Question

Explain mode of nutrition in unicellular Amoeba and multicellular Hydra. What is the function of Guard cells in plants?

Answer 1

Answer:

Explanation:

Explain mode of nutrition in unicellular Amoeba and multicellular Hydra.

The mode of nutrition in Amoeba is called Holozoic nutrition.  

The nutrition in amoeba takes place in the following steps:

1. Ingestion: The process of ingestion is nothing but intake of food into the body. Amoeba is unicellular and hence it does not have mouth, Amoeba takes the food into the body by forming structures called pseudopodia around the food particle. This pseudopodia forms a vacuole around the food particle called food vacuole and the vacuole is taken inside the cell.

2. Digestion: The food particle inside the vacuole is broken down into soluble particles by digestive enzymes inside the vacuoles.  

3. Absorption: The broken food particles is absorbed into the cytoplasm of amoeba by diffusion. The food particles which are unabsorbed are left inside the vacuole.

4. Assimilation: The absorbed food is converted into energy in this step.

5. Egestion: The undigested food in the food vacuole is thrown out from the cell.

What is the function of Guard cells in plants?

Guard cells are cells surrounding each stoma. They help to regulate the rate of transpiration by opening and closing the stomata. To understand how they function, study the following figures. As you look at the figures, keep in mind that an increase in solute concentration lowers the water potential of the solution, and that water moves from a region with higher water potential to a region of lower water potential.

Notice that in figure A the guard cells are turgid, or swollen, and the stomatal opening is large. This turgidity is caused by the accumulation of K+ (potassium ions) in the guard cells. As K+ levels increase in the guard cells, the water potential of the guard cells drops, and water enters the guard cells.

In figure B, the guard cells have lost water, which causes the cells to become flaccid and the stomatal opening to close. This may occur when the plant has lost an excessive amount of water. In addition, it generally occurs daily as light levels drop and the use of CO2 in photosynthesis decreases.