Chapter 6
Life Processes
Life Process
The basic essential activities performed by an organism to sustain life on earth is called as Life Process. There are seven important life processes which are common to all plants, birds, and animals, which includes: Growth, Movement, Respiration, Transportation, Excretion, Reproduction, and Nutrition.
Criteria For Life process
Growth– It is generally defined as an increase in the size, the number of cells, tissues and the whole organism. Growth is mainly classified into Primary and Secondary growth
Movement– All living organisms including animals and plants have the ability to move. Usually, animals move in search of food, shelter and to protect themselves from danger. Plants cannot move like animals, but they show some movements response to an environmental stimulus.
Respiration– All living organisms including animals and plants respire as they need energy to grow, move and repair the cells. Aerobic and Anaerobic are two types of respiration.
Excretion– It is the process of removing or eliminating metabolic waste from the body. Like animals and humans, plants do excretes during and transpiration process.
Reproduction- It is the biological process of giving birth to their young ones. There are two types of reproduction- Sexual and asexual reproduction. Every living organism on this planet earth reproduces for the continuity of the generations.
Nutrition– It is the process of taking in food and converting it into energy, which is used for growth and development. There are two types of nutrition – Autotrophic and Heterotrophic mode of nutrition.
Modes Of Nutrition
Nutrition In Plants
Plants are autotrophs
They prepare their own food
Nutrition In Animals
Animals are heterotrophs
They depend on plants or others
Autotrophic Nutrition
It is a kind of nutrition in which inorganic materials like CO2, water etc are utilized to prepare organic food by the process of photosynthesis. Example – Green plants
The organisms which carry out autotrophic nutrition are called autotrophs (green plants)
Autotrophs use simple inorganic material and convert it into complex high energy molecules(carbohydrates)
Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO2 and H2O and convert these into carbohydrates in the presence of chlorophyll, sunlight is called Photosynthesis.
Equation for photosynthesis:
6CO2 + 12H2O → C6H12O6 + 6 O2 + 6 H2O (In the presence of sunlight and chlorophyll)
Raw materials for Photosynthesis
Sunlight: It is an inorganic material
Chlorophyll: Sunlight is absorbed by chlorophyll
CO2: Enters through stomata and oxygen is released as a by-product through stomata on leaf
Water: water + dissolved minerals like nitrogen, phosphorus etc are taken up the roots of the soil
Site Of Photosynthesis
Some cells contain green pigments which are cell organelles called chloroplasts which contain chlorophyll.
Main Events Of Photosynthesis
Absorption of light energy by photosynthesis
Conversion of light energy into chemical energy + splitting (breaking) of water into hydrogen and oxygen
Reduction of carbon dioxide to carbohydrates
Stomata
Stomata are the tiny pores present on the surface of the leaves
Functions of Stomata
Exchange of gases O2/CO2
Loses a large amount of water (water vapour) during transpiration
Heterotrophic Nutrition
Kind of nutrition in which organisms do not possess the ability to synthesize their own food. They depend on autotrophs for their food supply directly or indirectly. Example – Animals, Fungi
Different modes under this category are as follows:
Holozoic Nutrition: Animals take in solid food and breakdown inside the body. Example – Amoeba, animals
Saprophytic Nutrition: Organisms feed on dead, decaying matter. Example – Fungi
Parasitic Nutrition: Parasites live inside or outside other organisms (host) and derive nutrition from it. Example – Cuscuta (plant parasites), Ticks etc
How do Organisms obtain their food?
Unicellular/Single-celled organisms – Food is taken up through the entire surface. Example – Amoeba, Paramecium
Process of intake of food by Amoeba:
Nutrition
Different organisms utilize different nutritional processes as it depends upon the source of carbon from where the food is taken.
Nutrition In Human Beings
The alimentary canal is basically a long tube extending from the mouth to the anus. Various regions are specialized to perform different functions
Human Digestive System
Mouth – intake of whole food
Teeth – Chewing/grinding of food
Tongue – Rolling of food + tasting of food + swallowing/pushing down the food
Salivary glands – secrete saliva + mucus (it is a sticky, gelatinous material that lines your lungs, throat, mouth, nose and sinuses) + starch is converted into glucose by saliva (Salivary amylase)
Oesophagus – Taking food from mouth to stomach by peristaltic movements (contraction and expansion of muscles of the oesophagus)
Stomach – Gastric glands present in the stomach secrete gastric juice
Small intestine – it is the site of the complete digestion of carbohydrates, proteins and fats
Walls of small intestine secrete intestinal enzyme which converts carbohydrates into glucose, fats in fatty acid + glycerol and proteins into amino acids
It has villi (finger projection) which help in the absorption of food into blood
It receives the secretions of the liver and pancreas
The food is acidic which is made alkaline for the pancreatic enzymes to act. The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats
Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules which increases the efficiency of enzyme action
Large intestine – it absorbs excess water and the rest of the material is eliminated from the body via the anus
Respiration In Human beings
Respiration involves:
Gaseous exchange (Breathing) – Intake of oxygen from the atmosphere and release of carbon dioxide
Cellular respiration – the breakdown of simple food in order to release energy inside the cell
Breakdown of Glucose by various Pathways:
The first step is the breakdown of glucose (a six-carbon molecule) into a three-carbon molecule called pyruvate which takes place in the cytoplasm
The pyruvate can be converted into ethanol and carbon dioxide which takes place in yeast during fermentation. Since the process occurs in the absence of air (oxygen), it is called anaerobic respiration
The pyruvate is broken down into a three-carbon pyruvate molecule in the presence of oxygen to give three molecules of carbon dioxide and water. This process takes place in mitochondria. Since this process takes place in the presence of oxygen, it is known as aerobic respiration
The pyruvate is converted into lactic acid when there is a lack of oxygen in our muscle cells, which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps.
The whole process of breakdown of glucose is shown below:
The energy released during cellular respiration is immediately used to synthesize a molecule called ATP which is used to fuel all other activities in the cell. In these processes, ATP is broken down giving rise to a fixed amount of energy which can derive the endothermic reactions taking place in the cell
The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms because the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air.
Types of Respiration
Aerobic respiration |
Anaerobic respiration |
Occurs in the presence of oxygen |
Occurs in the absence of oxygen |
Occurs in Mitochondria |
Occurs in Cytoplasm |
End products and water and carbon dioxide |
End products and lactic acid and alcohol |
More amount of energy is released |
Less amount of energy is released |
Human Respiratory System
Passage of air through the respiratory system:
Nostril – air is taken into the body
Nasal passage – it is a channel for airflow through the nose
Nasal cavity – it is lined with hair and mucous membrane. It warms, moisturizes and filters air before it reaches the lungs
Pharynx – it contains rings of cartilage which ensure that the air -passage does not collapse
Larynx – it houses the vocal cords and manipulates pitch and volume, which is essential for phonation. It is also known as the voice box
Trachea – Pharynx splits into the trachea and oesophagus. It connects the larynx (or voice box) to the bronchi of the lungs. It provides airflow to and from the lungs for respiration
Bronchi – They are the main passageway into the lungs. They are the extension of the windpipe that shuttles air to and from the lungs. The oxygen goes to the lungs and carbon dioxide leaves the lungs through them
Bronchioles – Bronchi get smaller when they reach closer to the lungs tissues and are called Bronchioles. They are the passageways by which air passes through the nose or mouth to the alveoli of the lungs
Alveoli – they are smaller tubes which finally terminate in balloon-like structures which are called alveoli. They allow carbon dioxide and oxygen to move between the lungs and the bloodstream
Blood capillaries – They are the sites of transfer of oxygen and other nutrients from the bloodstream to other tissues in the body. They also collect carbon dioxide and waste materials and return them to the veins.
Mechanism of Breathing
Inhalation |
Exhalation |
During inhalation, the thoracic cavity expands |
Thoracic cavity contracts |
Ribs lift up |
Ribs move downwards |
Diaphragm become flat in shape |
The diaphragm becomes dome shaped |
Volume of lungs increases and air enters the lungs |
Volume of lungs decreases and air exits from the lungs |
Exchange of gases between alveoli, blood and tissues
Oxygen-rich air reaches blood which combines with haemoglobin in RBC and oxygen is released in alveoli tissues (through blood vessels)
Carbon dioxide is released in the blood and dissolves into it and carried by blood vessels. The carbon dioxide is released in alveolar sacs which is sent out through nostrils
Terrestrial organisms – use atmospheric oxygen for respiration
Aquatic organisms – use dissolved oxygen for respiration
Respiration In Plants
Respiration in Plants is simpler than respiration in animals. Gaseous exchange occurs through:
Stomata in leaves
Lenticels in stem
General surface of the root
Transportation in Human beings
Human beings like other multicellular organisms need regular supply of food, oxygen etc. This function is performed by the circulatory system.
The circulatory system is human beings consists of:
Heart (pumping organ)
Arteries and veins (blood vessels)
Blood and lymph (circulatory medium)
Circulatory system in Human Beings
The lungs supply oxygen-rich blood to the left atrium of the heart
The left atrium relaxes when it is collecting the blood and contracts when blood is transferred to the left ventricle. The left ventricle expands when it receives blood
The blood is pumped out of the body when the muscles of the left ventricle contracts
Deoxygenated blood comes from the body to the upper chamber on the right i.e., the right atrium when it expands
The corresponding lower chamber i.e., the right ventricle expands when right atrium contracts. It transfers the blood to the right ventricle which in turn pumps it to the lungs for oxygenation
Right ventricles have thicker muscular walls so that they pump blood into various organs
Valves ensure that blood does not flow backwards when the atria or ventricles contract
Blood circulation in the Human Body
Double Circulation: Blood travels twice through the heart in one complete cycle of the body
Direction of blood flow through Human Heart
Pulmonary Circulation – Blood moves from the heart to the lungs and back to the heart
Systemic Circulation – Blood moves from the heart to the rest of the body and back to the heart
Blood
Blood is a connective tissue which is fluid in nature. The solid components of Blood(Blood corpuscles) are:
RBC(Red Blood Cells) – It carries oxygen and carbon dioxide and also contains Haemoglobin which imparts red colour to the blood
WBC(White Blood Cells) – It provides body defence by engulfing the germs and produces antibodies
Blood Platelets – During any injury, it helps in blood clotting
Liquid components (Plasma) – It is a yellow coloured fluid which is 90% water and 10% organic substances
Lymph
It is a yellowish fluid which escapes from the blood capillaries into the intercellular spaces
It contains less proteins than blood
It flows from tissues to the heart which helps in transportation and destroying germs
It carries digested and absorbed fat from intestine and drains excess fluid from extracellular space back into the blood
Types of Blood vessels
There are two types of blood vessels
Arteries
Veins
Arteries |
Veins |
Carry oxygenated blood from the heart to the body parts except pulmonary artery |
Carry deoxygenated blood from body parts to heart except pulmonary vein |
Also called distributing vessel |
Also called collecting vessel |
Thick and elastic |
Thin and less elastic |
Deep Seated (far from the skin) |
Superficial (near the skin) as compared to arteries |
Transportation in Plants
Plants take in carbon dioxide and photosynthesis energy stored in their chlorophyll-containing structures, the leaves
For plants, soil is the richest and the nearest source of raw materials such as nitrogen, phosphorous and other minerals, the absorption of which occurs through roots
The plant transport systems move energy stores from leaves and raw materials from roots. Both of these pathways are constructed independently through different conducting tubes
Xylem moves water and minerals obtained from soil whereas phloem transports the products of photosynthesis from leaves to other plant parts
Transport of water
Vessels, tracheids of roots, stems and leaves of the xylem tissue are interconnected forming a continuous system of water-conducting channels reaching all plant parts
Water moves into the root from the soil as a result of a difference created in the concentration of ions between the soil and the root. Thereby a steady movement of water is created into the root xylem, pushed upwards steadily
When there is an adequate amount of water supply, water lost through stomata is replaced by water from the xylem vessels in the leaf
Evaporation of water molecules from leaf cells creates a suction, pulling water from xylem cells of the roots. Transpiration is the process wherein water is lost in the form of vapour from the aerial parts of the plant
Advantages of Transpiration:
Helps in the absorption and the upward movement of water and minerals dissolved in it from roots to leaves
Helps in temperature regulation
Acts as a major driving force during the daytime, as transpirational pull helps in the movement of water in the xylem
Transport of food and other substances
Translocation occurs in the vascular tissue, phloem where apart from the transport of products of photosynthesis, it also transports amino acids and other substances which are specially delivered to the storage organs of fruits, roots and seeds and even to the growing organs
Translocation of food and other substances occurs in the sieve tubes with the aid of adjacent companion cells in both the directions
Translocation in phloem can be achieved by utilizing energy derived from ATP, for instance, transfer of sucrose into the phloem tissue
Excretion System in Human Beings
Excretory/urinary system consists of:
The Kidneys – The excretory organ
The ureters – The ducts which drain out urine from the kidneys
The urinary bladder – The urinary reservoir
The urethra – The channel to the exterior
Excretion
The metabolic activities in the body generates many kinds of wastes including nitrogenous wastes which are harmful for the body and hence needed to be removed. Excretion is a process by which these wastes are moved from our body. The unicellular entities remove these wastes by simple diffusion
Excretory wastes
Formation of Urine in Human Beings
Each kidney contains many filtration units called nephrons.
Nephrons are made up of a cluster of thin walled capillaries called glomerulus which is associated with a cup like structure called Bowman's capsule and the long tube which terminated through this capsule
The renal artery brings oxygenated blood to the kidneys along with the nitrogenous wastes like urea and uric acid and many other substances
The blood gets filtered through the glomerulus and this filtrate enters the tubular part of nephron
As this filtrate moves down the tubular part, glucose, amino acids, salts and excess water gets selectively reabsorbed by the blood vessels surrounding these tubules
The amount of water reabsorbed depends upon
How much excess of water is there in the body and
How much nitrogenous wastes need to be excreted out
So the fluid now flowing in the tubular part is urine which gets collected in collecting ducts of nephrons
These collecting ducts together leave the kidney at a common point by forming the ureter
Each ureter drains the urine in the urinary bladder where it is stored until the pressure of the expanded bladder leads to an urge to pass it out through urethra
This bladder is a muscular structure which is under nervous control
180 litres of filtrate is formed daily but only 2 litres is excreted out as urine so the rest is reabsorbed in the body
Structure of Nephron
Functions of Nephron
Excretion of nitrogenous wastes
To maintain the water and ionic balance(osmic regulation)
Artificial Kidney
Haemodialysis – The process of purifying blood by an artificial kidney. It is meant for kidney failure patients.
Excretion in Plants
Plants use different strategies for excretion of different products:
Oxygen and carbon dioxide is diffused through stomata
Excess water is removed by transpiration
Plants can also lose some of their old parts like old leaves and bark of trees
Other waste products like raisins and gums especially in old xylem cells which can also be lost by plants
Plants also secrete some waste substances into the soil around them