The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

Which of the five common ancestors, labeled V—Z, has given rise to the greatest number of species, both extant and extinct?

#Question id: 28553

#Unit 5. Developmental Biology

At which condition upregulate the translation of the PKA catalytic subunit PKA-C?

#Question id: 396

#Unit 1. Molecules and their Interaction Relevant to Biology

Identical heat lamps are arranged to shine on two identical containers, one containing water and one methanol (wood alcohol), so that each liquid absorbs the same amount of energy minute by minute. The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. Which of the following graphs correctly describes what will happen to the temperature of the water and the methanol?

#Question id: 1113

#Unit 4. Cell Communication and Cell Signaling

Consider this pathway:

epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP

The second messenger in this pathway is:

#Question id: 11292

#Unit 10. Ecological Principles

In an pond ecosystem the _____ is always greater than the _____ .

(a) number of primary producers . . . number of secondary consumers

(b) biomass of secondary consumers . . . biomass of primary consumer

(c) assimilation efficiency of primary consumers . . . assimilation efficiency of secondary consumers

(d) biomass of primary producers . . . biomass of primary consumers

#Question id: 4467

#Unit 3. Fundamental Processes

Both polymerase removal and repair enzyme recruitment are performed by a single protein called?