The Class 9 is an important year in a student’s life and Maharashtra State Board Science is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 9 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 9 Science Book syllabus.
1.Match the pairs and explain.
| A | B |
| Growth of pollen tube towards ovule | Gravitropic movement |
| Growth of shoot system | Chemotropic movement |
| Growth of root system | Phototropic movement |
| Growth towards water | Growth-irrelevant movement |
| Hydrotropic movement |
Answer:
| A | B |
| Growth of pollen tube towards ovule | Chemotropic movement |
| Growth of shoot system | Phototropic movement |
| Growth of root system | Gravitropic movement |
| Growth towards water | Hydrotropic movement |
2. Write notes on root pressure.
Answer: Take a small plant such as a balsam or tuberose with roots intact. Then, wash and clean its roots and keep it in the water consisting of a stain like safranin or eosin. Then, after 2-3 hours, observe the stem and the veins of the leaves. You can also take a compound microscope to observe the stained xylem of a transverse section of the stem of a plant. You can see that the root cells have reached the water and minerals in the soil. The water and minerals enter the cells on the root surface, as a result of the differences in concentration and these cells become turgid. The pressure that these turgid cells exert on the adjacent cells is the ‘root pressure’. Because of the effect of this pressure, water and minerals reach the xylem of the roots, which are continuously pushed forward so as to reduce the difference in concentration. This continuous movement also results in the formation of a water column that is continuously pushed ahead. This is enough pressure to lift the water up in shrubs, small plants and small trees.
3. Write notes on Transpiration.
Answer: When you observe a branch covered in a plastic bag, you will see that the plants via the stomata on their leaves releases water in the form of vapour. Stomata also has two cells called guard cells present around it, which controls the opening and closing of stomata. Transpiration takes place via these stomata. By the process of evaporation, the leaves give out water into the atmosphere, thus decreasing the water level in the epidermal level. In order to compensate for this water level, the water is then brought up to the leaves through the xylem. Transpiration helps in absorbing water and minerals and its distribution to all parts of the plant. Meanwhile, root pressure performs the important role of pushing the water up during the night time.
4. What is a Nerve cell?
Answer: Neurons are the special types of cells that conduct impulses from one place to another in the body. They are the structural and functional units of the nervous system. Nerve cells are the largest cells in the human body and may measure up to a few metres in length. They have the ability to produce and conduct electrochemical impulses. Meanwhile, the cells that support the nerve cells and help in their functioning are called neuroglia. Nerves are formed by the Nerve cells and neuroglial cells together.
5. Write a note on the human brain.
Answer: Located safely in the cranial cavity, the brain is the main controlling part of the nervous system. An adult human has a brain of about 1300 – 1400 grams in weight with approximately 100 billion neurons. It is seen that the left side of our brain has control over the right side of our body, while the right side of our brain controls the left side of the body. The left side of the brain also controls our speech, conversation, writing, logical thinking and more. Alternatively, the right side has control over artistic abilities.
Meanwhile, the brain consists of the Cerebrum, Cerebellum and the Medulla oblongata. Cerebrum is the largest part of our brain occupying two-thirds of the brain and consists of two cerebral hemispheres, which are connected to each other using tough fibres and nerve tracts. For this reason, it is also known as the large brain. Its surface has deep, irregular ridges and grooves, called convolutions. Convolution increases the surface area of the cerebrum to accommodate a large number of nerve cells.
Cerebellum, located at the back of the cranial cavity below the cerebrum is the smallest part of the brain. Instead of the deep convolutions, its surface has shallow grooves.
Medulla oblongata is the hindmost part of the brain that continues downwards as the spinal cord. There are also two triangular swollen structures known as pyramids on the upper side of the medulla oblongata.
6. Write notes on the reflex action.
Answer: Reflex action is the immediate response that is involuntary from the environment to a stimulus. At times, we might react to an incident without thinking or having any control over the reaction from our part. This is a response given to a certain stimulus from the surroundings. In these situations, proper co-ordination and control is achieved even without any intervention of the brain.
7. Name the hormones of the following endocrine glands and the function of each.
a) Pituitary
b) Thyroid
c) Adrenal
d) Thymus
e) Testis
f) Ovary
Answer: See the table below for the hormones of the following endocrine glands and their respective functions:
| Endocrine Glands | Hormones | Functions |
| Pituitary | Growth Hormone
Adrenocorticotropic hormone Thyroid stimulating hormone Prolactin Follicle stimulating hormone Luteinizing hormone Oxytocin Antidiuretic hormone | –Stimulates growth of bones
–Stimulates adrenal gland –Stimulates thyroid gland –Stimulates milk production –Controls growth of gonads –Controls menstrual cycle and ovulation –Contracts the uterus during parturition. –Regulates water-level in the body |
| Thyroid | Thyroxine
Calcitonin | –Controls growth of body and metabolic activities
–Controls calcium metabolism and calcium level in blood |
| Adrenal | Adrenaline and
Nor-adrenaline Corticosteroid | -Controls behaviour during crisis and emotional situations
–Stimulates heart and its conducting tissue and metabolic processes. Maintains balance of Na+ and K+ and stimulates metabolism |
| Thymus | Thymosin | Controls the cells that give rise to immunity |
| Testis | Testosterone | Is a stimulant for growth of secondary sexual
characteristics like beard, mustache, hoarse voice, etc. in men |
| Ovary | Oestrogen
Progesterone | -Stimulates growth of endometrium
-Stimulates growth of secondary sexual characteristics in women -Prepares the endometrium for conception and maintains pregnancy |
8. Draw and label Human Endocrine Glands.
Answer:
9. Draw a labelled diagram of nerve cells
Answer:
10. Explain chemical coordination in humans.
Answer: Chemical coordination or control in our human body is carried out with the help of hormones secreted by the endocrine glands. Since, these glands do not have arrangements of their to carry their secretions, it is released into the blood circulation. Even if endocrine glands are present at specific locations of the body, their secretions reach every body part with the help of blood. Meanwhile, the hormones released are restricted using a special mechanism that controls the quantity and the timing of the hormone secretion. When there is a boost in the blood glucose level, certain cells in the pancreas are stimulated and as a response they release more quantity of insulin.
11. Explain the difference between the excretory system of humans and plants.
Answer: Retaining the harmful and waste substances (such as uric acid, urea, ammonia and so on that are generated in living organisms) in the body for long, it can result in serious harm and even death. So, it becomes necessary to remove these harmful waste substances from the body. This removal of waste substances in the body is called excretion. In unicellular organisms, waste materials are directly eliminated across the cell surface, while the excretion process in multicellular organisms is more complex. Now, the excretion process is more simple in plants as compared to animals. Plants do not have any special organs or system for excretion in plants. During diffusion, gaseous substances are released. A large amount of the waste substances of plants are stored in the worn-out and old xylem in the form of resin and gum. Plants also release some waste materials into the surrounding soil via the roots.
12. Explain the coordination in plants with the help of a diagram.
Answer: Learn more about coordination in plants from here.
13. How does excretion occur in human beings?
Answer: The human excretory system includes the urinary bladder, a pair of ureters, a pair of kidneys and the urethra. Urine is produced by the kidneys by separating the waste and other unwanted excess substances from the blood. Find more about human excretory system from here.
14. Describe transportation systems in plants.
Answer: “Transportation is the process that involves the movement of water and necessary nutrients to all parts of the plant for its survival. “Learn more about transportation in plants .
15. From where do the plants get inorganic substances other than carbon dioxide and oxygen?
Answer: Plants have a need for inorganic substances such as magnesium, manganese, nitrogen, sodium, phosphorus and so on other than carbon dioxide and oxygen. Soil is the richest source of these substances for the plants. Roots of the plants absorb these substances from the soil and transport them.
16. What are the functions of the xylem and the phloem?
Answer: The xylem conducts the water, while the phloem conducts the food. Every part of the plant is connected with these conducting tissues.
17. Explain translocation
Answer: The food manufactured in leaves is transported to each cell in the plant body, while the excess food, except amino acids, is stored in roots, fruits and seeds. This process is called ‘translocation’ of materials. Phloem carries out the translocation in both the upward and downward direction. This is not a simple physical process and requires energy, which is obtained from ATP.
18. Your hands may begin to itch if you try to cut an elephant ’s foot (Amorphophallus) or arum leaves. Why does this happen?
Answer: In these plants, waste materials present are in the form of crystals of calcium oxalate, called raphides. They are needle-shaped, so they prickle and lead to irritation of the skin.
19. What is a nephron? Which part is the Bowman’s capsule?
Answer : Nephron is the functional unit of the kidney that conducts the basic function of filtration. Each nephron also has a thin-walled upper part termed the Bowman’s capsule, which is cup-like.
20. What is dialysis? Explain.
Answer: Any injury, infection or decreased blood supply can adversely affect the efficiency of kidneys. In such cases, excess of toxic substances are collected in the body, leading to death. If this results in kidney failure, nitrogenous wastes are separated from the blood using a man-made machine. This process of separating the nitrogenous waste from blood using this machine is known as dialysis. Nearly, 500ml blood is transmitted at one time via this machine. Purified blood is then re infused into the body of the patient.
21. What is control and coordination?
Answer: Control is the systematic regulation of different processes, while bringing about the different processes in the proper sequence is known as coordination. Proper coordination between different systems and organs participating at different steps of that activity is necessary for any activity in the body to be completed successfully.
22. What is necessary for the optimal efficiency of the body?
Answer: When there is proper coordination between various systems of an organism, then it helps to maintain a state of equilibrium known as ‘homeostasis.’ This state of equilibrium is necessary for the optimal efficiency of the body.
23. Which are the movements collectively called ‘growth relevant movements’?
Answer: All the below-listed movements of plants are related with growth. For this reason, all these movements are collectively called ‘growth relevant movements’. They are:
24. What is the function of a hormone called auxin?
Answer: A hormone known as auxin, which is manufactured in the apical part of the shoot helps in enlargement of cells.
25. What is the function of abscisic acid?
Answer: Abscisic acid, the hormone, is effective for the prevention and retardation of growth, leaf wilting and more.
26. What is nervous control?
Answer: Nervous control is the reason why humans can respond to changes in their surroundings. Along with these changes in the surroundings, impulses are formed in the human body. Nervous control plays a crucial role of empowering the body cells with the ability to respond to these impulses. This ability is dependant upon the complexity of organisation in the organism’s body structure. Unicellular organisms, such as the amoeba do not have a nervous system that can generate such impulses and responses. However, multicellular animals, like humans, have a nervous system to respond to the stimuli. Control and coordination is achieved using a special type of cells called nerve cells or neurons.
27. What are the types of nerve cells/neurons?
Answer : Nerve cells are classified into three types, based on their functions:
1. Sensory neurons that conduct impulses from sensory organs to the brain and the spinal cord.
2. Motor neurons help to conduct impulses from the brain or spinal cord to effector organs like muscles or glands.
3. Association neurons perform the function of integration in the nervous system.
28. Which are the three parts that the human nervous system is divided into?
Answer: The human nervous system is divided into the Central nervous system, Peripheral nervous system and Autonomic nervous system.
29. What does the central nervous system consist of?
Answer: The central nervous system consists of the spinal cord and brain.
30. What are “ventricles” and “central canal” ?
Answer: Ventricles are the cavities found in various parts of the brain, while the long tubular cavity of the spinal cord is known as the ‘central canal’.
31. What are meninges?
Answer: The protective layer, in the space between the delicate central nervous system and its bony covering are known as the meninges.
32. What is a spinal cord?
Answer: A part of the central nervous system that is held within the vertebral column is the spinal cord. Spinal cord is slightly thick but gradually tapers towards the end. There is a thread-like fibrous structure at its end, called the Filum terminale.
33. What is the peripheral nervous system?
Answer: The peripheral nervous system consists of the nerves originating from the central nervous system and connecting the system with all parts of the body. These nerves are of two types:
A. Cranial nerves are 12 in number and they originate from the brain. These nerves are associated with various parts in the head, thorax and abdomen.
B. The spinal nerves are 31 pairs in number and originate from the spinal cord. These nerves are also connected with arms, legs, skin and some other parts of the body.
34. What is an autonomic nervous system?
Answer: The autonomous nervous system consists of the nerves of involuntary organs like the heart, lungs, stomach and so on. These nerves cannot be controlled on our will.