A large proportion of archaeans are extremophiles, so called because they inhabit extreme environments with high acidity, salinity, and/or temperature. Such environments are thought to have been much more common on the primitive Earth. Thus, modern extremophiles survive only in places that their ancestors became adapted to long ago. Which of the following is, consequently, a valid statement about modern extremophiles, assuming that their habitats have remained relatively unchanged?
A) Among themselves, they should share relatively few ancestral traits, especially those that enabled ancestral forms to adapt to extreme conditions.
B) On a phylogenetic tree whose branch lengths are proportional to the amount of genetic change, the branches of the extremophiles should be shorter than the non-extremophilic archaeans.
C) They should contain genes that originated in eukaryotes that are the hosts for numerous species of bacteria.
D) They should currently be undergoing a high level of horizontal gene transfer with non-extremophilic archaeans.
Large-scale impacts of the (a) positive, and (b) negative phases of the North Atlantic Oscillation.
Angioplasty. One form is called balloon angioplasty, shown here. A balloon catheter is threaded into
Electrocardiography. (a) Electrodes are placed on the patient’s chest to record the electrical event
Large Octopus
Large intestine
After elections were held, it was desired to estimate the proportion of voters who regretted ...