VIRUSES

Viruses are microscopic organisms.

SHAPES:

Viruses exist in three kinds of shapes:

(1) ROUND VIRUSES:

(2) ROD LIKE VIRUSES:

(3) CRYSTAL LIKE VIRUSES

STRUCTURE OF VIRUS:

The body of virus is chemically made up of proteins and DNA.

* Outer protein coat.

* Inner core of DNA.

Viruses are heterotrophic and cannot prepare their own food. Thus they get food from other living organisms as parasite and produce many diseases in animals and plants.

DISEASES PRODUCED BY VIRUSES IN MAN:

* Polio.

POLIO VIRUS

* Influenza

INFLUENZA VIRUS

* Measles

MEASLES VIRUS

* Small pox.

SMALL POX VIRUS

Among plants, virus destroy leaves of tobacco, potato, tomato and cauliflower.

BACTERIA

Bacteria are microscopic organisms. They are few micrometers in length.

NUTRITION:

Bacteria are heterotrophic. They cannot prepare their own food due to lack of chlorophyll. Although, some bacteria can prepare food, they are called autotrophic bacteria.

CLASSIFICATION:

On the basis of their shape, bacteria are classified into three groups:

* COCCI (Round shaped).

* BACILLI (Rod shaped).

* SPIRILLA (Spiral shaped):

STRUCTURE:

Bacteria have no nucleus. However, DNA is present. Cell wall and cell membrane both are present in such a way that cell wall lies outside and cell membrane lies inside.

METHODS OF OBTAINING FOOD:

As bacteria are heterotrophic, so they get their food in two ways:

(1) As parasites.

(2) As saprophytes.

* PARASITES:

These are the bacteria which get their food from other living organisms. They live in the bodies of other animals and plants here they produce toxic substances due to which diseases are produced in animals and plants.

Among human beings, bacteria produce diseases of plague, tetanus, diphtheria, pneumonia and cholera.

* SAPROPHYTES:

These are the bacteria which get their food fromthe bodies of dead organisms.

USES OF BACTERIA:

* They are used to convert milk into curd.

* Some bacteria are helpful in making cheese.

* Sugar cane juice produces vinegar with the help of bacteria.

* Due to bacteria, dead bodies and plants cause the fertility of soil due to the release of salts and minerals to soil.

* They are used for fermentation to manufacture baking products.

FUNGI

Fungi is a group of plants. They mostly grow in the hot climate. These are the plants that lack chlorophyll and hence cannot manufacture their food, therfore they obtain their nutrition either from other organisms on whom they live as parasites or as saprophytes by decomposing dead organisms.

STRUCTURE OF FUNGI:

Mostly fungi are composed of thread like structures called hyphae. In multicellular fungi, the hyphal filament consist of many cells.

FUNGI CONSISTING OF HYPHAE

SIZE OF FUNGI:

Some of the fungi e.g., yeast are unicellular or microscopic. Other fungi are large in size and visible with the naked eye e.g., mushrooms, rhizopus, mucor e.t.c.

YEAST (UNICELLULAR FUNGI)

MUSHROOMS

USES OF FUNGI:

* Mushrooms are used as food.

* Penicillin is obtained from penicillium. This penicillin can be used for treatment of bacterial diseases.

PENICILLIUM


PENICILLIN

* Cheese can be prepared with the help of fungi.

CHEESE

* Fermentation process for alcohol formation is carried with the help of fungi.

DISADVANTAGES OF FUNGI:

* It may cause skin diseases in man and other animals.

* In children, it can cause lungs disturbance and nerve diseases.

* It can also destroy tomato and potato crops.

* It can cause rust and smut diseases in Wheat, barley, rice and sugarcane.

ALGAE

Algae are a large and diverse group of autotrophic organisms. These may be unicellular or multicellular. These are plant or plant like organisms. They are photosynthetic. Almost all algae have nucleus and chloroplasts.

ALGAE IN WATER

LOCATIONS:

Algae are prominent in bodies of water, common in terrestrial environments and also found in snow and ice or on the surfaces of moist soil or rocks.

TYPES OF ALGAE:

The different types of algae are:

(1) EUGLENOIDS (EUGLENOPHYTA):

There are approximately 800 species of euglenoids. They are either single celled or colonial. They occur in fresh water. They have no cell wall but have a protein coat. They have chloroplasts and some produce energy through photosynthesis or others feed by phagocytosis or by diffusion. They move using flagella. They reproduce asexually. They store paramylon as food.

(2) GOLDEN BROWN ALGAE (CHRYSOPHYTA):

There are approximately 40,000-100,00 species of algae. These are diatoms named for the yellow pigment they possess. They live both in fresh water and salt water. Their cell walls have no cellulose but mostly composed of pectin. They achieve their locomtion using one to two flagellae.

(3) FIRE ALGAE (PYRROPHYTA):

There are approximately 1100 species of fire algae. These are single celled algae and include dinoflagellates which have two flagella for locomotion. They live in salt as well as fresh water. They have cell walls made of cellulose. They store energy as starch. Dinoflagellates emit bright flashes of light when exposed to air which at night look like fire on an ocean's surface.

(4) GREEN ALGAE (CHLOROPHYTA):

There are approximately 7000 species of green algae. They are either single celled and microscopic forming the green scum found in stagnant ponds. Others are larger composed of many cells forming spherical colonies. These occur in fresh as well as sea water. The cell walls of green algae are mostly constructed of cellulose and calcium carbonate. The food reserves of green algae are starch and their cells have flagella which are used in a whip like fashion for locomotion.

(5) RED ALGAE (RHODOPHYTA):

There are 4000 species of red algae. These are marine plants that live in shallow waters and deep tropical seas. A few occur in fresh water. They have no flagella. Their cell walls are constructed of cellulose and polysacchrides. They store energy as specialized polysacchride known as floridean starch.

(6) BROWN ALGAE (PAEOPHYTA):

There are 1500 species of brown algae almost all of which occur in marine environments. They have cell walls made of cellulose and polysacchrides known as alginic acids. They have two flagella for locomotion. The food reserves of these algae are carbohydrate polymers.

(7) YELLOW GREEN ALGAE (XANTHOPHYTA):

There are approximately 450 species that occur in fresh water. They can be either single celled or form colonies. Their cell walls are made of cellulose and pectic compounds. The food reserves of these algae are carbohydrates. They have two or more flagella for locomotion. They derive their yellow green colour from the carotenoids and xanthophyll.

PROTOZOA

PROTOZOA:

These are single celled eukaryotic organisms consisting of membrane bound organelles (nuclei, mitochondria, Golgi complexes and Food vacuoles) within a cytosolic matrix.

CYTOPLASM OF PROTOZOA

CHARACTERISTICS:

These may range from 10-50 micrometer or can grow up to 1mm. These are easily seen under the microsope. They exist through an aqueous environment and soil. As predators, they prey upon bacteria and unicellular filamentous algae. They absorb food through the cell membrane but some e.g. amoeba surround food and engulf it. All protozoa digest their food in vacuoles.

CLASSIFICATION OF PROTOZOA:

Protozoa is divided into three classes:

CLASS 1: Gregarinida.

CLASS 2: Rhizopoda.

* Order 1: Monera.

* Order 2: Amoebea.

* Order 3: Foraminifera.

* Order 4: Radiolaria.

* Order 5: Spongida

CLASS 3: Infusoria.

GREGARINIDA:

It may be defined as parasitic protozoa which is devoid of mouth and do not possess the power of emiiting pseudopodia.

RHIZOPODA:

They are distinguished by their pseudopods (simple or branched) by means of which they move about and take their food.

* MONERA:

Monera are bacteria and mostly single celled organisms whose genetic material is loose in the cell.

* FORAMINIFERA:

It is a large group of amoeboid protists with reticulating pseudopods, fine threads of cytoplasm that branch and merge to form a dynamic net. They typically produce a shell made of calcium carbonate.

* RADIOLARIA:

It is amoeboid protozoa that produce intricate mineral skeletons typically with a central capsule dividing the cell into endoplasm and ectoplasm. They have needle like pseudopodia supported by bundles of micro tubules.

* INFUSORIA:

These are minute aquatic creatures like ciliates, euglenoids, protozoa and unicellular algae that exist in fresh water ponds.

SYSTEM TYPE OF PROTOZOA:

* A protozoa takes in food via water or stores the food in vacuoles. They eat algae and bacteria.

* A protozoa reproduces by splitting in half. This is called fission.

* A protozoa is usually asymmetrical.

* A protozoa is pale in color.

* A protozoa has no brain so they have a very low level reaction to the world around it.

* A protozoa has no inner or outer skeleton e.g. amoeba has a false foot that extends as it moves.

* A protozoa excretes water through vacuoles.

Below I am going to discuss some of the most important protozoas:

* ENTAMOEBA hISTOLYTICA:

It is an anaerobic protozoan associated with intestinal infection. It can infect humans and other animals. It consists of single nucleus containing a small central karyosome. It causes amebiasis. Entamoeba histolytica is transmitted through mouth by the ingestionof mature cyst through contaminated food and water. It moves through pseudopodia. It reproduces by binary fission. Amebiasis can be treated with Paromomycin and Diloxanide furoate. For intestinal disease or extra intestinal infection e.g. hepatic abscess, the drugs of choice are Metronidazole or Tinidazole followed by Paromomycin and Diloxanide furoate.

* GIARDIA LAMBLIA:

It is a flagellated protozoan that reproduces in small intestine and causes giardiasis (diarrheal condition). It has two nuclei and eight flagella. It reproduces by binary fission. It infects humans but it is also one of the most common parasite infecting cats and dogs. Giardiasis can be treated with Metronidazole, Tinidazole and Albendazole.

* PLASMODIUM KNOWLESI:

It is a malarial parasite infecting humans either naturally or artificially. It causes malaria . It has four modes of transmission which are as follows:

* From infected monkey to another monkey.

* From an infected monkey to human.

* From an infected human to another human.

* From an infected human back to monkey.

Malaria can be treated with Chloroquine and Primaquine.

* BALANTIDIUM COLI:

It is a parasitic species of ciliate protozoan that causes the disease Balantidiasis. It has two nuclei and reproduce by binary fission, conjugation, autogamy and cytogamy. It has two contractile vacuoles. It has a unique osmoregulatory capacity. Balantidiasis can be treated with Tetracycline and Diiodohydroxyquine.