Session 3 Phylogenetics and Time

Phylogeny A. This term refers to the evolutionary history of a species.

LE Paranthropus robustus Homo ergaster Homo sapiens Homo neanderthalensis ? Paranthropus boisei Australopithecus africanus Kenyanthropus platyops Australopithecus garhi Australopithecus anamensis Homo habilis Homo erectus Homo rudolfensis Australopithecus afarensis Ardipithecus ramidus Orrorin tugenensis Sahelanthropus tchadensis Millions of years ago

Systematics A. The science of studying relationships between extant (existing) and extinct species. B. Uses morphological and biochemical resemblances to establish relationship.

SYSTEMATICS EXTANT SPECIESEXTINCT SPECIES

Molecular Phylogeny – Looking at DNA/RNA nucleotide sequences over the history of a species. – Uses computers and DNA microarray assays to “speed up” the gathering of information. (Bioinformatics) – Lots of similarities? Very related. – Few similarities? Not AS related, but STILL related by common ancestry.

Molecular Phylogeny

LE Deletion Insertion

Geologic Time Scale – Eras – These are the largest periods of time. Separated by catastrophic global event. (See below) Eras are broken into smaller time frames called Periods. – Periods are broken into smaller time frames called Epochs. These time frames are based on strata fossil evidence of primary plants and animals found.

– Punctuated Equilibrium This way of speciation was proposed in 1976 by Stephen Jay Gould, a famous Harvard professor. In this method, long periods of stability (this is the equilibrium) are interrupted suddenly(this is the punctuated) by a major disruption(such as an asteroid hitting the earth) that causes a mass extinction of existing species to occur. Once all disruption has calmed down (usually after several years), a mass evolution of new species will occur to occupy all the new open niches that were created due to the mass extinction. (These punctuations usually mark/cause the end of an era.)

Pangaea – The super-continent formed 250 mya and then separated 180 mya. – Separates the Paleozoic Era from the Mesozoic Era. – Global effects? (Punctuated Equilibrium occurred.) – Life affected? All life forms. – This is supported through fossil and geologic evidence.

LE By about 10 million years ago, Earth’s youngest major mountain range, the Himalayas, formed as a result of India’s collision with Eurasia during the Cenozoic. The continents continue to drift today. By the end of the Mesozoic, Laurasia and Gondwana separated into the present-day continents. By the mid-Mesozoic Pangaea split into northern (Laurasia) and southern (Gondwana) landmasses. At the end of the Paleozoic, all of Earth’s landmasses were joined in the supercontinent Pangaea Millions of years ago Cenozoic Mesozoic Paleozoic North America Eurasia Africa India South America Madagascar Australia Antarctica Laurasia Gondwana Pangaea

Impact Theory (around 65 mya) (Punctuated Equilibrium occurred here too.) – Separates the Mesozoic Era from the Cenozoic Era. – Walter & Luis Alvarez came up with the theory. – Global Effects? Sunlight was absent from most of the earth. – Iridium, element found in asteroids, is found at the K/T boundary only in soil samples. – The impact point was around the modern day town of Chixalub, Mexico. (On the Yucatan Peninsula.)

LE 26-9 NORTH AMERICA Chicxulub crater Yucatán Peninsula

Snowball Earth (Punctuated Equilibrium occurred here too.) – Formed 750 mya lasted til 570 mya (Theory is an asteroid collision occurred knocking Earth out of orbit.) – Separates the Pre-Cambrian Era from the Paleozoic Era. – Global Effects? Most life dies, except around deep sea vents.

Snowball Earth

Taxonomy – Carolus Linneus developed this system of classification. – Uses Binomial Nomenclature (Remember the Rules.) to name species. – Hierarchy of Classification is seen in the system. – Taxons – D, K, P, C, O, F, G, S – Domain is most inclusive and least specific. – Species is the least inclusive and most specific. – System is useful in constructing phylogenetic trees.

Taxonomy of Life

Homologous structure vs. Analogous structures – Remember, Homologous structures indicate common ancestry. – Remember, Analogous do not indicate common ancestry (JUST similar function.) Fly wing vs. Bird wing

Homologous Structures

Analogous Structures

Cladogram or Phylogram – It is an “Either – or” evolutionary tree based on shared characteristics. – Common ancestor indicated at the “Y”

Clade

– Each branch called a clade. MUST be common ancestor and ALL of it’s descendents. Similar to a phylogenetic tree – not based on taxons though.

LE 25-10a Grouping 1 Monophyletic

– Construction of one: Ingroup (common structure) vs. outgroup (outcast) – Ingroup organisms get a 1; outgroup organism gets a 0. Shared Primitive Character – Trait that is common to many taxons or clades. (For example, a Backbone.) Shared Derived Character – Trait that is common to one clade only. (For example. Hair on mammals.)

LE Hair Amniotic (shelled) egg Four walking legs Hinged jaws Vertebral column (backbone) Character table CHARACTERS TAXA Lancelet (outgroup) LampreyTunaSalamander TurtleLeopard Turtle Leopard Hair Amniotic egg Four walking legs Hinged jaws Vertebral column Salamander Tuna Lamprey Lancelet (outgroup) Cladogram

Parsimony (A.K.A. “Occam’s Razor” – shave away unnecessary problems or KISS – Keep it super simple.) – These are Hypothesises based on maximum likelihood “least problematic” evolutionary paths. – THE ONE WITH THE LEAST PROBLEMS IS THE MOST LIKELY TO HAVE OCCURRED.