How can plants regulate molecules that come through the apoplastic route  in roots, before going into the xylem?

The following is a diagram of the circulatory system in mammals. What number represents a vein?

For oxygen exchange between respiratory and circulatory system to take place, partial pressure of O2 should be_________________ in pulmonary artery than in alveoli. 

Which type of cells can communicate via electrical impulses in animals?

In this diagram of countercurrent gas exchange, the following is TRUE:

The antigen-binding sites of an antibody molecule are formed from the molecule’s variable regions. Why do we say these regions are called variable?

Atlantic sharp-nosed shark feeds their young through a placenta and gives birth to live offspring What type of animal is this?

For oxygen exchange between respiratory and circulatory system to take place, partial pressure of O2 should be_________________ in pulmonary artery than in alveoli. 

The hypersensitive response has the following characteristics EXCEPT

Which of the following features DOES NOT improve the rate of diffusion?