CHAPTER 6 :
LIFE PROCESSES
Syllabus 2020-21 : Life processes: Topics covered : Basic concept of nutrition, respiration, transport and
excretion in plants and animals.
Life processes
The processes which together perform the function of maintenance of ‘life’ are called as life processes.
Nutrition, respiration, circulation, excretion are examples of essential life processes.
Nutrition
Nutrition is the process of taking in food and converting it into energy and other vital nutrients required for life.
There are two main modes of nutrition, autotrophic and heterotrophic.
AUTOTROPHIC NUTRITION
Organisms which can make their own food using simple inorganic materials like water and carbon dioxide in the presence of light and
chlorophyll are called autotrophs.
Examples of autotrophs : Plants, algae and cyanobacteria
HETEROTROPHIC NUTRITION
The organisms which cannot produce food on their own and depend on other sources/organisms are called heterotrophs.
Examples of heterotrophs :
Parasites (e.g. leeches, ticks)
Saprophytes (e.g. mushrooms), Holozoic (e.g. humans, dogs)
PHOTOSYNTHESIS
The process of photosynthesis can be explained in three stages :
• The chlorophyll present in leaves traps the light coming from the sun.
• The absorbed light energy gets converted into chemical energy. And water absorbed splits into hydrogen and oxygen molecules.
• At last, carbon dioxide gets reduced i.e. hydrogen molecules combine with carbon to form carbohydrates (sugar molecules).
Photosynthesis is usually represented by the chemical equation
6CO2 + 6H2O + light →C6H12O6 +6O2
Nutrition in Amoeba
Amoeba feeds by holozoic mode of nutrition. It takes in the food particle using pseudopodia, the process is called ingestion. The engulfed food gets enclosed in a food vacuole.
As the food vacuole passes through the cytoplasm, digestion, absorption and assimilation take place.When the food vacuole opens to outside, egestion of undigested food takes place.
Nutrition in Humans : Digestive System in Humans
The digestive system has an alimentary canal and digestive glands, which together function to
nourish the body.
Alimentary Canal
Alimentary canal starts with the mouth and ends with the anus. Oesophagus, stomach, small
intestine and large intestine are the parts of the alimentary canal.
Mouth
It is the opening of the alimentary canal and helps in ingestion of food.
The buccal cavity has teeth and tongue. The set of teeth helps in the
breaking down of food. The tongue helps in tasting and swallowing the
food.
The salivary glands open also in the buccal cavity and pour saliva which contains salivary amylase, an enzyme to break down starch. The salivary amylase converts starch into maltose.
Oesophagus
The swallowed food passes into the oesophagus. It is a muscular tube in which food is pushed down by peristaltic movements.
Stomach
The stomach is a thick-walled bag-like structure. The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices. Enzyme called pepsin present in the gastric juice breaks down proteins.
Hydrochloric acid helps in digestion of proteins and also kills harmful bacteria.
Mucus secreted by the wall of the stomach helps in protection from HCl.
Liver
The liver secretes bile which is stored in the gall bladder. Bile emulsifies the fats into smaller
globules. This process is called ‘Emulsification’. Lipase is the enzyme which acts on the emulsified fats and breaks them down into glycerol and fatty acids.
Pancreas
The pancreas secretes many digestive enzymes and its secretion is called as pancreatic juice.
Enzymes like trypsin, lipase, amylase are present in the pancreatic juice.
Small Intestine
The small intestine is the longest part of the alimentary canal, about 20 feet long in humans.
The internal surface of the small intestine is folded into finger-like projections called villi. They
increase the surface area for absorption of digested food. The digestion process gets completed and absorption takes place in the small intestine.
The end products of digestion are: Carbohydrates into glucose, fats into fatty acids and glycerol and proteins into amino acids.
Large Intestine
The large intestine is not involved in the digestion of food or absorption of nutrients.
The major function of the large intestine is to absorb water from the remaining indigestible food matter and make the stool solid. The waste is thrown out of the body through Anus.
Respiration
Respiration broadly means the exchange of gases.
At a cellular level, respiration means the burning of the food for generating the energy needed for other life processes.
Respiration may take place in the presence or absence of oxygen. Two Types of Respiration Aerobic respiration and Anaerobic respiration
Cellular respiration that takes place in the presence of oxygen to produce
energy.
Cellular respiration that takes place in the absence of oxygen to produce
energy. It takes place in multicellular organisms like plants and animals.
It takes place in smaller organisms like yeast and is also called fermentation.
Questions:
1) Differentiate between autotrophic and heterotrophic nutrition. ( 2 marks)
2) Write the three steps of photosynthesis.(3 marks)
3) Show nutrition in amoeba with the help of a neat labeled diagram.( 2 marks)
4) What is the role of liver in digestion of fats? ( 2 marks)
Respiration in Muscles
Respiration in muscles can be anaerobic when there is not enough oxygen.
Glucose gets broken down to carbon dioxide and lactic acid. This results in the accumulation of lactic acid that results in muscle cramps.
Human Respiratory System
Following are the main structures in the human respiratory system :
Nostrils: The inner lining of the nostrils is lined by hair and remains wet due to mucus secretion.
The mucus and the hair help in filtering the dust particles out from inhaled air.
Pharynx: It is a tube-like structure which continues after the nasal passage.
Larynx: This part comes after the pharynx. This is also& called voice box.
Trachea: This is composed of rings of cartilage. Cartilaginous rings prevent the collapse of
trachea.
Bronchi: A pair of bronchi comes out from the trachea, with one bronchus going to each lung.
Bronchioles: A bronchus divides into branches and sub-branches inside the lung.
Alveoli: There are air sacs at the end of bronchioles. Exchange of gases takes place between an alveolar surface and surrounding blood vessels. Alveoli provide a large surface area for exchange of gases.
Questions :
1)What are the different ways of breakdown of glucose? (3 marks)
2) Differentiate between aerobic and anaerobic respiration. (3 marks)
3) How do alveoli help in exchange of gases? ( 2 marks)
Transportation in Humans
Transportation in humans is done by the circulatory system which mainly consists of blood, blood vessels and heart. It is responsible for the supply of oxygen, nutrients, removal of carbon dioxide and other excretory products.
Heart
It is the muscular pumping organ which is located near the chest slightly towards the left. Blood
delivers oxygen, hormones, glucose and other components to various parts of the body
Humans have four chambers in heart:
Left atrium, Right atrium, Left ventricle, Right ventricle
Double Circulation
In the human body, blood circulates through the heart twice.
Once it goes through the heart during pulmonary circulation and second time during systemic circulation. Double circulation ensures complete separation of oxygenated and deoxygenated blood which is necessary for optimum energy production in warm-blooded animals. Hence, circulation in human beings is called double circulation.
The blood vessels :
Veins – It supplies deoxygenated blood to the heart. They are thin-walled and have valves.
Capillaries – They are very thin tube-like vessels making a network between arteries and veins.
Arteries – These are muscular tubes responsible for supplying oxygenated blood away from the heart to all other parts of the body. They are thick-walled and have no valves.
Transportation in Plants
Phloem
Phloem transports nutrients and sugars (in all directions) like carbohydrates, produced by the
leaves to other parts of the plant.
Transport of food in the plant through phloem is called as translocation.
Xylem
Xylem tissue transports water (unidirectional) in plants from root to all other parts of the plant..
Questions:
1) Differentiate between an artery and vein.( 2 Marks)
2) Why does blood get circulated twice in human heart?
(2 marks)
3) How does food and water get transported in plants?
( 2 marks)
Excretion in human beings:
❖ Removal of harmful waste from the body is called excretion.
❖ The metabolic activities in the body generate many kinds of wastes including nitrogenous wastes which are harmful for the body and hence need to be removed.
The excretory system in humans includes:
A pair of kidneys,
A pair of ureters: Set of tubes which
come out of each kidney and goes to the urinary bladder.
A urinary bladder: Bag like structure
where Urine is collected. Urine is
expelled out through urethra.
Urethra - It produces urine as a waste product.
Kidney: Kidney is a bean-shaped organ which lies near the vertebral column in the abdominal cavity.
The kidney is composed of many filtering units, called nephrons. Nephron is called the functional unit of kidney.
Nephron :
It is composed of tubes and a filtering part, called glomerulus.
The glomerulus is a network of blood capillaries to which renal artery is
attached.
The glomerulus is enclosed in a capsule like portion, called bowman’s capsule. The bowman’s capsule extends into a fine tube which is highly coiled.
Tubes from various nephrons converge into collecting duct, which finally goes to the ureter.
Urine formation in the kidney: The urine formation involves three steps:
• Glomerular filtration.
• Tubular absorption
• Secretion
Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.
The purpose of making urine is to filter out waste products from the blood i.e., urea which is produced in the liver.
Haemodialysis: The process of purifying blood by an artificial kidney. It is meant for kidney failure patient.
QUESTIONS :
1)Name the filtration unit of kidney. Write down its functions.(2 marks)
2) Draw a well labeled diagram of human excretory system and also write down the function of
each part.(3marks)
3) Explain the process of urine formation.(2 marks)
4) Draw a neat diagram of excretory unit of human kidney and label the following parts:( 2 marks for
labeling and 1 mark for diagram)
A.Bowman’s capsule
B. Renal Artery
C. Glomerulus
D. Collecting duct
CHAPTER 8
HOW DO ORGANISMS REPRODUCE?
Syllabus for 2020-21Reproduction: Reproduction in animals and plants (asexual and sexual) reproductive health need and methods of family planning. Safe sex vs HIV/AIDS. Child bearing and women’s healt
REPRODUCTION:-Reproduction is the process by which living organisms produce new individuals of the same kind.
Reproduction is necessary for the survival and increase in population of a species. If organisms do not reproduce, their population decreases and species will become extinct.
There are two ways by which organisms reproduce:
Asexual Reproduction and Sexual reproduction
ASEXUAL REPRODUCTION:-In this process, only a single parent is involved and no gamete formation
takes place.
Kinds of Asexual reproduction
1.Fission
2.Fragmentation
3.Regeneration
4.Budding
5.Spore formation
6.Vegetativepropagation
FISSION:-The term “fission” means to divide. Fission is an asexual reproduction by which a unicellular
organism divides and forms two or more new individuals. It is of two types-
(I)Binary fission (II) Multiple fission
(I)Binary fission:-During binary fission, the parent cell divides into two daughter cells. First the nucleus
divides and forms two nuclei. Then the cytoplasm divides and forms two daughter cells. E.g.:- Amoeba,
Paramaecium and Leishmania.
BINARY FISSIONINAMOEBA
BINARY FISSION INLEISHMANIA
(II)Multiple fission: - In this method, the unicellular organism gets divided into many daughter cells.
Each daughter cell forms a new organism. The parent cell breaks down and leaves many daughter
cells. E.g.:- Plasmodium (malaria parasite), Leishmania.
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