Organization Of Life Online Test 8th Science Lesson 8 Questions in English

Explanation

There are animals like amoeba which cannot be seen by our naked eye. There are animals like blue whale and elephants which are of huge size. The variations are not only seen size but also in the complexity of their, cells, tissues of the body structure. This is called organization of life.

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The biological organization are arranged from cellular level to organism level. It goes like tissue, organ, organ system and organisms.

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Each of this represents a level of organization and hierarchy. This organizations are of two levels, they are lower levels and higher levels of organism.

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Cell is the smallest structural and functional unit of living organisms and it is capable of performing specific function. It is also called the building blocks of life.

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Single-celled organisms like Amoeba are able to carry out all the processes of life, like higher organisms. The body of Amoeba looks like a single cell, while higher animals are made up of billions of cells. Bacteria, yeasts and Amoeba have a single cell body and are called as unicellular organisms.

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Organisms such as human beings, cows and trees are made of a large number of cells and are called multicellular organisms. Thus, the body has different levels of organisation. Cells make up tissues, tissues make up organs, and organs make up organ systems.

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Based on the structural organization, organism can be classified into prokaryotes and eukaryotes. In some of the organism like bacteria, cyanobacteria and mycoplasma, no true nucleus is seen. These organisms are called prokaryotes

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In the cells of amoeba, animals and plants, a well-defined nucleus, covered by membrane is seen. These organisms are called eukaryotes. Bacteria does not have true nucleus

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The biological organization shows the hierarchy in organization levels from simplest to more complex: atoms, to molecules, cells, tissues, organs, organ systems, organisms. Though atoms and molecules make up the cells, they are considered as non-living.

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The biological organization shows atoms, to molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem and finally biosphere. Whereas population, community, ecosystem and biosphere are of ecological importance.

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A white material surrounds the yellow part of the egg. White material is albumin which solidifies on boiling. The yellow part is yolk. It is a part of the single cell.

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Cell is the structural and functional unit of life. Cells are often called as “building blocks of life”. The study of cells is called cell biology.

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Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such
as proteins and nucleic acids.

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Cells vary widely in shape and size. There is a central spherical nucleus and a variety of cytoplasmic living cell organelles like the endoplasmic reticulum, mitochondria. Golgi-bodies, centrioles, ribosomes, lysosomes, etc., present in an animal cell.

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The size of cells varies in different animals which are measured in units of micron (µm). (1cm =10 mm: 1 mm = 1000 microns.)

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The average cell size varies from 0.5 to 20 µm in diameter. The cells of bacteria are the smallest in size (1-2 µm). In human body, the smallest cell is RBC (7 µm in diameter), the longest one is the nerve cell which reaches a length of about 90 -100 cm and the human egg (ovum) is 100 µm in size.

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Among multicellular animals, the largest cell is, egg of an ostrich. It measures about 170 mm × 180mm in diameter. It is about 25,000 times bigger than a red blood cell. Mycoplasma with a diameter of 0.0001 mm is the smallest bacterium.

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A stem cell is essentially a ‘blank’ cell, capable of becoming another more differentiated cell type in the body, such as a skin cell, a muscle cell, or a nerve cell. They are microscopic in size

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Stem cells can be used to replace or even heal the damaged tissues in the body. They can serve as a built-in repair system for the human body, replenishing other cells as long as a person is still alive.

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Cells are of different shapes. Normally they are correlated with their functions. Some cells are oval or round, while certain others are elongated.

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Cells are sometimes quite long. Some are branched like the nerve cell or a neuron. Some of our WBC cells are Amoeba like with irregular boundaries.

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Our body is developed from a single cell called zygote. The 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.

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Tissues are groups of cells that have a similar structure and act together to perform a specific function. They are of two type’s simple and complex tissues.

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Simple tissues are made up of cells of same type or kind e.g. glandular tissue and complex tissues are made up of different kind of tissues e.g. tissues of dry skin. Hence, simple tissue is homogeneous and complex tissue is heterogeneous.

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Depending on the basis of their structure and function, tissues can be classified into four types – Epithelial, Muscular, Connective, Nervous tissue.

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

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Organs are structures made up of two or more types of tissues, organized to carry out a particular function. Example: Brain, heart, lungs, kidney, liver etc., each of which has specific functions. Most organs are made of all four types of tissue. 

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The intestine, for example, is made of epithelial tissue as the inner lining, which helps in enzyme secretion and nutrient absorption.

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Epithelial tissue is covered by layers of muscle tissue, which help in peristaltic movements to move the food.

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The intestine is also supplied by blood tissue (connective tissue) which helps in transporting nutrients absorbed by the intestine, and is connected to the brain through the nerve tissue, which conveys instructions from the brain.

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The eye is one of the important sensory organs in the human body. It is composed of muscular tissue, connective tissue, neural tissue and mainly responsible for vision, differentiation of colour.

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The human eye can differentiate approximately 10 – 12 million colours and maintaining the biological clock of the human body.

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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.

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The human eyes are the most complicated sense organ in the human body, with several parts fixed together form a spherical structure. Every part of the human eye is mainly responsible for a certain action. The structure of a human eye can be broadly classified into the external structure and internal structure.

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Sclera is a tough and thick white sheath that protects the inner parts of the eye. We know it as the ‘White of the eye’.

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Conjunctiva is a thin transparent membrane that is spread across the sclera. It keeps the eyes moist and clear by secreting small amounts of mucus and tears.

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Cornea is the transparent layer of membrane that is spread over the pupil and the iris. The main role of the cornea is to refract the light that enters the eyes.

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Iris is a pigmented layer of tissues that make up the coloured portion of the eye. Its primary function is to control the size of the pupil, depending on the amount of light entering it.

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Pupil is the small opening located at the middle of the Iris. It allows light to come in. Iris primary function is to control the size of the pupil.

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Lens 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.

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Retina is the layer present at the back of the eye where all the images are formed. It is the third and inner most coat of the eye.

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Retina is the third and inner most coat of the eye which is very sensitive to light because of the presence of Photoreceptors (rods and cone cells)

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The retina functions by converting the light rays into impulses and sending the signals to the brain through the optic nerve.

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Optic nerve is located at the end of the eyes, behind the retina. The optic nerve is mainly responsible for carrying all the nerve impulses from the photoreceptors to the human brain, without which vision would not be possible.

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Aqueous Humour is a watery fluid that is present in the area between the lens and the cornea. It is responsible for the nourishment of both the lens and the cornea

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Vitreous Humour is a semi-solid, transparent, jelly-like substance. that covers the interior portion of the eyes. It plays an important role in maintaining the shape of the eye and also causes refraction of light before it reaches the retina.

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A group of organs form the organ system, and together they perform a particular function. The heart and the blood vessels together make the cardiovascular system.

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Organs such as nose, pharynx, trachea, lungs and diaphragm work together as the respiratory system.

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Other examples of organ system include the endocrine system, integumentary system, muscular system, reproductive system, skeletal system, urinary system, immune system, etc. Stomach is an organ.

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Our respiratory system consists of organs like trachea, bronchus and lungs which are responsible for exchange of air between the atmosphere and the blood. Together, these organ form what is called the respiratory tract.

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We inhale air through the nostrils, which lead to the nasal cavity. The inner surface of this cavity is lined with cilia and mucus producing cells, which make it sticky and moist.

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The cilia and mucus trap dust and germs and prevent them from going deeper into the respiratory tract. The blood vessels in the nose help to warm the inhaled air.

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After passing through the nasal cavity, the air enters the pharynx. Then it goes into the trachea or the windpipe which is an elastic tube extending down the length of the neck and partly into the chest cavity

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Between the pharynx and the trachea lies a small air passage called the larynx commonly known as the “voice box”. The larynx has fold of tissue which vibrate with the passage of air to produce sound.

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The trachea divides into two branches called bronchi (singular: bronchus). Each bronchus leads to a lung, where it divides and redivides to finally form air passages called bronchioles.

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The lungs are organs in the chest cavity that allow our body to take in oxygen from the air. They also help to remove carbon dioxide from the body. The lungs lie on either side of the breast bone and fill the inside of the chest cavity.

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The left lung is slightly smaller than the right lung to allow room for the heart. Within the lungs, each bronchiole leads to a bunch of air sacs called alveoli (singular: alveolus).

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The lungs are two spongy elastic bags, on each side of the thoracic cavity. The thoracic cavity is bound dorsally by the vertebral column and ventrally by the sternum, laterally by the ribs and on the lower side by the dome shaped diaphragm.

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Alveoli are tiny air sacs in the lungs that take up the oxygen we breathe in and keep your body going. Although they are microscopic, alveoli are the workhorses of your respiratory system

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You have about 480 million alveoli, located at the end of bronchial tubes. The total area of the air- sacs in the lungs above 2000 square feet or more than one hundred times the body’s surface area. Alveoli, is meant for the exchange of oxygen and carbon dioxide.

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On an average, an adult human being at rest breathes in and out 15 – 18 times in a minute. During heavy exercise, the breathing rate can increase up to 25 times per minute.

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

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During inspiration, the sternum is pushed up and outward and the diaphragm is pulled down. Here exchange of gases takes place between the air and the blood

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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.

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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.

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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.

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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 tissue in the body.

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Homeostasis is a property of a human biological system where the self-regulating process tends to maintain the balance for the survival. The regulation takes place in a defined internal environment. Mammals are capable of maintaining a constant body temperature despite the changes in the external temperature. Behavioural and physiological responses are two important regulating mechanisms that maintain the stability of Homeostasis.

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In simple terms, it could be referred as a balance in a system to maintain a stable internal environment for the survival of the animal. If the homeostasis regulates successfully, life continues or if unsuccessful, death or disaster occurs.

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All the processes of integration and coordination 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

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When the body temperature raises sweat is produced to bring the temperature down. When the body temperature lower heat is produced by the muscular work by shivering. This is an example for homeostasis. The control of blood glucose level is another example in which insulin hormone is secreted whenever the blood glucose level raises and glucagon hormone is secreted whenever the blood glucose level reduces.

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Maintenance of body fluid concentrations, body temperature are done by various bio- physical and bio-chemical methods. Human beings are warm blooded in nature i.e. they maintain their body temperature as constant.

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Diffusion is the movement of particles from an area of higher concentration to lower concentration. The overall effect is to equalize concentration throughout the medium

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The movement of molecules (ions) from a region of higher concentration to lower concentration is called diffusion. E.g. You can smell incense stick after lighting because the smoke diffuses in the air and makes its way to your nose.

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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.

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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.

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 Isotonic: Here the concentration of external and internal solution of the organism are the same.

 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

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The term osmoregulation was coined by HOBER in 1902. It ensures that the fluids in the body do not get too diluted or concentrated.

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Osmoregulation is the process by which an organism regulates the water balance in its body and maintains the homeostasis of the body. It includes controlling excess water loss or gain and maintaining the fluid balance and the osmotic concentration, that is, the concentration of electrolytes.

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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.

Explanation

Cellular respiration is the process by which organisms break down glucose into a form that the cell can use as energy. This energy is then made available to living cells in the form of ATP. Cellular respiration takes place in the cytoplasm and mitochondria of the cells. The Cellular respiration is classified into two types: aerobic respiration and anaerobic respiration.

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In this type of respiration, the food substances are completely oxidized into H2O and CO2 with the release of energy. It requires atmospheric oxygen and all higher organisms respire aerobicdy.

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In Anaerobic respiration, partial oxidation of food takes place and the organisms release energy in the absence of oxygen. This type of respiration occurs in organisms like yeast. Ethyl alcohol and carbon dioxide are the by-products of this process.

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Aerobic respiration releases 19 times more energy than anaerobic respiration from the same amount of glucose. In aerobic respiration each glucose molecules produce 36 ATPs.

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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.

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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. As complex chemical units are broken down into more simple substances, the waste products released in the process of catabolism are removed from the body through the skin, kidneys, lungs, and intestines.

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The repeated anabolism and catabolism reactions maintain the homeostatic condition in the organism. The metabolic process is the cause for maintaining ionic balance in the body. It is also responsible for movement, growth, development, maintenance and repair of the cells, tissues and the human body. These metabolic reactions occur in different organs of living species.

Explanation

Basal metabolism refers to the minimum energy required to maintain the normal activities of the body during complete rest in a warm atmosphere 12 – 18 hours after the intake of food.