The difference between flora, fauna and vegetation are as below

Flora	Fauna	Vegetation
Flora is a plant life occurring in a particular region or time, generally the naturally occurring indigenous native plant life.	Fauna is total number of animals found in a particular region at particular time.	It refers to the plant forms of region. It is broad and general term used for a plant forms, which does not include particular taxa or any botanical characteristics.

The terms exotic and endemic refers to

Exotic Species	Endemic Species
Any species of a plant living in any other place except its native place is said to be exotic species. e.g., Eichhornia crassipes is native of Amazonian basin but it was introduced in India, so it is a exotic species in India.	Endemic species are restricted to a particular area, e.g., Rauwolfia serpentina is found only in India, so it is an endemic species found only in India.

There is a need to standardise the naming of living organisms such that a particular organism is known by the same name all over the world. Botanists have solved this problem by setting International Code for Botanical Nomenclature (ICBN). Scientific naming ensures that each organism has only one name in any part of the world. ICBN ensures that such name has not been used for any other organism.

Each name has two components the generic name and the specific epithet. This system of naming is called bionomial nomenclature given by Carolus Linnaeus. e.g., mango has the scientific name Mangifera indica and potato is known as Solanum tuberosum.

Solanum is the largest genus of flowering plants which includes few economically important plants, e.g., potato, tomato, tobacco and brinjal. All these plants show some common morphological structures related to vegetative and reproductive similarities. So, they have the same common name of genus Solanum.

Cell, the basic structural and functional unit is composed of many cell organelles, i.e., ER, Golgi apparatus, ribosomes, mitochondria, chloroplasts etc., each with a specific function. Each of these organcells are made up of various moleclules such as proteins, lipids, enzymes, metallic ions like $\mathrm{Mg}^{2+}, \mathrm{Ca}^{2+}, \mathrm{Mn}^{2+}, \mathrm{Na}^{+}$etc, which helps in the functioning of cell organelles.

e.g., molecular constituents like proteins (60-70\%), lipids (25-30\%), RNA (5-7\%) DNA, $\mathrm{Mn}^{2+}$ ETS, ATP synthase, etc. found in mitochondria function togather in a coordinated way to carry out cellular respiration and release energy, thus making it power house of cell.

Thus, the molecular constituents of a cell organelle, forms the basis of its functioning irrespective of its individual molecular properties.

The number and kind of organism is not constant, because of the following reasons Mechanisms adding new organisms by

(i) Sexual reproduction

(ii) Mutation

(iii) Evolution

Mechanisms reduing the number of organisms are

(i) Environmental threats

(ii) Loss of habitat

(iii) Anthropogenic activities