Bellwork: 02/13/2013Using the following phylogenetic tree:1.What are the uses of a phylogenetic tree?2.What do the numbers on the chart represent?3.What are “homologous characteristics?”4.What is/are the homologous characteristic(s)

between #1 and #2? #5 and #6?

Bellwork: 02/13/2013

Groups of 4 or Less:1) What is potentially problematic about a combination

of the bottleneck effect & polygyny?2) What are four conditions that favor fossilization?3) How is homologous structures different than

analogous structures? Give an example of each.4) What is the driving force behind human founder

effects? What aspects of human founder effects is incompatible with the definition of genetic drift?

5) What is adaptive radiation? During which time period would you expect the largest radiation event & why? (Keep in mind that extinction events end time periods)

Before we start:

What is a scientific theory?– It makes falsifiable predictions with consistent accuracy across a

broad area of scientific inquiry– It is well-supported by many independent strands of evidence,

rather than a single foundation– It is consistent with pre-existing theories and other experimental

results– It can be adapted and modified to account for new evidence as it

is discovered, thus increasing its predictive capability over time.– It is among the most parsimonious explanations, sparing in

proposed entities or explanations.

Other Scientific Theories:• The Atomic Theory• Theory of Matter and Energy• Theory of Plate Tectonics• Theory of Quantum Mechanics• Theory of of Molecular Bonds• Theory of the States of Matter• Theory of Homeostasis • Theory of Gravity• Theory of Evolution (USA and Turkey are the only

Westernize countries that still argues about this)

Keep In Mind:• The theory of evolution and:

– Creationism– Neo-creationism– Intelligent design– Creation science (“science”)

• Are not equal on an scientific level.

Humans, for example:

Humans, for example:•(A) Pan troglodytes, chimpanzee, modern •(B) Australopithecus africanus, STS 5, 2.6 My •(C) Australopithecus africanus, STS 71, 2.5 My •(D) Homo habilis, KNM-ER 1813, 1.9 My •(E) Homo habilis, OH24, 1.8 My •(F) Homo rudolfensis, KNM-ER 1470, 1.8 My •(G) Homo erectus, Dmanisi cranium D2700, 1.75 My •(H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My •(I) Homo heidelbergensis, "Rhodesia man," 300,000 - 125,000 y •(J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y •(K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y •(L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y •(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y •(N) Homo sapiens sapiens, modern

Humans, for example:

Evolution….After Darwin…

Fossils

Fossil Record• Fossil any preserved remnant or impression

of an organism that lived in the past• Most form in sedimentary rock, from

organisms buried in deposits of sand and silt. Compressed by other layers.

• Also includes impressions in mud

• Most organic matter replaced with minerals by Petrification

• Some fossils may retain organic matter• Encased in ice, amber, peat, or dehydrated• Pollen

Fossil Formation

Conditions that Favor Fossilization:

• Having Hard parts – shells, bones, cysts• Get buried, trapped

– Marine species– Marsh, flooding areas

• Abundant species (with many individuals)• Long lived species (as a species)• Avoid eroding away• Get discovered

Limitations of Fossils record

• Has to die in right place under the right conditions. Most things don’t get into the fossil record

• Biased: Highly favors hard parts, abundant, long lived species organisms.

• Lots of missing organisms• Hard to find, only certain areas highly

researched (North America, Europe)

Biogeography

Biogeography

Biogeography

Biogeography

• Study of geographic distribution

• Use to study how lineages of animals evolved

• History of earth

• Patterns of adaptations for different environments

Comparative Embryology

• Compare developmental patterns to understand common ancestry

Molecular biology

• Study of DNA sequences to understand evolutionary relationships

• Quantifiable relevant means of comparison• Compare degree of similarity• Uses conserved sequences of DNA• Mitochondrial DNA, RNA, proteins• Revolutionized our understanding of

evolutionary biology

Population Genetics

• The study of genetic changes in populations over time

• Quantify molecular differences within and among populations– Traits exhibit variation– Traits we have identified genes for

• Population= group of individuals of the same species living in the same area at the same time

• Gene pool= Genetic composition of a population (all alleles in a population at a given time)

Microevolution How does it happen?

• Mechanisms:• Gene flow• Genetic drift

–Bottleneck effect–Founder effect

• Mutations• Natural Selection• Artificial Selection

Gene Flow

• The loss or gain of alleles (genes) in a population due to migration of fertile individuals or gametes between populations

• Migration– Immigration– Emmigration

Genetic drift

• Gene pool contains alleles available for the next generation

• Genetic drift is a change in allele frequency due to random chance

• Affect small populations• Limits alleles available to subsequent generations• Two types

– Bottleneck – Founders effect

Bottleneck EffectGenetic drift resulting from the reduction of a population, typically by natural disaster, surviving population does not represent the original population’s gene pool

Bottleneck: 19th Century

The northern elephant seal bottleneck

• large US California and Baja California populations were hunted for oil and skins

• by end 1800’s, ~ 20 individuals remained on Guadalupe Island off Baja California

• population rebounded to ~120,000 by 1980

Microunga angustirostris

Inbreeding in California Sea Otters

• Sea otters, once abundant along the west coast of the U.S., were almost wiped out by fur hunters in the 18th and 19th centuries.

Inbreeding in California Sea Otters• California population reached a low of 50

individuals (now over 1,500). As a result of this bottleneck, the population has less genetic diversity than it once had.

Inbreeding in California Sea Otters• Population is still at a low density and Lidicker

and McCollum (1997) investigated whether this resulted in inbreeding.

• They determined genotypes of 33 otters for PAP locus, which has two alleles S (slow) and F (fast)

Bottleneck: 88,000 years ago

Bottleneck: 43,000 years ago

Bottleneck: dermal immunity

Founder Effect

• Genetic drift attributed to colonization by a limited number of individuals from a parent population

Founder Effect

• Examples– Islands– Mayflower– Amish

Figure 18.5

Before You Go: Groups of 2 or 31) What is potentially problematic about a combination

of the bottleneck effect & polygyny?2) What are four conditions that favor fossilization?3) How is homologous structures different than

analogous structures? Give an example of each.4) What is the driving force behind human founder

effects? What aspects of human founder effects is incompatible with the definition of genetic drift?

5) What is adaptive radiation? During which time period would you expect the largest radiation event & why? (Keep in mind that extinction events end time periods)

Mutations

• An error in replication of a nucleotide sequence (DNA), or any other alteration of the genome that is not due to recombination

• Mutagens

Mutation

Natural Selection• Differential success in the reproduction of

different phenotypes resulting from the interaction of organisms with their environment

• Results in adaptations

Adaptation

• A feature or characteristic that increases reproductive success (including survival)

• Increases fitness relative to an alternate trait

Natural SelectionHow Does it Happen?

• Directional selection– 1 extreme is favorable

• Diversifying selection– 2 extremes favorable

• Stabilizing selection– Intermediate favored

Mechanisms of Natural Selection

Bellwork: 02/23/2012

1) What is a mutagen & how are they associated with natural selection?

2) What is the importance of mitochondrial DNA to molecular biologists?

Macroevolution

• Grand scale

• Form new species- speciation

• Existing species go extinct- extinction

Speciation

• The origin of new species in evolution

• Speciation is the process of forming new species– While many take place slowly over generations– some events can be observed in our life times

• Species= biological species concept– Members of a group of populations that interbreed or

potentially interbreed with each other, under natural conditions, and produce viable offspring

Rate of Evolution

• Punctuated equilibrium

• Gradualism

Adaptive Radiation

• Speciation as a result of new or novel environment

• Occurs at a relatively rapid rate

• Must have:– Resource– Selection pressure

• New environment or massive extinction

• Ex: islands

Figure 18.14

Reproductive barriers

Pre-zygotic

Post-zygotic

How distinct species are maintained

Reproductive Barriers• Lead to speciation by blocking gene flow• Pre-zygotic barriers prevent successful

fertilization between species.– Habitat, behavior, temporal, mechanical, gametic

isolation• Post-zygotic barriers allow fertilization but

prevent successful development / reproduction of hybrid.– Reduced hybrid viability– Reduced hybrid fertility– Hybrid breakdown

Habitat Isolation

• Two organisms that use different habitats even in the same geographic area are unlikely to encounter each other to even attempt mating.– Two species of garter snakes occur in the same

areas but because one lives mainly in water and the other is primarily terrestrial, they rarely encounter each other.

Behavioral Isolation• Many species use elaborate behaviors unique to that species

to attract mates.

Temporal Isolation• Two species that breed during different times

of day, different seasons, or different years cannot mix gametes.– The western spotted skunk and the eastern

spotted skunk ranges overlap, yet they do not interbreed because one mates in late summer and the other in late winter.

Temporal Isolation

Mechanical Isolation

–Physical/ structural mechanism that prevents reproduction–Flower structure forms a mechanical barriers to pollinated by insects or other animals.–many insects have elaborate reproductive organs (lock and key) that if they do not fit together sperm transfer between closely related species is prevented.

Mechanical Isolation

Post- Zygotic• Reduced hybrid viability:

– Miscarriage, early death

• Reduced hybrid fertility:– Sterile– Unattractive to oppositesex

• Hybrid breakdown:– 1st generation is viable &

fertile– 2nd generation is unviable or

infertile– Occurs in plants

Reduced hybrid fertility: Liger

Reduced hybrid fertility: Zebroid

Reduced hybrid fertility: Grolar Bear?

Modes of Speciation• Allopatric speciation

– A mode of speciation induced when the ancestral population becomes segregated by a geographic barrier

• Parapatric speciation– A mode of speciation that occurs when neighboring

populations with modest gene flow diverge

• Sympatric speciation– A mode of speciation occurring as a result of a radical change

in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population

Allopatric Speciation• Takes place in separate areas.• Populations become

separated by a geologic barrier, blocking gene flow

• Mountains rise up, rivers cut canyons.

• Populations accumulate differences, diverge genetically

Antelope squirrels of the Grand canyon rim

Parapatric Speciation

• Takes place in largerange

• Variable environmental • Variable selection

pressure• Non-random mating

Parapatric Speciation

Peripatric Speciation

Sympatric speciation

• Takes place within habitat of parent species

• Reproductive barrier forms within a subset of population

• Maybe genetic that immediately blocks reproduction

• Maybe behavioral

Behavioral Sympatric Speciation

Understanding Evolution

• Phylogeny– Technique to understand evolutionary

relationships– Phylogenetic trees

Shared Derived Characteristics• Trait uniquely shared by a taxonomical group

Convergent Evolution• Evolutionary pattern where two or more non

related taxonomical groups independently evolved same/similar characteristics

• Similar structures evolve under similar environmental conditions

Convergent Evolution

Ocotillo Allauidia North America Madagascar

Convergent Evolution

Convergent Evolution

Armadillo, North America

Giant Pangolin, Africa

Spiny Anteater, Australia

Giant Anteater, South America

Convergent Evolution

In a group no larger then 3• For each of the following terms, make up a

short story & a picture that describes the reason & the change of your species that demonstrates the term’s definition.

1)Founder Effect2)Bottleneck Effect3)Habitat Isolation4)Behavioral Isolation