Excretion in Frogs : Frogs have well developed system composed of a pair of kidneys. Kidneys contain many filtering units called nephrons. These nephrons filter waste prouct from blood. The waste then goes to collecting tubules and finally to urinary bladder through ureters. Frogs are ureotelic animals.

Differences between eyes of cockroach and eyes of frog.

A simple epithelium is an epithelial tissue made up of only one layer of epithelial cells. These cells are in direct contact with the basement membrane. And often the layer underneath the basement membrane is a connective tissue. The simple epithelium is primarily involved in absorption and filtration.

The first segment of earthworm is called a peristomium and it contains the buccal cavity of the earthworm.

The median dorsal line is the dorsal blood vessel which runs throughout the length of an earthworm.

An organ is composed of similar or dissimilar type of tissues and is responsible for a specialized function.

Neural tissue is made up of nerve cells or neurons. They facilitate conduction of nerve impulses.

Muscular tissues are made of muscle fibres and help in articulation of limbs and movement of other organs.

Earthworms are protandrous,i.e.,the tests mature earlier than the ovaries. Self fertilisation is not possible in them because of the relative position of the openings of male and female reproductive organs.

Some important features found in eyes of cockroach are 
(i) They are located on the dorsal side of head
(ii) They are compound eyes and composed of 2000 hexagonal units called ommatidia.
(iii) They receive several images of an obeject. The number of ommatidia produces a mosaic vision which has more sensitivity and less resolution.

Sclerties The body of cockroach is externally covered by hard brown chitinous plates called sclerites, which constitute the exoskeleton.

Form - Elongated, oviod, dorsoventrally, flattened body>
Size -  About 38 mm long and about 12 mm wide.
Colour - Brown or black in colour.
Symmetry - Bilateral

Some important features of hyaline cartilage are
(i) It is translucent
(ii) It is glassy-bluish green
(iii) It is not mineralised
(iv) It does not have white or yellow fibers

The yellow bone marrow is composed of adipose tissues. It storest fat and produce corpuscles in emergency and is present in the shafts of long bones.