The Tree of Life II; the History of Life on Earth I Flashcards
(26 cards)
What is the principle used to test cladograms?
Parsimony
Parsimony refers to the idea that the simplest explanation, requiring the least number of changes, is preferred.
What is an outgroup in cladistic analysis?
A taxon that is known to fall outside the clade being studied
The outgroup helps to establish the direction of character changes.
How many characters are used in the example character matrix?
Five characters
What is the main goal when mapping characters onto cladograms?
To count the number of evolutionary changes required by each tree
What is a polytomy in a cladogram?
A node that gives rise to more than two branches
Polytomies indicate uncertainty about relationships among taxa.
What are the two key features of Linnaeus’s classification system?
- Binominal nomenclature
- Linnaean hierarchy
What does binominal nomenclature consist of?
A genus and a specific epithet
For example, Homo sapiens, where Homo is the genus and sapiens is the specific epithet.
Why is a rank-free classification recommended over the Linnaean hierarchy?
- Insufficient ranks for all clades
- Non-comparability of ranks
- Many traditional taxa are paraphyletic
What are the four eons of the geologic time scale?
- Hadean
- Archean
- Proterozoic
- Phanerozoic
What is the significance of sedimentary layers in determining relative ages?
Older layers are buried beneath younger layers
How can absolute ages of geologic events be determined?
By studying radioactive isotopes in minerals
What are the three eras of the Phanerozoic eon?
- Paleozoic
- Mesozoic
- Cenozoic
What is the current estimated age of the Universe?
About 13.8 billion years
What event marks the beginning of the Universe?
The Big Bang
What is the oldest material found in the Solar System?
Inclusions in meteorites rich in calcium and aluminum
What is the age of the oldest minerals found on Earth?
Up to 4.4 billion years
What are zircons, in relation to Earth’s early history?
Individual mineral grains that provide evidence of early Earth’s conditions
They suggest the presence of liquid water on Earth by 4.4 Ga.
What are the oldest probable body fossils?
Microfossils of simple round cells or strings of cells dating back to nearly 3.5 billion years ago
What are stromatolites?
Microbial trace fossils formed by microbial mats
They are produced through the precipitation or trapping of calcium carbonate.
What eon is associated with the presence of a variety of different groups of living creatures?
Archean Eon
The Archean Eon is one of the four principal eons in Earth’s history, marking the time when life began to emerge.
What are stromatolites?
Microbial trace fossils produced by microbial mats inducing or trapping calcium carbonate
Stromatolites are significant as they provide evidence of early life and are formed in specific environmental conditions.
How do stromatolites build upwards?
By accretion
Accretion refers to the gradual accumulation of material, which in the case of stromatolites involves the trapping of particles by microbial mats.
In what type of environments are stromatolites largely restricted today?
Harsh environments with few animals
In modern ecosystems, grazing animals limit the distribution of stromatolites, which were more widespread during the Precambrian.
What factor may have contributed to the widespread presence of stromatolites in the Precambrian?
Lack of grazing animals and changes in ocean chemistry
The absence of herbivorous organisms allowed stromatolites to thrive in various environments.
