Macroevolution Flashcards
What is a synapomorphy?
a derived trait shared with a group of animals and their CA, and not found in any other group
What are some synapomorphies from the group Mammalia?
- milk production and mammary glands
- 3 middle ear bones
- hair in embryos
What synapomorphies do archaeocetes (early relatives of cetaceans) share with the clade?
- teeth shape
- similar ankle bones
- involucrum (thick inner ear bone)
Name some archaeocetes and their brief anatomy
- indohyus and pakicetus (terrestrial, quadrapedal, dense bones suggest somewhat aquatic lifestyle)
- ambulocetus (amphibious, webbed feet and reduced limb size suggests paddling lifestyle)
- dorudon (aquatic, jaws and teeth more adapted for active aquatic diet, hind legs almost completely reduced for fully swimming lifestyle)
What are the two modern clades of cetaceans?
odontocetes (toothed) and mysticetes (filter feeding)
Which historical figure supported the idea of extinction and recognized the similarities of ancient fossils?
George Cuvier
What were some of Lamarck’s beliefs?
correct:
- complex life originated from simpler microbes
incorrect:
- adaptation occurs through inheritance of well used traits and the loss of unused traits (i.e giraffe necks got longer because they needed to reach higher)
- early life spontaneously appeared
What is epigenetics and one of its critiques?
- the change in gene expression as a result of environmental cues
- clashes with evolutionary theory as some changes can be reversible/last only a few generations (not long enough for evolution)
Explain Darwin’s idea of descent with modification
- all species share a common ancestry with earlier life
- all life has variations that can be inherited
- changes occur via natural selection as a result of variation
What is a homologous structure?
traits similar due to inheritance from a common ancestor
What were Darwin’s 4 observations?
1) there is variation within individuals of the same species
2) traits can be passed down from parent to offspring (inheritance)
3) more individuals are born into a population than can be steadily supported
4) individuals compete for resources and only those with suitable traits can survive
What are alpha and omega rates, and what does it mean if alpha > omega?
alpha = origination rate
omega = extinction rate
when alpha > omega, diversity is increasing
What is Wallace’s line?
hypothetical line that explains a drastic shift in species between Australia and Southeast Asia
i.e species on the right side of the line are only found in Australia
What was the vicariance event that separated dinosaur populations in the Cretaceous?
formation of the Western Interior Seaway (physical barrier separating populations)
Why are there so many marsupial fossils in Australia and South America?
Both continents were connected via Gondwana and shared marsupial species before being separated (vicariance event)
What is the difference between dispersal and vicariance?
dispersal = movement of organisms to establish a new population
vicariance = natural phenomenom/geological events that fragment a population into multiple newer populations
What did the breakup of Pangaea cause?
- increase in shallow shelf habitats
- increased marine diversity
What are some examples of species from the Cambrian explosion?
- Hallucigenia
- Opabinia
- Marella
What molecular reason is hypothesized to be behind the Cambrian diversification?
introduction of Hox genes and other cluster genes
Define the punctuated equilibrium theory
diversity has long stable periods (stasis) interrupted by brief but rapid (punctuated) diversification events
Why is the punctuated equilibrium model controversial?
- definition of “brief” in a geological scale is subjective
- opposes well-believed gradualism/anagenesis theory (slow speciation from one species to another without increasing # of species)
Name the mechanism/innovative trait for the following adaptive radiations:
a) Devonian insects + plants
b) Cambrian period
c) Cretaceous plants
d) African cichlids
a) insects = wings, plants = seeds and vascular tissue
b) various novel body plans, predation
c) flowers
d) double jaw
What are the “big 5” extinctions?
- End-Ordovician (440 MYA)
- Late Devonian (365 MYA)
- End-Permian (250 MYA)
- Late Triassic (210 MYA)
- End-Cretaceous (65 MYA)
What happened during the Permian extinciton?
- extinction of +90% of all species
- loss of 96% of marine species
- loss of 70% of terrestrial vertebrates
- caused by a release of volcanic gases (Siberian traps) that triggered ocean warming + acidification, anoxic conditions, lowered ocean levels
- notable species lost: ammonites, many crinoids, trilobites, many synapsids
What happened during the End-Cretaceous extinciton?
- meteor struck the Yucatan Peninsula and caused global environmental changes (debris cloud, loss of vegetation, created cold and dark conditions)
- loss of all non-avian dinosaur species
What temperature increase is the tipping point for irreversible damage?
4c
