Question

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63. animals with an open circulatory system

1. no blood vessels

2. 1 atrium and 1 ventricle

3. 1 atrium and 2 ventricles

4. 2 atria and 1 ventricle

5. 2 atria and 2 ventricles.

A unicellular Protista may use a contractile vacuole to expel excess water. Contractile vacuoles most likely would be found in Protista that

1. live in a freshwater environment.

2. live in a marine (salt water) environment.

3. are internal parasites of animals.

What is the mechanism for the filtration of blood within the nephron?

1. active transport

2. high pressure of blood forcing water and small molecules out of the capillaries.

3. osmosis

4. diffusion

Answer 1

1. No blood vessels

Explanation: in open circulatory system, blood vessels are absent. Blood flow openly in hte body cavities, directly bathing the body tissues.

2. B. live in a marine (salt water) environment

Explanation: Marine water is salty. Hence cells require extra mechanism to excrete the water to hypertonic environment. Contractile vacuoles help to excrete the water via this mechanism.

3. high pressure of blood forcing water and small molecules out of the capillaries.

Explanation:

Net filteration pressure= glomerular hydrostatic pressure - glomerular colloid osmotic pressure - capsular hydrostatic pressure + capsular colloid osmotic pressure.

Pressure favoring filtration are:
-glomerular hydrostatic pressure
-capsular colloid osmotic pressure

Pressure opposing filtration are:
- glomerular colloid osmotic pressure
- capsular hydrostatic pressure