What are life processes?

The basic functions performed by living beings which help them to survive and maintain
themselves are called life processes. These processes continue even when the organism is
at rest or asleep. The life processes are as follows:

1. Nutrition
2. Respiration
3. Growth
4. Reproduction
5. Transportation
6. Excretion
7. Response to stimuli

Q. What criteria do we use to decide whether something is alive or not?

Ans. Living things show different features i.e. Life processes, they also keep repairing and
maintaining structures, all of which involve molecular movement within the cells of their
body, which is not seen in non-living entities.

STUDY OF LIFE PROCESSES IN DETAIL

1. NUTRIRION

The process of taking in food by living organisms for its growth, maintenance and survival is
known as Nutrition.

Nutrition
Autotrophic

Auto means self and trophic means nutrition. Those organisms who can prepare their own
food by utilizing inorganic raw materials are called autotrophs. Ex. Green plants.

Heterotrophic

Hetero means different and tropic means nutrition. Those organisms that depend on other
organisms for food are called heterotrophs. Ex. Cow, humans etc.

AUTOTROPHIC NURTRITION

Green plants prepare their food by a process called photosynthesis (photo-light and
synthesis-to prepare). It’s a process during which green plants utilize raw materials like
water, CO,, chlorophyll and sunlight to prepare food in the form of glucose.

The overall reaction of the process is

Write photosynthesis reaction

The raw materials for photosynthesis: CO₂, H₂O, chlorophyll, sunlight

The end products for photosynthesis: glucose, H₂O, O,

The storage form of carbohydrate in plants is starch

The storage form of carbohydrate in animals is glycogen.

Steps involved in the process of photosynthesis:

 1. Absorption of light energy by chlorophyll.

2. Conversion of light energy into chemical energy.

3. This energy is utilized to split water molecules into hydrogen and oxygen.

4. Reduction of CO, into carbohydrates.

Exception: In some desert plants the above mentioned steps need not take place
sequentially.

Xerophytic plants keep stomata open at night and close during day to check transpiration,

During night from the open stomata they take up CO, and prepare a stable compound-
which is broken up during day time to release CO, within leaf to carry out photosynthesis.

Stomata

Diagram of stomata

They are tiny pores present on the under st The stomatal opening is boarded by two bean
shaped cells called guard cells.

Opening and clasing of stomatal pore is a function of guard cells.

The guard cell swell when water flows. Into them causing the stomatal pore to open.

Similarly, the pore closes when the guard cells shrink when waater moves out of them,

FUNCTIONS

1. Help in exchange of gases.

2. Help in transpiration.

Heterotrophic nutrition

Saprophytic nutrition

Parasitic nutrition

Holozoic nutrition

1. Saprophytic nutrition: mode of nutrition in which the organism obtain nutrient from
dead and decaying matter eg. In fungi like bread mould, yeast, mushroom etc. They
digest their food outside their body with the help of digestive enzymes and then
absorb the digested food within their bodies. (extracellular digestion).

2. Parasitic nutrition: some organisms derive nutrition from the bodies of plants and
animals without killing them. The organisms which obtain food is the parasite and
the organism from which the food is derived is called the host. Ex. Plants Cuscuta,
Orchid and Animalslice, ticks, tapeworm, etc.
 3. Holozoic nutrition, it refers to the mode of nutrition in which the food is in the form
of solid, is ingested, digested, absorbed into the cells and then utilized. Ex. Amoeba,
frog, and humans.

DIGESTION IN UNICELLULAR ORGANISMS – AMOEBA

When amoeba comes in touch with the food partic called pseudopodia which engulf the
prey.

When the tips of the pseudopodia fuse they capture the food into the bag like structure
called the food vacuole,

The food vacuole acts as a temporary stomach and secretes digestive enzymes to digest
the food.

The digested food gets absorbed and then diffused into the cytoplasm and then is
assimilated.

The remaining undigested material is moved to the surface of the cell and thrown out.

Diagram of digestion in amoeba

DIGESTION IN PARAMOECIUM

Diagram of paramecium

The cell has a definite shape and food is taken at a specific spot, called the oral groove.

The food is moved into this spot by the movement of cilia which cover the entire surface of
the cell.

DIGESTION IN MULTICELLULAR ORGANISMS-HUMANS

The organs which are responsible for ingestion, digestion, absorption, assimilation and
egestion constitute the digestive system. The digestive system comprises of alimentary
canal and associated digested glands. Alimentary canal in human is 9 m long and consists
of following parts:

◆ MOUTH

Guarded by lips and opens into the buccal cavity (oral cavity) having teeth, tongue and
salivary glands.

Food is crushed and grounded with teeth.

Salivary glands secrete an enzyme called salivary amylase which helps in breaking down
starch into sucrose (sugar).

The muscular organ tongue helps in mixing of saliva with food. It also helps in tasting.

FOOD PIPE

The food starts passing through the food pipe by showing muscular contraction and
relaxation movement called peristalsis.

In the food pipe no digestion takes place.

➤ Food pipe is also called Esophagus.

STOMACH
A thick muscular J shaped organ

Present in the upper abdomen,

Walls of the stomach have special glands called Gastrie Glands which help in digestion.

➤ The gastric glands seeretes gastric juices which comprises of

MUCUS

Protects the inner lining of stomach from the action of acid under normal conditions.

HYDROCHLORIC ACID

ENZYME – PEPSINE and rennin

Helps in killing microbes present in food.

It’s a protein digesting enzyme which breaks proteins into amino acids.

Makes the medium acidic for the enzyme pepsin to act.

Rennin digests the milk protein

SMALL INTESTINE

At the juncture of the stomach and small intestine a muscle is present called the sphincter
muscle which regulates the entry of food into the small intestine.

It's the longest part of the alimentary canal which is extensively coiled.
The length of the small intestine varies according to the food that the animals eat.

The upper part of the small intestine receives secretion from two main glands-liver and
pancreas.

PANCREAS

It secretes pancreatic juice which contains enzymes like

1. Trypsin protein digesting enzyme. It needs alkaline medium to act.

2. Lipases fat digesting enzyme.

LIVER

It secretes fluid called bile which helps in emulsification of fats.

The digestion of food gets completed in small intestine with the help of secretion of
intestinal juice (Succus enteriens) secreted by the walls of the intestine.

In small intestine

CARBOHYDRATES gets completely broken down into GLUCOSE

Protein gets completely broken down into AMINO ACID

FATS gets completely broken down into FATTY ACIDS AND GLYCEROL

The digested food is absorbed by the walls of the small intestine which are richly supplied
with finger like projections called villi. Villi are richly lined with blood vessels and thus help
in efficient absorption of food.

The absorbed food reaches the body cells where it is used for various purposes like
obtaining energy, building new tissues and repairing old tissues.

LARGE INTESTINE

The undigested food enters the large intestine where the excess water is absorbed

The undigested food is stored in the rectum and thrown out from the anus from time to time
with the opening and closing of the anal sphincter muscle.

Draw digestive system diagram

Respiration: The process by which a living being utilises the food to get energy, is called
respiration. Respiration is an oxidation reaction in which carbohydrate is oxidized to
produce energy. Mitochondria is the site of respiration and the energy released is stored in
the form of ATP (adenosine triphosphate). ATP is stored in mitochondria and is released as
per need.

Steps of respiration:

Breaking down of glucose into pyruvate: This step happens in the cytoplasm. Glucose
molecule is broken down into pyruvic acid. Glucose molecule is composed of 6 carbon
atoms, while pyruvic acid is composed of 3 carbon atoms.

Fate of Pyruvic Acid: Further breaking down of pyruvic acid takes place in mitochondria and
the molecules formed depend on the type of respiration in a particular organism.
Respiration is of two types, viz. aerobic respiration and anaerobic respiration.
Respiration involves

Gaseous exchange: Intake of oxygen from the atmosphere and release of CO2 → Breathing.

Breakdown of simple food in order to release energy inside the cell → Cellular respiration

Aerobic respiration: This type of respiration happens in the presence of oxygen. Pyruvic
acid is converted into carbon dioxide. Energy is released and water molecule is also formed
at the end of this process.

Anaerobic respiration: This type of respiration happens in the absence of oxygen. Pyruvic
acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed in
case of anaerobic respiration in microbes, like yeast or bacteria. Lactic acid is formed in
some microbes as well as in the muscle cells.

Pain in leg muscles while running:

• When someone runs too fast, he may experience throbbing pain in the leg
muscles. This happens because of anaerobic respiration taking place in the
muscles.
 • During running, the energy demand from the muscle cells increases. This is
compensated by anaerobic respiration and lactic acid is formed in the
process.
• The deposition of lactic acid causes pain in the leg muscles. The pain
subsides after taking rest for some time.

Terrestrial organisms: Use atmospheric oxygen for respiration.

Aquatic organisms: Use dissolve oxygen for respiration.

Exchange of gases:

For aerobic respiration, organisms need a continuous supply of oxygen, and carbon dioxide
produced during the process needs to be removed from the body.

Different organisms use different methods for the intake of oxygen and expulsion of carbon
dioxide.

Diffusion is the method which is utilized by unicellular and some simple organisms for this
purpose.

In plants also, diffusion is utilized for exchange of gases.

In complex animals, respiratory system does the job of exchange of gases.

Gills are the respiratory organs for fishes.

• Insects have a system of spiracles and trachease which is used for taking
in oxygen.
• Terrestrial organisms have developed lungs for exchange of gases.
• Availability of oxygen is not a problem in the terrestrial environment so
breathing rate is slower as compared to what it is in fishes.

The human respiratory system is composed of a pair of lungs. These are attached to a
system of tubes which open on the outside through the nostrils.

Following are the main structures in the human respiratory system:

Nostrils: There are two nostrils which converge to form a nasal passage. 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. Further, air is warmed up when it
enters the nasal passage.

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 in the absence of air.

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: These are air sacs at the end of bronchioles. The alveolus is composed of a very
thin membrane and is the place where blood capillaries open. This is alveolus, where the
oxygen mixes with the blood and carbon dioxide exits from the blood. The exchange of
gases, in alveoli, takes place due to the pressure differential.

Draw diagram of respiratory system