Melatonin maintains circadian rhythm of the body.

Gastric glands have three major types of cells namely-
(i) mucus neck cells which secrete mucus
(ii) peptic or chief cells which secrete the proenzyme pepsinogen; and
(iii) parietal or oxyntic cells which secrete HCI and intrinsic factor (factor essential for absorption of vitamin B₁₂).

Adrenal glands, also known as suprarenal glands, are small, triangular-shaped glands located on top of both kidneys.

The growth in plants is indeterminate while that in animals is determinate. A branch of plant can grow up to varied lengths, while a particular organ of an animal grows up to a definite size only.

1. The easiest way is by looking at their seeds. Seeds of mono cots have one cotyledon while that of dicots have two cotyledons.
2.Dicots have tap root system, while monocots have fibrous root system.
3.Dicots show reticulate venation, while monocots show parallel venation

Glycocalyx is significant in the following ways
(i) It protects the cell from loss of water and nutrients
(ii) Serves as a protective layer against attack by phagocytosis and viruses.
(iii) Helps in attachment to a surface
(iv) Provides virulence.

The body of earthworm bears a series of circular grooves called the annuli. The annuli divide the body into 100-120 small parts termed as segments or meatmeres.

Meristerms are divided into three types i .e ., apical meristerm, intercalary meristerm and lateral meristerm.

Differences pinnately compond leaf different from a palmetly compound leaf are

All chordates have a notochord, but only in vertebrate the vertical column develops from notochord, so all chordates are not vertebrates.All vertebrates are chordates as they have notochord in embryonic stage

Diatoms are called the jewels of the plant kingdom because of cell wall ornamentation and presence of golden brown chromatophores.
There are two types of diatoms, i.e., the pennate diatom and centric diatom. Pennate diatoms are like small rectangular soap boxes. Centric diatoms are circular.

HIV has two single RNA strands in its nucleoid. Reverse transcriptase enzyme catalyses the formation of DNA from RNA. It is found in some RNA viruses called retroviruses, e.g., HIV

Non- living things also show growth, e.g., a mountain or sand dune grows by accumulating material externally on surface. But, this growth is considered as external growth in comparison to the growth of living things which is internal.

The living things possess following features, which are not present in non - living things
(i) growth and metabolism
(ii) reproduction
(iii) ability to sense stimuli (consciousness)
(iv) ability to self-replicate and self-organise