4. Answer the following questions in 60-80 words:
(2 x 4 = 8 marks)
a) Describe the process of fertilisation in plants with the help of a diagram.
b) Explain double circulation and state its importance in the human body.
Answers
Answer:
(a) Fertilisation occurs after pollen grains fall on the stigma. ... The male gamete present in the pollen moves downward through the pollen tube and reaches the ovule. This gamete fuses with the egg to form a zygote. This process is known as fertilisation.
(b)It is called a double circulatory system because blood passes through the heart twice per circuit. The right pump sends deoxygenated blood to the lungs where it becomes oxygenated and returns back to the heart. The left pump sends the newly oxygenated blood around the body.
Answer:
a- Fertilisation occurs after pollen grains fall on the stigma. ... The male gamete present in the pollen moves downward through the pollen tube and reaches the ovule. This gamete fuses with the egg to form a zygote. This process is known as fertilisation.
b- In double circulation, blood flows twice through the heart, during each cycle of passage through the body. Double circulation is important to keep the oxygenated and deoxygenated blood separate from each other in the body and prevent their mixing. Such separation allows a highly efficient supply of oxygen to the body.
