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VIII-SCIENCE-ORGANIZATION OF LIFE-EVALUATION QUESTION ANSWERS
ORGANIZATION OF LIFE
TEXT BOOK EXERCISES
I. Choose the best answer.
1. ________is tough and thick white sheath that protects the inner parts of the eye.
a) sclera b) conjunctiva
c) cornea d) iris
Ans : a) sclera
2. _________ cells are specialised cells that can be transformed into any kind of cells.
a) Nerve b) Stem
c) Heart d) Bone
Ans : b) Stem
3. Maintenance of constant internal environment of the body is known as ___________.
a) Homeostasis b) Homeophytes
c) Homeokinesis d) Homeophilics
Ans : a) Homeostasis
4. In the absence of oxygen, glucose is broken down in to __________.
a) Lactic acid b) Citric acid
c) Acetic acid d) Nitric acid
Ans : a) Lactic acid
5. The process of air passing in and out the lungs is called ___________.
a) Inhalation b) Exhalation
c) Breathing d) None of these
Ans : c) Breathing
6. Osmosis is the movement of water molecules from a ____________.
a) Higher concentration to a b) Lower concentration
region of lower concentration. to a region of higher concentration.
c) Both of these d) None of these
Ans : b) Lower concentration to a region of higher concentration.
7. The erythrocyte is placed in ______________ solution which has lesser concentration of solutes and greater concentration of water than in the cytoplasm.
a) Hypotonic b) Hypertonic
c) Neutral d)Acidic
Ans : a) Hypotonic
II. Fill in the blanks:
1. _________ is the structural and functional unit of living organisms.
Ans : Cell
2. The largest cell is an egg of an ______________.
Ans : Ostrich
3. _________ is a good example for anaerobic respiration.
Ans : Yeast
4. _________ nerve is located at the end of the eyes behind the retina.
Ans : Optic
5. The size of the cells are measured in units of _________
Ans : micron
III. Match the following.
Ans:
IV. State true or False. If false, correct the statement.
1) In hypotonic condition, concentration of the external and the internal solution of the organism are same.
Ans : False
Correct statement :In Isotonic condition, concentration of the external and the internal solution of the organism are same .
2) Diffusion is the movement of particles from an area of lower concentration to higher concentration .
Ans : False
Correct statement :
Osmosis is the movement of particles from an area of lower concentration to higher concentration
3) Human beings are warm blooded in nature.
Ans : True
4) The larynx has fold of tissue which vibrate with the passage of air to produce sound .
Ans : True
5) Aqueous humour plays an important role in maintaining the shape of the eye.
Ans : False
Correct statement: Vitreous humour plays an important role in maintaining the shape of the eye.
V. Answer very briefly.
1. What is cell differentiation?
The single cell called zygote, undergoes continuous mitotic division and forms the foetus consisting multitude of cells of different shape, size and content. Foetal cells gradually attain change in structure and function.This process is known as cell differentiation.
2. State different types of tissues.
a. Epithelial (Covering) tissue.
b. Muscular (Contractile) tissue.
c. Connective (Supporting) tissue.
d. Nervous tissue
3. Mention the function of ‘Alveoli’.
Alveoli are tiny air sacs in the lungs that are located at the end of bronchial tubes, which is microscopic in nature. It is meant for the exchange of oxygen and carbon dioxide.
4. Name the processes by which air enters and comes out of our lungs.
Inhalation
The process of taking air into the lungs is called inspiration or inhalation.
Exhalation
The process of expelling air from the lungs is called expiration or exhalation.
5. Differentiate osmoconformers and osmoregulators.
6. Define - Metabolism.
Metabolism is the sum of chemical reactions by which living organisms sustain their life. Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances).
VI. Answer briefly.
1. Define - Prokaryotic cell.
Typically unicellular microorganisms that lack a distinct nucleus and membrane bound organelles are called prokaryotic cells.
In some organisms like bacteria, cyanobacteria and mycoplasma, the true nucleus is absent. These organisms are called prokaryotes.
2. Tabulate the differences between aerobic and anaerobic respiration.
3. Why the human eye is compared with camera?
The human eye can be compared to a camera as both functions by gathering, focusing and transmitting the light through the lens for creating an image of an object.
4. Which organ and organ system help to maintain homeostasis?
Homeostasis is a property of human biological system where the self-regulating process tends to maintain the balance for the survival.
The liver, kidney, and brain (hypothalamus), autonomic nervous system and the endocrine system help to maintain homeostasis.
VII. Answer in detail.
1. Draw the struture of human eye and label its parts.
2. Explain osmosis with an example.
Osmosis is the movement of solvent particles across a semipermeable membrane from a dilute solution into a concentrated solution. The solvent moves to dilute the concentrated solution and equalize the concentration on both sides of the membrane.
The movement of liquids in and out of cells is dependent on the concentration of the solution surrounding it.
There are three types of situations in which this could vary.
Isotonic:
Here the concentration of external and internal solution of the organism are the same.
Hypotonic:
Here the external solution concentration is less compared to the concentration of the inner solution of an organism. In this case water will rush into the organism.
Hypertonic:
Here the external solution concentration is greater than the concentration of the inner solution of an organism. In this case the water will rush out of the organism.
3. Differentiate between inhalation and exhalation.
4. Explain about the types of metabolism with an example.
Metabolism is the sum of chemical reactions by which living organisms sustain their life. Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances).
a. Anabolism
Anabolism or constructive metabolism, is all about building and storing. It supports the growth of new cells, the maintenance of body tissues, and the storage of energy for use in the future. During anabolism, small molecules are changed into larger, more complex molecules of carbohydrate, protein, and fat.
Example
Glucose → Glycogen and other sugars
Amino acids → Enzymes, hormones, proteins
Fatty acids → Cholesterol and other steroids
b. Catabolism
Catabolism or destructive metabolism, is the process that produces the energy required for all activity in the cells. In this process, cells break down large molecules (mostly carbohydrates and fats) to release energy. This energy release provides fuel for anabolism, heats the body, and enables the muscles to contract and the body to move.
The waste products released in the process of catabolism are removed from the body through the skin, kidneys, lungs, and intestines.
Example
Carbohydrates → Glucose
Glucose → CO2 , Water and Heat
Protein → Amino acid
5. Explain the mechanism of breathing.
Mechanism of breathing:
Inspiration (Inhalation)
The process of taking air into the lungs is called inspiration or inhalation. During inspiration, the sternum is pushed up and outward and the diaphragm is pulled down.This increases the volume of the thoracic cavity and thus the pressure decreases. The air outside the body flows into the lungs. Here exchange of gases takes place between the air and the blood.
Expiration (Exhalation)
The process of expelling air from the lungs is called expiration or exhalation. Upon exhalation, the lungs recoil to force the air out of the lungs. The inter costal muscles relax, returning the chest wall to its original position. During exhalation, the diaphragm also relaxes, moving higher into the thoracic cavity. This increases the pressure within the thoracic cavity relative to the environment. Air rushes out of the lungs due to the pressure gradient. This movement of air out of the lungs is a passive event.
Exchange of gases in the Alveoli:
The content of oxygen in the inhaled air in alveoli is more than the blood flowing through the capillaries. So, the oxygen moves into the blood by simple diffusion. Haemoglobin in the blood combines with oxygen to form oxyhaemoglobin. The blood carrying oxygen reaches the heart through blood vessels. The heart pumps it to all the tissues in the body. The tissues release carbon dioxide which is carried back to alveoli by the blood. Carbon dioxide diffuses from the blood to the air in the alveoli and is sent out of the body when the air is exhaled.
VIII. Higher Order Thinking Questions.
1. Why do we need instant energy?Does glucose give that energy? Explain.
We need instant energy to replenish the energy lost during tiring work.
We may lose energy during a very sunny day.
Glucose is a simple sugar. It easily breaks down in the cell with the help of oxygen and provides instant energy to the organism. Glucose does not need digestion, it is directly absorbed into the blood.
Hence, when glucose is directly taken, it does not get digested and acts as an instant source of energy.
2. How are they preparing pickles? What are the causes involved in that?
There are different types of pickles that fall into two categories on fermentation aspects.
(i) “salt-stock pickle” that use a concentrated brine (up to 16% salt) where preservation is due to salt and not to fermentation, and
(ii) “vinegared pickles” where raw materials are packed in vinegar (acetic acid), salt and sometimes added sugar to help develop different flavor and texture in pickles.
Unfermented pickles are usually pasteurized by heating.
IX. Value Based Questions.
As these questions test your understanding, knowledge on concepts and attitude, it is better that the questions should be answered by you. So read the questions carefully and try to answer the questions on your own.
