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Students can Download Chapter 13 Kinetic Theory Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 13 Kinetic Theory

Summary
Introduction
The kinetic theory was developed in the nineteenth century by Maxwell, Boltzmann and other. It gives a molecular interpretation of pressure and temperature of a gas. It also explains gas laws and Avogadro’s hypothesis. It correctly explains specific heat capacities of many gases. It help us to find molecular sizes and masses.

Molecular Nature Of Matter
The scientific atomic theory is credited to John Dalton. Atomic theory is not the end of quest, but the beginning. Atoms consist of a nucleons and electrons. The nucleous itself is made up of protons and neutrons. The protons and neutrons are again made up of quarks. Even quarks may not be the end of the story.

There may be string-like elementary entities. In this chapter we shall limit ourselves to understanding the behavior of gases.

Behavior Of Gases
Gas Laws
1. Boyles law
The law states that at a given temperature, the volume of a given mass of gas varies inversely as its pressure.
It can be written as
\(P a \frac{1}{V}\) (at constant T)
PV = constant
PV = μ RT
μ → No. of moles, R → universal gas constant, T → temperature
Boyles law is not obeyed by gasses at all temperatures and pressure. Usually, Boyles, law is obeyed by gases at high temperature and low pressure (Graph is given below).

A real gas which obey this law is called ideal or perfect gas.

Variation of ‘R’ \(\left(=\frac{\mathrm{PV}}{\mathrm{T}}\right)\) with Pressure (for different temperatures)

Variation of R \(\left(=\frac{\mathrm{PV}}{\mathrm{T}}\right)\) with Pressure for temperature T₁ > T₂ > T₃ is shown in the above graph. The above graph shows that, all real gases approach ideal gas behavior at low pressure and high temperature.

At low pressure or high temperature, the molecules are for apart and molecular interactions are negligible. Without interactions the gas behaves like an ideal gas.

Note:
R = 8.324 J mol^-1 k^-1.
Variation of V with P for different temperature:

The above graph shows experimental PV curves for steam at three temperature The dotted line are the theoretical curves. (According to Boyles law). The theoretical value and experimental value comes in agreement at high temperatures and low pressures.

2. Charles law
Charles law states that the volume of a given mass of gas is proportional to its temperature when its pressure is kept constant.
V a T (P is constant)
i.e.,

The graph between V and T:

The above graph shows experimental T-V curves (solid lines) for Co₂ at three pressures compared with Charles law (dotted lines). T is in unit of 300 k and V in units of 0.13 litres.

Question 1.
Why theoretical value does not agree with experimental value?
Answer:
According to Charles law the graph between T and V is straight line. It means that when temperature decreases, the volume of gas decreases and finally becomes zero.

Practically volume will not be zero. Because the molecules require some finite space to exist. This implies that we cannot reduce its temperature to zero value. A zero kelvin temperature is only an idealized concept.

Dalton’s law of Partial Pressures:
It states that, the total pressure of a mixture of ideal gases is the sum of partial pressures.

Proof:
Consider a mixture of non-interacting ideal gases. μ₁, moles of gas 1, μ₂ moles of gas 2 etc. in a vessel of volume V at temperature T and pressure P. Using Boyles law, we can write
PV = (μ₁ + μ₂ +…………..)RT
P = \(\frac{\mu_{1} \mathrm{RT}}{\mathrm{V}}+\frac{\mu_{2} R T}{V}+\ldots \ldots \ldots\)
P = P₁ + P₂ +……………………

Kinetic Theory Of An Ideal Gas
The kinetic theory of gases has been developed by Clausius, Maxwell, Boltzmann and others. The theory is based on the following postulates.

• The gas is a collection of large number of molecules. The molecules are perfectly elastic hard spheres.
• The size of a molecule is negligible compared with the distance between the molecules.
• The molecules are always in random motion
• During their motion, the molecules collide with each other and with the walls of the containing vessel.
• The collisions are elastic and hence the total K.E energy and the total momentum of the colliding molecules before and after collisions are the same.
• The kinetic energy of a molecule is proportional to the absolute temperature of the gas.
• There is no force of attraction or repulsion between molecules.

The pressure of an ideal gas:

Consider molecules of gas in a container. The molecules are moving in random directions with velocity V. This is the velocity of a molecule in any direction. The velocity V can be resolved along x, y and z directions as V_x, V_y, and V_z respectively.

If we assume a molecule hits the area A of the container with velocity V_x and rebounds back with -V_x. (The velocities V_x and V_y do not change because this collision is perfectly an elastic one).

Therefore, the change in momentum imparted to the area A by the molecule
= mv_x^– – mV_x
= 2mV_x

To find the total number of collisions taking place in a time t, consider the motion of the molecules towards the wall. The molecules covers a distance V_xt along the x direction in a time t. All the molecules within the volume AV_xt will collide with the area in a time t.

If ‘n’ is the number of molecules per unit volume, the total number of molecules hitting the area A,
N = AV_xt n.

But on an average, only half of those molecules will be hitting the area, and the remaining molecules will be moving away from the area. Hence the momentum imported to the area in a time t
Q = 2mv_x × \(\frac{1}{2}\) AV_xtn.
= nmV_x²At
The rate of change of momentum,
\(\frac{Q}{t}\) = nmV_x²A
But rate of change of momentum is called force, ie. force F = nmV_x²A
∴ Pressure P = nmV_x² (P = \(\frac{F}{A}\))
Different molecules move with different velocities. Therefore, the average value V_x² is to be taken. If \(\overline{\mathbf{v}}_{\mathbf{x}}^{2}\) is the average value then the pressure.

\(p=n m \bar{v}_{x}^{2}\) ……………….. (1)

\(\overline{\mathbf{v}}_{\mathbf{x}}^{2}\) is known as the mean square velocity. Since the gas is isotropic (having the same properties in all directions), we can write

Kinetic Interpretation of gas laws:

Question 2.
Derive the ideal gas equation from P = \(\frac{1}{3} \mathrm{nm} \overline{\mathrm{v}}^{2}\)
Answer:
The average kinetic energy of the molecule is
KE = \(\frac{1}{2} m \bar{v}^{2}\) …………………….(3)
The eq (2) can be modified as

The average Kinetic energy of a molecule remains constant when the temperature is constant. That is when the temperature varies, \(\overline{\mathrm{KE}}\) also varies accordingly. The kinetic energy of a molecule is related to its absolute temperature by an equation
\(\overline{\mathrm{KE}}\) = \(\frac{3}{2}\)K_BT
Substitute equation (5) in equation (6); we get

N = μ N₀
P V = μ N₀K_BT
P V = μ R T…………………… (8)
(N_BK_B = R)
This is the ideal gas equation

Deduction of Boyles law:
If the temperature is constant for gas, the eq (8) can be written as
PV = Constant
This is called Boyles law

Deduction of Charles law:
If pressure of a gas is constant, the eq (8) can be written as
V a T

This is called Charles law.

Deduction of Avogadro’s Hypothesis:
If P₁, T₁, and V constant, N₀ will be constant, ie. equal Volumes of all gases, under the same conditions of pressure and temperature will contain the same number of molecules. This is known as Avogadro’s hypothesis.

Law Of Equipartion Of Energy
Degrees of freedom:
Degrees of freedom is number of independent ways by which a molecule can possess kinetic energy of translation, rotation and vibration.

Law of equipartition energy:
The total kinetic energy of a molecule is equally divided among the different degrees of freedom.

K.E. per degree of freedom:
The average energy per degree of freedom

Where K_B is Boltzman constant.

Degrees of freedom and energy of monoatomic gas:
A monoatomic atom has 3 degrees of freedom, ie; it can move in x, y and z-direction. The average energy of single monoatomic gas in the x-direction,

Note:
1. If a molecule is restricted to move in plane. It has 2 degrees of freedom.
2. If a molecule is restricted to move in a line, it has only 1 degrees of freedom.

Degrees of freedom and energy of single diatomic molecule (rigid rotator)

Consider a diatomic molecule as a rigid rotator (Rigid rotator means that the molecule does not vibrate). A rigid diatomic molecule has 3 translation degrees of freedom and 2 rotational degrees of freedom.
(Rotational degrees of freedom is shown in the above figure).
∴ Total average energy of diatomic rigid rotator,

Note:
A diatomic molecule has 3 rotational degrees of freedom. But we consider only 2 degrees of freedom. We neglect rotation along the line joining the atoms. Because it has very small moment of inertia.

Degrees of freedom and energy of single diatomic molecule of nonrigid rotator:
Molecules like ‘co’ even at moderate temperatures have a mode of vibration. The vibration energy of a diatomic molecule.

Where K is the force constant of the oscillator and y the vibrational coordinate. The vibration energy mode contain two terms (1) Kinetic energy (2) Potential energy. Hence a single mode of vibration of molecule is considered as 2 degrees of freedom (potential energy and kinetic energy)
∴ The total vibrational energy of a single-mode
= 2 × \(\frac{1}{2}\)K_BT
= K_BT
∴ The total energy of diatomic nonrigid rotator

Degrees of freedom and energy of polyatomic molecule, (non- rigid rotator):
If a polyatomic molecule has ‘f’ modes of vibration, total number of degrees freedom = 3 vibration + 3 rotator+f vibration.
∴ Total average energy of single polyatomic molecule,

Specific Heat Capacity
Monoatomic Gases (Molar specific heat capacity):
The energy of a single monoatomic gas = 3 × \(\frac{1}{2}\) K_BT
The energy of one mole monoatomic gas = 3 × \(\frac{1}{2}\) K_BT × N_A
[one-mole atom contain Avogadro number (N_A) of atoms]

A Diatomic Gas (Molar specific heat capacity):
A rigid diatomic molecule has 5 degrees of freedom : 3 translational and 2 rotational.
∴ energy of single diatomic (rigid) molecule = 5 × \(\frac{1}{2}\) K_BT
for one mole of diatomic molecule, energy U = 5 × \(\frac{1}{2}\) K_BT × N_A

Nonrigid diatomic molecule having a vibrational mode (Molar specific heat capacity):
If the diatomic molecule is not rigid but has a vibration mode. The energy of one mole,

Polyatomic Gas (Molar specific heat capacity):
In general a polyatomic molecule has 3 translational, 3 rotational degrees of freedom and a certain number (t) of vibrational modes.

The energy of one mole polyatomic gas,

Note: The experimental value of C_P and C_V of polyatomic gases are greater than the predicted values. The theoretical value and experimental value will be equal when we include vibrational modes of motion in the calculation.

Specific heat capacity of solids:
Consider a solid of N atoms. Each atom is vibrating about its mean position. Each vibration mode has two degrees of freedom (corresponding to potential energy and kinetic energy). Hence an oscillation in one dimension has average energy of

2 × \(\frac{1}{2}\) K_BT = K_BT
∴ Total energy in three dimension
= 3 × K_BT
= 3K_BT.

For one mole of solid, total energy,
U = 3K_BT × N_A
[N_A = Avagadro number]
= 3N_AK_BT
U = 3RT …………………. (1) [∴ R = K_BN_A].
We know specific heat capacity,

Note:
In solids, we do not consider the translational and rotational degrees of freedom. We consider only vibrational degrees of freedom.

Specific heat capacity of water:
We treat water like a solid. A water molecule has 3 atoms. Each atom in the molecule is vibrating about its mean position. A single vibration mode has 2 degrees of freedom (1) potential energy (2) kinetic energy.

ie; The energy of one atom in one dimensional vibration mode =
2 × \(\frac{1}{2}\) K_BT = K_BT

The energy of one atom having 3 dimensional vibration mode = 3 × K_BT
The energy of one H₂0 molecule having 3 dimension vibration mode
U = 3 × 3K_BT × N_A
U = 9RT [∵ R = K_B N_A]
∴ Specific heat capacity,
\(\mathrm{c}=\frac{\mathrm{dU}}{\mathrm{dT}}=\frac{\mathrm{d}}{\mathrm{dT}}(\mathrm{RT})\)
C = 9R.

Mean Free Path
Molecules in a gas have large speeds. Yet a gas leaking from a cylinder in a kitchen takes considerable time to diffuse to the other corners of the room. Why?

The molecules in a gas have a finite size. So they collide with other molecules during their motion. As a result, they cannot move straight like path. Their paths are continuously deflected.

Mean free path:
The mean free path is the average distance covered by a molecule between two successive collisions.

Expression for mean free path:

Suppose the molecules of a gas are spheres with diameterd. Let 〈v〉 be the average velocity of the molecule.
The volume covered by a molecule during its motion, in a time Δt = πd² 〈v〉 Δt.
If ‘n’ is the number of molecules per unit volume, the total number of molecules in the above volume
= πd² 〈v〉 Δt n.
The number collisions in a time Dt,
= πd² 〈v〉 Δt n.
Number of collisions in one second,
= n π d² 〈v〉
∴ The time between two successive collisions,
\(\tau=\frac{1}{n \pi d^{2}\langle v\rangle}\).
The average distance between two successive collisions,

In this derivation, we imagined the other molecules to be rest. But actually all other molecules are moving. Hence we must take relative velocity 〈v_r〉 instead of 〈v〉. A more exact treatment gives
\(\ell=\frac{1}{\sqrt{2} \mathrm{n} \pi \mathrm{d}^{2}} \dots(1)\)
The mean free path given by the above equation depends inversely on the number density and the size of the molecule.

Students can Download Chapter 5 Digestion and Absorption Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 5 Digestion and Absorption

What is digestion?
This process of conversion of complex food substances to simple absorbable forms is called digestion.

DIGESTIVE SYSTEM:
It includes

• Alimentary canal
• Associated glands.

Alimentary canal:

The human digestive system
1. The alimentary canal begins with the mouth, and it leadsto the buccal cavity or oral cavity.

2. The oral cavity has a number of teeth and a musculartongue. Each tooth is embedded in a socket of jaw bone. This type of attachment is called thecodont.

3. Human being forms two sets of teeth during their life, a set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont.

Dental formula of adult human
An adult human has 32 permanent teeth which are of four different types (Heterodont dentition).

• incisors (I)
• canine (C)
• premolars (PM)
• molars (M).

Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is
\(\frac{2123}{2123}\)

• The hardest part of teeth is made up of enamel, helps in the mastication oWood.
• The tongue is attached to the floor of the oral cavity by the frenulum.
• The upper surface of the tongue has small projections called papillae, some of which bear taste buds.
• The oral cavity leads pharynx which serves as a common passage for food and air.
• The oesophagus and the trachea (wind pipe) open into the pharynx.
• A cartilaginous flap called epiglottis prevents the entry of food into the glottis – opening of the wind pipe – during swallowing.
• The oesophagus is a thin, long tube which passing through the neck, thorax and diaphragm and leads to a ‘J’ shaped bag like structure called stomach.
• A muscular sphincter (gastro-oesophageal) regulates the opening of oesophagus into the stomach.

The stomach, located in the upper left portion of The abdominal cavity, has three major parts:

1. A cardiac portion into which the oesophagus opens
2. A fundic region and
3. A pyloric portion which opens into the first part of small intestine

Small intestine is distinguishable into three regions:

1. A ‘U’ shaped duodenum
2. A long coiled middle portion jejunum and
3. A highly coiled ileum

The opening of the stomach into the duodenum is guarded by the pyloric A sphincter. Ileum opens into the large intestine.

Large intestine:
It consists of

• caecum
• colon
• rectum.

Caecum:
It is a small blind sac consists of some symbiotic micro-organisms. A narrow finger-like tubular projection, the vermiform appendix which is a vestigial organ, arises from the caecum. The caecum opens into the colon.

colon:
It is divided into three parts-an ascending, a transverse and a descending part. The descending part opens into the Rectum.

Rectum: It opens out through the anus.
Wall layers of alimentary canal:
It consists of four layers namely

1. Serosa
2. muscularis
3. sub-mucosa &
4. mucosa.

1. Serosa is the outermost layer and is made up of a thin mesothelium with some connective tissues.
2. Muscularis is formed by smooth muscles
3. The submucosal layer is formed of loose connective tissues containing nerves, blood and lymph vessels.
4. The innermost layer lining of the alimentary canal is the mucosa.
   • In duodenum, glands are also present in sub-mucosa.
   • Mucosa forms irregular folds (rugae) in the stomach and small finger-like foldings called villi in the small intestine
   • The cells lining the villi produce numerous projections called microvilli giving a brush border appearance.
   • These modifications increase the surface area.
   • Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal.
   • Mucosal epithelium has goblet cells which secrete mucus that help in lubrication.
   • Mucosa also forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (crypts of Lieberkuhn).

Digestive Glands:
It includes

1. salivary glands
2. liver
3. pancreas.

1. Salivary glands:
Saliva is mainly produced by three pairs of salivary glands

• parotids (cheek)
• sub-maxillary/sub-mandibular (lower jaw)
• sublinguals (belowthe tongue).

The duct systems of liver, gall bladder and pancreas These glands situated just outside the buccal cavity secrete salivary juice into the buccal cavity.

2. Liver:

• It is the largest gland of the body weighing about 1.2 to 1.5 kg in an adult human.
• It is situated in the abdominal cavity, just below the diaphragm and has two lobes.
• The hepatic lobules are the structural andfunctional units of liver containing hepatic cells arranged in the form of cords.
• Each lobule is covered by a thin connective tissue sheath called the Glisson’s capsule.
• The bile secreted by the hepatic cells passes through the hepatic ducts and is stored in gall bladder.
• The duct of gall bladder (cystic duct) along with the hepatic duct from the liver forms the common bile. duct
• The bile duct and the pancreatic duct open together into the duodenum which is guarded by sphincter of Oddi.

3. Pancreas:
It is a heterocrine (both exocrine and endocrine) elongated organ situated between the limbs of the ‘U’ shaped duodenum.

Secretions of exocrine and endocrine:

• The exocrine portion secretes an alkaline pancreatic juice containing enzymes
• The endocrine portion secretes hormones, insulin and glucagons.

DIGESTION OF FOOD:

1. The process of digestion is accomplished by mechanical and chemical processes.
2. The teeth and the tongue with the help of saliva masticate and mix up the food thoroughly. *Mucus in saliva helps in lubricating and adhering the masticated food particles into a bolus.

Contents of saliva:
It contains electrolytes (Na⁺, K+⁺, Cl^–, HCO^–“) and enzymes, salivary amylase and lysozyme.
The chemical process of digestion is initiated in the oral cavity by the carbohydrate splitting enzyme, the salivary amylase( pH 6.8).

Digestion of starch:
About 30 percent of starch is hydrolysed here by salivary amylase (optimum pH 6.8) into a disaccharide -maltose.

Enzyme for preventing infections:
Lysozyme present in saliva acts as an antibacterial agent that prevents infections.

• The bolus is then passed into the pharynx and then into the oesophagus by swallowing or deglutition.
• The bolus further passes down through the oesophagus by successive waves of muscular contractions called peristalsis.
• The gastro-oesophageal sphincter controls the passage of food into the stomach.

Mucosa of stomach and gastric glands:
Gastric glands have three major types of cells namely

Digestion in stomach:
1. The food mixes thoroughly with the acidic gastric juice of the stomach by the churning movements of its muscular wall and is called the chyme.

2. The proenzyme pepsinogen, in the presence hydrochloric acid gets converted into the active enzyme pepsin, the proteolytic enzyme of the stomach.

3. Pepsin converts proteins into proteoses and peptones (peptides).

4. The mucus and bicarbonates play an important role in lubrication and protection of the mucosal epithelium from concentrated hydrochloric acid- pH (pH 1.8).

Special type of proteolytic enzyme in infants:
Rennin is a proteolytic enzyme found in gastric juice of infants which helps in the digestion of milk proteins. The bile, pancreatic juice and the intestinal juice are the secretions released into the, small intestine.

Pancreatic juice:
It contains inactive enzymes

Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into aqtive trypsin.

Contents of Bile and functions:
The bile released into the duodenum contains bile pigments (bilirubin and bili-verdin), bile salts, cholesterol and phospholipids but no enzymes Bile helps in emulsification of fats, i.e., breaking down of the fats into very smalfmicelles.

Bile also activates lipases. The intestinal mucosal epithelium has goblet cells which secrete mucus. The secretions of the brush border cells of the mucosa alongwith the mucus constitute the intestinal juice or succu sentericus.

Intestinal juice/succus entericus:
It contains enzymes like

1. disaccharidases (eg: maltase)
2. dipeptidases
3. lipases,
4. nucleosidases etc.

How does the intestine protect itself from digestion?
1. The mucus alongwith the bicarbonates from the pancreas protects the intestinal mucosa from acid as well as provide an alkaline medium (pH 7.8) for enzymatic activities.

2. Sub-mucosal glands (Brunner’s glands) also help in this.

The breakdown of biomacromolecules occurs in the duodenum region of the small intestine. The simple substances thus formed are absorbed in the jejunum and ileum regions of the small intestine. The undigested and unabsorbed substances are passed on to the large intestine.

Functions of large intestine:

1. Absorption of some water, minerals and certain drugs
2. Secretion of mucus which helps in adhering the waste (undigested) particles together and lubricating it for an easy passage.

The undigested, unabsorbed substances called faeces enters into the caecum of the large intestine through ileo-caecal valve, which prevents the back flow of the faecal matter. It is temporarily stored in the rectum till defaecation.

• The sight, smell and the presence of food in the oral cavity can stimulate the secretion of saliva.
• Gastric and intestinal secretions are also stimulated by neural signals.
• The muscular activities of different parts of the alimentary canal controlled by neural mechanisms, both local and through CNS.

ABSORPTION OF DIGESTED PRODUCTS:

1. The end products of digestion passthrough the intestinal mucosa into the blood or lymph.
2. It is carried out by passive, active or facilitated transport mechanisms.
3. Small amounts of monosacharides like glucose, amino acids and some of electrolytes like chloride ions are generally absorbed by simple diffusion.
4. Fructose and some amino acids are absorbed with the help of the carrier ions like Na⁺. This mechanism is called the facilitated transport.
5. Transport of water depends upon the osmotic gradient.
6. Various nutrients like amino acids, monosacharides like glucose,electrolytes like Na⁺ are absorbed into the blood by active transport and hence requires energy.

How does fat absorption occur?
Fatty acids and glycerol being insoluble, cannot be absorbed into the blood. They are first incorporated into small droplets called micelles which move into the intestinal mucosa. Then, the fat globules are coated with small protein called as chylomicrons which are transported into the lymph vessels (lacteals) in the villi.

These lymph vessels ultimately release the absorbed substances into the blood stream. The maximum absorption occurs in the small intestine. The absorbed substances finally reach the tissues which utilise them for their activities. This process is called assimilation.

The digestive wastes, solidified into faeces in the rectum initiate a neural reflex causing an urge for its removal. The egestion of faeces to the outside through the anal opening (defaecation) is a voluntary process and is carried out by a mass peristaltic movement.

DISORDERS OF DIGESTIVE SYSTEM:
Jaundice:
The liver is affected, skin and eyes turn yellow due to the deposit of bile pigments.

Vomiting:
It is the ejection of stomach contents through the mouth. This reflex action is controlled by the vomit centre in the medulla. „

Diarrhoea:
The abnormal frequency of bowel movement and increased liquidity of the faecal discharge is known as diarrhoea. It reduces the absorption of food.

Constipation:
In constipation, the faeces are retained within the rectum as the bowel movements occur irregularly. ‘

Indigestion:
In this condition, the food is not properly digested leading to a feeling of fullness. The causes are inadequate enzyme secretion, anxiety, food poisoning, overeating, and spicy food.

NCERT SUPPLEMENTARY SYLLABUS
Calorific value of carbohydrate, protein and fat:
Carbohydrates, proteins and fats are chief sources of energy in humans. These are oxidized and released energy stored in ATP, it is used for many activities of the cell.

calorific value kcal = 4.184kJ):
It is defined as the amount of heat produced in calories (cal) or in joules (J) from complete combustion of 1 gram food in a bomb calorimeter (a closed metal chamber filled with 02). One kilocalorie is the amount of heat energy needed to raise the temperature of one kilogram of water through 100C(1.80F).

The calorific values of carbohydrates, proteins and fats are 4.1 kcal /g, 5.65 kcal /g and 9.45 kcal/g, respectively. The actual amounts of energy liberated in the body by these nutrients referred to as the physiologic value of the food, and are 4.0 kcal /g, 4.0 kcal Ig and 9.0 kcal /g respectively.

DEFICIENCY DISEASES:
The low amount of nutrients (Vitamin A, iron and iodine) in the diet cause deficiency disorders The important among them is protein energy malnutrition (PEM). lt is major health and nutritional problems in India.

Young children (0-6 years) require more protein for each kilogram of body weight than adults. So they are more vulnerable to malnutrition. Malnutrition leads to permanent impairment of physical and mental growth and childhood mortality and morbidity. The details of the disorders are given below.

The child suffering from PEM can recover if adequate quantities of protein and carbohydrate rich food are given.

Students can Download Chapter 3 Structural Organisation in Animals Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 3 Structural Organisation in Animals

What is a tissue?
In multicellular animals, a group of similar cells along with intercellular substances perform a specific function. Such an organization is called tissue.

ANIMAL TISSUES:
The tissues are different and are broadly classified into four types:

• Epithelial
• Connective
• Muscularand
• Neural.

Epithelial Tissue:
This tissues are found in the covering ora lining for some part of the body. The cells are compactly packed with little intercellular matrix.
There are two types of epithelial tissues namely:

1. SIMPLE EPITHELIUM
2. COMPOUND EPITHELIUM

1. Simple epithelium:

• Squamous
• Cuboidai
• Columnar

1. Squamous epithelium:
It forms single thin layer of flattened cells with irregular boundaries. They are found in the walls of blood vessels and air sacs of lungs and are involved in a functions like forming a diffusion boundary.

2. Cuboidai epithelium:
It is composed of a single layer of cube-like cells. This is commonly found in ducts of glands and tubular parts of nephrons in kidneys. Its main functions are secretion and absorption.

3. Columnar epithelium:
It is composed of a single layer of tall and slende cells. Their nuclei are located at the base. Free surface may have microvilli. They are found in the lining of stomach and intestine and help in secretion and absorption.

Ciliated epithelium:
If the columnar or cuboidai cells bear cilia on their free surface they are called ciliated epithelium Their function is to move particles or mucus in a specific direction overthe epithelium. They are present in bronchioles and fallopian tubes.

Glandular epithelium:
The modified columnar or cuboidal cells perform secretion and are called glandular epithelium.
They are mainly of two types:

• Unicellular (goblet cells of the alimentary canal)
• Multicellular(salivary gland).

On the basis of the mode of pouring of their secretions, glands are divided into two categories namely exocrine and endocrine glands.
Exocrine glands:
They secrete mucus, saliva, earwax, oil, milk, digestive enzymes and other cell products. These products are released through ducts or tubes.

Endocrine glands:
They do not have ducts. Their products called hormones are secreted directly into the blood.

2. Compound epithelium:
It is multi-layered of cells.
a. Their main function is to provide protection against chemical and mechanical stresses.

b. They cover the dry surface of the skin, the moist surface of buccal cavity, pharynx, inner lining of ducts of salivary glands and of pancreatic ducts.

Three types of cell junctions are found in the epithelium and other tissues. These are called as tight, adhering and gap junctions.

1. Tight junctions help to stop substances from leaking across a tissue.
2. Adhering junctions perform cementing to keep neighbouring cells together.
3. Gap junctions facilitate the cells to communicate with each other by connecting the cytoplasm of adjoining cells for rapid transfer of ions and molecules.

Connective Tissue:
Connective tissues helps to linking and supporting othertissues/organs of the body. They include

• cartilage
• bone
• adipose
• blood.

Collagen or elastin:
In all connective tissues except blood, the cells secrete fibres of structural proteins called collagen or elastin.
The fibres provide strength, elasticity and flexibility to the tissue.
These cells also secrete modified polysaccharides, which accumulate between cells and fibres and act as matrix (ground substance).
Connective tissues are classified into three types:

• Loose connective tissue
• Dense connective tissue and
• Specialised connective tissue

Loose connective tissue:
They are loosely arranged in a semi-fluid ground substance. For example,
Areolar tissue:
It is present beneath the skin. It contains fibroblasts (cells that produce and secrete fibres),macrophages and mast cells.

Adipose tissue:
It is the loose connective tissue located mainly beneath the skin. The cells of this tissue are specialised to store fats.

Dense connective tissues.
In this Fibres and fibroblasts are compactly packed and are called dense regular and dense irregular tissues. In the dense regular connective tissues, the collagen fibres are present injows between bundles of fibres.
eg:

• Tendons, which attach skeletal muscles to bones
• ligaments which attach one bone to another.

Dense irregular connective tissue has fibroblasts and many fibres (mostly collagen) that are present in the skin.

Specialized connective tissues: They are Cartilage, bones and blood.

Cartilage:
Cells of this tissue (chondrocytes) are enclosed in small cavities within the matrix. Most of the cartilages in vertebrate embryos are replaced by bones in adults. Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, limbs and hands in adults.

Bones:
They have a hard ground substance rich in calcium salts and collagen fibres which give bone its strength. Bones support and protect softer tissues and organs. The bone cells (osteocytes) are present in the spaces called lacunae.

Limb bones, such as the long bones of the legs, serve weight-bearing functions. They also interact with skeletal muscles attached to them to bring about movements. The bone marrow in some bones is the site of production of blood cells.

Blood:
It is a fluid connective tissue containing plasma, red blood cells (RBC), white blood cells (WBC) and platelets. It also helps in the transport of various substances.

Muscle Tissue:
It consists of long, cylindrical fibres arranged in parallel arrays. These fibres are composed of numerous fine fibrils, called myofibrils. Muscle fibres contract (shorten) in response to stimulation, then relax (lengthen) and in their uncontracted state. Muscles play an active role in all the movements of the body Muscles are of three types, skeletal, smooth, and cardiac.
1. Skeletal muscle:
It is the tissue is closely attached to skeletal bones. In a typical muscle such as the biceps, striated (striped) skeletal muscle fibres are bundled together in a parallel fashion.

2. Smooth muscle:
These fibres taper at both ends (fusiform) and do not show striations. The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue. Smooth muscles are ‘involuntary’ as their functioning cannot be directly controlled.

3. Cardiac muscle tissue:
It is a contractile tissue present only in the heart. Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together In Communication when one cell receives a signal to contract, its neighbours are also stimulated to contract.

Neural Tissue:
Neurons, the unit of neural system are excitable cells The neuroglial cell which constitute the rest of the neural system protect and support neurons. Neuroglia make up more than one half the volume of neural tissue in our body.

Nerve impulse transmisssion:
When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma membrane and reaches at the neuron’s endings, or output zone, triggers events that may cause stimulation or inhibition of adjacent neurons and other cells.

ORGAN AND ORGAN SYSTEM:
Each organ in our body is made of one or more type of tissues. For example, our heart consists of all the four types of tissues, i.e., epithelial, connective, muscular and neural. In animals morphology refers to the external appearance of the organs or parts of the body.

EARTHWORM:
Earthworm is a reddish brown terrestrial invertebrate The common Indian earthworms are Pheretima and Lumbricus.

Morphology:
They have long cylindrical body.lt is divided into more than hundred short segments which are similar. The dorsal surface of the body is marked by a dark median mid dorsal line (dorsal blood vessel). The ventral surface is distinguished by the presence of genital openings (pores).

Anterior end consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth . The prostomium is sensory in function. The first body segment is called the peristomium (buccal segment) which conjoins the mouth.

In a mature worm, segments 14-16 are covered by a prominent dark band of glandular tissue called clitellum. Thus the body is divisible into three prominent regions.

• preclitellar
• clitellar &
• postclitellar segments

Four pairs of spermathecal apertures are situated 5^th – 9^th segments. A single female genital pore is present in the mid-ventral line of 14^th segment. A pair of male genital pores are present on 18th segment.

Numerous minute pores called nephridiopores open on the surface of the body. In each body segment, except the first, last and clitellum, there are rows of S-shaped setae, Setae plays an important role is in locomotion.

Anatomy:
The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which is the epidermis, two muscle layers and an innermost coelomic epithelium. The epidermis is made up of a single layer of columnar epithelial cells which contain secretory gland cells. A terminal mouth opens into the

1. buccal cavity (1 – 3 segments) which leads into muscular pharynx.
2. Oesophagus (5 – 7 segments), continues into a muscular gizzard (8 – 9 segments).

It helps in grinding the soil particles and decaying leaves etc. The stomach extends from 9 – 14 segments. The food of the earthworm is decaying leaves and organic matter mixed with soil. Calciferous glands, present in the stomach, neutralise the humic acid present in humus.

Intestine starts from the 15^th segment onwards and continues till the last segment. A pair of short and conical intestinal caecae project from the intestine on the 26^th segment. The characteristic feature of the intestine between 26 – 35 segments is the presence of internal median fold of dorsal wall called typhlosole.

This increases theeffective area of absorption in the intestine. The alimentary canal opens to the exterior by a small rounded aperture called anus. These simpler molecules are absorbed through intestinal membranes and are utilised. Pheretima shows closed type of blood vascular system, consisting of blood vessels, capillaries and heart.

Blood glands are present on the 4^th, 5^th and 6^th segments. They produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature.

In Earthworms respiratory exchange occurs through moist body surface into their blood stream. The excretory organs occur as segmentally arranged coiled tubules called nephridia They are of three types:

• septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine,
• integumentary nephridia, attached to lining of the body wall of segment 3 to the last that open on the body surface and
• pharyngeal nephridia, present as three paired tufts in the 4^th, 5^th and 6^th segments

Nephridia:
It regulate the volume and composition of the body fluids. A nephridium starts out as a funnel that collects excess fluid from coelomic chamber. The funnel connects with a tubular part of the nephridium which delivers the wastes.

Nervous system:
It is represented by ganglia arranged segment wise on the ventral paired nerve cord (3^rd and 4^th segments). The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body.

Sensory system does not have eyes but does possess light and touch sensitive organs to distinguish the light intensities and to fee the vibrations in the ground. Worms have specialised chemoreceptors (taste receptors) which react to chemical stimuli. Earthworm is hermaphrodite (bisexual), i.e., testes and ovaries are present in the same individual.

There are two pairs of testes present in the 10^th and 11^th segments. Their vasa deferentia run up to the 18^th segment where they join the prostatic duct. Two pairs of accessory glands are present one pair each in the 17^th and 19^th segments. The common prostrate and spermatic duct opens to the exterior by a pair of male genital pores on the ventro-lateral side of the 18^th segment.

Four pairs of spermathecae are located in 6^th – 9^th segments (one pair in each segment).They receive and store spermatozoa during copulation. One pair of ovaries is attached at the 12^th and 13^th segments. Ovarian funnels are present beneath the ovaries which continue into oviduct, join together and open on the ventral side as a single median female genital pore on the 14^th segment.

A mutual exchange of sperm occurs between two worms during mating. Mature sperm and egg cells and nutritive fluid are deposited in cocoons produced by the gland cells of clitellum.

Fertilisation:
Fertilisation and development occur within the cocoons which are deposited in soil. The ova (eggs) are fertilised by the sperm cells within the cocoon. The cocoon holds the worm embryos. After about 3 weeks, each cocoon produces two to twenty baby worms. Earthworms development is direct, i.e., there is no larva formed.

Earthworms are known as ‘friends of farmers’ because they make burrows in the soil and make it porous which helps in respiration and penetration of the developing plant roots. The process of increasing fertility of soil by the earthworms is called vermicomposting. They are also used as bait in game fishing

COCKROACH:
Cockroaches are are included in class Insecta of Phylum Arthropoda. They are nocturnal omnivores that live in damp places throughout the world. They are found in human homes and thus are serious pests and vectors of several diseases.

Morphology:
The adults of the common species of cockroach, Periplaneta americana are about 34 – 53 mm long with wings that extend beyond the tip of the abdomen in males. The body of the cockroach is segmented and divisible into three distinct regions – head, thorax and abdomen. The body is covered by a hard chitinous exoskeleton.

Exoskeleton has hardened plates called sclerites that are joined to each other by a thin and flexible articular membrane (arthrodial membrane). Head is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck It has compound eyes. A pair of antennae arise from sockets lying in front of eyes. They help in monitoring the environment.

Anterior end of the head bears appendages forming biting and chewing type of mouth parts. It consists of a labrum (upper lip), pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe, acting as tongue (hypopharynx), lies within the cavity enclosed by the outhparts.
Thorax consists of three parts:

1. prothorax
2. mesothorax
3. metathorax.

Each thoracic segment bears a pair of walking legs. The first pair of wings arises from mesothorax and the second pair from metathorax. Forewings (mesothoracic) called tegmina are opaque dark and leathery and cover the hind wings when at rest. The hind wings are transparent, membranous and are used in flight.

The abdomen in both males and females consists of 10 segments. In females, the 7^th sternum is boat shaped and together with the 8^th and 9^th sterna forms a genital pouch whose anterior part contains female gonopore, spermathecal pores and collateral glands.

In males, genital pouch lies at the hind end of abdomen bounded dorsally by 9^th and 10^th terga and ventrally by the 9^th sternum. It contains dorsal anus, ventral male genital pore and gonapophysis. Males bear a pair of short, threadlike anal styles which are absent in females. In both sexes, the 10^th segment bears a pair of jointed filamentous structures called anal cerci.

Anatomy:
The alimentary canal is divided into three regions: foregut, midgut and hindgut The mouth opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus.

Oesophagus opens into a sac like structure called crop used for storing of food. The crop is followed by gizzard or proventriculus. Gizzard helps in grinding the food particles. A ring of 6 – 8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.

At the junction of midgut and hindgut is present another ring of 100 – 150 yellow coloured thin filamentous Malphigian tubules. They help in removal of excretory products from haemolymph. The hindgut is differentiated into ileum, colon and rectum. The rectum opens out through anus.

Blood vascular system of cockroach is an open type Blood vessels are open into space (haemocoel). Visceral organs located in the haemocoel are bathed in blood (haemolymph).The haemolymph is composed of colourless plasma and haemocytes.

Heart of cockroach consists of elongated muscular tube lying along mid dorsal line of thorax and abdomen. Blood from sinuses enter heart through ostia and is pumped anteriorly to sinuses again. The respiratory system consists of a network of trachea, that open through 10 pairs of small holes called spiracles present on the lateral side of the body.

Thin branching tubes carry oxygen from the airto all the parts. Exchange of gases take place at the tracheoles by diffusion. During excretion Malpighian tubules absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic.

In addition, the fat body, nephrocytes and urecose glands also help in excretion. The nervous system of cockroach consists of segmentally arranged ganglia joined by paired longitudinal connectives. Three ganglia lie in the thorax, and six in the abdomen.


The nervous system of cockroach is spread throughout the body. If the head of a cockroach is cut off, it will still live for as long as one week. In the head region, the brain is represented by supra-oesophageal ganglion which supplies nerves to antennae and compound eyes. In cockroach, the sense organs are antennae, eyes, maxillary palps, larfial palps, anal cerci, etc.

Compound eves of cockroach:
The compound eyes are situated at the dorsal surface of the head. Each eye consists of about 2000 hexagonal ommatidia. With the help of several ommatidia, a cockroach can receive several images of an object. This kind of vision is known as mosaic vision with more sensitivity but less resolution, being common during night (hence called nocturnal vision).

Cockroaches are dioecious Male reproductive system consists of a pair of testes lying one on each lateral side in the 4^th – 6^th abdominal segments. From each testis arises a thin vas deferens, which opens into ejaculatory duct through seminal vesicle. The ejaculatory duct opens into male gonopore situated ventral to anus.

A characteristic mushroom shaped gland is present in the 6^th – 7^th abdominal segments which functions as an accessory reproductive gland. The external genitalia are represented by male gonapophysis or phallomere The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation.

The female reproductive sysytem consists of two large ovaries, lying laterally in the 2^nd – 6^th abdominal segments. Each ovary is formed of a group of eight ovarian tubules or ovarioles, containing a chain of developing ova. Oviducts of each ovary unite into a single median oviduct (also called vagina) which opens into the genital chamber.

Sperms are transferred through spermatophores. Their fertilised eggs are stored in capsules called oothecae. On an average, females produce 9 – 10 oothecae, each containing 14 – 16 eggs. The development of P. Americana is paurometabolous, meaning there is development through nymphal stage.

The nymph grows by moulting about 13 times to reach the adult form. The next to last nymphal stage haswing pads but only adult cockroaches have wings.

FROGS:
Frogs are belong to class Amphibia of phylum Chordata. The most common species of frog found in India is Rana tigrina. Their body temperature varies with the temperature of the environment. Such animals are called cold blooded or poikilotherms They have the ability to change the colour to hide them from their enemies (camouflage).

This protective coloration is called mimicry. During peak summer and winterthey take shelter in deep burrows to protect them from extreme heat and cold. This is called as summer sleep (aestivation) and wintersleep (hibernation).

Morphology:
The skin is maintained in a moist condition. The frog never drinks water but absorb it through the skin. Body of a frog is divisible into head and trunk. A neck and tail are absent. Above the mouth, a pair of nostrils is present. Eyes are bulged and covered by a nictitating membrane that protects them while in water.

On either side of eyes a membranous tympanum (ear) receives sound signals. The forelimbs and hind limbs help in swimming, walking, leaping and burrowing. The hind limbs end in five digits and they are larger and muscular than fore limbs that end in four digits.

Feet have webbed digits that help in swimming. Frogs exhibit sexual dimorphism. Male frogs can be distinguished by the presence of sound producing vocal sacs and also a copulatory pad on the first digit of the fore limbs which are absent in female frogs.

Anatomy:
The body cavity consists of organ systems such as digestive, circulatory, respiratory, nervous, excretory and reproductive systems. The digestive system consists of alimentary canal and digestive glands. The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced.

The mouth opens into the buccal cavity that leads to the oesophagus through pharynx. Oesophagus is a short tube that opens into the stomach which in turn continues as the intestine,rectum and finally opens outside by the cloaca. Liver secretes bile that is stored in the gall bladder. Pancreas, a digestive gland produces pancreatic juice containing digestive enzymes.

Digestion of food takes place by the action of HCI and gastric juices secreted from the walls of the stomach. Partiailv digested food called chyme is passed from stomach to the first part of the intestine, the duodenum. The duodenum receives bile from gall bladder and pancreaticjuicesfrom the pancreas through a common bile duct.

Bile emulsifies fat and pancreatic juices digest carbohydrates and proteins. Final digestion takes place in the intestine. Digested food is absorbed by the numerous finger-like folds in the inner wall of intestine called villi and microvilli. The undigested solid waste moves into the rectum and passes out through cloaca.

In water, skin acts as aquatic respiratory organ (cutaneous respiration). Dissolved oxygen in the water is exchanged through the skin by diffusion. On land, the buccal cavity, skin and lungs act as the respiratory organs. The respiration by lungs is called pulmonary respiration.

The lungs are a pair of elongated, pink coloured sac- like structures present in the upper part of the trunk region (thorax). Air enters through the nostrils into the buccal cavity and then to lungs. During aestivation and hibernation gaseous exchange takes place through skin. The blood vascular system involves heart, blood vessels and blood.

The lymphatic system consists of lymph, lymph channels and lymph nodes. Heart is a muscular structure situated in the upper part of the body cavity. It has three chambers, two atria and one ventricle and is covered by a membrane called pericardium. Atriangularstructure called sinus venosus joins the right atrium.

It receives blood through the major veins called vena cava. The ventricle opens into a saclike conus arteriosus on the ventral side of the heart. The blood from the heart is carried to all parts of the body by the arteries (arterial system).The veins collect blood from different parts of body to the heart and form the venous system.

Special venous connection between liver and intestine as well as the kidney and lower parts of the body are present in frogs. The former is called hepatic portal system and the latter is called renal portal system.

The blood is composed of plasma and cells. The blood cells are RBC (red blood cells) or erythrocytes, WBC (white blood cells) or leucocytes and platelets. RBC’s are nucleated and contain red coloured pigment namely haemoglobin. The lymph is different from blood. It lacks few proteins and RBCs.

The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder. Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons. Two ureters emerge from the kidneys in the male frogs. The ureters act as urinogenital duct which opens into the cloaca.

In females the ureters and oviduct open seperately in the cloaca. The thin-walled urinary bladder is present ventral to the rectum which also opens in the cloaca. The frog excretes urea and thus is a ureotelic animal.

The chemical coordination of various organs of the body is achieved by hormones which are secreted by the endocrine glands. The endocrine glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads.

The nervous system is organized into a central nervous system (brain and spinal cord), a peripheral nervous system (cranial and spinal nerves) and an autonomic nervous system (sympathetic and parasympathetic). There are ten pairs of cranial nerves arising from the brain. Brain is enclosed in a bony structure called brain box(cranium).

The brain is divided into fore-brain, mid-brain and hind-brain. Forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired diencephalon. The midbrain is characterised by a pair of optic lobes. Hind-brain consists of cerebellum and medulla oblongata.

The medulla oblongata passes out through the foramen magnum and continues into spinal cord, which is enclosed in the vertebral column. Frog has different types of sense organs, namely organs of touch (sensory papillae), taste (taste buds), smell (nasal epithelium), vision (eyes) and hearing (tympanum with internal ears).

Eyes in a frog are a pair of spherical structures situated in the orbit in skull. External ear is absent in frogs and only tympanum can be seen externally. The ear is an organ of hearing as well as balancing (equilibrium).

Male reproductive organs consist of a pair of yellowish ovoid testes which are found adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium. Vasa efferentia are 10 – 12 in number that arise from testes. They enter the kidneys on their side and open into Bidder’s canal.

Finally it communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca. The cloaca is a small, median chamber that is used to pass faecal matter, urine and sperms to the exterior.

The female reproductive organs include a pair of ovaries. They are situated near kidneys and there is no functional connection with kidneys. A pair of oviduct arising from the ovaries opens into the cloaca separately. A mature female can lay 2500 to 3000 ova at a time.

Fertilisation is external and takes place in Water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult. Frogs are beneficial for mankind because they eat insects and protect the crop.

Frogs maintain ecological balance because these serve as an important link of food chain and foodweb in the ecosystem. In some countries the muscular legs of frog are used as food by man.