5. Thinking Critically Paramecium, a single-celled fresh-water organism, takes in water by osmosis. Paramecium uses an organelle called a contractile
vacuole to remove excess water from the cell.

(a) Describe what would happen to Paramecium if it did not have
a contractile vacuole.

(b) Predict the effect of placing Paramecium in salt water.

(A) Protozoa and some low-level multicellular animals There are no organs responsible for excreting liquid waste. Such waste can penetrate the cell surface directly into the water outside of it. If paramecium does not contain vacuoles will cause it to lose the balance of body fluids The contractile vacuole compression rate depends on the osmotic pressure of the water in which the animal lives, i.e. the compression rate decreases. if the osmotic pressure of the water in which it resides increases But it will speed up if the osmotic pressure of water decreases.

(B) The water mixed with salt has a higher concentration than fresh water. So the water diffuses into the paramecium. Therefore, the contractile vacuole is less compressed to remove water from the cell than when in fresh water.

the answers are as following:

1. c. double helix, nucleosome, coil, supercoil, chromosome

2. b. g2 phase, preparation for mitosis

3. d. interphase consists of the g1, s, and g2 phases

4. c. metaphase

5. a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set