Grade :-8(Science) Living Being

                                       Unit :-16      Living being

Micro-Organism :The organism that are seen only through a microscope are called micro-organisms or microbes .The micro –organisms that are harmful and causes of diseases are called Pathogens (Patho=diseases ,gnes =causing)

Microbiology :The branch of biology consisting the study of micro-organism is called microbiology .

Classification of micro-organism :Micro- organism are divides into 5 majors groups :

1)Virus      2)Bacteria    3)Protozoa   4)Fungi            5)Algae

1)Virus :A microscopic obligatory parasite that causes of various disease in plants and animals is called virus. The branch of biology consisting the study of viruses is called virology .Viruses can exist outside of the living cell for long period of time but they can reproduces only inside the specific cell of living host so viruses are  called  obligatory parasite .Virus show the properties of both living being and non living being ,so virus are called borderline of living being and non living being .

                                                                Fig .Bacteriophase Virus

Types of virus :On the basis of nucleic acid :-They are 2 types :

i)D.N.A. virus :e.g. Bacteriophase  ,small pox virus .

ii)R.N.A. virus :e.g. Polio virus ,Paramyxo virus .

On the basis of host :They are 3 types :

i)Animal virus :Rhino virus ,HIV virus .

ii)Plant virus :Tobacco mosaic virus .

iii)Bacteriophase virus .The virus that attack the bacteria is called bacteriophase virus .

Living characteristics of viruses :

i)They reproduce in large number  .

ii)They contains genetic materials i.e. D.N.A. and R.N.A.

iii)They  transmit heredity characteristics from one generation to another generation .

iv)They infects other organism and causes of various diseases .

Non living characteristics of viruses :

i)Viruses do not have a cellular structure .

ii)They do not perform metabolic activities .

iii)They do not respiration .

Mode of transmission :The particular virus attack on particular organism and particular organs and they transmit by means of air, water, food ,blood etc .

Controls measures of viral diseases:

I)By burning the viral diseased plants.

ii)By destroying the insects like aphids .

iii)Human beings can protected from viral diseases by the use of vaccines .

2.)Bacteria :Bacteria are the most primitive ,simplest ,and smallest unicellular microscope organisms .It was discovered by Antony van Leeuwenhoek in 1676 A.D. They are found everywhere i.e. in water, in soil, in animals ,in plants etc. The branch of biology consisting the  study of bacteria is called bacteriology .Bacteria show characteristics of both animals as well as  plants therefore, they are also called boarder of line between plants and animals .  Bacteria are found in different shape .

On basis of shape they are classified into  four types :

1) Coccus: They are oval in shape .

2)Bacillus:They are rod shaped .

3.)Spirillum :They are spiral in shaped .

4)Filament or mycelia :They are thread like or filamentous in shape .

Characteristics of bacteria  :

 i)They are unicellular and microscopic organism .

ii)The Bacterial cell are prokaryotic cell .i.e. It does not contains nucleus .

iii)They have cell wall .

iv)They contains chlorophyll but some contains bacterial chlorophyll .

 v)They may be heterotrophic, or  autotrophic, or

saprophytic .

vi)Large number of bacteria are the parasite and causes of different diseases .

Advantages of bacteria :

i)Bacteria i.e. Lactobacillus and acidophilus help in making curd from milk .

ii)They decompose waste matter into harmless substances .i.e. compost manure .

iii)They help to produce vinegar .

iv)They help to produces some alcohol .

v)Some bacteria present in soil help to convert atmospheric nitrogen into nitrates and increase the fertility of soil .

v)Some bacteria produce vitamins B complex groups .

vi)Some bacteria are used to make antibiotics .

Disadvantages

i)A large number of bacteria are the causes of diseases in human beings i.e. cholera, typhoid .

ii)Some bacteria are causes of plants diseases I.e. leaf spot .

iii)Some bacteria are the causes of the food poisonous .

iv)Some bacteria destroys cooked foods ,fruits, vegetables during summer month .

v)Some bacteria reduces the fertility of soils .

Controls measures of bacterial diseases :

i)By burning the diseases plants .

ii)by using diseases free seed .

iii)By spraying antibacterial drugs .

iv)By using antibiotics .

v)By vaccination against diseases .

3.)Fungi :Fungi are a group of non green plants i.e. yeast ,mushroom etc. They do not contains chlorophyll so they can not form their own foods ,Therefore some fungi are saprophytic are found on decaying organic materials of dead organism and some are parasite are found on tissues of living organism .The branch of biology consisting the study of fungi is called mycology .

                                                                     Fig. Mushroom

Characteristics of fungi .

i)The plant body of fungi  is not divided into root ,stem and  leaf .

ii)They do not  bear chlorophyll .

iii)They are unicellular or multi cellular .

iv)They are parasite or saprophyte  .

v)They reproduces both asexually and sexually .

Advantages of fungi :

i)Edible mushroom are rich in proteins vitamins and minerals.

ii) Large number of antibiotics are made from species of fungi .

iii)Large numbers of vitamins i.e. Vitamins-B complex, vitamins –E are obtained from yeast .

iv)  Large numbers of enzyme are made from yeast .

v)Saprophytic  yeast help to decompose dead plants animals that increase the fertility of soil .

Disadvantages of fungi :

i)A number of diseases are caused by the species of fungi .

ii)High fever and allergies are the causes of fungi .

iii)They are also causes of large number of plants diseases .

iv)Some species of fungi also destroys the articles of i.e. leather ,clothes ,electric appliances in monsoon season

Controls measures of fungi :

i)It can be controlled by keeping the milk, foods ,meats, and vegetables in cold places .

ii)It can be controlled by using salt .

iii)It can be controlled by adding sugar .

iv)Fungal growth in human skin can be controlled by personal cleanliness.  

Modification of parts of plants 

:The roots, stem and leafs of different parts of plants are modified to perform various functions and adopt in their habit .This process is modification of parts of plants .

1.)Modification of roots :

Root: The parts of plants  which develops from the radicals parts of seed and does not bear any leaf,bud or flower is root .It non green and grows downwards in the soil .

Functions of roots :i)It help to fix the plants body  in the soil.

ii)It help to absorb water and minerals from the soils.

Types :It is mainly two types :

1)Tap root  system : A  root system that  form  a single main root that grows down is called tap root system . The main root of this root system is called primary root. It gives rise secondary roots. The tip of each root is protected by special a special structure is called root cap. Such roots are found in dicotyledonous .ie.Pea, mustard  etc

                                                                     Fig. Tap root

2.) Fibrous root  system : A  root system which forms a dense network of roots that is closer to the soil surface is called fibrous  root system. Such roots are found in monocotyledonous plants i.e. Maize, wheat, rice, .

                                                              Fig.   Fibrous root

Roots of plants are modified for following functions :

1)Modification of roots for storage of  foods

2.)Modification of roots for mechanical supports .

3.)Modification of roots for vital function .

1.)Modification of roots for storage of foods :In modification of roots system to storage foods both tap and fibrous roots are modified as storage organs by changing  their shape and size following ways :

i)Fusiform :They are spindle shape i.e. swollen in middle and tappers to wards the apex and the base .i.e. radish

ii)Napiform :The spherical in shape i.e. Turnip.

iii)Conical :They are conical  in shape i.e. carrot

iv)Tuberous :They are thick and fleshy but does not take a definite shape .i.e. mirabills ,potato .

v)Nodules : They are swelling at the tips like nodules i.e. Ginger .

2.)Modification of roots for mechanical support : In modification of roots system for mechanical support both tap and fibrous roots are modified as mechanical organs  by changing  their shape and size following ways :

i)Prop root :They are pillar or column shaped ,grow vertically downward .i.e. banyan tree .

ii)Stilt root :They are slender aerial in shape  and develop from lower basal nodes .i.e. maize, wheat, bamboo, sugarcane.

iii)Floating root :They are spongy ,soft and light  with air spaces .i.e.

3.)Modification of roots for vital function : In modification of roots system for vital functions both tap and fibrous roots are modified as vital organs  by changing  their shape and size following ways :

i)Nitrogen fixing root :They convert atmospheric nitrogen into nitrates by help of symbiotic bacteria found in their  root nodules   .i.e. beans ,pea.

ii)Respiratory  roots :Some roots in marshy area develop a conical spikes which grow upward to take oxygen from surrounding  is called respiratory roots .i.e. rhizophora, mangrove  plants .

iii)Parasitic roots :These roots penetrate the host ,tissue and absorb the nutrients from the host plants i.e. cuscuta ,mistletoe .

iv)Assimilatory roots .These roots are containing chloroplast and they can manufacture food just like leaf ,such root are called photosynthetic or assimilatory roots .i.e. tinospora ,trapanatans .

2.)Modification of stem :

Stem :The aerial portion of plants axis  which develop from the plumule of the embryo is called stem .It consist of two parts i.e. i) Node :The points of stem from where the leaves and other branches arise is called node .  ii)Inter nodes :The portion between two nodes is called internodes 

.Functions : i) It help for support to the leaves ,fruits ,and flower .

ii)It help for  the conduction of water and minerals from the root to leaves .

Stems of plants are modified for following functions :

i)Stem are modified to store foods .

ii)Stem are modified to help for  reproduction .

iii) Stem are modified to store water .

There are three types of modification in stem for their functions :

 1)Underground modification of stem :Ginger ,onion, Potato ,

2.)Sub –under ground modification of stem :Dubbo grass ,strawberry ,pineapple

3.)Aerial medication of stem :i.e. passiflora, morning glory ,lemon.

3.)Modification of leaf :

Leaf :A  lateral out growth of the stem arising from the node and having a bud is called leaf .Each leaf consist of 3 parts :i.e.

 i)Leaf base :The base part of leaf which is attached to the stem is called leaf base .

 ii)Petiole :The stalk of leaf which connect  of leaf base and other parts of leaf is called petiole .

 iii)Lamina :The broad and expanded parts of leaf is called lamina .

Functions of leaf :i)It help to manufacture of food for whole plants body .

ii)It help to exchange gases and removal of excess of water .

iii)Certain  plants of leaf help in vegetative propagation .

Leafs of plants are modified for following functions :

i)Leaf are modified to reduces the rate of transpiration .

ii)Leaf are modified to protects the plants .

iii)Leaf are modified for the storage of foods .

iv)Leaf are modified for climbing .

There are following major  types of modification in leaf for their functions :

i)Leaf tendrils :Help to climb the plants i.e. pea,

ii)Leaf spines: Help to reduce loss of water :Date palm

iii)Leaf scales :Help to store food and water   i.e. ginger .

iv)Bladder :Help to trap tinny aquatic organism .i.e. Utricularia.

v)Pitcher :It help to trap and digest insects i.e. nepenthes 

Parts of flower :A complete flower(i.e. flower having sepal, petal, stamen, and pistil) is divided into 4 parts :

i)Calyx(Sepal): The outer most whorls(cover) of flower is calyx .it is small leaf like and green in colour .It help to protect the flower during bud stage .  

ii)Corolla(Petal): The 2^nd outer most whorls of the  flower is called corolla .It is bright ,coloured ,and attractive parts of flower.It help to attract insects towards the flowers for pollination.

Caylax and corolla do not directly involve in the reproduction ,so it also called accessory whorls .

iii)Androcium (stamens): The reproductive parts of plants is called is androcium. It is divided into two parts i.e. filament and anther and anther consist of pollen sac that produce male gamete pollen grains .

iv)Gynocium(pistil or carpel): The female reproductive parts of flower is called gynocium.It is divided into 3 parts i.e. stigma ,style ,and ovary and ovary consist of  ovules that contains female gametes eggs .A sac like structure containing 8 cells including eggs cell and present in the ovule iscalled embryo sac.

Androcium and gynocium directly take parts in reproduction ,so it is called reproductive whorls .

 Pollination: The process of transfer of pollen grains from anther to stigma of flower is called pollination .It two types

Fig .Cross pollination

i)Self pollination	ii)Cross pollination
i)The process of transfer of pollen grains from the anther of flower to stigma of same flower or another flower of same plant is called self pollination. ii)It occurs only in bisexual flower. iii)It required only one plant .	i)The process of transfer of pollen grains from the anther flower of one plant to the stigma of another plant of same species . ii)It occurs in unisexual as well bisexual flower. iii)It required two or more than two plants .

Double fertilization in plant: The fertilization in flowering plant involves the fusion of two male gametes separately i.e. one male gamete fuse with egg cell form zygote and another male gamete fuse with secondary nucleus or nuclei of two polar bodies to form endospermic nucleus .Therefore the whole mechanism plant fertilization is called double fertilization .During double fertilization zygote develop into embryo and endospermic nucleus into endosperm that supply nutrients to the embryo.After fertilization sepal ,petal,stamens and pistil of flower fall off and ovary develop into fruit and ovules into seeds.

2.)Fruit :The ripened ovary of seed bearing flowering plants is called fruits .If only the ovary take parts in the formation of fruits is called true fruits .i.e. Mango,toamato, etc. If thalamus or calyx form major parts of fruits is called false fruits .i.e. apple, pear etc. 

Parts of fruits :Fruits consist of main two parts :

1)Pericarp :It develop  from ovary .It is thin or thick walled .If it is thick walled cosist of 3 layers :i.e. i)Outer epicarp ii)Middle mesocarp iii)Inner endocarp

2)Seed : It develop from ovules .

3.)Seed:A ripened ovule of flower plant that contains embryo and its foods source covered by protective coat is called seed .Under suitable condition seeds germinate and gives baby plants .

  Types of seeds :They are two types :

i)Monocotyledon seed :The seeds having only one cotyledon are called monocotyledon seed .For example : wheat, maize .

ii)Di cotyledon seed :The seeds having two cotyledon are called Di cotyledon .For example : pea, gram, bean .

Structure of a Seed

 A typical seed consists of the following parts:

                                                        Fig .Parts of seed

·         Tesla: It is the outer coat of the seed that protects the embryonic plant.

·         Micropyle: It is a tiny pore in the testa .It permits water to enter the embryo before active germination.

·         Cotyledon:  In some plants contains high quantities of starch and will provide a source of food for the developing embryo  to germination, in other plants this role is performed by an endosperm. In monocotyledons, there is just one cotyledon whereasin dicotyledons there       are two cotyledon.

·         Radicle: This is the embryonic root which will de.velop into the primary root of the plant during germination.

·         Plumule: This is the embryonic shoot. It appears as a bud that will give rise to the shoot .

·         Endosperm: In many plants, a separate part for storage of starch develops and this is called the endosperm. It is seen in maize and wheat.

Dispersal of seeds: The process by which seeds are carried away from the parent plants over a large area  by different media is called dispersal of seeds .The seeds which are released from the fruits are distributed by various natural agents are called agents of dispersal of seeds .

There are following 4 major types of agents of dispersal of seeds :

i)Dispersal of seeds by wind :for example : In cotton ,Poppy

ii)Dispersal of seeds by water :Coconut, lotus, water lily .

iii)Dispersal of seeds by animals : For example :Guava, Cherry , tomato .

iv)Dispersal of seeds by splitting of fruits :For example :Pea , bean, Lady`s finger .

Germination of seed : The process by which the embryo in the seed becomes active and begin to grow into a new plant is called germination .

Dormant seeds : The seeds which do not germinate when provided with all the conditions  necessary for germination are called dormant seeds .

Dormancy :The total time period after maturation during which a seed will not germinate when provided with all the necessary conditions for germination is called dormancy .

Types of germination :  On basis of  of cotyledon:The germination of seeds are divided into two types :

1)Epigeal  germination :The germination of seeds in which the cotyledon comes out  of the soil forming the first leaves of the plants is called epigeal germination of seed .For example : Germination of seeds in cotton, beans .

2)Hypogeal germination :The germination of seeds in which the cotyledon remains below the soil is called htpogeal germination of seeds . For example :Germination in mango, maize , gram .

Conditions for germination : following basic conditions are required for the germination of seeds :

i)Water :When seeds absorbs water by micropyle it become soft and swell and burst due to pressure created by swelling of inner parts . As result embryo comes out from seed coat .

ii)Oxygen :A germinating seeds requires a lot of energy which is produced by the oxidation of the stored food in seed in presence of oxygen .So if seed goes deep into the soil it do not germinate .

iii )Suitable temperature :Most of seed requires 25⁰C -  30⁰C for best germination ,therefore at very low temperature seeds go into state of dormancy .

Functions of seeds :

i)It take parts in germination and young new plants is produced .

ii)The cotyledons of seeds store the foods materials that help in germination of seeds .

iii)Seeds contains of large amounts of reserves foods i.e. starch ,oil. Proteins ,and fats .

 Life cycle of flowering plants : When anther of a stamen become matured the wall of anther burst and male gamete pollen grains are exposed ,then released pollen grains are transferred to the stigma of matured Gynocium by help of water ,air and insect .The process of transfer of pollen grains from anther to stigma is known as pollination .After pollination pollen tube is developed from each pollen grains .The pollen tube thus developed penetrates the stigma and moves toward ovary through style .Each pollen tube consist of two male nuclei one fuse with ovule and form a zygote other with polar nuclei and form endospermic nuclei .Finally after  series of change ovule change into seeds and ovary into fruits .After the maturation of seeds ,the fruit dries and ruptures and the seeds are dispersed .Under suitable condition seeds germinate into new baby plants Thus the life cycle of flower plant completes .

 Life cycle of flowering plants : When anther of a stamen become matured the wall of anther burst and male gamete pollen grains are exposed ,then released pollen grains are transferred to the stigma of matured Gynocium by help of water ,air and insect .The process of transfer of pollen grains from anther to stigma is known as pollination .After pollination pollen tube is developed from each pollen grains .The pollen tube thus developed penetrates the stigma and moves toward ovary through style .Each pollen tube consist of two male nuclei one fuse with ovule and form a zygote other with polar nuclei and form endospermic nuclei .Finally after  series of change ovule change into seeds and ovary into fruits .After the maturation of seeds ,the fruit dries and ruptures and the seeds are dispersed .Under suitable condition seeds germinate into new baby plants Thus the life cycle of flower plant completes .