Describe various types of epithelial tissues with the help of labelled diagrams.

(i) A tissue is defined as a group of cells along with intercellular substances performing a specific function in the body.

(ii) The four basic types of animal tissues are epithelial, connective, muscular, and nervous tissue.

(iii) Epithelial cells are compactly packed without intercellular space and they line the body's surface and its cavities, ducts, and tubes.

(iv) Based on the structure and function, epithelial tissues are classified into two main groups: simple epithelium and glandular epithelium.

(v) Connective tissue is the most abundant and widely distributed body tissue.

(vi) Areolar tissue is the most generalised of all connective tissue which connects and supports other tissues.

(vii) Adipose tissue is a specialised loose connective tissue in which fibroblasts are modified for fat storage.

(viii) Tendons and ligaments are specialised types of fibrous connective tissues.

(ix) Tendon attaches a skeletal muscle to a bone, whereas the ligament attaches bone to bone.

(x) Skeletal tissue is a supporting tissue or a mineralised hardened connective tissue that consists of cartilage and bone (osseous) tissue.

(xi) Bone is a living tissue and is the main component of the skeletal system.

(xii) Mammalian bone is characterised by the presence of Haversian systems or osteon.

(xiii) Blood is a fluid connective tissue with transport functions.

(xiv) The most specialised property of muscular tissue is contractibility.

(xv) Based on structure, location and functions, muscular tissue is classified into three types: skeletal, smooth and cardiac muscle.

(xvi) Skeletal muscle is the muscle tissue attached to bones. Smooth muscle is a component of internal organs.

(xvii) Cardiac muscle makes up the contractile walls of the heart.

(xviii) Neural tissue is specialised for the conduction of electrical impulses that carry information.

(xix) Neurons are the basic units of nervous tissue.

(xx) A neuron consists of three distinct portions: cell body and its processes, axons and dendrites.

2. Earthworm:

(i) Earthworms have a long cylindrical body divided into segments called metameres. The ventral surface contains the genital pore, and the dorsal surface contain a mid-dorsal line.

(ii) First body segment is called the peristomium, which contain the mouth. 14-16 segments are covered by a dark band called clitellum.

(iii) Single genital pore is present on the mid-ventral line of the 14th segment. A pair of male genital pores are present on the 18th segment on the ventrolateral side.

(iv) Earthworms lack respiratory organs and respire through moist skin.

(v) Excretory organs are coiled segmental tubules called nephridia. There are three types of nephridia: Septal nephridia, integumentary nephridia, and pharyngeal nephridia.

(v) Earthworm is a hermaphrodite. Two pairs of testis are present in the 10th and 11th segments. 

(vi) One pair of ovaries is attached to the intersegmental septum of the 12th and 13th segments. Female genital pore open on the ventral side of the 14th segment. The mutual exchange of sperm takes place during mating.

(vii) Closed vascular system consists of the heart, blood vessels, and capillaries. 

3. Cockroach:

(i) The body of cockroach is covered with a chitinous exoskeleton and is divided into head, thorax and abdomen.

(ii) Head bears a pair of long antennae, and a pair of compound eyes.

(iii) Thorax bears three pairs of jointed appendages and two pairs of wings on mesothorax and metathorax.

(iv) The abdomen, the largest and broadest part, in both males and females consists of 10 segments.

(v) Anal cerci, a pair of many jointed structures are present on the tergite of 10th segment in both sexes.

(vi) Anal styles, a pair of small, spine-like unjointed structures are present on sternite of 9th segment in males only.

(vii) Hepatic caeca are present at the junction of foregut and midgut.

(viii) Malpighian tubules are present at the junction of midgut and hindgut and help in excretion.

(ix) A pair of salivary glands is present near the crop.

(x) The blood is also known as haemolymph which flows freely within the body cavity.

(xi) Fertilization is internal.

(xii) Females produce $10-40$ ootheca bearing developing embryos.

(xiii) Metamorphosis is regulated by two hormones, ecdysone secreted by prothoracic glands and juvenile hormone secreted by corpora allata.

4. Frogs:

(i) Digestion starts in the stomach, and final digestion occurs in the small intestine. Digested food is absorbed by villi and microvilli present in the inner wall of the small intestine.

(ii) Skin acts as aquatic respiratory organ (cutaneous respiration). On land, skin, the buccal cavity, and the lungs act as respiratory organs.

(iii)The vascular system of frog is a well-developed closed type. The heart is 3-chambered. 

(iv)The frog excretes urea and thus is a ureotelic animal.

(v)The system for control and coordination is highly evolved in the frog. It includes both neural system and endocrine glands

(vi) Frog's male reproductive organs consist of a pair of yellowish ovoid testes, and female reproductive organs include a pair of ovaries that are situated near the kidneys.

(vii)Fertilisation is external and takes place in water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult.