8th Std Science Solution in English | Lesson.18 Organisation of Life

Lesson 18. Organisation of Life

Lesson 18. Organisation of Life 

I. Fill in the blanks:

1. ______________ is the structural and functional unit of living organisms.

Ans : Cell

2. The largest cell is egg of an ______________.

Ans : Ostrich

3. ______________ is a good example for anaerobic respiration.

Ans : Fermentation

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 : Microns

II.Choose the correct answers:

1. —————- is tough and thick white sheath that protect the inner parts of the eye.

1. sclera
2. conjunctiva
3. cornea
4. iris

Ans : sclera

2. Maintenance of constant internal environment of the body is known as _________

1. Homeostasis
2. Homeophytes
3. Homeokinesis
4. Homeophilics

Ans : Homeostasis

3. In the absence of oxygen, glucose is broken down in to ______________

1. Lactic acid
2. Citric acid
3. Acetic acid
4. Nitric acid

Ans : Lactic acid

4. ______________ cells are specialised cells that can be transformed into any kind of cells.

1. Nerve
2. Stem
3. Heart
4. Bone

Ans : Stem

5. The process of air passing in and out the lungs is called ______________.

1. Inhalation
2. Exhalation
3. Breathing
4. None of these

Ans : Breathing

6. Osmosis is the movement of water molecules from a ______________

1. Higher concentration to a region of lower concentration.
2. Lower concentration to a region of higher concentration.
3. Both of these
4. None of these

Ans : 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.

1. Hypotonic
2. Hypertonic
3. Neutral
4. Acidic

Ans : Hypertonic

III True of False

1. In hypotonic condition, concentration of the external and the internal solution of the organism are same .

Ans : False

Cu. st. : 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

Cu. st. : 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 .

Ans : True

5. Aqueous humour plays an important role in maintaining the shape of the eye

Ans : False

Cu. st. : Vitreous humour plays an important role in maintaining the shape of the eye

IV. Match the following

I Match the following examples for catabolism.

II. Match the following examples for anabolism:

V. Arrange the following words in correct sequence.

Tissues, organ system, organism, cell, organ

Ans : cell → tissues → organ → organ system → organism

VI. Answer the following questions shortly

1. What is cell differentiation?

• Our body develops from a single cell called zygote.
• The zygote undergoes mitotic division to form many cells of different shape, size and content.
• These cells attain change in structure and function which is called differentiation. This form the foetus.

2. State different types of tissues.

Depending on the basis of their structure and function, tissues can be classified into four types.

• Epithelial (covering) tissue for protection.
• Muscular (contractile) tissue for movements and locomotion.
• Connective (supporting) tissue for binding different structures of body.
• Nervous tissue for conduction of nerve impulses.

3. Mention the function of ‘Alveoli’?

• Alveoli are tiny air sacs in the lungs.
• They are the workhouses of the respiratory system.
• The exchange of oxygen and carbon dioxide take place in alveoli of the lungs.

4. Name the processes by which air enters and comes out of our lungs?

• The process of taxing air into the lungs is called inspiration or inhalation.
• The process of expelling air from the lungs is called expiration or exhalation.

5. Differentiate between Osmoconformers and Osmoregulators?

There are two major types of Osmoregulation:

Osmoconformers:

These organisms try to maintain the osmolality of their body matching with their surroundings. Most of the invertebrates, marine organisms are osmoconformers.

Osmoregulators:

These organisms maintain their internal osmolality, which can be extremely different from that of the surrounding environment, through physiological processes.

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).

VII. Answer in briefly:

1. Define Prokaryotic cell?

Organisms in which no true nucleus is seen are called prokaryotic. Ex : Bacteria.

2. Tabulate the difference between aerobic and an 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.

• The iris of the eye controls the size of the pupil depending on the amount of light entering it.
• The pupil is like the eyehole of a camera which allows light to come in.
• Lens : It is a transparent, biconvex, and an adjustable part of an eye, made up of protein. The lens with the help of the cornea refracts light focused on the retina, therefore creating images on it.
• The retina consists of photoreceptors and converts light rays into impulses to be sent to the brain. It is light sensitive. The retina is compared to the film in a camera.

4. Which organ and organ system help to maintain homeostasis?

• Homeostasis is a property of a human biological system where the self –regulating process tends to maintain the balance for the survival.
• Behavioural and physiological responses are two important regulating mechanisms that maintain the stability of homeostasis.
• All the processes of integration and co – ordination of function are mediated by nervous and hormonal system.
• The liver, kidneys, and brain (hypothalamus), autonomic nervous system and the endocrine system help to maintain homeostasis.

VIII. Answer in detail

1. Draw the V.S 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 cells is dependent on the concentration of the solution surrounding it.

There are 3 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).

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.

For example,

• Glucose → Glycogen and other sugars
• Amino acids → Enzymes, hormones and proteins

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.

• Carbohydrates → Glucose
• Glucose → CO₂, Water and heat

5. Explain the mechanism of breathing.

• 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 the pressure decreases.
• The air outside the body flows into the lungs. Here exchange of gases takes place between the air and the blood.
• 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 intercostal 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.

பயனுள்ள பக்கங்கள்

• 9th Standard All Books – Download

• 8th Standard All Books – Download

• Lesson 7 (Plant Kingdom) Answers – More Info