Question

(a) Explain the process of nutrition in amoeba with the help of a diagram.
(b) With the help of a flow chart explain the process of circulation of blood between human heart and body?

Answer 1

The mode of nutrition in amoeba is holozoic.

Mechanism of Nutrition

Ingestion : The food is ingested at the point where it comes in touch with the cell surface with the help of pseudopodia. Pseudopodia engulf the food into the cytoplasm.

Invagination: Pseudopodia secretes a sticky and toxic fluid which adheres and kills the prey. It is then taken in by invagination.

Pinocytosis: Also called cell drinking. There are pinocytosis channels at certain points through which the cell ingests the food digestion in amoeba takes place. The food taken in remains in a food vacuole or gastric vacuole formed by the cell membrane and small part of the cytoplasm. The vacuoles are transported deeper into the cells by cytoplasmic movements. Here they fuse with lysosomes that contain enzymes. Two enzymes amylase and proteinase have been reported. Thus, amoeba can digest sugars, cellulose and proteins. Fats, however, remain undigested.

The contents of the vacuole become lighter and the outline of the vacuole becomes indefinite indicating that the digestion is complete.

(b) Circulation of blood between heart and body

Right atrium

I Right atrioventricular valve

I

V

Right ventricle

I Right semilunar valve

I Pulmonary artery

V

Lungs

I Pulmonary vein

I

V

Left atrium

I Left atrioventricular valve

I

V

Left ventricle

I Left semilinar valve

I Aorta

V

Body

I Vena cava

I

V

Right atrium

The human circulatory system is really a two-part system whose purpose is to bring oxygen-bearing blood to all the tissues of the body. When the heart contracts it pushes the blood out into two major loops or cycles. In the systemic loop, the blood circulates into the body’s systems, bringing oxygen to all its organs, structures and tissues and collecting carbon dioxide waste. In the pulmonary loop, the blood circulates to and from the lungs, to release the carbon dioxide and pick up new oxygen. The systemic cycle is controlled by the left side of the heart, the pulmonary cycle by the right side of the heart.