Exam 2: Unit 25 and Unit 26

Define Cladistic analysis

Classifies organism according to the order in time that branches arose along a dichotomous phylogenetic tree

• Clad is an evolutionary branch

• use novel homologies to define branch points on phylogenetic trees

Define outgroup comparison

The one most closely related to the ancestor

What is principle of maximum parisnary

Sometimes referred to as the KISS principle

• Keep It Simple Stupid

• Find the simplest explanation that is consistent with the facts

What is the phylogenic tree hypothesis?

They’re guesses backed by evidence

used to make predictions about the past

Explain how an organisms evolutionary history is documented in its genome

Molecular systematics helps us to uncover evolutionary relationships

Important for organisms where we have fossils

Different genes evolve at different rates

DNA that codes for rRNA changes relatively slowly

• used to study divergence hundred of millions years ago

Mitochondrial DNA, mtDNA, evolves relatively rapidly

• used for more recent divergences

Define molecular clocks

Measuring the absolute time of evolutionary change based on the observation that same genes evolve at a regular rate

• calibrated by comparing the number of genetic differences against the dates of the evolutionary branch points that are known in fossil record

Define Biological Systematics

Study of the diversification of living forms, both past and present, and the ancestral relationships among living things through time

Define Taxonomy

Developed by Linnaeus in 18th century

Set up a binomial name system

Important part of systematics

How are phylogenetic relationships determined?

Morphological and Molecular Homologies

• In general, organisms that share similar morphologies or similar DNA sequences are likely to be more closely related then organisms with different structures and sequences

Define Anaologus structures

structures that 2 different organisms have that shared essentially the same purpose

Define Heterochrony

Evolutionary change in rate or timing of developmental events

ex: human brain size, skull keeps growing which allows us to have a large brain

Define paedomorphosis

Sexually mature adults retains features that were juvenile structures in its ancetors

Define homeotic genes (HOX genes)

Unique to animal evolution. Master set of developmental genes that dictate the basic body plan of an animal

Define evolution structural novelties

Unique structures that help advance the evolution of various groups of animals

ex: eye ability to see images or birds ability to fly

Define exaplotion

Origin function is then modified and relocated for a new purpose

What is phylogeny

Tree of life

8 kingdoms system to organize life

Define mass extinction

Rate of extinction dramatically increases over that is normally called background extinction and survivors undergo massive evolution because they take advantage of the space

What are some theories of the Cambrian explosion?

Dramatic increase in oxygen levels in oceans

• have more energy available

New types of predators

Evolution of hard body parts to fight off predators

What are some theories of the Permian extinction (The Great Dying)

End of the paleozoic

Took place on land and ocean (95% marine and 70% terrestrial)

Took less than 5 million years

Possible cause for this is plate tectonics

What are some theories about the Cretaceous extinction?

End of the mesozoic

KT boundary: layer of iridium that separates dinosaur fossils to no fossils

Chicxulub crater: underneath guilt of mexico. showed evidence for an asteroid hitting Earth and killing off dinosaurs

What are some theories of the Pleistocene extinction?

Humans may have been the cause

• May have migrated from Asia to America 25 million years ago

Who proposed continental drift and what does this mean?

Proposed by Alfred Wegener in 1912 (pioneer of polar research)

Hypothesized that continents were slowly drifting around the Earth

Largely rejected until 1950s when there were numerous strong discoveries that supported this hypothesis

His ideas are now incorporating into the theory of plate tectonics

What is the theory of plate tectonics?

Earth is made of up three different areas

• Core: 4,300 miles made of iron and nickel. Extremely hot

• Mantle: 1,800 miles made up of magnesium, aluminum, etc. Very thick consistency

• Crust: 3-20 miles thick. Not continuous and has many cracks where the continents are attached to. Each crack is referred to as a plate and are constantly moving at an extremely slow pace

Define convection current

Between the mantle and core, where the area that the mantel touches the core will heat up and rise, it will then get heavy and fall back down. This causes a repeated process, happens in many different directions

What effect does the convection current cause?

Creates friction and pulls Earth’s crust with it. This cayses rips in the crust which are called ridges

Define subduction zone

Crust of the ocean goes under the crust of a continent

• also called oceanic trench

What is the cause for earthquakes?

Plates are locked together for long periods of time which builds up pressure underneath and they suddenly release which causes a major earthquake

Define Pangea

All continents located close to the equator at the end of the Paleozoic

By the end of the Mesozoic, it breaks to 2 continents (North: Laurasia and South: Gondwana)

End of mesozoic, the continents begin to take their shape

Presently, the continents are how they presently are now

What is the evidence for plate tectonics?

Fossils of the same dinosaur found on different continents

Lungfish found in part of Central South America, Africa, and some part of Australia

4 pieces of evidence:

• Apparent fit of the continents

• Fossil correlation

• Rock and mountain correlation

• Paleoclimate data

What is the importance of stromatolites?

Earliest evidence of life on Earth

Structures are found of western coast of Australia that were created by living organisms

• Biofilm

Produce oxygen because the material to build them is photosynthetic

• initially (3 billion years ago the oxygen reacted with iron to make iron oxide (FE2O3)

• the oxygen precipitates iron of the oceans

Define biofilm

A thin layer of actively growing bacteria which is the black top on a stromatolites called the cyanobacterial that has a sticky and slimy material

What was oxygen like in early life?

Very toxic to early life when it began to accumulate in the atmosphere and ocean

Probability of a massive check off in early life (oxygen tearing life apart)

Life then evolved through anti-oxidizing mechanisms in cells

Life then found a way to take advantage of the oxidizing power of oxygen by incorporating it into the mechanisms of cellular respiration

• using oxidative phosphorylation in cellular respiration, life then had the ability to produce large quantities of ATP compared to anaerobic conditions

• allowed cells to become larger and structurally more complex

Define antioxidizing mechanisms

Chemical pathways in cells that make oxygen harmless. This saved life from going completely extinct

Define Endosymbiotic theory

How eukaryotes evolved from prokaryotes

What has the fossil record informed biologists?

All life that has lived on this place, over 99% has gone extinct

• What lives today is only a small % of what lived on the Earth

What type of rock are fossils usually found?

Usually found in sedimentary rock which are formed when rock on land erodes and flows into a river which then flows into a large oyd of water and layers of rock build up and fuse together

Define relative dating

Process determining chronological sequences of fossils or biological events without pinpointing extinct numerical age

• Younger fossils are in upper levels of sedimentary rocks compared to lower levels which are older fossils

List the geological time scale in order

(4600 million years of Earth’s history)

Origins of Earth

Oldest fossils (3500 MYBP)

Precambrian (life as a single celled organisms)

First animals (700 MYBP)

Paleozoic (600 MYBP) ancient animals

Mesozoic (250 MYBP) middle animals

Cenozoic (65 MYBP) recent animals

What occurred during the Paleozoic Area?

Cambrian (590-505 MYBP) origins of most invertebrates

Ordovician (505-438 MYBP) marine algae diversity

Silurian (438-408 MYBP) appearance of jawed fish, invasion of land by vascular plants

Devonian (408-360 MYBP) invasion of land by amphibians, first insects

Carboniferas (360-286 MYBP) extensive forests (coal deposits), origins of reptiles

Permian (286-248 MYBP) radiation of reptiles, mass extinction of marine invertebrates

What is coal the remain of?

It is the remain of plants during the carboniferous period

What occurred during the Mesozoic Periods?

Triassic (298-213 MYBP) gymnosperms dominate plants, first mammals and birds

Jurassic (213-144 MYBP) dinosaurs dominant

Cretaceous (144-65 MYBP) flowering plants appear, mass extinction of dinosaurs

What occurred during the Cenozoic epics?

Pleistocene (1.8 MYBP) when we have the ice ages and appearance of extremely large animals and early appearance of own ancestors

Has 7 but the teacher only went in depth on this one

Absolute dating (radiometric dating)

(Hint: talking about 2 isotopes)

Carbon 14: isotope that has a halflife of 5700 years and decays back to carbon 12

Potassium 40: half life of 1.25 billion years. Decays into Argon 40

Define Spontaneous generation

Theory that organisms could develop directly from non-living matter

Who disproved spontaneous generation?

Explain the experiment which was used to disprove it

Louis Pasteur in 1862

• Heated vegetable soup to kill any organisms (sterilized it), then left it out to spoil so living organisms would grow in it

• Did the same thing again but kept the broth in a sealed container with a swan neck flask so it kept the broth sterile by keeping water in the neck which allowed air in because at the time, air was believed to be a vital source

• Once the neck was broken off, organisms appeared in the soup which showed that organisms are alive and in the air and produce when the broth is no longer sterile

Define Biogenesis

“Life from life”

Life can only come from life

What are the four possible chemical evolutions of the first cells?

1. abiotic synthesis of organic monomers

2. Joining monomers together, monomers to polymers

3. Aggregation of protobionts (pro life form; still not living organisms but instead the assembly of them)

4. Origin of heredity (coding and passing code onto next generation)

Explain the first chemical stage of the origins of life: abiotic synthesis of organic monomers (testable hypothesis)

First proposed by Oparin and Haldane

• very different atmosphere initially (early earth)

• First atmosphere is decreasing atmosphere (no free oxygen)

• Earth became a soup of macromolecules where all the basic monomers were formed completely abiotically

Miller and Urey experiment proved this hypothesis could be correct

Explain the second chemical stage of the origins of life: Joining monomers together, monomers to polymers

Believed catalyst to polarize the monomers were variations of various iron and nickel compounds in hot sand, clay, or rock

Believed that the splashing of the amino acids onto the sand, clayk or rock would be catalyzed to join together into short polypeptides

• Formation of proteinoids

Clay is a possible very effective catalyst because its so small that is picks up extra electrons and the clay molecules can become negatively charged which can the attract metal ions

Explain the third chemical stage of the origins of life: Aggregation of protobionts (pro life form; still not living organisms but instead the assembly of them)

Liposomes are possible early aggregations

protobionts can form by self-assembly

Living cells may have been preceded by protobionts, aggregates of abiotically produced molecules

Explain the fourth chemical stage of the origins of life: Origin of heredity (coding and passing code onto next generation)

RNA may have been the first genetic material

Chemical aggregates that were the forerunners of cells would not build on the past and evolve until the development of some mechanisms for replicating their characteristics some mechanism of heredity)

molecules could make copies of themselves

RNA could have been the template on which DNA nucleotides were assembled

• RNA then takes on role as intermediates in the translation of genetic information