BOTANY

CLASSIFICATION OF PLANT KINGDOM

• Depending upon the morphology and the modes of reproduction and life cycle the plants are classified as follows:

(A) Cryptogams (Seedless plants)

• (i) Thallopyta
• (a) Algae
• (b) Fungi
• (ii) Bryophyta
• (iii) Pteridophyta

(B) Phanerogams or Spermatophyta (Seed bearing plants)

• (i) Gymnospermae (Naked Seeded plants)
• (ii) Angiospermae (seeds enclosed within the fruit)
• Salient features of the different groups

(A) Cryptogams

• (i) Thallophyta
• The members lack the differentiation of plant body into true roots, stems and leaves.
• They do not possess the mechanical (Collenchyma and Sclerenchyma) and conducting (xylem and phloem) tissues.
• The organs for reproduction i.e. gametangia are simple and unicellular, they do not possess a layer of jacket.
• The gemetophytic stage (haploid phase) is dominant over to the sporophytic stage (diploid phase) in the life cycle of these members.
• The thallophytes have been further divided into two main subdivisions on the basis of mode of nutrition i.e.-

(a) Algae

1.    They contain photosynthetic pigments like chlorophyll, carotene, xanthophill; Due to presence of these pigments, they are green, red, brown or yellow in colour. They manufacture their own food i.e., they are autotrophic.

2.    Their plant body may be unicellular (eg. Chlamydomonas, Chlorella), colonial (Volvox), filamentous (Spirogyra, Ulothrix) or a large thallus (eg. Ficus, Laminaria, Saragassum, Ulva). However the thallus is not diffentiated into true roots, stems and leaves.

3.  Cell-wall is composed of cellulose.

4.    Conducting tissues i.e. xylem and phloem are absent.

5.    Mostly aquatic, some are terrestrial.

(b) Fungi

1.    They lack photosynthetic pigments, so they are non-green and heterotrophic, i.e. they do not synthesize their own food but they are depend on others.

2.    They may be unicellular (eg. Yeast), or filamentous (eg. Mucor, Rhizopus, Penicillium).

3.    Cell wall is composed of fungous-cellulose and chitin.

4.    The stored form of food material is fat or oil.

5.    The mode of nutrition is either Parasitic or Saprophytic.

6.    Most of the species are terrestrial but some are aquatic (eg. Saprolegnia).

(ii) Bryophyta

• They are a group of lower plants. Which can be distinguished by the following characters.
• They are called amphibians of plant kingdom, having small and green plants they occur near moist and shady places.
• The plant body is a thallus (not differentiated into true root, stem and leaves) fixed to the soil by hair like structures called rhizoids. The thallus is flat and green in liverworths (eg. Riccia, Marchantia, Pellia, Notothylus) and leafy & erect in mosses (eg. funaria sphagnum).
• They do not bear flowers and lack vascular or mechanical tissues. The sporophyte is attached to the gametophyte and depends upon it for nutrition.

(iii) Pteridophyta

• They show following characters:
• The dominant stage of life cycle is a sporophate, which is differentiated into roots, stems, and leaves.
• Vascular tissues (oxlem and phloem) are present.
• The gametophytic and sporophytic stages are independent of each other. The gametophytic stage requires the presence of water for fertilization e.g. Lycopodium, Selaginella. Equisetum, Marseilea, Dryopteris (fern). etc.

(B) Phenerogams or Spermatophyta

• Spermatophyta are a group of higher plants that bear fruits and seeds. Their body is differentiated into true roots, stem, and leaves. The vascular tissues are very well developed. Like Pteridophytes, the sporophytic phase of life cycle is dominant over gametophytic phase. The gametophytic phase of life cycle is completed with the sporophyte. They have been divided into two subdivisions based on the structure of ovule. They are:

(i) Gymnospermae

1.    The ovules are naked i.e. the ovules are not enclosed within the ovary. After fertilization, they develop into naked seeds.

2.    Microspores and Megaspores are produced within the male and female cones respectively.

3.    There is single fertilization.

4.    Most of the forms are trees eg. Cyeas, Pitus Cedihis Ephedra Gnetum, Ginkgo etc.

5.    The ovules are enclosed within the ovary so after fertilization they develop into seeds enclosed within the fruit.

6.    Male and Female gametophytes are highly reduced.

7.    The flowers are the organs of reproduction (whereas in gymnosperms. It is mostly cones).

8.    There is double fertilization, which leads into the formation of diploid zygote and triploid endosperm.

PHOTOSYNTHESIS

• Photosynthesis is the single most important physio-biochemical process on which the existence of life on earth depends. It is the ability of green plants to utilise the energy of light to produce carbon containing organic material from stable inorganic matter by photosynthetic process. It is from the carbohydrate produced by photosynthesis that directly or indirectly all of the organic compounds, which compose of living world, are derived. The oxidation of organic compounds releases stored energy to be utilised by organisms to drive essential metabolic processes. Any energy released during oxidation of organic compounds is ultimately derived from light energy intercepted by green plants during photosynthesis.
• In simple terms, photosynthesis can be defined as “the formation of carbon containing compounds from carbon dioxide and water by plant cells. Water and oxygen are the byproducts.”
• Ruben and Kamen demonstrated by using isotopes of oxygen and carbon that the source of liberated oxygen is water.
• Of these components, water is obtained from the soil by roots of the terrestrial plants and by the general surface by hydrophytes. As a source of light, sun light is utilised. The terrestrial plants absorb CO2 from the atmosphere where is present upto 0.03 per cent while hydrophytes obtain it from the water where it is found dissolved up to 0.3 percent or even more. Due to this reason the hydrophytes produce much more photosynthetic products as compared to terrestrial plants. The CO2 is absorbed by the hydrophytes through the general surface while by the terrestrial plants through the leaves.

Chloroplasts

• The site of photosynthesis: All the green parts of the plant carry out photosynthesis and the leaves of all plants are ideally developed for this purpose. The process of photosynthesis takes place entirely within the subcellular organelles called the chloroplasts. Chloroplasts of higher plants are lens shaped or ellipsoidal and are found only in the green cells of plants, they are collectively known as plastids. The chloroplasts are most abundant in the elongated cells of the palisade tissue in the leaf but they also occur in the cells of the spongy mesophyll. The chloroplasts contain the green colouring pigment called chlorophyll.
• The chlorophyll plays a purely catalytic role in photosynthesis. It is a complex organic molecule and contains magnesium at the centre. Chlorophyll absorbs light by does not absorb green light. Other pigments like carotene and xanthophylls are also associated with the chlorophyll in the green plant cells; their presence in green leaves is usually marked by the greater abundance of the chloroplast.

Mechanism of photosynthesis

• The process of photosynthesis can be divided into two sets of separate but interconnected reaction sequences. The first chain of events is called the light reaction or primary process of photosynthesis. This is followed by the second sequence called the dark reaction or the secondary process of photosynthesis.

SEXUAL REPRODUCTION IN PLANTS

• This is very common type of reproduction in the antiospermic plants. In these plants the vegetative branch at some stage fat maturity or vegetative phase) changes to the reproductive phase i.e. flower. The period and time of bearing flower varies from species to species. Flowers may be bisexual or unisexual. Meiosis (reduction division) occurs in the male and female parts of a flower to form male (pollen g rains) and female (ovun) gametes. In order to produce seeds (to reproduce) male and female gametes fuse together to form zygote that divides mitotically and develops into a seed. The male gamete (pollen grains) are male gamete (pollen grains) are motile and reach up to the ovum for fertilization. This process of transference of pollen grains from the anther of a flower to the stigma of the same or of different flower is called pollination. It is of two types.

  (1)   Self-pollination: If the pollen grains are transferred to the stigma of the same flower or between two flowers borne by the same parent then it is self-pollination or autogamy.

  (2)   Cross-pollination: If the pollen-grains are transferred to the stigma of a different flower borne by a different flower borne by a different plant then it is called cross-pollination or allogamy.

• Adaptations for Self-pollination: The following are the adaptations that a plant shows to favour self-pollination:
  (1)   Homogamyation becomes obligatory, eg. Oxalis.

Fertilization

• As the pollen grains reach the stigma of the pistil their development starts. The outer wall called exine breaks and the inner walls called intine grows out as pollen tube. The pollen tube enters the ovule through micropylar end. The ovule has an embryo, which consists of three groups of cell. One egg cells and two synergids lie towards the micropylar end, two definitive nuclei in the centre and three antipodal cells opposite to micropyle. Each ovule consists of a stalk called the funicle, the region of the ovule where funicle is attached is called as chalaza. As pollen tube reaches the ovule it discharges the two male gametes. One gamete fuses with the egg cell to form he diploid zygote. The second fuses with the two definitive or central nuclei to form the triploid endosperm. This is called double fertilization, which is characteristic of angiosperm only.
• Seed formation: After fertilization, the part of the flower like sepals, and patals are shed followed by the mitotic division of the zygote. Which leads to formation of embryo. A distinct layer of epidermis can be noted on the surface. Cotyledons are formed, new protective coats are formed and embryo remains dormant. This is the seed.

SEEDS

• Fertilised ovule having the capacity to germinate is called a seed
• Seeds are produced for the commercial production of crops

Classification

Breeer’s seed

• Seeds produced after hybridization or mutation are called breeder’s seeds
• When such seeds contain sufficient hereditary characters, they are called Nucleus seeds
• Such seeds possess genetic purity and high quality

Foundation seed

• The second category of seed in terms of genetic purity is called foundation seed.
• Such seeds are produced by some organisation such as National Seed Corporation, State Seed Corporation and Tarai Seed Corporation

Certified seed

i.     These are produced from foundation seeds by two methods

ii.    In the first method seeds are produced by any government organisation and in the second method under production programmes by certified farmers.

Test (Tetrazolium test)

i.     It is used for testing the germinating power of a seed

ii.    Seeds are kept in water at night and then dipped for 2 to 4 hours in the solution of 2.3,5 Tetrazolium chloride or bromide.

iii.   Colour tetrazolium comes in contact with the enzyme present in the embryo and turns the living  cells red.

According to Indian Seed Act, 1966 which is effective from 1 October, 1969 seeds have to be certified before their commercial use.

Seed dormancy

• It is a chemical condition where the germinaring power of an embryo is reduced even in suitable weather conditions. As a result seeds are not properly developed.

FRUIT FORMATION 

• A fruit is ripened ovary. In some plants like apple and pear. The fruit is developed from other part than ovary. These are called false fruit. The fruit growth depends upon the development of the seeds, which synthesize hormones. Fruits protect the seeds and help in dispersal. The pericarp in fruit develops from ovary wall. The pericarp has three layers epicarp. mesocarp and endocarp.

Dispersal of fruits and Seeds

• Plants produce large number of seeds and fruits. In nature, they are carried to far away places to overcome crowding. This phenomenon is called dispersal. There are various external agencies like air, water, and animals etc. that bring about dispersal.

  (1)   Dispersal by air

  (a)   Eg. Moringa, Shorea by wings.

  (c)   Helianthus, Calotropis, Cotton, Clematis by parachute mechanism.

  (2)   Dispersal by water, eg. Lotus fruit- they have spongy thalamus.

  (3)   Dispersal by animal, eg. Xanthlum Urena fruits are provided with hooks and sticky glands.

  (4)   Dispersal by explosive devices, eg. Oxalis.

MORPHOLOGY OF PLANTS

• The knowledge of external morphology of angiosperms is essential for the study of all branches of botany i.e. Anatomy, Physiology and Systematics in particular. A typical anagiosperm plant has an underground root system and an aerial shoot system. The shoot system consists of branched or unbranched stem bearing leaves. The reproductive shoot is the flower with its differentiated organs. It is essentially concerned with the reproduction in plants. Broadly, external morphology of an angiosperm plant, can be divided into two classes:

  1.    Vegetative morphology: root, stem, and leaf

  2.    Reproductive morphology: inflorescence flower and fruit.

Vegetative morphology

Root

• When the primary root, which is a direct prolongation of the radicle, remains distinct through out of life of the plant and gives off lateral branches it is termed as the tap root system et. in mustard. In many plant other than original root system i.e. from radicle it is known as adventitious root system eg. onion, grasses etc. They along with their usual functions may also be suitably modified to carry out several other functions.

  (a)   Modifications of Taproot: In many plants the taproot becomes swollen and assumes various forms due to the storage of food.

  (b)   Modifications of Adventitious root: Adventitious root may be modified to carry on the storage of food, mechanical support, and other vital functions,(a)   Modifications of Taproot: In many plants the taproot becomes swollen and assumes various forms due to the storage of food.

  (b)   Modifications of Adventitious root: Adventitious root may be modified to carry on the storage of food, mechanical support, and other vital functions,

Stem

• The stem is the ascending aerial portion of a plant and develop from the plumule. It is differentiated into nodes and internodes and bears leaves, branches and flowers. Leaves and branches develop from the nodes. In contrast to the root, they possess, buds which may be situated in the axil of the leaf or terminally. A bud is a young undeveloped condensed shoot consisting of a short stem and a number of tender leaves arching over its growing apex. The habit to the plant is displayed by its stem. Herbs are small plants with soft stems. Medium sized plants with hard and woody stems that branch profusely to attain a bushy appearance are called Shrubs. Trees are plants having stout and long trunks with professed branching according to their life span. The plants may be annuals, biennials, and perennials. Plants, which complete their life cycle in one season, only are termed annuals, eg. Rice, sunflower etc. Biennials complete their life cycle in two seasons eg. Radish, cabbage. Plants that usually survive for a number of years and produce flowers and fruits during specific period each year are termed perennials eg. Mango, bamboos.
• Modification of Stem: Besides their usual function, stems often get modified to perform other functions such as perennation and vegetative propagation as the result; their forms are greatly changed. There are three types of modified stems:

  1.     Underground modifications of stems: They appear like roots but are distinguishable from the roots in having scale leaves at the nodes and buds, such stems also act as a means of vegetative propagation.

  2.    Sub-aerial modification of stem: In some cases aerial branches and adventitious roots develop at the nodes, which may behave as an independent plant when detached.

  3.     Aerial modification of stem: They greatly vary in form but can be distinguished easily by their position in the axil of a leaf or at the apex.

Leaf
 

• The left is a flattened lateral outgrowth of the stem and bears a bud in its axil. A typical angiosperm leaf consists of three parts:
• (1)             Leaf base (2) Petiole
• (3)             Lamina
• In many plants the leaf base is swollen and is termed pulvinus. The arrangement of veins in the lamina is termed as ventation. It is of two types:

  (1)   Reticulate: When the veins are forming a network, it is characteristic feature of the dicots.

  (2)   Parallel: When the veins are parallel and do not form a network. It is characteristic of monocots.

• Phyllotaxy: It may be defined as the arrangement of leaves on the stem. It is of three main types:
• (1) Alternative, eg. China rose
• (2) Opposite, eg. guava, Calotropis
• (3) Whorled, eg. Nerium
• Simple and Compound leaf: A leaf is said to be simple when its lamina is entire or incised but the incisions do not touch the mid rib. When the incision of the lamina goes down to the mid-rib the leaf becomes compound and it has a number of leaf segments, these leaf segments are known as leaflets. A leaflet is like a simple leaf but it lacks a bud in its axil. A compound leaf is said to be pinnate when the leaflets are lateral to the mid-rib, it may be unipinnate, eg. Rose: Bipinnate, eg. gold mohur (Delonix) and Tripinnate, eg. Moringa. In palmately compound leaves the petiole bears a number of leaflets which resemble a palm. Depending upon the number of leaflets, it may be Unifoliate, eg. Lemon, Bifoliate, Trifoliate, eg. Wood apple; Quadrifoliate eg. Marsilea and Multifoliate eg Bombax, Cleome.
• Modification of leaves: Some of the important modifications of leaves are:

  (1)   Tendril: Modified for the purpose of climbing, eg. Pea.

  (2)   Spine: Modified for the purpose of defence, eg. Opuntia.

  (3)   Scale leaves: eg. In Onion.

  (4)   Pitcher: In some of the insectivorous plants, eg. Nepenthes, the lamina assumes the form of a pitcher with a lid to trap the insects, the inner walls of the pitchers posses a number of digestive glands which secrete a fluid.

  (5)   Phyllode: When the petiole becomes leaflike, it is termed as phyllode, eg. Australian Acacia.

REPRODUCTION MORPHOLOGY

• Flowers, constitute the reproductive organs. A flower is a specialized shoot essentially meant for sexual reproduction and has evolved as a result of progressive speculation of reproductive structures.

Inflorescence

• It is a reproductive shoot bearing a number of flowers in terminal or axillary position. It is of three types recemose, cymose and special type. In racemose, the main axis is unlimited in growth, whereas in cymose, the growth of main axis is limited. It is of following types

  (1)   Raceme: The main axis of inflorescence bears stalked flowers, eg. Mustard, Radish etc.

  (2)   Spike: This is like raceme but the flowers are sessile, eg. Adhatoda.

  (3)   Catkins: The main axis of inflorescence, which is a long and pendulous bears unisexual flowers, eg. Mulberry.

  (4)   Spadix: The main axis inflorescence is fleshy enclosed by one or several large and brightly coloured bracts called the spathes, eg. Banana.

  (5)   Corymb: The main axis is short and bears stalked flowers in such a manner that they are placed almost at the same level, eg. Lantana, Cherry.

  (6)   Umbel: It has very shortened and suppressed axis, flowers have stalks of equal length, and it is umbrella like in appearance eg. Coriander, Carrot.

  (7)   Head of Capitulum: The main axis is flattened, more or less convex structure. On the receptacle, florets are arranged in a centripetal order, eg. Sunflower.

Special types of inflorescence

(1)   Hypanthodium: The main axis forms a cup shaped receptacle with a small opening at the top. Flowers are arranged within the cup eg. Ficus.

(2)   Cyathium: Here, one central flowers (represented by a single pistil) is surrounded by a large number of male flowers (each represented by single statements) the whole structure is enclosed in cup like structure, eg. Euphoribia, Pedialanthus.

(3)   Verticillaster: Flowers are sessile and appear in a flase whorl or vertically around the stem. Eg. Ocinum (Tulasi).

FLOWER

• The flower is a highly specialized condensed structure. The axis of the flower is known as thalamus. A typical flower shows four sets of members arranged in successive whorls. They are calyx, corolla, androceium, and gynaecium. Calyx and corolla constitute accessory whorls and Androecium and Gynaecium constitute the essential whorls of the flower.
• When calyx and corolla are undistin-tuishable, they are known as perianth (common among monocots). In absence of accessory whorls, it is known as achlamydous. When all the four parts of a flower are present, it is termed as complete. In the absence of any one of these, it is termed as incomplete. When both male and female component (androecium and gynoecium respectively) are present in the same flower, it is termed as bisexual or hermaphrodite. Unisexual, flowers it may be staminate (when gynaecium is absent) or pistillate (when androecium is absent). A flower without any functional stamen or pistil, it is known as neuter or sterile. If male and female flowers develop on the same plant. It is called monoecious, otheriwse, it is dioecious.
• A flower is said to be an actinomorphic when its symmetry remains undisturbed, even after cutting the flower into two halves through the axis where as zygomorphic flowers are those where their symmetry get disturbed after cutting the flower into more than two halves through their main axis. All the flowers, broadly, can be divided into 3 types, depending upon the relative positions of the floral parts on thalamus. I.e.

  (1)   Hypogyny: When the other floral part i.e. sepals, petals, stamens are inserted on thalamus below the ovary in the flower, eg. China rose.

  (2)   Epigyny: When the other floral parts are inserted above the ovary in the flower, the ovary in this case is said to be inferior, eg. Guava, Cucumber etc.

  (3)   Perigyny: When the other floral parts are inserted at the same level at the ovary, eg. Rose, Pea etc.

FRUIT

• Fruit is a characteristic feature of the flowering plants. It may develop either after fertilization of without fertilization. The fruit, which is produced without fertilization, is called parthenocarpic fruit, eg. Banana. Citrus, Grape etc. Fruits are of two types:

  (a)   True fruits: which develop from the ovary.

  (b)   False fruits: which develop from any other floral parts except ovary.

Common fruits and their edible parts

	Name of fruit	Type of fruit	Edible part
1	Apple, Pear, Loqual	Pome	Edible
2.	Banana	Berry	Mesocarp
3.	Cashewnet	Nut	Stalk and cotyledons
4.	Coconut	Fibrous drupe	Entire seed, endosperm
5.	Cucumber	Pepo	Mesocarp, endocarp and placenta
6.	Date palm	One seeded berry	Fleshy pericarp
7.	Fig	Syconus	Fleshy thallamus
8.	Jack	Sorosis	Bracts, perinath and seeds
9.	Grapes	Berry	Pericarp and placentae
10.	Guava	Berry	Thaliamus and pericarp
11.	Litchii	One seeded nut	Fleshy aril
13.	Mango	Drupe	Mesocarp
14.	Pea, Gram	Legume	Cotyledons
15.	Orange	Hesperidium	Juicy placentae
16.	Papaya	Berry	Mesocarp
17.	Pine apple	Sorosis	Bracts, receptacle, parianth
18.	Pome granate	Balusta	Juicy seed coat
19.	Straw berry	Etario of achenes	Fleshy thallamus
20.	Tomato	Berry	Pericarp and placentae

PLANT HORMONES

1.    Hormones are chemical messengers and coordinators that control and regulate the physiology and growth of both plants and animals.

2.    Auxin is the most important plant hormone

3.    Auxin is synthesised at the tips of stem and young leaves.

4.    The chief function of Auxin is to increase the length of the cell.

5.    Other functions of auxin:

       i.   Prevention of abscision

       ii.  Formation of callus

       iii. Apical dominance

       iv. Root initiation

       v.  Parthenocarpy

       vi. Cell elongation

6.    Giberellin is another very important plant hormone

7.    It is usually helpful in stem growth

8.    Other functions of giberellin

       i.   Development of leaves and internodes

       ii.  Parthenocarpy

       iii. Cell elongation

9.    Cytokinin is mainly responsible for increasing the rate of cell division

10.  Other functions of cytokinins

       i.   Prevention of apical dominance

       ii.  To prevent disintegration of chlorophyll and protein in the leaves

11.  Floreign is the hormone which induces flowering

12.  Growth inhibiting hormones

       i.   Abscisis acid

       ii.  Ethylene

ESSENTIAL NUTRIENTS FOR PLANT GROWTH

Element	Source		Ionic form
Carbon, Oxygen,	Air	Carbonate (CO3)
Hydrogen,	Water	H & OH
Nitrogen	Soil	Ammonium (NH4), Nitrates (NO3)
Phosphorus	Soil	K+
Calcium	Soil	Ca++
Magnesium	Soil	Mg++
Sulphur	Soil	So3-, SO4-
Iron	Soil	Fe++, Fe+++
Manganese	Soil	Mn++, Mn +++
Boron	Soil	BO3
Zinc	Soil	Zn++
Chlonne	Soil	C1-

2.    The mixing of minerals with water is called Hydration

3.    During distintegration of a compound (mineral the removal of hydrogen ion is called hydrolysis

4.    Hydroxides are formed after hydrolysis, which react with carbon dioxide present in the solution. This process is called carbonation.

ECOSYSTEM

• Organisms interact with each other and also with physical conditions that are present in their habitats. The organisms and the physical features of the habitat form an ecological complex i.e. Ecosystem. The term ecosystem was coined by A.G. Tansley in 1935. The function of ecosystem is related to the flow of energy and cycling of materials through structural components of the ecosystem. All ecosystems of the earth are connected to one another, e.g., river ecosystem is connected with ecosystem of oceans.

Components of Ecosystem

• Ecosystem has biotic and abiotic component.
• Abiotic Components: Abiotic components are basic inorganic and organic compounds such as soil, water, calcium, oxygen, carbonates, and phosphates. It also includes climatic components such as moisture, wind currents and solar radiation etc.
• Biotic Components: It includes living elements of the ecosystem and includes producers, consumers decomposers and transformers.

  (a)  Producers: The producers are autotrophic like chemosynthetic and photosynthetic bacteria, blue green algae and all other green plants. They use radiant energy of sun in photosynthetic process in which CO2 is assimilated and the light energy is converted into chemical energy and O2 is evolved as a by-product.

  (b)   Consumers: They are heterotrophic living members of ecosystem, which consume the food synthesized by producers. They are of three types.

  (i)    Primary consumers: Those are purely herbivorous animals that are dependent for their food and producers or green plants. The herbivores of ecosystem are known as “key industry animals”.

  (ii)   Secondary consumers: These are carnivores and omnivores, which eat primary consumers and producers.

  (iii)  Tertiary consumers: These top carrneivores, which feed upon other carnivores, omnivores and herbivores.

  (c)   Decomposers and transformers: They are living components of the ecosystem and are fungi and bacteria. Decomposers attack the dead remains of producers and consumers and degrade the complex organic substances into simpler compounds. These simple organic matters are attacked by another kind of bacteria, transformers which finally change these organic compounds into the inorganic form that are suitable for reuse by producers or green plants.

Food Chain

• Organisms of an ecosystem are linked together in food chains. Green plants alone are able to trap in solar energy and convert it into chemical energy. The plants are eaten by consumers, which are being eaten by their predators. Thus, food from one trophic level reaches the other trophic level and in this way a chain is established. This is known as food chain. A food chain many be defined as the transfer of energy and nutrients through succession of organisms through repeated process of eating and being eaten.

Biomes

• It is a recognizable community unit formed as a result of interaction of regional climates with regional substrata. The members of a biome are the plants and animals inhabiting it. The terrestrial environment is classified into four major biomes
• (a) The Tundra Biomes
• (b) The Forest Biomes
• (c) The Grassland Biomes
• (d) The Desert Biomes

ECOLOGY

• The word ‘ecology’s first proposed by a zoologist named Reiter in 1885, is derived from Greek words, Oikos meaning the dwelling place or home and logos meaning the discourse or study.
• The things of the world are classified into two major groups i.e. biotic component and abiotic component. The biotic component includes all types of living organisms, both plants and animals and the abiotic component includes the non-living materials (soil, water, air etc) and the forces of nature (light, gravity and molecular energy).

BIOGEOCHEMICAL CYCLES

• About 30 to 40 elements are needed for the normal growth and development of organisms. The important elements are carbon, nitrogen, oxygen, phosphorus, calcium, magnesium, potassium etc. also known as macro elements. While sodium, copper, zinc, cobalt, boron molybdenum and strontium etc are known as trace elements.
• The movement of all these nutrients in an ecosystem is cyclic and flows from non-living to living and back to non-living and such a cyclic process is known as biogeochemical cycle. They are of three types.

Hydrologic or water cycle

• It involves an interchange of water between the earth surface and atmosphere via precipitation, evaporation, transpiration, cloud formation surface water run off and percolation. Water covers about 73% of the earth’s surface occurring in Lakes Rivers, ponds and oceans etc. From these water bodies the water keeps on evaporating in the atmosphere and percolated water keeps on transpire through leaves into the atmosphere. The water present in atmosphere after cooling and condensation form clouds that result in snowfall and rain etc. Thus there is a continuous cycling of water.
• Clouds                                          Ice on mountains and Poles
• Transpiration                                Rain    
• Plants                                           Soil      Water
• Evaporation                                 Oceans, Rivers

Gaseous Cycles

• Carbon cycle: By volume, carbon dioxide in atmosphere is nearly 0.03%. It involves the cycling of carbon, the basic compound of all the organic compounds that build all the living things. The carbon is returned to the atmosphere from carbohydrate, lipid & protein break down. Atmospheric carbon dioxide and dissolved Co2 in water are the basic source of carbon. It moves from atmospheric reservoir to producers, from produce to consumers and from both to the decomposers and finally backs to the atmospheric reservoir.

Nitrogen Cycle

• Nitrogen is essential for the synthesis of amino acids and proteins in animals and plants. It is 78% in atmosphere and is not of much use of plants and animals. Nitrogen is directly taken from the air by nitrogen fixing root nodule bacteria or by free living aerobic bacteria (Azotobacter) or by anaerobic soil bacteria (clostridium)
• The bacteria make nitrogen available to the plants in the form of nitrates. When nitrogen is absorbed as nitrate it has to be reduced to acid and protein synthesis. The breakdown of dead tissues by decay bacteria releases ammonia from protein and other nitrogenous compounds. Nitrosomonas bacteria oxidize ammonia into nitrites and still other bacteria (Nitrobacter) oxidize nitrite to nitrate (Nitrification).

Oxygen Cycle

• About 21.94% oxygen is present in the atmosphere. It is essential for life on the earth. It is produced as a by-product of plants during the process of photosynthesis. It is consumed by both, animals and plants in respiration and is returned to the environment in the form of carbon dioxide. The carbon dioxide is taken up by green plants for carbohydrate synthesis.
• Sedimentary Cycle: Mineral elements are sedimented in rocks in the form of their salts. Mineral salts come directly from earth crust by weathering. Soluble salts then enter the water cycle. By movement of water minerals move from the soil to stream lakes and ultimately to sea where they remain permanently. Other salts return to the earth’s crust through sedimentation. They become incorporated into sediments or beds and after weathering of rocks they again enter the cycle.

NOISE

Source	Sound level (In DB)	Sound
Self whisper	25	Very quiet
Ordinaryconversation	60	Moderate loud
Food blender	85	Very loud
Motorcycle(25 Mt. Away)	90	Very loud
Jet plane(100Mt away)	105	Uncomfortable loud
Thunderclap	120	Uncomfortable loud
Hooting of trains	130	Uncomfortable loud
Jet plane take off		Painful
Rocket engine	180	Painful