Chapter 12- Phylogenetic Trees Flashcards
How do you go from a table of synapomorphies to building a phylogenetic tree? Be
able to take the table in the slides and reconstruct the tree on your own.
Synamorphies a features that unite a group of taxa, so we observe:
The outgroup, or species that split first at the base of the tree.
Then we keep using different synamorphies and genomic methods to determine which groups split off next, and so on and so forth.
Why does DNA information sometimes make a more accurate tree than phenotypic
characteristics?
Sometimes organisms of different species will have similar traits or synamorphies, that have evolved as a result of convergent evolotion rather than sharing a more recent common ancestor. An example of this would be insect wings vs. bird wings.
What is the difference between a monophyletic, paraphyletic, and polyphyletic trait?
A monophyletic trait is a trait that is shared within all species of a common ancestor.
A paraphyletic trait is a trait that is shared in many of the species with a common ancestor, however some of these species have lost the trait. Ex: vestigial wings or appendix?
A polyphyletic trait is a trait that appears in species that do not share a common ancestor with that trait. Ex: convergent evolution.
What is the difference between homologous and analogous traits? How do
homologous and analogous traits evolve? What is convergent evolution?
Homologous traits are traits that appear in different species because these species shared a common ancestor.
Analogous traits are traits that are present in different species that do not share a common ancestor with that trait, meaning that the trait evolved independently due to convergent evolution.
How is the age of an object determined from amounts of radioisotopes? How old
is the earth? How do we know the age of the earth and fossils in different strata?
Scientists use radiometric dating to determine the age of rocks and fossils by measuring the decay of radioactive isotopes in a sample. Radioactive isotopes break down at a predictable rate, so geologists can use equipment like a thermal ionization mass spectrometer to calculate the age of a sample.
The earth is about 4.5 billion years old.
How does a mass extinction differ from the background extinction? Why do
scientists think we are on the verge of a sixth mass extinction?
Mass extinctions occur quickly and wipe out large amounts of species at a time- 75%. Only five have happened on Earth. Background extinctions are a natural evolution and elimination process of species and considered the natural extinction rate, 10-100 species per year.
Scientist think we are on the verge of another mass extinction because the climate is changing too fast for species to adapt and as a result there has been an increase in the extinction rate.
What was the atmosphere like prior to cyanobacteria? How do we know? How
did cyanobacteria and other photosynthetic organisms change the atmosphere?
Initially, iron-rich rocks sequestered
oxygen until they became saturated.
Atmosphere was mostly CO2, Methane, and water vapor.
Cyanobacteria greatly increased the Oxygen content of the atmosphere.
When did eukaryotes appear in the fossil record? What is the endosymbiosis theory of eukaryotes, and who engulfed whom? Which came first – mitochondria or chloroplasts?
How do we know the endosymbiosis theory is very likely true?
The oldest evidence of eukaryotes is microfossils that are around 1.5 billion years old, found in rocks in northern Australia. These fossils are believed to be the remains of microalgae.
Eukaryotes evolved from a fusion of Archaean cells with bacteria, with the Archaean engulfing the bacteria but not eating it.
Mitochondria evolved earlier than chloroplasts
What likely caused the Cambrian explosion?
Cyanobacteria building pinnacle reefs on the shallow sea floor
A gooey mat of microbes covering the sea floor
A small, perhaps temporary, increase in oxygen
What is the order of emergence of organisms onto land? What are the likely driving forces of land colonization by each of these groups of species?
When did colonization of land occur for each?
Colonization of land by primitive plants in the ORDOVISION period due to availability of resources for photosynthesis.
Plants became the first multicellular life on land in the SILURIAN period, with the evolution of vascularization.
Colonization of land by arthropods in the EARLY DEVONIAN period due to increase of oxygen.
Colonization of land by vertebrates also in the DEVONIAN- fish like species.
When did mammals arise? Dinosaurs? Large carnivores?
Mammals arose in the last TRIASSIC period with small shew like little guys.
First Dinosaurs were in the Triassic and Jurassic, with large Sauropods and other large herbivores evolving during the JURASSIC (Think of the brontosaurus from Jurassic park).
Large carnivores, theropods like T-rex evolved during the CRETACEOUS.
Mammals were still there but sort of on the down-low.
What happened during the Cretaceous/Paleogene extinction? What species perished
and which survived? Why did certain species fare better than others?
CRETACEOUS-PALEONGENE EXTINCTION- 10km meteor in the Yucatan Peninsula
7 billion times the explosion of the nuclear bomb in Hiroshima
Material injected into the atmosphere rained back down over a period of months, blocking out the sun.
Iridium is a very rare isotope found in meteorites, a layer of this found in the rock strata of this time period.
- Most things that were very large like the dinosaurs starved, unable to sustain their large biomass.
-Small things like mammals and small bird-like theropods were able to survive.
What distinguishes a phototroph from a chemotroph? An autotroph from a
heterotroph?
Phototrophs use light as their source of energy while chemotrophs get their energy only from chemical reactions.
Autotrophs derive carbon from the atmosphere while heterotrophs get their carbon from other organisms (living or dead).
What synapomorphies unite prokaryotic life?
No membrane-bound organelles,
No nuclear envelope,
A single, circular chromosome.
How do protists differ from bacteria and archaea?
Protists are eukaryotes- (simplest eukaryotes, ex: algae)
