles of Geology

5 year H.M.S. BEAGLE voyage to the GALAPAGOS ISLANDS

GALAPAGOS ISLANDS are relatively young… formed 5 mya

FINCHES

DARWIN’S DARWIN’S OBSERVATIONSOBSERVATIONS

Earthquake in Chile- land lifted 3 feet around harbor.

Marine Fossil Shells in the Andes Mountains (14Kfeet).

Galapagos finches (13)

Galapagos tortoises

Angrecum Orchid & pollinator with a long tongue.

Thousands of species observed and documented.

WHAT IS FITNESS???WHAT IS FITNESS???

Having the “right stuff” at the “right time”

Favorable traits give the organism who has it an ADAPTIVE ADVANTAGE

HIGH REPRODUCTIVE SUCCESS!!!

Populations adapt to their environment as the proportion of favorable genes increase

POPULATION ADAPTED TO HIDE FROM PREDATORSIN THIS CASE, THE RIGHT STUFF IS BEING BROWN.

RECAP OF EVENTSRECAP OF EVENTS

1. 1800ish LAMARCK’s Inheritance of Acquired Characteristics

2. 1831 BEAGLE VOYAGE3. 1858 DARWIN’s On the Origin of

Species by Means of Natural Selection

1. Descent with modification 2. Modification by natural selection

TYPES OF NATURAL TYPES OF NATURAL SELECTIONSELECTION

Stabilizing selection

Directional selection

Disruptive selection

Sexual selection

Artificial selection

STABILIZING SELECTION

Stabilizing SelectionStabilizing Selection

eliminates extreme individuals.

A plant that is too short may not be able to compete with other plants for sunlight.

However, extremely tall plants may be more susceptible to wind damage.

Combined, these two selection pressures act to favor plants of medium height.

DIRECTIONAL SELECTION

Directional SelectionDirectional Selection

selects against one extreme.

In the familiar example of giraffe necks, there was a selection pressure against short necks, since individuals with short necks could not reach as many leaves on which to feed.

As a result, the distribution of neck-length shifted to favor individuals with long necks.

DISRUPTIVESELECTION

Disruptive selectionDisruptive selection eliminates intermediate individuals.

imagine a plant of extremely variable height that is pollinated by three different pollinator insects: one that was attracted to short plants, another that preferred plants of medium height, and a third that visited only the tallest plants.

If the pollinator that preferred plants of medium height disappeared from an area, medium height plants would be selected against, and the population would tend toward both short and tall plants, but not plants of medium height.

Sexual SelectionSexual Selection

The evolutionary process is sped upthrough ARTIFICIAL SELECTION