Zoology lecture notes and study materials

Epithelial Tissue: (Types, Structure, Functions & Examples)


classification of epithelial cells

Classification of Epithelial Tissue in Animals

Epithelial Tissue: (Structure, Classification and Functions)
(Structure Classification and Functions of Simple and Compound Epithelium)

What is Epithelium?

Ø  Epithelium is a tissue system in animals.

Ø  Epithelium constitutes the outer layer of body surfaces, linings of the alimentary canal and the walls of hollow structures.

Ø  It covers the internal or external surfaces of the body.

Ø  Epithelial cells are held together by carbohydrate based cementing materials.

Ø  They also possess special junctions between the cells.

Ø  The bottom layer of epithelium is rest on the basement membrane.

Ø  The basement membrane composed of a network of fibrous proteins particularly rich in collagens.

Ø  Epithelial layers are NOT provided with any blood vessels.

Ø  The cells of the epithelium obtain nutrients and oxygen by diffusion from the lymphatic vessels.

Ø  Nerve endings occur in the epithelial tissues for receiving stimuli.

What are the Functions of Epithelial Tissue?

Ø  Epithelium provides protection to the underlying structures.

Ø  Protect organs from injuries by external agencies or pressure.

Ø  Prevent infection by microorganisms.

Continue reading

biological chemistry

Biological Importance of Water


biological functions of water

Biological Importance of Water

Water is the mother liquid of all forms of life. The essentiality of water for living systems is quite evident as without water, there is no life. No other substance on earth is abundant as water. All aspects of cell structure and functions are adapted to the physical and chemical properties of water. The following are the important biological significance or importance of water in the living system.

(1).  Water is a ‘universal solvent’.

(2).   Water can dissolve most of the biologically important molecules.

(3).  It is the solvent of life. The life originated in water and adapted to survive only in the presence of water.

(4).  About 70 to 90% of a cell occupies water.

(5).  Water acts as a medium for the diffusion of molecules in the cell.

(6).  Osmotic concentration of cell is maintained by water and dissolved solutes.

(7).  The turgidity of the cell is maintained by the water.

(8).  Translocation of inorganic and organic compounds in the living system takes place through the water.

(9).  Carbohydrates, the product of photosynthesis, in plants are transported through the water.

(10).  Water is the source of H+ ions for photosynthesis.

Continue reading

Ecology Lecture Notes

Characteristics of Hydrophytes with PPT (Classification and Adaptations)


Water plants adaptations PPT

Hydrophytes: Classification and Adaptations
(Morphological, Anatomical and Physiological Adaptations of Aquatic Plants)

What is an adaptation?

Ø  “Any feature of an organism which enables it to exist under conditions of its habitat is called adaptation”.

Ø  Adaptations are for withstanding adverse conditions of environment and to utilize the maximum benefit of the environment (nutrition or conditions).

Ø  Adaptations in plants may be in:

1.   Morphological features

2.   Anatomical features

3.   Physiological characters

4.   Reproductive characters

Classification of plants based on water relation (Warming, 1990)

(1). Hydrophytes: plants growing in or near water.

(2). Xerophytes: plants adapted to survive under very poor availability of water.

(3). Mesophytes: plants growing in an environment which is neither very dry nor very wet.

What are hydrophytes?

Ø  Hydrophytes (aquatic plants, water plants) are plants growing in or near water.

Ø  These plants are adapted to survive in excess of water in their surroundings.

Ø  Greek: Hudor = water; Phyton = plant: water plant

Ø  Examples: Utricularia, Vallisneria, Hydrilla, Chara, Ceratophyllum, Trapa

Ø  Aquatic plants are the producers of the aquatic ecosystem.

Ø  They fix sunlight and ensures the survival of an aquatic ecosystem.

Ø  Even though plants originated in water, except algae, most of the aquatic plants are evolved from their mesophytic relatives.

Continue reading

biological chemistry

How Hydrogen Bond is Formed in Water?


biological significance of hydrogen bonds in water

Hydrogen Bond: Formation, Structure and Properties of Hydrogen Bonds in Water

The life was originated and started its evolution in water. Without water, life could not have existed on this planet. The properties of water, both physical and chemical, enabled water as the ‘solvent of life’. The water possesses some unusual physical and chemical properties. These ‘unusual properties’ of water makes water as the solvent of life. The unusual properties of water are due to presence of Hydrogen Bonds in them. The present post describes the method of formation of hydrogen bonds in water its properties.

How Hydrogen Bond is formed in Water?

Ø  Water is a polar solvent.

Ø  The polarity of a molecule due to uneven of distribution charges in them.

Ø  Uneven charge distribution causes a dipole formation.

Ø  One part (pole) of water molecule is slightly positive.

Ø  The other part (pole) of water molecule is slightly negative.

Ø  This type of difference in the distribution of positive and negative charges in a molecule is due to the huge difference in the electronegativity of the atoms in them.

Ø  Electronegativity is the ability of an atom to attract bonded pair of electrons towards its nucleus.

Continue reading

Human Physiology Lecture Notes

Difference between Sympathetic and Parasympathetic Nervous Systems


difference between parasympathetic and sympathetic nervous system

Sympathetic vs Parasympathetic Nervous Systems
(Similarities and Differences between Sympathetic and Parasympathetic Nervous Systems)

The involuntary or reflex functions in the body are controlled by a part of peripheral nervous system called Autonomous Nervous System (ANS). ANS regulate the functions of internal organs (visceral functions) particularly the functions of heart, stomach and intestine.  The Autonomic Nervous System composed of two components:

            (1). Sympathetic Nervous System (SNS)

           (2). Parasympathetic Nervous System (PNS or PSNS)

Sympathetic Nervous System (SNS): They are the part of ANS which originate from the spinal cord of the thoracic and lumbar region. They control the ‘fight-or-flight’ response or the ‘sympatho-adrenal response’ in the body. SNS prime the body for acting in threatening situations for survival. The sympathetic nervous system acts in the body as complementary to the action of Parasympathetic Nervous System.

Parasympathetic Nervous System (PNS or PSNS): Part of ANS originates from the spinal cord and medulla which control the ‘rest-and-digest’ or ‘feed-and-breed’ activities in the body. They act in the body as complementary to the action of SNS.

The present post describes the similarities and differences between Sympathetic Nervous System and Parasympathetic Nervous System

Similarities between Sympathetic and Parasympathetic Nervous System

Ø  Both are the part of ANS.

Ø  Both originate from the spinal cord.

Ø  Both have huge influence on physiological process of the body such as respiration, circulation, digestion, urination and reproduction.

Ø  Both have role in maintaining the homoeostasis of the body.

Ø  Both composed of pre-ganglionic and post-ganglionic neurons.

Difference between Sympathetic and Parasympathetic Nervous System

Continue reading