Practice Questions

TLS Online TPP Program

#Question id: 20333

Choose true statements about Ax21-mediated quorum sensing;
a. It is a highly conserved sulfated peptide secreted by Xanthomonas oryzae.
b. Ax21 is sulfated by RaxST, which is a putative tyrosine sulfotransferase.
c. Sulfated Ax21 is secreted via the RaxABC type I secretion system
d. Sulfated Ax21 secreted is recognized by the rice XA21 receptor.

#Unit 4. Cell Communication and Cell Signaling

a and b
a, b and c
a, c and d
a, b, c and d

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TLS Online TPP Program

#Question id: 12016

#Unit 10. Ecological Principles

The ability of a desert rodent's kidneys to form highly concentrated urine is largely attributable to

TLS Online TPP Program

#Question id: 12017

#Unit 10. Ecological Principles

All of the following allow hermaphroditic animal species to avoid inbreeding EXCEPT

TLS Online TPP Program

#Question id: 12018

#Unit 10. Ecological Principles

The amount of energy entering a food chain depends on the

TLS Online TPP Program

#Question id: 12019

#Unit 10. Ecological Principles

Chickadees were given an opportunity to store seeds in 72 possible storage sites consisting of holes drilled in small trees that had been placed in an aviary. Typically, the seeds were placed in only 4 or 5 storage sites. The chickadees were then removed from the aviary, the seeds removed from the storage sites, and each hole covered. A day later, the chickadees were returned to the aviary and they spent nearly 5 times as long pulling at the covers on storage sites than at the covers on sites where they had not stored food. This experiment indicates that chickadees

TLS Online TPP Program

#Question id: 12020

#Unit 10. Ecological Principles

Bird species X stores seeds in a large number of separate caches in the summer and then locates the caches in the winter. Compared with a bird species that does not store seeds, species X can be expected to have a proportionately larger

TLS Online TPP Program

#Question id: 12083

#Unit 10. Ecological Principles

In bottom sediments of lakes and streams, organic matter is broken down by heterotrophic microorganisms and ammonia is released. Under aerobic conditions, specialized bacteria convert ammonia to nitrate (nitrification). This nitrate, together with nitrate from other sources, diffuses into the deeper sediments, where it may undergo anaerobic conversion to nitrogen gas (denitrification). These sediments typically contain oligochaete worms that live with their heads buried and their tails waving back and forth in the overlying water. Plastic columns were packed with freshly collected stream sediments and then covered with layers of nitrate enriched water. A similar set of columns was packed with sediment that had been sterilized and then covered with either nitrate-enriched water or distilled water. Oligochaete worms were collected and acclimated to 20°(C)Following acclimation, worms were rinsed in distilled water and then added to three sediment columns. The columns were incubated in the dark at 20°C and monitored every three days for changes in the concentration of nitrate in the overlying water. Nitrate concentrations in each of the experimental treatments were plotted against time, as shown in the graph below

It can be concluded from the figure that