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Thursday, 30 July 2015

Life process Notes

Life processes

– The processes that are necessary for an organism to stay alive. 
Eg. Nutrition, respiration, etc.

 Criteria of life- (i) Growth (ii) Movement

 Nutrition- The process in which an organism takes in food, utilises it to get energy,
for growth, repair and maintenance, etc. and excretes the waste materials from the

Types of nutrition
1. Autotrophic nutrition (Auto =self: trophos = nourishment) 
E.g. Plants, Algae, blue green bacteria.

o Process – Photosynthesis(Photo=light; Synthesis= to combine)

o Raw materials- (i) Carbon dioxide (ii)Water

o Energy conversion- Light/Solar energy to Chemical energy

o Role off Chlorophyll- To trap the sun‘s energy for photosynthesis

o Factors- (i) Carbon dioxide (ii) Water(iii) Light (iv) Temperature

o Events/ Steps of photosynthesis-

(i) Absorption of light energy by chlorophyll

(ii) Conversion of light energy to chemical energy & Splitting of water molecule into Hydrogen & oxygen

(iii) Reduction of Carbon dioxide to Carbohydrate

o Gaseous exchange- 
(i) Gas used- Carbon dioxide
(ii) By product - Oxygen

o Source of raw materials-

(i) Carbon dioxide –Land plants- Air, Aquatic plants- Water
(ii) Water & Minerals - Soil

2. Heterotrophic nutrition (Hetero =others: trophos = nourishment) 
Eg. Animals, plants lacking chlorophyll like fungi.
(a) Saprophytic nutrition: Organisms feeds on dead decaying plants or animals material.
E.g. Fungi, Bacteria

(b) Parasitic nutrition: Organisms obtain food from the body of another living (host)

o Endoparasite: Parasite lives inside the body of the host e.g. tapeworm roundworm.

o Exoparasite : Parasite lives on the body of the host. E.g. lice, leech.
Note- The parasite benefits while the host is usually harmed 
e.g. Cuscutta-plant parasite (amar bel), plasmodium (malarial parasite).

(c) Holozoic nutrition: Organism (mostly animals) take in whole food and then digest it into
smaller particles with enzyme. Eg. Amoeba, Paramoecium. Animals, human beings.

o Steps in Holozoic nutrition

(i) Ingestion: taking in of food.

(ii) Digestion: breaking down of complex food into simpler, absorb able form.

(iii) Assimilation: Utilization of digested food from the body.

(iv) Egestion: Removing undigested food from the body

o Nutrition in human beings

 Alimentary canal-

Mouth → Oesophagus → Stomach → Small intestine → Large intestine

 Important gland/juices
Peristaltic movements- 
Rhythmic contraction of muscles of the lining of  Alimentary canal to push the food forward.

 Sphincter muscle- Helps in the exit of food from the stomach.

 Villi- Small finger like projections on the walls of- 

(v) Small intestine- To increase the surface area for the absorption of food.

(vi) Large intestine- For absorption of water.

 Respiration- 
The process by which digested food is broken down with the help of Oxygen to release energy.

o Types of respiration- (i) Aerobic respiration (ii) Anaerobic respiration
o Some common features of Respiratory organs-

(i) Large surface area- for greater rate of diffusion of respiratory gases.

(ii) Thin permeable walls – to ensure easy diffusion & exchange of gases.

(iii) Extensive blood supply- Respiratory organs are richly supplied with blood
vessels for quick transport of gases.

o Gaseous exchange in plants-
 Process – Diffusion
 Direction of diffusion depends on- 
(i) Environmental conditions
(ii) Requirement of the plant.

 Day time- Carbon dioxide given out during respiration is used for photosynthesis. Therefore only Oxygen is released, which is a major activity during the day.

 Night time – Only respiration takes place. Therefore only Carbon dioxide is released, which is a major activity during the night.

o Gaseous exchange in animals-

Terrestrial animals- take Oxygen from the atmosphere.

Aquatic animals- take Oxygen dissolved in water. (Oxygen content is low in water,            therefore they breathe faster.

o Human Respiratory system-

External nostrils → Nasal cavity → Trachea→ Bronchi → Bronchioles →Alveoli

 Rings of cartilage present in the throat ensure that the trachea (air passage)

does not collapse when there is less air in it.

 Lungs – 

(i) Present in the thoracic cavity

(ii) They are spongy, elastic bags consisting of Bronchi, Bronchioles and Alveoli

o Respiration occurs in two phases

(i) External-Breathing, which is a mechanical process.

(ii) Internal - Cellular respiration

o Mechanism of breathing

 It includes : (i)Inhalation (ii) Exhalation

o Exchange of gases-
 Unicellular organisms- By Diffusion
 Animals- (i) As the body size is large, diffusion alone is not enough.
(ii) Respiratory pigments also required.
(iii) Respiratory pigment in human beings is Haemoglobin,
which is present in red blood corpuscles.
(iv) It has very high affinity for Oxygen.
(iv) Carbon dioxide is more soluble in water than Oxygen, so it
Gets dissolves in blood and is thus transported.
 Transportation
o Transportation in human beings-
 Blood- (i) It is a fluid connective tissue.
(ii) Components- (1) Fluid medium- Plasma
(2) Red blood corpuscles
(3) White blood corpuscles
(4) Platelets suspended in plasma
(iii) Plasma transports food, Oxygen, Carbon dioxide,
Nitrogenous wastes, etc.
 Functions of blood- (i) Transport of respiratory gases.
(ii) Transport of nutrients.
(iii) Transport of waste products.
(iv) Defence against infection Blood vessels- (i) Arteries (ii) Veins (iii) Capillaries
 Heart-
(i) It is a muscular organ, which works as a pump in the circulatory system.
(ii) It is the size of our fist.
(iii) It has two sides, which are separated by a partition so that the oxygenated
deoxygenated blood do not get mixed up.
(iv) It has four chambers-
Two upper chambers called Atria.
Two lower chambers called Ventricles.
 Working of heart-
Left side- (i) Left atrium relaxes & the Oxygenated blood enters it fromthe lungs through the pulmonary vein.

(ii) Left atrium contracts & the blood enters the left ventricle
through the valve.
(iii) Left Ventricle contracts and the blood is pumped into the
largest artery ‗Aorta‘ and is carried to all parts of the body.
Right side- (i) Right atrium relaxes & the deoxygenated blood from the body
enters it through superior and inferior Vena cava.
(ii) Right atrium contracts & the blood enters the right Ventricle
through the valve.
(iii) Right Ventricle contracts and the blood is pumped into the
Pulmonary artery and is carried to lungs.
 Valves- Unidirectional to prevent the backward flow of blood.
 Pulmonary vein is the only vein that carries Oxygenated blood.
 Aorta is the only artery that carries Deoxygenated blood.
 Double circulation in man- because the blood passes through the heart twice in
one complete cycle of the circulation.
 Capillaries- (i) Form the connection between arteries & veins.
(ii) Walls are one cell thick only for easy exchange of blood.
 Platelets- Plug the leaks of arteries and veins by clotting the blood.
 Lymph- Extracellular fluid similar to plasma but colourless with lesser
 Function of lymph- (i) Transportation of digested & absorbed fats from
the small intestine.
(ii) Drains excess fluid from the intercellular spaces
back in the blood.
 Higher animals- E.g., birds, mammals.
(i) Oxygenated blood & Deoxygenated blood are completely
separate for efficient Oxygen supply.
(ii) This is to fulfil higher energy needs and to maintain body
temperature (warm blooded animals).
 Amphibians & reptiles- have 3 chambered heat where little mixing of
Oxygenated blood & Deoxygenated blood takes place. Therefore their body
temperature varies with the temperature of the environment. (cold blooded
o Transportation in plants-
 Plants need less energy needs- because they do not move and therefore have a
slow transport system
 Transport of water-
(i) Takes place by xylem tissue present in roots, stem, leaves and
is therefore interconnected.
(ii) Root cells take up ions from the soil, which creates a
concentration difference between root and soil. Column of
water therefore rises upwards.
 In very tall plants- transpiration creates a suction pressure, which pulls the
water upwards.
 Importance of transpiration-
(i) Helps in upward movement of water in plants.
(ii) It regulates the temperature in plants.
 Transport of food-
(i) Takes place by phloem tissue.
(ii) Movement of prepared food in plants is called translocation.translocation.

 Excretion- The biological process of removal of harmful metabolic wastes in living
o Excretion in human beings-

 Organs of excretory system- (i) Kidneys (iii) Urinary bladder
(ii) Ureters (iv) Urethra
 Kidneys-
(i) Two in number
(ii) Bean shaped
(iii) Present in abdomen on either side of the backbone
(iv) Basic unit is nephron.
a. Glomerulus- Group of capillaries (cluster) present in Bowman‘s
capsule to receive blood from renal artery and filters it.
b. Bowman‘s capsule- Cup shaped structure, which contains
c. Convoluted tubule- is long and reabsorbs vital nutrients like
glucose, amino acids, salts, urea and water.
Note-Vital functions of kidneys- (a) Filtration & removal of Nitrogenous wastes
(b) Reabsorption of vital nutrients
 Ureters- Transport the urine formed in the kidneys to the urinary bladder.
 Urinary bladder- Muscular bag like structure to store urine.
 Urethra- Helps in removal of urine when the Urinary bladder is full.
 Artificial kidney- Principle: Dialysis
o Excretion in plants-
 Gaseous wastes- CO2 in respiration & O2 in photosynthesis are removed by
the process of diffusion.
 Excess water- is removed by transpiration.
 Other wastes- (i) Stored in cellular vacuoles or in leaves, which fall off or as
gums, resins, etc. in old xylem.
(ii) Excreted in soil.
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