LIFE PROCESSES [Class 10]

 

LIFE PROCESSES

 Life Processes – The important processes carried out by the living organism to maintain and sustain life are called ‘Life Processes’.

Eg. Nutrition, Respiration, transportation, Excretion

 

Unicellular Organisms	Multicellular Organisms
In unicellular organisms entire body is in contact with the environment. Therefore the exchange of gases and other substances takes place across the cell membrane by the way of simple Diffusion.	In Multicellular all the cells are not in direct contact with the environment. So, simple diffusion doesn’t meet the requirement of the cells. We have specialised tissues and organs for different life processes.

 NUTRITION

The process of obtaining, consuming and utilizing food by the living organism is defined as Nutrition. 

Autotrophs	Heterotrophs
The organisms which prepare their own food using simple inorganic substances like carbon dioxide and water are called as Autotrophs. Eg. Green plants	The organisms which cannot prepare their own food and depend either directly or indirectly on Autotrophs to obtain complex organic substances for nutrition are called as Heterotrophs. Eg. Animals

 AUTOTROPHIC NUTRITION

Photosynthesis – This is the process in which plants prepare their food using carbon dioxide and water in presence of sunlight and chlorophyll and is converted to carbohydrates.

6CO₂  +  12H₂O  ------------------------à C₆H₁₂O₆  +  6O₂  +  6H₂O

Steps

1.              Light energy is absorbed by the chlorophyll
2.              Light energy is converted to Chemical energy
3.              Water molecule splits into hydrogen and oxygen
4.              Carbon dioxide is reduced to carbohydrates

•         Chlorophyll helps to capture the light energy
•         Carbon dioxide enters the leaf through small openings called ‘Stomata’
•         The opening and closing of stomata is controlled by the guard cells.

HETEROTROPHIC NUTRITION

In this mode of nutrition organism obtain the food the outside source.

·         In amoeba food is captured at any point along the cell membrane (pseudopodia)

·         In paramecium food enter the body through one fixed point at cell membrane.

·         Saprophytes – Organisms obtain food from dead and decaying matter. Eg. fungi

·         Parasites – Organisms depends on the host for the nutrition. Eg. Leech, worms

Holozoic nutrition – In this the whole food consumed is broken down and digested with the help of enzymes. Eg. Human beings

 Digestion in human beings takes place along the alimentary canal. (Mouth, oesophagus, food pipe, stomach, duodenum, small intestine, large intestine, anus)

 Enzymes – These are different catalyst which helps to convert the convert the complex food molecules to the simple absorbable form.

 Steps in digestion

1)      Mouth – In mouth teeth break the food in smaller particles. Saliva secreted by salivary glands mixes with the food and makes it soft. This soft ball called ‘Bolus’ is pushed towards the oesophagus.

Epiglottis, a cartilaginous flap closes the pharynx (wind pipe) while the food passes through oesophagus.

Salivary gland à amylase à starch to maltose

 

2)      Stomach – stomach expands when food enters into it. Gastric glands present in the inner lining of stomach secrets few digestive enzymes and helps in further digestion of food.

    Hydrochloric acid à destroys microbes

    Mucus à protects the inner lining of the stomach from the action of acid.

    Pepsin à Proteins to polypeptides (chain of amino acids)

    Rennin àMilk proteins to curd

In stomach the food is converted to semi liquid form called as ‘Chyme’.

Food is passed to the small intestine in small amounts. This is regulated by the “Sphincter Muscles”.

3)      Duodenum – This is the beginning part the small intestine. In this portion the Bile Juice from the Liver and Pancreatic Juice from the Pancreas add to the food.

Bile juice à Emulsify the fats

Pancreatic juice                      trypsin -  digests proteins

                                                Lipase - fats to simple fats

 

4)      Small Intestine – This is the longest part of alimentary canal. It is fitted in a compact space in coiled manner.

Walls of small intestine secrets intestinal juice, which contains different enzymes that helps in final digestion of food.

    Proteins - Amino Acids

    Carbohydrates - glucose

    Fats - Fatty acids and glycerol

The walls of small intestine have numerous finger like projections called “Villi”. This increases the surface area for absorption of digested food. Villi are rich in blood vessels and absorb the digested food. This is carried to every cell of the body and utilized for obtaining energy, building new tissues and repair of old tissues.

 

5)      Large Intestine – The remaining food material passes to the large intestine. The Villi here absorbs the water.

 6)      Anus – This is the exit of the alimentary canal. The rest of the material is thrown off the body through anus. This exit is controlled by Anal Sphincter.

          Peristalsis – This is the contraction and relaxation movement of the muscles of the entire alimentary canal. This helps the food to move forward in the digestive track.

 

RESPIRATION

This is the process in which the organic molecules are stepwise oxidised to release energy.

Glucose molecule (6 carbon atoms) breaks to form three-carbon molecule called Pyruvate.

 Types of respiration

Aerobic respiration	Anaerobic Respiration
1) This takes place in presence of oxygen 2) Pyruvate breaks to carbon dioxide and water.   3) Large amount of energy is released 4) This takes place in higher organisms. Human beings	1) This takes place in absence of oxygen. 2) Pyruvate is converted to Ethanol and carbon dioxide. This takes place during fermentation. 3)  Small amount of energy is released 4)  This takes place in lower organisms. Yeast, bacteria

 

     Sometimes, in our muscles cells, due to the lack of oxygen, the Pyruvate molecules break to form Lactic acid. This activity causes cramps in muscles.

The energy released in cellular respiration is used to synthesize ATP molecule.

This serves as a fuel for other cellular activities.

 

Plants – In plants exchange of gases take place by diffusion.

During day time, CO₂ released during respiration is utilized for photosynthesis and O₂ is released. Therefore oxygen release is the major event.

At night, there is no photosynthesis and so CO₂ elimination is major event.

 Aquatic organisms use dissolved oxygen for respiration. As the amount of dissolved oxygen is comparatively low the rate of breathing is faster in aquatic organisms.

Gills are the respiratory organs of fish.

 Respiration in Human Beings

·         Respiratory system includes nose, pharynx, trachea, bronchi, bronchioles, alveoli and lungs.

·         Air enters the respiratory system through nostrils. Fines hairs and mucous in the nostrils filters the air. The air becomes moist and warm according to the body temperature

·         The air passes through the throat, trachea and then to the bronchi which leads to each lung. The ‘C’ shaped cartilaginous rings keeps the trachea open, prevents it from collapsing, and this ensures the continuous flow of air.

·         The bronchi are further branched in to bronchioles and terminate with the balloon like structures called ‘Alveoli’. Alveoli contain the networks of capillaries. This increases the surface area for the exchange of gases.

·         The Haemoglobin, a pigment present in RBC take up the oxygen and carry it to the tissues all over the body.

·         Carbon dioxide is transported in the dissolved form in our blood.

 

TRANSPORTATION

Transport system in man

1.      Blood

2.      Blood vessels

3.      Heart

 

1)      Blood – Blood is the fluid connective tissue which carries essential gases and other required materials to each and every cell of the body.  This consists of

·         Plasma

·         Red Blood Corpuscles

·         White Blood Corpuscles

·         Platelets

 

2)      Blood vessels – Arteries, Veins and Capillaries

·         Arteries are blood vessels which carries oxygenated blood from heart to different parts of the body. Blood emerges from the heart under high pressure. Therefore, arteries have thick and elastic walls.

·         Veins – Veins carry de-oxygenated blood from different parts to the body to the heart. Veins do not need thick walls as the blood is no longer under pressure.

Valves are present in veins to ensure the flow of the blood only in one direction.

·         Capillaries – These are very thin blood vessels (one celled thick) which help in exchange of material between cells and blood.

 

3)      Heart

 

Size – Fist size                       

Shape – Conical

Position – Obliquely placed little towards left in the thoracic cavity between the lungs.

The Heart has four chambers – upper chambers ‘Atrium’ and lower chambers ‘Ventricles’

 

The pressure required to maintain the flow of the blood is created by contraction and relaxation of the muscles. Atriums and ventricles contracts and relax simultaneously.

  

Action	Change in Right Side	Change in left side
Atriums Relax (Ventricles Contract)	De-oxygenated blood from all parts of the body flows to right Atrium. (through superior and inferior venacave)	Oxygenated blood from lungs comes to left Atrium (through pulmonary vein)
Atriums Contract (Ventricles relax)	De-oxygenated blood from right Atrium flows to Right Ventricle. (through tricuspid valve)	Oxygenated blood from left Atrium flows to left Ventricle. (through bicuspid valve)
Ventricles Contract	De-oxygenated blood from right Ventricle goes to lungs (through pulmonary artery)	Oxygenated blood from left Ventricle goes out of heart through Aorta.

Important Terms

·         Pericardium – This is the double layered muscular sac in which heart is placed.

·         Pericardial Fluid – This is the fluid present between the layers of Pericardium.

       This protects the heart from mechanical shocks and friction.

·         Atriums – Upper chambers of heart

·         Ventricles – Lower chambers of heart

·         Septum – Muscular layer that separates the right and left portion of heart.

       This is useful to prevent mixing of oxygenated and de-oxygenated blood.

·         Tricuspid Valve – This is the valve present between right Atrium and right Ventricle.

·         Bicuspid Valve – This is the valve present between left Atrium and left Ventricle.

     (Valves prevents the backward flow of the blood)

·         Coronary Artery – This is the artery that supplies oxygenated blood to the muscles of heart.

·         Coronary Sinus – This is the vein which carries deoxygenated blood from the muscles of heart to the right Atrium.

·         Semi lunar valves – These are the valves present at the beginning of the arteries to prevent the backward flow of the blood.

·         Systole – Contraction of heart muscles

·         Diastole – Relaxation of heart muscles

·         Heart Beat – One Systole + One Diastole = One Heart Beat

·         Stethoscope – Instrument used to measure heart beat. (72 beats/minute)

·         Sphygmomanometer – Instrument used to measure blood pressure.

(80/120 mm Hg)

·         Blood Pressure – The force that blood exerts against the wall of the blood vessel is called as ‘Blood Pressure’.

·         Pulse – Relaxation and Contraction of the artery forms a wave like movement called ‘Pulse’.

Double Circulation

(Blood goes to the heart twice during each cycle)

1)      Pulmonary Circulation – Circulation of blood from heart to lungs and lungs to heart.

2)      Systematic Circulation – Circulation of blood from heart to tissues of body and body        to heart.

·         Significance – This keeps oxygenated blood separate from the de-oxygenated blood.

 Amphibians and Reptiles have three-chambered heart. They can tolerate mixing of oxygenated and de-oxygenated blood as their energy requirement is less compared to that of mammals.

Fishes have two chambered heart. Blood is pumped towards gills and from Gills the oxygenated blood is directly supplied to the body of the fish.

 Platelets – Platelets initiates blood clotting. If there is leakage in any blood vessels these platelets helps to plug these leaks.

 Lymph – Some of the plasma, proteins and blood cells escape through the pores of the blood vessels into the intercellular spaces of the tissues. This colourless fluid is called as Tissue fluid or lymph.

 Transportation in Plants

Two conducting tissues of plants – Xylem and Phloem

·         Xylem conducts water and mineral salts from soil to the leaves.

·         Phloem conducts the products of photosynthesis to the other parts of the plant.

This is called as Translocation.

The food is mostly stored in roots, fruits and seeds.

Transpiration – The loss of water molecules in the form of vapour from the aerial parts is known as ‘Transpiration’. This is fast during the day time as the stomata are open for exchange of gases.

This helps for the absorption of water and mineral salts from roots to leaves.

This also helps for the temperature regulation.

 

EXCRETION

The process by which the metabolic wastes are eliminated from the body is called as ‘Excretion’.

 Excretion in Human Beings

This includes a pair of Kidneys, a pair of Ureters, Urinary Bladder and Urethra.

 Kidney

Position – located at the back of abdominal cavity one on the either side of the backbone

Hilum – depression point at each kidney

Renal capsule – tough connective tissue capsules covering kidneys.

Nephron – structural and functional unit of kidneys

Bowman’s capsule – cup shaped structure at the beginning of nephron

Glomerulus – network of capillaries formed in the Bowman’s capsule.

 Urine formation

·         Blood vessel entering the Bowman’s capsule breaks into tough network of capillaries called ‘Glomerulus’.

·         The pressure created enables the filtration of the blood. This filtrate contains nitrogenous wastes, sodium and potassium bicarbonates along with water, glucose, vitamins and amino acids. This passes to the Henle’s loop.

·         Surrounding capillaries absorb the essential nutrients from the filtrate.

·         Lastly, potassium, ammonium salts, hydrogen ions and uric acid is secreted in the filtrate. This combines with the urea, nitrogenous wastes and excess of salts and forms urine.

·         The urine formed in the kidneys passes through the ‘Ureters’ and finally is collected in the ‘Urinary bladder’.

·         The pressure of the expanded bladder leads to the urge to pass out the urine through ‘Urethra’.

 Excretion in plants

Oxygen is given out as the bi-product of photosynthesis.

Excess of water is given out by the way of ‘Transpiration’.

There’s no specialised tissue for excretion.

Excretory wastes are stored in some of the parts like roots, barks and leaves. Later the plants get rid of these parts naturally.

In some cases it is stored as resins and gums.