Samacheer Kalvi Class 8 Science Unit 18 Organisation of Life Solutions
Welcome to NCTB Solutions. Here with this post we are going to help 8th class students by providing Solutions for Samacheer Kalvi Class 8 Science Unit 18 Organisation of Life. Here students can easily find all the solved solution for Organisation of Life Exercise questions. Also here our Expert Science Teacher’s solved all the questions with easily understandable language with proper guidance so that all the students can understand easily. Here on this post students will get Unit 18 Organisation of Life exercise solutions. Here all the solutions are based on Tamil Nadu State Board latest syllabus.
Unit 18 Organisation of Life Exercise Questions Solutions :
(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
Answer :
Correct Option → (a)
Sclera is tough and thick white sheath that protects the inner parts of the eye.
(2) __ cells are specialized cells that can be transformed into any kind of cells
(a) Nerve
(b) Stem
(c) Heart
(d) Bone
Answer :
Correct Option → (b)
Stem cells are specialized cells that can be transformed into any kind of cells.
(3) Maintenance of constant internal environmental of the body is known as
(a) Homeostasis
(b) Homeophytes
(c) Homeokinesis
(d) Homeophilics
Answer :
Correct Option → (a)
Maintenance of constant internal environmental of the body is known as 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
Answer :
Correct Option → (a)
In the absence of oxygen, glucose is broken down in to 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
Answer :
Correct Option → (c)
The process of air passing in and out the lungs is called Breathing.
(6) Osmosis is the movement of water molecules from
(a) Higher concentration to a region of lower concentration
(b) Lower concentration to a region of higher concentration.
(c) Both of these
(d) None of these
Answer :
Correct Option → (a)
Osmosis is the movement of water molecules from Higher concentration to a region of lower 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
Answer :
Correct option → (a)
The erythrocyte is placed in “Hypotonic” solution which has lesser concentration of solutes and greater concentration of water than in the cytoplasm.
(II) Fill in the blanks
(1) __ is the structural and functional unit of living organisms.
(2) The largest cell is egg of an __
(3) __ is a good example for anaerobic respiration.
(4) __ nerve is located at the end of the eyes behind the retina.
(5) The size of the cells are measured in units of __
Answer :
(1) → Cell
(2) → Ostrich
(3) → Fermentation
(4) → Optic nerve
(5) → micron (um)
(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.
(2) Diffusion is the movement of particles from an area of lower concentration to higher concentration.
(3) Human beings are warm blooded in nature.
(4) The larynx has fold of tissue which vibrate with the passage of air to produce sound.
(5) Aqueous humour plays an important role in maintaining the shape of the eye.
Answer :
(1) → False
Reason : In hyportonic solution the concentration of the external solution is less compared to the concentration of the inner solution of the organism.
(2) → False
Reason : Diffusion means the movement of the particles form an are of higher concentration to the lower concentration.
(3) → True
(4) → True
(5) → True
(V) Answer very briefly
(1) What is cell differentiation?
Answer :
Cells changes and attain gradually change in structure and function this process is known as cell differentiation.
(2) State different types of tissues.
Answer :
There are four types of tissue :-
(1) Epithelial
(2) Muscular
(3) Connective
(4) Nervous.
(3) Mention the function of ‘Alveoli’.
Answer :
Function of alveoli is to exchange of oxygen and carbon dioxide.
(4) Name the processes by which air enters and comes out of our lungs.
Answer :
Air enter in our body by inspiration, or inhalation.
Air exit in our body by expiration, or exhalation.
(5) Differentiate osmoconformers and osmoregulators.
Answer :
- Osmoconformers :
Osmoconformers try to maintain the osmolality of their body matching with their surroundings.
- Osmoregulators :
Osmoregulators are try to maintain their internal osmolality which can be extremely different from that of the surrounding environment though physiological processes.
(6) Define – Metabolism.
Answer :
Metabolism is defined as to the breakdown of food and its transformations into energy cellular products and waste elimination.
or
The sum of the chemical reaction of anabolism and catabolism is known as metabolism.
(VI) Answer briefly
(1) Define – Prokaryotic cell.
Answer :
The organism such as bacteria, cynobacteria and mycoplasma in which true nucleus is absent these organism and this type of cell is known as prokaryotic cell.
(2) Tabulate the differences between aerobic and anaerobic respiration.
Answer :
| Aerobic respiration | Anaerobic respiration |
| (1) Aerobic respiration takes place in the presence of oxygen. | (1) It takes place in the absence of air. |
| (2) The end products of aerobic respiration are carbon dioxide and water | (2) The end products of anaerobic respiration are CO2 and ethanol or lactic acid. |
| (3) Common in all higher plants and animals. | (3) The common certain micro organisms and human muscle. |
(4) Which organ and organ system help to maintain homeostasis?
Answer :
The endocrine system help to maintain the homeostasis.
(VII) Answer in detail :
(2) Explain osmosis with an example.
Answer :
- Osmosis :
Osmosis is the movement of solvent particles across a semipermeable membrane from a dilute solution into a concentrated solution. The solvents moves to dilute the concentrated solution and equalize the concentration on both sides of the membrane. Osmosis have three types :-
(a) Isotonic : the external concentration and internal concentration of the organism is same.
(b) Hypotonic : in this the external concentration the solution is less compared to the inner concentration of solution in organism.
(c) Hypertonic : in this the external concentration of the solution is greater than the inner concentration of the solution.
(3) Differentiate between inhalation and exhalation.
Answer :
| Inhalation : | Exhalation : |
| (1) The muscles of the diaphragm contract. | (1) The muscles of the diaphragm relax. |
| (2) The diaphragm goes downward | (2) The diaphragm goes upward. |
| (3) The ribs move upwards and outwards. | (3) The ribs are move downwards. |
| (4) The volume of thoracic cavity increases. | (4) The volume of thoracic cavity decreases |
| (5) Air enters the lungs through the nose | (5) Air goes out of the lungs through the nose |
(4) List out the different types of metabolism with an example.
Answer :
Metabolism is the sum of chemical reactions by which living organism sustain their life. Metabolism consist of two types anabolism and catabolism
(a) Anabolism : it is constructive metabolism in this it all about the building and storing it supports the growth of new cells ,the maintenance of the body tissue and the storage of energy for the use in future. In this small molecules are charged into larger more complex molecules of carbohydrates, proteins and fat.
For example – Glucose → glycogen and other sugars.
(b) Catabolism : it is destructive type of metabolism in this the process produces energy required for all activity in the cells . in this metabolism the cells breaks down large molecules mostly carbohydrates and fats.
For example – Glucose → CO2, water and heat. Protein → amino acids
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