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: 5675

#Unit 5. Developmental Biology

Following are the statements related to mammalian chaemotaxis:

A. During chaemotaxis, the oocyte and its accompanying cumulus cells secrete molecules that attract only uncapacitated sperm toward the egg during the last stages of sperm migration.

B. These chaemotactic compound are hormone progesterone, which is made by the cumulus cells.

C. Progesterone has been shown to bind to a receptor that activates Ca2+ channels in the cell membrane of the sperm tail, leading to sperm hyperactivity and provides directional cue.

D. Cumulus cells also secrete a substance, CRISP1, that attracts sperm and hyperactivates them through CatSper channels similar as in sea urchins.

Which of  the following statement is incorrect?

#Question id: 4884

#Unit 8. Inheritance Biology

True breeding brown dogs with genotype aabb were cross to true breeding white dogs with genotype AABB. All F1 offspring having white phenotype were allowed to intercross to produce F2 progeny as following number –

A- - - 118 white,

aa B- 32 black

aa bb 10 brown

A Male Dog with AaBb genotype was cross with female dog with aabb genotype. What is probability of Black phenotype among their offspring if A gene link B gene at 10 map unit at cis configuration?

#Question id: 13188

#Unit 10. Ecological Principles

The following figure is a model of seedling establishment as a function of distance from a parent tree. Initial seed density measures the number of seeds falling to the ground. Seed survivorship measures the proportion of seeds that survive to the adult stage at each distance

Which of the following factors is most likely to generate the seed survivorship curve shown? 

#Question id: 2936

#Unit 2. Cellular Organization

The stable attachment of sister kinetochores to microtubules emanating from opposite spindle poles is called:

#Question id: 15603

#Unit 12. Applied Biology