The pressure-flow model, first proposed by Ernst Münch, Phloem loading at the source and phloem unloading at the sink establish the pressure gradient.

a.) In source tissues, an accumulation of sugars in the sieve elements generates a lower or negative solute potential (ψs).

 b.) source tissue, causes a steep drop in the water potential (ψ), due to water potential gradient, water enters the sieve elements and causes turgor pressure (ψp ) decrease.

c.) In sink tissues, phloem unloading leads to a lower sugar concentration in the sieve elements, generating a higher or less negative solute potential.

d.) As the water potential of the phloem rises above that of the xylem, water tends to leave the phloem in response to the water potential gradient, causing a decrease in turgor pressure in the sieve elements of the sink.

Which of the following statements of sink and source tissue is FALSE?

#Question id: 9618

#Unit 9. Diversity of Life Forms

Generally, within a lineage, the largest number of shared derived characters should be found among two organisms that are members of the same

#Question id: 9619

#Unit 9. Diversity of Life Forms

A common ancestor for both species C and E could be at position number 

#Question id: 9620

#Unit 9. Diversity of Life Forms

The two extant species that are most closely related to each other are

#Question id: 9621

#Unit 9. Diversity of Life Forms

If this evolutionary tree is an accurate depiction of relatedness, then which of the following should be correct?

1. The entire tree is based on maximum parsimony.

2. If all species depicted here make up a taxon, this taxon is monophyletic.

3. The last common ancestor of species B and C occurred more recently than the last common ancestor of species D and E.

4. Species A is the direct ancestor of both species B and species C.

5. The species present at position 3 is ancestral to C, D, and E

#Question id: 9622

#Unit 9. Diversity of Life Forms

Which of the following numbers represents a polyphyletic taxon? 

#Question id: 10127

#Unit 6. System Physiology – Plant

In higher plants, the multi-subunit protein supercomplex has two complete reaction centers and some antenna complexes. The core of the reaction center consists of two membrane proteins known as D1 and D2, Which contained a multi-subunit protein supercomplexes;