The pressure-flow model explains phloem translocation as a flow of solution (bulk flow) driven by an osmotically generated pressure gradient between source and sink.

a) Phloem translocation, both active and passive mechanisms were considered. All theories, both active and passive, assume an energy requirement in both sources and sinks.

b) In sources, energy is necessary to move photosynthate from producing cells into the sieve elements. This movement of photosynthate is called phloem loading.

c) In sinks, energy is essential for some aspects of movement from sieve elements to sink cells, which store or metabolize the sugar. This movement of photosynthate from sieve elements to sink cells is called phloem unloading.

d) The Active mechanisms of phloem transport further assume that energy is required in the sieve elements of the path between sources and sinks simply to maintain structures.

From the given statements find out the correct for pressure-flow model.

#Question id: 11154

#Unit 9. Diversity of Life Forms

Concerning growth in genome size over evolutionary time, which of these does not belong with the others?

#Question id: 11155

#Unit 9. Diversity of Life Forms

Nucleic acid sequences that undergo few changes over the course of evolutionary time are said to be conserved. Conserved sequences of nucleic acids

#Question id: 11156

#Unit 9. Diversity of Life Forms

Species that are not closely related and that do not share many anatomical similarities can still be placed together on the same phylogenetic tree by comparing their

#Question id: 11157

#Unit 9. Diversity of Life Forms

Typically, mutations that modify the active site of an enzyme are more likely to be harmful than mutations that affect other parts of the enzyme. A hypothetical enzyme consists of four domains (A—D), and the amino acid sequences of these four domains have been determined in five related species. Given the proportion of amino acid homologies among the five species at each of the four domains, which domain probably contains the active site?

#Question id: 11158

#Unit 9. Diversity of Life Forms

Which of these items does not necessarily exist in a simple linear relationship with the number of gene-duplication events when placed as the label on the vertical axis of the graph below?

#Question id: 11159

#Unit 9. Diversity of Life Forms

Which kind of DNA should provide the best molecular clock for gauging the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?