Everyday Biology Questions CBSE Class 9 Biology Worksheets Set 02

Questions with Answers

Question 1. What does a prokaryotic cell lack?
Answer:
A prokaryotic cell lacks a well-defined nucleus: there is no nuclear membrane and no nucleolus. Its DNA lies free in the cytoplasm. It also lacks membrane-bound organelles such as mitochondria, Golgi bodies and plastids. Bacteria and blue-green algae are prokaryotes.
In simple words: No true nucleus and no membrane-bound organelles.

Teacher's Note:
1. Eukaryotic cells have a true nucleus.
2. Prokaryotic cells are generally much smaller.

Question 2. What component of blood plays the main role in clotting?
Answer:
Blood platelets (thrombocytes). On an injury they release substances that, along with calcium and clotting proteins, convert fibrinogen into fibrin threads which trap blood cells and form a clot.
In simple words: Platelets.

Teacher's Note:
1. Fibrin forms the net of the clot.
2. Haemophilia is a disease where clotting is slow.

Question 3. What is the name of the junction between the axon of one neuron and the dendrite of the next neuron?
Answer:
The junction is called a synapse. Nerve impulses cross it with the help of chemicals called neurotransmitters.
In simple words: Synapse.

Teacher's Note:
1. A neuron is the structural unit of the nervous system.
2. Impulses travel from dendrite to cell body to axon.

Question 4. Who discovered the virus?
Answer:
The Russian biologist Dmitri Ivanovsky first showed in 1892 that the agent causing tobacco mosaic disease passes through filters that stop bacteria. Later work by Beijerinck and Stanley established viruses.
In simple words: Dmitri Ivanovsky, in 1892.

Teacher's Note:
1. Viruses are non-cellular and multiply only inside living cells.
2. Tobacco mosaic virus was the first virus discovered.

Question 5. Who first discovered the antibiotic penicillin?
Answer:
Alexander Fleming discovered penicillin in 1929 from the mould Penicillium notatum.
In simple words: Alexander Fleming, in 1929.

Teacher's Note:
1. Penicillin kills bacteria, not viruses.
2. Antibiotics are medicines against bacterial infections.

Question 6. Which mammals have oval (elliptical) red blood cells?
Answer:
Camels and llamas. In most mammals red blood cells are circular, biconcave discs without a nucleus; the camel family is an exception in shape, but even in them the cells have no nucleus.
In simple words: Camel and llama.

Teacher's Note:
1. Mammalian red cells lose their nucleus when mature.
2. Oval red cells in camels help in survival in dehydrated conditions.

Question 7. Name the pigment which functions as an oxygen carrier in prawns and crabs.
Answer:
Haemocyanin, a blue copper-containing pigment present in the plasma. In humans the oxygen carrier is haemoglobin, which contains iron.
In simple words: Haemocyanin.

Teacher's Note:
1. Haemoglobin contains iron and is red.
2. Haemocyanin contains copper and is blue.

Question 8. What is an allergy?
Answer:
Allergy is an over-reaction of the body's defence system to certain harmless substances such as dust, pollen or some foods, which are called allergens. Cells release histamine which causes sneezing, itching, redness and swelling.
In simple words: An exaggerated immune reaction to a harmless substance.

Teacher's Note:
1. Antihistamine medicines relieve allergy.
2. Asthma may be triggered by allergens.

Question 9. Why does blood not coagulate inside the blood vessels?
Answer:
Blood in the vessels contains an anticoagulant called heparin, and the inner lining of the vessels is smooth, so platelets do not break and start clotting.
In simple words: Heparin and the smooth vessel lining prevent clotting.

Teacher's Note:
1. Clotting starts only on injury or rough surfaces.
2. Heparin is made by certain cells in the liver and lungs.

Question 10. Who is the father of genetics?
Answer:
Gregor Johann Mendel (1822 to 1884), who worked on garden peas and gave the laws of inheritance.
In simple words: Gregor Mendel.

Teacher's Note:
1. Mendel's work was recognised only after his death.
2. He studied seven pairs of contrasting characters in peas.

Question 11. Which artery carries deoxygenated blood?
Answer:
The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs. All other arteries carry oxygenated blood.
In simple words: The pulmonary artery.

Teacher's Note:
1. Pulmonary veins carry oxygenated blood to the heart.
2. Arteries carry blood away from the heart.

Question 12. What is meant by pacemaker?
Answer:
The pacemaker of the heart is the sinoatrial (S.A.) node, a patch of special muscle tissue in the right atrium. It starts the heartbeat impulses and sets the rate of the heart.
In simple words: The S.A. node, which starts each heartbeat.

Teacher's Note:
1. An artificial pacemaker is a device to correct slow heartbeat.
2. Heart muscle beats on its own without nerve impulses.

Question 13. What are coacervates?
Answer:
Coacervates are droplets formed when colloidal particles such as proteins gather together with a layer of water around them. They look like tiny cells and were proposed by Oparin as the possible forerunners of the first living cells.
In simple words: Cell-like droplets of colloids, thought to be an early step towards life.

Teacher's Note:
1. Oparin and Haldane proposed the theory of chemical origin of life.
2. Coacervates can absorb substances from their surroundings.

Question 14. Who proposed the theory of natural selection?
Answer:
Charles Darwin, in his book 'On the Origin of Species' (1859). Alfred Russel Wallace independently reached the same idea.
In simple words: Charles Darwin.

Teacher's Note:
1. Organisms best suited to their environment survive and reproduce more.
2. Natural selection explains evolution.

Question 15. What is the name given to a plant which bears both male and female flowers separately on the same plant?
Answer:
Such plants are called monoecious. Examples are maize, castor and cucumber. Plants with male and female flowers on different plants, such as papaya, are dioecious.
In simple words: Monoecious.

Teacher's Note:
1. Bisexual flowers have both stamens and carpels in the same flower.
2. Papaya is dioecious.

Question 16. What is parthenocarpy?
Answer:
Parthenocarpy is the formation of fruit without fertilisation, so the fruit is seedless, for example banana and seedless grapes.
In simple words: Seedless fruit formation without fertilisation.

Teacher's Note:
1. It can be induced by plant hormones such as auxin.
2. Seedless fruits are popular because they are easy to eat.

Question 17. What are lenticels?
Answer:
Lenticels are small pores in the bark (cork) of woody stems through which gases are exchanged between the inner tissues and the air.
In simple words: Small breathing pores in woody stems.

Teacher's Note:
1. Stomata are pores on leaves; lenticels are on stems.
2. Lenticels appear as raised dots on a twig.

Question 18. What is meant by guttation?
Answer:
Guttation is the loss of water in liquid form through special pores called hydathodes at the edges of leaves. It occurs at night or early morning, when there is high humidity and root pressure.
In simple words: Drops of water pushed out at the leaf edges.

Teacher's Note:
1. Transpiration is loss of water as vapour.
2. You can see drops of water on grass leaves in the morning.

Question 19. What are assimilatory roots?
Answer:
Roots which contain chlorophyll and carry out photosynthesis are called assimilatory roots. Examples are Tinospora and Trapa (water chestnut).
In simple words: Green roots which make food.

Teacher's Note:
1. Roots are normally non-green and underground.
2. Assimilatory roots are an adaptation.

Question 20. Which part of the onion plant is modified into the bulb?
Answer:
The stem. In an onion the stem is a very small disc, and the fleshy, overlapping leaf bases around it store food and form the bulb.
In simple words: A short stem with fleshy leaves.

Teacher's Note:
1. Potato is a stem tuber, carrot is a root.
2. Onion is a modified underground stem for storing food.

Question 21. What is a reflex action?
Answer:
A reflex action is a quick, automatic, involuntary response to a stimulus, controlled by the spinal cord without the brain taking a decision, for example withdrawing the hand from a hot object. The pathway is called the reflex arc.
In simple words: A sudden automatic response without thinking.

Teacher's Note:
1. Reflex arc: receptor, sensory neuron, spinal cord, motor neuron, effector.
2. Reflex actions protect us from harm.

Question 22. Name the fossil animal which is the connecting link between reptiles and birds.
Answer:
Archaeopteryx. It had feathers and wings like a bird but also teeth, a long tail with bones and claws like a reptile.
In simple words: Archaeopteryx.

Teacher's Note:
1. Connecting links show how one group evolved into another.
2. Fossils are remains of organisms of the past.

Question 23. What are haustoria?
Answer:
Haustoria are special roots of parasitic plants such as Cuscuta (dodder). They enter the tissues of the host plant to absorb water and food.
In simple words: Roots of a parasite that suck food from the host.

Teacher's Note:
1. Cuscuta has no chlorophyll or roots of its own.
2. A parasite depends on the host for food.

Question 24. What causes the common cold, influenza and polio?
Answer:
These diseases are caused by viruses. Antibiotics do not work against viruses; vaccines can prevent diseases such as polio.
In simple words: Viruses.

Teacher's Note:
1. Mumps and rabies are also viral diseases.
2. Polio is prevented by oral polio vaccine.