• It consists of cells which form membranes.
• This membrane covers the body surface and the glands.
• The covering or protective tissues in the animal body are epithelial tissues.
• Epithelium covers most organs and cavities within the body.
• It also forms a barrier to keep different body systems separate.
• The skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all made of epithelial tissue.
• The cells are tightly packed and form a continuous sheet.
• They have only a small amount of cementing material between them and almost no intercellular spaces.
• These are divided into four types:-

SIMPLE

• The cells are extremely thin and flat and form a delicate lining.
• The lining of oesophagus and the mouth are covered with squamous epithelium.

STRATIFIED

• The cells are arranged in many layers to prevent wear and tear.
• Since they are arranged in a pattern of layers, the epithelium is called stratified squamous
• The skin, which protects the body, is made of squamous epithelium.

COLUMNAR

• The columnar (meaning ‘pillar-like’) epithelium facilitates movement across the epithelial barrier.
• It is present where absorption and secretion occur, as in the inner lining of the intestine, tall epithelial cells are present.
• In the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like projections on the outer surfaces of epithelial cells.
• These cilia can move, and their movement pushes the mucus forward to clear it. This type of epithelium is thus ciliated columnar epithelium.

CUBOIDAL

• Cuboidal epithelium (with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support.
• Epithelial cells often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface.
• Sometimes a portion of the epithelial tissue folds inward and a multicellular gland is formed.
• This is glandular epithelium.

The nucleus is a membrane-enclosed organelle, found in most eukaryotic cells, which stores the genetic material (DNA). The nucleus is surrounded by a double lipid bilayer, the nuclear envelope, which is embedded with nuclear pores. The nucleolus is inside the nucleus, and is where ribosomes are made.

Golgi apparatus, Mitochondria, Ribosomes, Nucleus are parts of Eukaryotic Cells.
Functions

• They produce energy (ATP) and therefore are called the 'powerhouse of the cell'.
• Helps in regulating cell metabolism.
• Mitochondria possess their own DNA, RNA and components required for protein synthesis

A n s w e r :

The functions of the mitochondria, chloroplasts and peroxisomes are not coordinated with the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles. Hence, they are not part of the endomembrane system.

Cells are of different shape, size and structure according to the function they need to perform. So, if all the cells become of same size, shape and structure, it will be very difficult for multicellular organisms including humans to adapt better to the environment and survive. Also, the division of labour among the cells will be lost thus leading to difficulties in survival.

Nerve cells are usually branched and very long as they need more surface area to transmit the signals. Due to their long size they can easily carry messages in each and every portion around the body.

In mammals, after maturation, the nucleus disappears from the RBC to provide adequate space for hemoglobin to carry oxygen. Nucleus is responsible for cell division so the blood cells don't divide, they are produced by other cells within bone marrow. This is an adaptation which allows the red blood cell to carry more oxygen.

Structurally, plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements.

Plant Cells

• In addition to containing most of the organelles found in animal cells, plant cells also have a cell wall, a large central vacuole, and plastids. ...
• Plant cells with visible chloroplasts.
• The internal structure of a chloroplast, with a granal stack of thylakoids circled.

Mesosome is a convoluted membranous structure formed in a prokaryotic cell by the invagination of the plasma membrane. Its functions are as follows:

(1) These extensions help in the synthesis of the cell wall and replication of DNA. They also help in the equal distribution of chromosomes into the daughter cells.

(2) It also increases the surface area of the plasma membrane to carry out various enzymatic activities.

(3) It helps in secretion processes as well as in bacterial respiration.

The characteristics of prokaryotic cells are:

• Membrane bound cell organelles such as Mitochondria, Golgi apparatus, Chloroplasts are absent.
• A membrane bound well defined nucleus is absent.
• Genetic material is circular DNA and occurs naked in the cell cytoplasm. It is attached to the cell membrane and called nucleoid.
• The cell size ranges from 0.1 to 5.0 micrometre in size.
• The cell wall is a rigid structure which is made up of polysaccharides.

Answer: If the plasma membrane ruptures or breakdown then the cell will not be able to exchange material from its surrounding by diffusion or osmosis. Thereafter the protoplasmic material will be disappeared and the cell will die.

If there was no Golgi apparatus, various substances would not be in a position to be transformed in proper forms for further use. Certain substances, like protein and lipid, are important for the formation of plasma membrane. Hence the absence of Golgi apparatus will hamper the formation of new cells during cell division.

Key is a taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on contrasting characters generally in a pair called couplet. It represents the choice made between two opposite options, which results in acceptance of only one and rejection of the other. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Keys are generally analytical in nature.

• The flower with its pale is sessile, and is placed in the axil of another bract in such a way that the pale is exactly opposed to it, though at a slightly higher level.

• The bract is not, however, the one from which the axis terminating in the flower arises, but is a bract produced upon it, and gives origin in its axil to a new axis, the basal portion FIG.

• One argument that has been adduced in support of the axillary bud theory is derived from the Palaeozoic type Cordaites, in which each ovule occurs en an axis borne in the axil of a bract.

   

  he female flowers are equally simple, consisting of a bract, from whose axil arises usually a very short stalk, surmounted by two carpels adherent one to the other for their whole length, except that the upper ends of the styles are separated into two stigmas.

Stomata are small pores present in the epidermis of leaves. They regulate the process of transpiration and gaseous exchange. The stomatal pore is enclosed between two bean-shaped guard cells. The inner walls of guard cells are thick, while the outer walls are thin. The guard cells are surrounded by subsidiary cells. These are the specialised epidermal cells present around the guard cells. The pores, the guard cells, and the subsidiary cells together constitute the stomatal apparatus.

The xylem and phloem within a vascular bundles are arranged in an alternate manner on different radii is called radial vascular bundle. The xylem and phloem are situated at the same radius of the vascular bundles is called conjoint. 

1. Exarch: It is a type of primary xylem in which the protoxylem lies towards the periphery while the metaxylem lies towards the pith.
2. Endarch: It is a type of primary xylem in which the protoxylem lies towards the pith (centre) and the metaxylem lies towards the periphery of the organ.

Exarch xylem is the arrangement in which the protoxylem (the first formed primary xylem cells in a plant shoot/root) is directed towards the periphery and metaxylem (later formed primary xylem cells in a plant shoot/root) is directed towards the centre. Its development follows a centripetal pattern and is characteristics of roots. 

The first formed xylem elements are called protoxylem, while the later formed primary xylem is called metaxylem.

Protoxylem is the initially formed Xylem that develops before the plant organ is completely grown and Metaxylem is formed later.

The exterior portion of the cerebrum is called the cortex or the cerebral mantle. The cortex is extremely convoluted, due to which, it has a large surface area. 

Stomatal apparatus is a pair of guard cells with or without surrounding subsidiary cells which function as a value to open or close a stomatal pore for gaseous exchange and transpiration. 

Each stoma is made of two bean-shaped cells called the guard cells. The guard cells are dumb-bell shaped in grasses. They contain chloroplasts and small vacuoles. They are thick-walled in the area of contact and thin-walled elsewhere. As the guard cells swell up due to endosmosis, their thin-walled sides expand. The thick walls of the two guard cells also bend outwardly and create a pore in between them.

Vascular bundles wherein xylem and phloem lie side by side are called as radial bundles while conjoint vascular bundles have xylem and phloem separated from one another as are found in leaves.
A conjoint vascular bundle can be collateral or bicollateral. Collateral vascular bundles have xylem and phloem arranged in same radium with xylem present towards the inner side and phloem towards the outer side. Bicollateral bundles have phloem on both sides of the xylem as compared to collateral bundles wherein phloem is present on one side of xylem only. In leaves, xylem is present near upper epidermis and phloem near the lower one with phloem on one side of xylem thus collateral, not bicollateral bundles. On the basis of the presence of absence of cambium, collateral bundles are grouped as open or close bundles, those with cambium are termed as open vascular bundles while the vascular bundles without cambium are termed as closed.
Leaves lack cambium in vascular bundles making them closed type, this vascular bundles in leaves are found irregularly scattered in the mesophyll with the largest and the oldest one at centre and is termed as midrib vein. Each vascular bundle has a bundle sheath of compactly arranged barrel shaped parenchyma cells which cover both xylem and phloem. Xylem is present near upper epidermis and phloem near the lower one. Xylem has protoxylem and metaxylem vessels with protoxylem present towards upper epidermis, thus conjoint, collateral close vascular bundle with endarch xylem. 

Simple permanent tissues are composed of cells which are structurally and functionally similar. They are of three types – parenchyma, collenchyma and sclerenchyma.

1. Parenchyma –

Parenchyma tissue consists of relatively unspecialised cells with thin cell walls. They are live cells. They are usually loosely packed, so that large spaces between them.  This tissue provides support to plants and also stores food. In some cases, it contains chlorophyll and performs photosynthesis, and then it is called as chlorenchyma. In aquatic plants, large air cavities are present in parenchyma to give buoyancy to the plants to help them float. Such a parenchyma type is called aerenchyma. The parenchyma of stems and roots also stores nutrients and water.

ii. Collenchyma –

The cells of collenchyma tissue are living, elongated and irregularly thickened at the corners. There is very little or no intercellular space. It allows easy bending in various parts of a plant (leaf, stem) without breaking. Thus, provides flexibility to the plant. It also provides mechanical support to plants.  

iii. Sclerenchyma –

The cells of sclerenchyma tissue are dead. They are long and narrow as the walls are thickened due to deposition of lignin. The walls of cells are so thick that there is no internal space inside the cell. This tissue is present in stems, around vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts. It provides strength to the plant parts and makes the plant hard and stiff.

• Meristematic Tissue:

Meristematic tissues are growth tissues and found in the growing regions of the plant. According to their position in plant, meristems are apical, lateral and intercalary.

1. Apical meristem - Apical meristem is present at the growing tips of stems and roots and increases the length of the stem and the root.
2. Lateral meristem – Lateral meristems are found beneath the bark. The girth of the stem or root increases due to lateral meristem (cambium).
3. Intercalary meristem - Intercalary meristem is the meristem at the base of the leaves or internodes (on either side of the node) on twigs. It increases the length of the organs such as leaves and internodes.

Characteristics of Meristematic Tissues:

1. Their cells are similar in structure and have thin cellulose cell walls.
2. The cells are active and have dense cytoplasm.
3. They contain few vacuoles or no vacuoles at all.
4. The meristematic cells are compactly arranged and do not contain any intercellular space between them.

Complex permanent tissues –

Complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function. Xylem and phloem are examples of such complex tissues. They are both conducting tissues and constitute a vascular bundle.

1. Xylem –

Xylem is a vascular and mechanical tissue. It consists of tracheids, vessels, xylem parenchyma and xylem fibres. Except xylem parenchyma, all xylem elements are dead and bounded by thick lignified walls. Tracheids and vessels are tubular structures which transports water and minerals vertically. The parenchyma stores food and helps in the sideways conduction of water. Fibres are mainly supportive in function.

ii. Phloem –

Phloem contains tubes but performs no mechanical function. Phloem is made up of four types of elements: sieve tubes, companion cells, phloem fibres and the phloem parenchyma. Sieve tubes are tubular cells with perforated walls. Phloem is unlike xylem in that materials can move in both directions in it. Phloem transports food from leaves to other parts of the plant. Except for phloem fibres, phloem cells are living cells.

Characteristics of Solanaceae Family

The following are the characteristic features of the Solanaceae family:

Vegetative Characters

• Root System: Taproot system.
• Stem: Erect or climber; Solanaceae includes herbs, shrubs, small trees, and climbers.
• Leaves:  Alternate, simple or pinnately compound (rarely); exstipulate; reticulate venation.

Floral characters

• Inflorescence: Racemose- terminal or axillary raceme; Cymose- solitary in Solanum.
• Flower: Complete, bisexual, actinomorphic, hypogynous.
• Calyx: Five sepals, gamosepalous; valvate aestivation.
• Corolla: Five petals, gamopetalous, valvate aestivation.
• Androecium: Five stamens, epipetalous; anthers basifixed.
• Gynoecium: Syncarpous, bicarpellary, bilocular, superior ovary, axile placentation.
• Fruit: Berry/ capsule.
• Seed: Numerous, endospermous

Characteristics of Liliaceae Family

The following are the important characteristics of the Liliaceae family.

Vegetative Characters

• Root: Fibrous root system.
• Stem: Erect; Liliaceae includes perennial herbs which propagate through bulbs or rhizomes.
• Leaves:  Alternate, simple; exstipulate; parallel venation.

Floral characters

• Inflorescence: Cymose- solitary; umbellate clusters.
• Flower: Complete, bisexual, actinomorphic; hypogynous, perianth present.
• Perianth: Indistinctive sepal and petal; six tepals (3+3), often united tepals; valvate aestivation.
• Androecium: Six stamens in two whorls (3+3).
• Gynoecium: Syncarpous, tricarpellary, trilocular, superior ovary with axile placentation.
• Fruit: Mostly Capsule and sometimes berry.
• Seed: Endospermic seeds.

• The arrangement of ovules within the ovary is known as placentation.
• The placentation is of different types namely, marginal, axile, parietal, basal, central and free central.
• In marginal placentation the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. Example- pea
• When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentaion is said to be axile. Example- china rose.
• In parietal placentation, the ovules develop on the inner wall of the ovary or on peripheral part and ovary become twochambered due to the formation of the false septum. Example- mustard
• In free central, the ovules are borne on central axis and septa are absent. Example- Dianthus
• In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it. Example – sunflower.

• The plant is described beginning with its habit, vegetative characters such as roots, stem and leaves and then floral characters inflorescence and flower parts.
• After describing various parts of plant, a floral diagram and a floral formula are presented, which is represented by some symbols.
• In the floral formula, Br stands for bracteate K stands for calyx , C for corolla, P for perianth, A for androecium and G for Gynoecium, G for superior ovary and G for inferior ovary, for male, for female , ⊕ for actinomorphic and for zygomorphic nature of flower.
• Fusion is indicated by enclosing the figure within bracket and adhesion by a line drawn above the symbols of the floral parts.
• A floral diagram provides information about the number of parts of a flower, their arrangement and the relation they have with one another.
• The position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram.
• Calyx, corolla, androecium and gynoecium are drawn in successive whorls, calyx being the outermost and the gynoecium being in the centre.
• Floral formula also shows cohesion and adhesion within parts of whorls and in between whorls.