Practice Questions

TLS Online TPP Program

#Question id: 7297

How is the ABC model for floral identity in Arabidopsis similar to the models for homeotic gene function derived from studies in Drosophila?

#Unit 5. Developmental Biology

The key resposnsibility of homeotic genes in both is patterning of dorsal-ventral asymmetry.
In both organisms, one homeotic gene is expressed at the two ends, a second expressed in to domains more central to that of the first and a third expressed more centrally, thus contributing unambiguous identities to all regions of the organism.
In both organisms, homeotic genes interact, so that it is often the combination of genes present that is critical in specifying structure in adult.
The ABC model of Arabidopsis is essentially identical to the Drosophila model for homeotic gene function, in that the Drosophila version of the A gene is abdominal-A, the Drosophila version of the B gene is Abdominal-B, and the Drosophila version of the C gene is Ultrabithorax.

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TLS Online TPP Program

#Question id: 12966

#Unit 10. Ecological Principles

You are planning a dive in a lake, and are eager to observe not many underwater organisms but be able to observe them both close up and far away. You would do well to choose

TLS Online TPP Program

#Question id: 12967

#Unit 10. Ecological Principles

Which of the following is the best explanation for why net primary productivity in terrestrial ecosystems tends to increase toward the tropics?

TLS Online TPP Program

#Question id: 12968

#Unit 10. Ecological Principles

Most terrestrial ecosystems have a pyramidal structure of where biomass of producers > primary consumers > secondary consumers > tertiary consumers. However, some aquatic ecosystems have an inverted pyramidal structure where the standing biomass of producers < primary consumers. An explanation for this is:

TLS Online TPP Program

#Question id: 12969

#Unit 10. Ecological Principles

In which of the following habitats would one expect to find the highest diversity of vascular plants?

TLS Online TPP Program

#Question id: 12970

#Unit 10. Ecological Principles

In deep-sea hydrothermal vents near the Galapagos Islands, bacteria obtain energy by oxidizing hydrogen sulphide released from the vents. Giant tube worms, which lack mouths and digestive systems, harbour the bacteria in their tissues and use them as a source of organic molecules. Clams obtain energy by filtering bacteria directly from the water, and numerous crabs and octopi feed on the clams. In this unique ecosystem, the bactena are playing the role of

TLS Online TPP Program

#Question id: 12971

#Unit 10. Ecological Principles

One group of ecologists has suggested that producers are limited by competition for resources, primary consumers (herbivores) are limited by predation, and secondary consumers (carnivores) are limited by food. If this were true, at which of the following trophic levels would one expect to find substantial evidence for competitive exclusion?