Red blood cells are not considered to be prokaryotic, because they are part of an eukaryotic organism. Red blood cells begin life with the full complement of organelles, including a nucleus and mitochondria, but RBCs in humans shed their organelles during maturation. In actuality, though, only mammalian RBCs lack nuclei; RBCs in other animals still hold on to their traditional eukaryotic characteristics.

Red blood cells are not considered to be prokaryotic, because they are part of an eukaryotic organism. Red blood cells begin life with the full complement of organelles, including a nucleus and mitochondria, but RBCs in humans shed their organelles during maturation. In actuality, though, only mammalian RBCs lack nuclei; RBCs in other animals still hold on to their traditional eukaryotic characteristics.

Connective tissues have cells scattered throughout an extracellular matrix. They connect different body systems. Blood is considered as a type of connective tissue because of two reasons.

(i) Like the other connective tissues, blood is mesodermal in origin.

(ii) It connects the body systems, transports oxygen and nutrients to all the parts of the body, and removes the waste products. Blood has an extra-cellular matrix called plasma, with red blood cells, white blood cells, and platelets floating in it.

The cells of nervous tissue are highly specialized and the cells of this tissue are called nerve cells or neurons.

• Nervous tissue stimulates and transmits the stimulus very rapidly from one place to another within the body.
• The brain, spinal cord and nerves are composed of the nervous tissue.
• A neuron consists of a cell body which comprises of nucleus and cytoplasm, from which long thin hair-like parts arise.
• The neuron has a single long part, called the axon, which transmit the nerve impulse to body parts.
• The neuron has short, branched parts called dendrites.
• Many nerve fibers combine together by connective tissue and form a nerve.
• Nerve impulse enables animals to move rapidly in response to stimuli.

ANSWER

Muscle tissue is a soft tissue that composes muscles in animal bodies and gives rise to muscles' ability to contract. 

There are mainly three types of muscle tissue:-

1)Skeletal(Striated) Muscle:
Structure: Skeletal muscle is called "striated" because of its appearance consisting of light and dark bands visible using a light microscope. A single skeletal muscle cell is long and approximately cylindrical in shape, with many nuclei located at the edges (periphery) of the cell.

Function: 

• Movement of the skeleton under conscious control, including movement of limbs, fingers, toes, neck, etc.
• Movement of tissues of facial expression under conscious control, e.g. ability to smile and to frown.

2)Smooth(Non-Striated) Muscle:

   Structure: Unlike Skeletal and Cardiac muscle tissue, Smooth muscle is not striated. Smooth muscle fibres are small and tapered - with the ends reducing in size, in contrast to the cylindrical shape of a skeletal muscle. Each smooth muscle fibre has a single centrally located nucleus.

   Function: Contractions of smooth muscle constrict (i.e. narrow = reduce the diameter of) the vessels they surround. This is particularly important in the digestive system in which the action of smooth muscle helps to move food along the gastrointestinal tract as well as breaking the food down further. Smooth muscle also contributes to moving fluids through the body and to the elimination of indigestible matter from the gastrointestinal system.

3)Cardiac(Semi-Striated) Muscle:

   Structure: Cardiac muscle fibers are striated, branched (sometimes described as Y-shaped), and have a single central nucleus. These fibers are attached at their ends to adjoining fibers by thick plasma membranes called intercalated discs.

   Function: Pumping of blood through the heart: Alternate contraction and        relaxation of cardiac muscle pumps

De-oxygenated blood through the Right Atrium and Right Ventricle to the lungs, and oxygenated blood through the Left Atrium and Left Ventricle to the aorta, then the rest of the body.   

Glandular epithelium is a type of epithelial tissue which covers the glands (both exocrine and endocrine) of our body. Their main function is secretion. Both endocrine and exocrine glands produce their secretions through the glandular epithelium via special cells called goblet cells. Glandular epithelium in the reproductive tract is called endocervical glandular epithelium and helps in sexual functions by secreting lubricating fluid during sexual excitation. The glandular epithelium also lines the intestine where it helps in the absorption of nutrients. Thus it aids in digestion. Thus glandular epithelium is a multifunctional tissue that combines with other tissues to perform vital functions of the body.

• 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.