Experts in deer ecology generally agree that population sizes of deer that live in temperate climates are limited by winter snow. The deer congregate in ?yarding? areas under evergreen trees because venturing out to feed in winter is energetically too expensive when snowfall depths accumulate to above 40 cm. Deer often stay yarded until the spring thaw. Snow depth over 40 inches for more than 60 days results in high mortality due to starvation.  This observation best illustrates which of the following principles about factors that limit distribution of organisms?

#Question id: 10468

#Unit 6. System Physiology – Plant

Why are stomata required in leaf surface?

#Question id: 10467

#Unit 6. System Physiology – Plant

The COP1-SPA complex acts as a positive regulator as well as acts as negative regulator  by shown in statements;

a) Act as negative regulator−that targets transcription factors for degradation during phytochrome and cryptochrome responses

b) Acts as a positive regulator−that targets transcription factors for degradation during phytochrome and cryptochrome responses

c) Acts as a negative regulator− during UV-B signaling by interacting with the C-terminal region of UVR8 in the nucleus UVR8- COP1-SPA complex then activates the major transcription factor HY5, which controls the expression of many of the genes induced by UV-B

d) Acts as a positive regulator during UV-B signaling by interacting with the C-terminal region of UVR8 in the nucleus UVR8- COP1-SPA complex then activates the major transcription factor HY5, which controls the expression of many of the genes induced by UV-B

Whichof the following combination from avbove statements of UVR8 is true?

#Question id: 10466

#Unit 6. System Physiology – Plant

In Arabidopsis, phot1 mutants have a normal avoidance response and a poor accumulation response, phot2 mutants lack the avoidance response but retain a fairly normal accumulation response, while phot1/phot2 double mutant lack both the avoidance and accumulation responses. These results indicate that,

#Question id: 10465

#Unit 6. System Physiology – Plant

This feature is an adaptive, as the redistribution of chloroplasts within the cells modulates light absorption and prevents photodamage, diagram shows of chloroplast distribution patterns in Arabidopsis palisade cells in response to different light intensities;

m) A-low light, B-high light, C-darkness

n) A-high light, B-darkness, C-low light

Based on the above light intensities, each shows different chloroplasts position such as,

i) chloroplasts avoid sunlight by migrating to the side walls of palisade cells

ii) chloroplasts move to the bottom of the cell, although the physiological function of this position is unclear

iii) chloroplasts optimize light absorption by accumulating at the upper and lower sides of palisade cells

Which of the following correct combinations shows light intensities and chloroplast movements?

#Question id: 10464

#Unit 6. System Physiology – Plant

As with cryptochrome and phytochrome, the N-terminal photosensory region of the phototropins controls the activity of the C-terminal half of the protein, which contains a serine/threonine kinase domain. Following are some statements about photosensory region of the phototropins.

a) The activation of the C-terminal kinase domain then leads to receptor autophosphorylation on multiple serine residues that is required for all phototropin-mediated responses

b) In the dark, the N-terminal region, including the LOV domains, “cages” and inhibits the activity of the kinase domain

c) In the light, the N-terminal region, including the LOV domains, “cages” and inhibits the activity of the kinase domain

d) Absorption of blue photons by the LOV domains results in primary photochemical changes that lead to the uncaging of the kinase domain and its activation by the unfolding of the Jα-helix

Which one of the following combination of above statements is correct?

#Question id: 10463

#Unit 6. System Physiology – Plant

LOV1 and LOV2, each binding a chromophore flavin mononucleotide (FMN), which one of the following statements shows incorrect prediction about LOV domains?