Manuals and records basically help in understanding past flora and fauna of a given area. Take an example of a thriving city. There may had been a dense forest, rich in biodiversity, where we get to see densely populated cities today. The manuals and records of that area helps us in knowing about past richness in biodiversity.
We also come to know about extinct species, through manuals and records. Some of the extinct species may be close or distant relatives of some existing species. We can develop some evolutionary relationships between them.

This is a very big world and there is huge diversity of animals and plants in this world. People of different parts of the world speak different languages. Even in a country, like India, a simple bird, like crow is known by hundreds of names. Think of a scientist's difficulty in understanding about crows in different languages. Moreover, there can be thousands of species of birds. It is practically impossible to study each and every species of plants and animals. Classification makes it easy to study living beings, by keeping them under various groups and subgroups.
So, all animals which are capable of flying and have beaks are kept under Aves. Similarly, all animals, having body hair and external ears are kept under mammalia. This makes our task to study them, far easier. An easy way to study helps us in understanding the living world in a better way. It can be said that classification definitely helps in a better and systematic study of living beings.

Taxonomical Aids help scientists keep a record and study common and uncommon characteristics of animals and plants. This study helps them to decide about the correct place of a species in the given taxonomical category.
Herbarium :
Collected plant species are dried for preservation. The place where they are kept as collection is known as herbarium.
Botanical Gardens :
Here live plants are reared for ready reference. Through live plants botanists can study certain features, like mode of reproduction, pattern of pollination, etc.
Museums :
Dead animal specimens are preserved in museums. Extinct species, like Dodo are kept in certain museum and act as good reference source.
Zoological Parks :
They are helpful in studying live specimens of animal species. Certain ferocious animals are easier to study in zoological parks.
Keys :
Keys are pairs of contrasting characters, out of which either of the characters is carried forward across generations and another is discarded to gain better adaptability. These keys are good tool to understand how complex organisms evolved from simpler organisms.
Manuals and Records :
Manuals and records show historical data about flora and fauna of a particular geographical location.

General Rules for Nomenclature:
i) Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.
ii) The first word in a biological name represents the genus.
iii) The second component denotes the species.
iv) Both the words in a biological name, when handwritten, are separately underlined or printed in italics to indicate their Latin origin.
v) The first word denoting the genus starts with a capital letter while the second word denoting species starts with a small letter.

The key for identification of plants is a taxonomic key. It is an important taxonomic aid. Key can be defined as a set of alternate characters arranged in such a manner that by selection and elimination one can quickly find out the name of an organism.
Depending upon the category, a key may be class key, order key, family key, genus key and species key.
Taxonomic keys can be of two types
(i)  Indented or Yoked key
(ii)  Bracketed key
Indented key provides a sequence of two or more alternate characters from which selection and elimination are carried out. In bracketed key, the alternate characters are given numbers in brackets. e.g., take three genera of family-Ranunculaceae to explain this.
(i) Ranunculus  Leaves alternate or radical, flowers not subtended by involucre, carpels ovuled, fruit achene.
(ii) Clematis  Leaves opposite, compound petal absent, sepals 4, carpels with one ovule and fruits achenes.
(iii)  Nigella  Flowers regular, carpels united at base, many ovules, fruit follicles.

The scientist will first identify the family to which the plant belongs
He will further follow the given steps
(i)  Using genus key, the genus is identified.
(ii)  Using species key, identification is carried out
(iii)  As the genus is known, the species is provided now with a latinised name as per guidelines.
(iv)  Type specimen or holotype is placed in a recognised herbarium or museum.
(v) Name, description and report of the discovery is published in a reputed scientific journal.

(i) Species is a basic unit of classification, where individuals share common characteristics.
(ii)  It is a natural population or group of natural population of individuals having similar morphology, anatomy, physiology and cytology.
(iii)  Species is an assemblage of structurally similar individuals, which can interbreed freely, but are reproductively isolated from members of other species.
Higher plants and animals : These are sexually reproducing organisms. So, the third definition of species is applicable in case of higher plant and animals.
Bacteria : The second definition of the species can be applied to bacteria. As bacteria do not reproduce sexually. Therefore, the criterion of free interbreeding and reproductive isolation cannot be applied to them.

(i)  Common name: Mustard.
(ii)  Parts of the name: First part represents the genus or generic name, while the second part represents the specific name.
(iii) They are written in Italics in order to highlight their Latin origin.
(iv) Linn written at the end of the name, is the abbreviation of the name of scientist Linnaeus, who gave the name to the plant.

A living thing has multiple levels of organisation. Each lavel of organisation has its own properties, which are not found in its constituents.
Examples of three tissues supporting the statements are
(i) Cardiac Muscle Tissue : It is contractile tissue present only in heart. Cell junctions fuse the plasma membrane of cardiac muscle cells and make them stick together. When one cell receives a signal to contract. It means a single cell cannot contract, while there are some fusion points, which allow the cells to contract as a unit.
(ii)  Blood : It is a fluid connective tissue. The individual components of blood, i.e., RBCs, WBCs and platelets have different properties but as a unit they make the blood, a tissue serving many functions.
(iii)  Bone : It is a hard connective tissue that forms the framework of the body. The individual cells inside the bone do not have this property.

An organism is said to be living, if it shows certain characteristic features that make it different from non-living things.
The following properties are defining features of a living organisms.
(i)  Growth : All living organisms show growth either by multiplication or by increase in size. Growth in living things is internal.
(ii)  Reproduction : All living things produce offsprings, possessing features similar to their parents. Thus, reproduction is essential to maintain the continuity of life on earth.
(iii)  Metabolism : It is the sum total of reactions occurring inside the body by which living things assimilate energy and use it for growth.
(iv)  Cellular Organisation : The cells are the structural and functional unit of every living organism.