UNIT 16: LIVING ORGANISMS
Bacteria
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The study of bacteria is known as bacteriology.
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These are parasitic, prokaryotic, simple,
microscopic and unicellular organisms with cell wall.
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Chlorophyll is present.
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They are found everywhere.
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Bacteria are microorganisms, which are of 0.2
micron to 2 micron diameter.
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Bacteria are divided into four types as coccus,
bacillus, spirillum and filament or mycelia.
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Antonie Van Leeuwenhoek discovered bacteria at
first in 1676 A.D.
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In 1848 A.D. Eherenworg gave name to this small
animal as bacteria.
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Along
with this in 1854 Cohn classified bacteria as the form of plant.
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Louis
Pasteur and Robert Koch exhibit that bacteria is responsible for transmitting
different types of diseases in plant, animal and human.
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They are harmful as well as useful to us.
Importance of
Bacteria
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Lactobacillus and Acidophillus bacteria help to prepare curd (yogurt) from
milk.
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Bacteria aid in making compost fertilizer.
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Help to degrade the body of living organism.
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Some bacteria like Rhizobium convert nitrogen
present in the free state in
the atmosphere into nitrate.
Harmful effect of
Bacterial
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Due to different type of bacteria different
diseases, in humans are caused such as due to Diplococcus pneumonia, Pneumonia
is caused, cholera due to Vibrio cholera, typhoid due to Salmonella Typhi, etc.
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Some bacteria like Pseudomonas decrease the
fertility power of soil.
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In summer some bacteria spoils the cooked food,
fruits, flowers, and green leaves by rotting.
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Some bacteria cause diseases like spots in
plants, weak roots, etc.
Control of
bacterial diseases
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Use of seed not infected by bacterial diseases.
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Use of anti-bacterial medicine under doctors’
supervision.
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Maintaining personal & environmental
hygiene.
Fungi
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Study of fungi is called mycology.
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These do not contain chlorophyll.
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They are parasitic and saprophytic in nature.
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Unicellular & multi-cellular.
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Found in all types of environment.
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They prepare their food from dead organisms, so
are called saprophytic.
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Root, stem, leaves are not found.
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Reproduction is sexual and asexual both.
Importance of
fungi
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As mushroom has protein, vitamin and minerals,
it has importance as nutrient.
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Different types of antibiotics are produced from
species of fungi, such as penicillin.
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We can get vitamin B complex, vitamin E from
yeast. It is also used for making bread.
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The decaying or decomposing of animals and
plants after dead and mixing it in soil increases fertility.
Harmful effects of
Fungi
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Skin diseases.
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Poisonous.
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Allergy.
Controlling
measures of Fungi
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Keeping food stuffs in refrigerators.
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By using salt for fungal growth in fruit and
vegetables.
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By using preservatives.
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Maintaining personal hygiene.
Virus
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The
science that studies about virus is called virology.
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The name virus has come from latin language virion,
which means poison.
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Viruses are ultramicroscopic, parasites that
spread diseases.
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Viruses show living behavior inside the body of living
organisms whereas inactive outside of living organisms. Therefore, virus is
called obligatory parasite.
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Iwanwisky discovered virus at the first in 1892
A.D.
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He showed
that mosaic disease is caused in tobacco plants by TMV (Tobacco Mosaic Virus).
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The size of virus is very small from 25nm to
250nm. They are 50 times smaller than bacteria. Virus brings different kinds of
diseases.
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On the basis of virus, they are classified into:
o
Animal virus: polio virus, retro virus, rhino
virus etc.
o
Plant virus: TMV virus
o
Bacteriophase virus
Transmission of
virus
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Transmits, when the leaves of plants are rubbed
with each other.
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Virus transmits, when grafting is done between
healthy and unhealthy plants.
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Virus transmits, when insect like aphid during
eating parts of plant.
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Some viruses such as mosaic virus of wheat
transmit from soil.
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In animals, virus transmits through direct contact
while spitting, blowing nose, coughing etc.
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Transmits from faeces, food and water.
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Virus also transmits while coming in direct
contact with the wound or cut part of the patient.
Control Measures
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To control the plant virus, infected part should
be burnt.
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To control the plant virus, insect should be
killed.
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Virus that spreads in human can be controlled by
vaccination on time.
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Personal, environmental hygiene.
Modification of
different parts of plants
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There are so many plants around us.
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Most of the plants consist root, stem and
leaves.
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These parts are also modified into different
forms according to the location, structure and function to perform different
works.
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This is called modification.
Modification of
Roots
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The underground part of plant is called root.
Its color is usually white, brown and light yellow.
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Roots are mainly of two types:
o
Tap root
system
o
Fibrous
root system
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Modification in root of plant is for major three
functions.
o
For storage of food: turnip, carrot,
radish
o
For mechanical support: banyan tree,
bamboo, maize, sugarcane, peepal and in some climber plants.
o
For vital functions: floating like in
lotus and hydrilla, absorption of food in some parasitic plants, for respiration
etc.
Modification of
Stem
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Modification of stem is in different form
according to their environment:
o
Underground
modification: bulb of onion and garlic, tuber of potato, rhizome of ginger
etc. for storage of food.
o
Sub –
Aerial Modification: creeper in pumpkin, runner in strawberry, dog
grass, offset in pistil (jalkumbhi) etc.
o
Aerial
Modification:
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Aerial stem is modified into different shape.
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In some plant, stem is like a leaf and stores
food. For example; cactus. Leaf of this kind of plants develops as a thorn.
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Some plants have thread like stem.
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Some plants have hard, twisted, long,
cylindrical stem like wood.
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Green colored stems prepare and store food.
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Some plants also store water in their stems.
Modification of
leaves
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Leaf arises from stems and branches of plants.
Leaves are the main parts of plants to prepare food. The leaves of plants
modify in different ways and perform special functions.
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Tendril
is formed partially in some leaves, example; leaf of pea. These tendrils are
coiled like wire.
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Leaves are modified into thorns or spines in some plants. Mainly leaves of xerophytic
plants and leaves of cactus are modified into thorns. They reduce water loss (transpiration).
Thorn also protects plant.
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Leaves of some plants are dry and like a paper.
In some plants, leaf is like a stick.
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Bladder
of leaf is found in carnivorous
plant. It helps in trapping small insects and digests them.
Seeds
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Seeds are of different shapes and sizes.
Generally seeds are of two types:
o
Monocotyledonous
o
Dicotyledonous
Monocotyledonous
Seeds
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It contains only one cotyledon.
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Endosperm is present.
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Embryo is small.
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Plumule is very small.
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Seed is attached to seed coat.
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Maize, paddy, wheat etc. are some examples of
monocotyledonous seed.
Dicotyledonous Seeds
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It contains two cotyledons.
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Endosperm is absent.
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Embryo is large.
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Plumule is large.
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Seeds are separate from seed coats.
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Pea, gram, mango etc. are some examples of
dicotyledonous seed.
Function of Seeds:
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Seed has so many functions, some of them are:
o
Germination:
New plant grows from seed. Root and stem of new plant arises from embryo in a
seed.
o
Storage
of food: Food is stored in seed. Seed uses the food present in itself while
germination.
o
Protection:
Seed coat protects embryo.
Dispersal of
Seeds:
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Seeds need to be dispersed to grow new plant.
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Seed is
dispersed in different ways. They are:
o
By air: seeds of cotton, grass etc.
o
By water: seeds of lotus, coconut,
betel nut etc.
o
Fruit bursts itself forcefully: seeds of
pea, sesame etc.
o
By human and animals: seeds of different
fruit etc.
Germination of
Seed
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Generally, embryo is passive inside seed.
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If it is activated, new plant will grow from the
seed.
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To grow a plant from seed is only possible in
suitable and favorable condition.
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Suitable air, water and temperature are
necessary to grow plant.
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In this way, the process of developing plant from a seed in favorable environment is
called germination of seed.
Life Cycle of
flowering plant
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Most of the flowering plants consist leaves, roots,
stem and flower.
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Flower is attractive and colorful parts.
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Most of the flowers have pleasant smell.
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Flower has four parts: calyx, corolla, androecium
and gynoecium.
Calyx:
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Group of sepals is called calyx.
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It is outermost part.
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It covers, supports and protects internal parts
or flower.
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It is generally green in color.
Corolla
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Corolla is group of petals.
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Petals are colorful parts of flower.
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It is attractive has pleasant smell.
Androecium
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Androceium is the group of stamens.
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Each stamen has stalk which is called filament.
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Topmost part of each stamen is swollen which is
called anther.
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Anther consist pollen sacs.
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Pollen sacs contain millions of pollen grains.
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Pollen grains develop male gametes or male
reproductive cells.
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Androceium consists male reproductive cells, so
it is male reproductive part of flower.
Gynoecium
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It is located centrally in the flower.
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It is group of carpel or pistil.
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Pistil has three parts:
o
Ovary: it
is lowermost swollen part at base. Ovary consists ovule. Ovule is female gamete.
o
Style: middle
part of pistil which long stalk.
o
Stigma: Tip
of the pistil which is knob like.
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Since, gynoecium consist female reproductive
cell, so it is called female
reproductive part of flower.
Bisexual flower:
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The flower which contains both androecium and
gynoecium are known as bisexual flower.
Unisexual flower:
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The flower which contains only one either
androecium or gynoecium are called as unisexual flower.
Pollination
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It is the process of transfer of pollen grains
from anther to stigma of a flower.
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Different agents like wind, insects, birds etc.
are helpful for pollination.
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After pollination fertilization takes place.
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Pollination is of two types:
o
Self
Pollination
o
Cross
Pollination
Self Pollination
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The process of transferring pollen grains of one
flower to the stigma of same flower is called self-pollination.
Cross Pollination
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The process of transferring pollen grains from
one flower to the stigma of different
flower of same species is called
cross pollination.
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For cross pollination, external agents like
birds, insects, air, butterflies are required.
Fertilization
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The process of fusion of male gamete and female
gamete to form zygote is called
fertilization.
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Pollen grain germinates and pollen tube comes out from each pollen grain after pollination.
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This pollen tube bears male gamete.
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Pollen tube goes downwards through style and
reaches to ovary.
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The male gamete fuses with female gamete in the
ovule inside the ovary.
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As a result zygote
is formed.
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Zygote develops into embryo.
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Ovule develops into seed.
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Ovary develops into fruit.
Flower: The
Reproductive Part of a flowering plant
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In this way reproduction takes place in flower.
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So flower is called the REPRODUCTIVE PART of a flowering plant.
