Biology : It is concerned with the study of living organisms.
Biology has three branches—
(a) Zoology : It deals with the study of animals.
(b) Botany : It deals with the study of plants.
(c) Microbiology : It deals with the study of micro-organisms like bacteria, viruses etc.
Habitat : It is a place where an organism grows naturally.
Mesophytes : Plants which grow under average conditions of temperature and rainfall are called mesophytes e.g. Mangifera indica (Mango), Azadirachta indica (Neem), Hibiscus.
Xerophytes : Plants which grow in dry places where they cannot get normal supply of water are called xerophytes e.g. Opuntia, Nerium Casuarina, Asparagus, Acacia, Parkinsonia.
Hydrophytes : Plants growing in abundance of water are called hydrophytes. Hydrophytes may be submerged, partly submerged, floating or amphibious, e.g. Submerged—Vallisnaria, Hydrilla.
Floating—Eichhornia, Pistia.
Rooted plants with floating leaves—Nymphaea, Nelumbium.
Amphibious—Limnophila.
Halophytes : Plants growing in saline soils (soils in which the concentration of simple inorganic salts is high) are called halophytes, e.g. Salicornia bracteata, Spartina, Tamarix, Chenopodium.
Epiphytes : Plants which grow on other plants are called epiphytes. Unlike parasites they do not depend on host plant for food materials. Roots of epiphytes are of two kinds. Clinging roots and hanging roots. They contain a dead, hygroscopic (water absorbing) tissue velamen. e.g. Bulbophyllum, Vanda.
Mangroves : Plants growing in saline marshes and mouths of rivers are called mangroves.
For efficient aeration they produce pneumatophores (respiratory roots) e.g. Rhizophora, Sonneretia, Avicennia.
Trees : Tall plants of several feet height with a clear, hard and woody stem are called trees. They survive for years. They have a main trunk at the top of which arise a number of branches, e.g. Mango, Neem, Polyalthia, Casuarina. Banyan etc.
Shrubs : Medium sized plants with a hard and woody stem often much branched and bushy are called shrubs. e.g. Hibiscus rosa-sinensis, Nerium, Gossypium.
Twinners : Plants in which weak stem twines around the support are called twinners, e.g. Dolichos, Clitoria, Dioscorea.
Lianas : Very thick and woody perennial climbers commonly met with in forests are called lianas, e.g. Hiptage, Bauhinia vahlii, Ventilago, Tinospora.
Herbs : Small plants with a soft stem are called herbs. Their heights vary from a few millimetres to a metre. Life span is short. Most of the vegetable plants are herbs. e.g. Wheat, Gram, Onion, Sunflower, Ginger, Radish.
Ephemerals : Plants completing their life cycle from seed to seed within 4 to 6 weeks are called ephemerals, e.g. Artemesia, Tribulus, Solanum xanthocarpum.
Annuals : Plants which live for one year are called annuals. They grow, produce flowers and fruits within one year, and then die off, e.g. Brinjal, Wheat, Rice, Gram.
Biennials : Plants which live for two years are called biennials. They attain their full vegetative growth in the first year. They produce flowers and fruits only in the second year and then they die off, e.g. Radish, Turnip, Carrot, Beet etc.
Perennials : Plants which live for many years are called perennials. They continue to grow from year for year. These plants produce flowers, fruits and seeds continuously, e.g. Rose, Mango, Neem, Banyan.
Autotrophs : Most of the plants synthesize their own food in their leaves from the raw materials absorbed from soil and air, and nourish themselves. Such plants are called autotrophs.
Photoautotrophs : These are green plants which utilise solar energy for synthesising their own food by photosynthesis, e.g. Mango, Mustard, photosynthetic bacteria like Rhodospirullum, chlorobium and Chromatium.
Chemoautotrophs : They use the energy released during the oxidation of chemicals for synthesizing their own food, e.g. Chemosynthetic bacteria. (Sulphur bacteria, Nitrification bacteria, Iron bacteria).
Heterotrophs : Plants which cannot make their own food and depend on other sources for supply of nutrients, are called heterotrophs.
Parasites : Plants which grow on other living plants and absorb necessary nutrients from them are called parasites. To absorb nutrients from the host plant, parasites produce certain special roots called sucking roots or haustoria, e.g. all disease causing fungi like Phytophthora, Puccinia and Ustilago.
Saprophytes : Plants that grow on dead and decaying organic matter are called saprophytes, e.g. Neottia, Monotrapa, Sarcodes, some fungi (Rhizopus, Agaricus), etc.
Symbionts : When two organisms live together as if they are parts of the same plant and are of mutual help to each other, they are called symbionts. The relationship between the two is called symbiosis.
Insectivorous Plants : Some autotrophic plants normally grow in soils devoid of nitrates. They modify their leaves into traps for capturing insects and get readymade proteins by digesting them e.g. Nepenthes, Drosera, Utricularia, Dionaea.
Oxylophytes : Plants that grow in acidic soils are called oxylophytes.
Psychrophytes : Plants that grow in cold soils are called psychrophytes.
Lithophytes : Plants which grow on rocks are called lithophytes.
Psammophytes : Plants which grow on sand and gravel are called psammophytes.
Chersophytes : Plants that grow on waste land are called chersophytes.
Endophytes : Plants living within other living plants are called endophytes.
Trophophytes : Plants which behave as mesophytes in rainy season, and as xerophytes in summers are called trophophytes.
Cryophytes : Plants that grow on ice are called cryophytes.
Chasmophytes : Plants which grow in rock crevices are called chasmophytes.
Plurivores : Parasites which can grow on many host plants are called plurivores (Cuscuta).
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