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TLS Online TPP Program

#Question id: 1104

Which of the following statements is true of signal molecules?

#Unit 4. Cell Communication and Cell Signaling

  1. When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.

  2. In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.

  3. In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus.

  4. Protein kinase A activation is one possible result of signal molecules binding to G protein coupled receptors.

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TLS Online TPP Program

#Question id: 13137

#Unit 10. Ecological Principles

Reproductive value (Vx ) calculated from population life-table data provides a measure of the 
TLS Online TPP Program

#Question id: 13138

#Unit 10. Ecological Principles

Life-history characteristics associated with K-selected ordgtanisms include K
TLS Online TPP Program

#Question id: 13139

#Unit 10. Ecological Principles

The logistic equation above is used to describe the rate of change of a population, N, with time, t, where r is the intrinsic rate of increase and K is the carrying capacity. Which of the following statements is true for this equation?
TLS Online TPP Program

#Question id: 13140

#Unit 10. Ecological Principles

One summer the moose population on Island was unusually high, and park naturalists noticed signs of malnutrition among the  adults.  The wolf population  was  fairly  low,  near  20.  That  winter,  for  the  first  time  in  many  years,  a substantial  number of seemingly healthy adult moose as well as calves and crippled animals were killed and eaten by wolves. This description is part of a general situation in which the wolf and moose populations
TLS Online TPP Program

#Question id: 13141

#Unit 10. Ecological Principles

Five similar populations of a herbaceous annual plant are monitored for three years; then, the numbers of individuals in populations I-IV are increased by an experimenter. Subsequent changes in the sizes of all the populations are shown in the graph below.

If size distributions of individuals do not vary among these populations, which of the following relationships best illustrates the occurrence of population regulation?
TLS Online TPP Program

#Question id: 13142

#Unit 10. Ecological Principles

The Norway rat (Rattus Norvegicus), a widespread pest, was controlled for about a decade by the anticoagulant warfarin. This chemical substance, placed in food pellets, is absorbed by the intestinal tract and inhibits the clotting of blood. After a population decline for about 10 years, rat populations increased and stabilized. In one European population, as illustrated in the graph below, the percentage of rats resistant to warfarin has remained fairly stable over a number of years.

Resistance to warfarin is governed by a dominant autosomal gene, R. More than 15 percent of the resistant animals are heterozygous at this locus (Rr). The table below indicates the response to warfarin and relative reproductive fitness of individuals that are homozygous or heterozygous for the dominant gene (R). The RR individuals have a 20-fold increase in vitamin K requirement over individuals.

Fitness is a measure of the reproductive success of a particular genotype. The highest fitness is 1.00.
There is a substantial number of heterozygotes in the population. Which of the following is the best explanation of this observation?