BIOLOGY 3 Marks Question

→ In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals.
→ A key belief of the organic farmers is that biodiversity furthers health.
→ The use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides.
→ An important part of the biological farming approach is to become familiar with the various life forms that inhabit the field, predators as well as pests, and also their life cycles, patterns of feeding and the habitats that they prefer. This will help develop appropriate means of biocontrol.
→ Different biocontrol agents are as follows :
Ladybird and Dragonflies:
→ These beetles are useful to get rid of aphids and mosquitoes.
Bacillus thuringiensis :
→ An example of microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt).
→ These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where eaten by the insect larvae.
→ In the gut of the larvae, the toxin is released and the larvae get killed.
→ The bacteria disease will kill the caterpillars, but leave other insects unharmed.
→ The scientists have introduced Bt toxin genes into plants. Such plants are resistant to attack by insect pests.
Trichoderma:
→ Trichoderma species are free living fungi that are very common in root ecosystems.
→ This fungi is used as biocontrol agent for the treatment of plant disease.
→ They are effective biocontrol agents of several plant pathogens.
Baculoviruses:
→ The majority of baculoviruses used as biocontrol agents are in the genus Nucleopolyhedrovirus.
→Baculoviruses are pathogens that attack insects and other arthropods.
→ Various biocontrol agents have shown no negative impacts on plants, mammals, birds, fish or even on non target insects.
→ Inspite of this, they are desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated

→ Antibiotics are chemical substances which is produced by microbes. It kills pathogenic microbes or slow down their growth.
→ This chemicals are called antibiotics. (anti = opposite, bio = life)
e.g. Penicillin is the first discovered antibiotic.
Discovery: 
→ Alexander Fleming while working on staphylococci bacteria once observed a mould growing in one of his unwashed culture plated around which staphylococci could not grow. 
→ He found out that it was due to a chemical produced by the mould and he named it penicillin after the mould penicillium notatum.
→ This antibiotic was extensively used to treat American soldiers wounded in world war II.
→ Fleming, chain and flory were awarded the Nobel prize in 1945, for this discovery.

(a) single cell protein (SCP)
→ The source of single cell protein is a non harmful bacteria which is an alternative source of good protein.
→ For example; edible mushrooms-fungi which is used by humans is a source of protein.
→ Microbes can be cultured on industrial waste to produce protein.
→ Microbes like spirullina and Methylophilus methylotropus can easily grow on materials like waste water from potato processing plants, straw, molasses, animal manure and
wcen sewage to produce large quantities and can serve as food rich in protein, minerals, fats, carbohydrates and vitamins.
(b) soil
→ For the fertility of soil, microbes play an important role.
→ By decomposition of organic matter, microbes enrich the soil with nutrients.
→ Many species of bacteria and cyanobacteria can fix atmospheric nitrogen into the soil.
Example: symbiotic bacterium: Rhizobium
Free living bacterium :
Azospirillum and Azotobacter
Cyanobacteria anabena, nostoc and ocillatoria

→ Many products which are useful for mankind are produced by microbes on industrial level. For example: beverages, antibiotics, chemicals, enzymes and other biochemical molecules.
→ Saccharomyses cerevisiae Yeast is used to prepare wine, beer, whiskey, brandy or rum like beverages and also used for bread making. Saccharomyses cerevisiae (brewer's) yeast is used to produce ethanol from cereals and fruit juices.
→ Antibiotics are chemical substances which are produced by microbes. They kill pathogenic microbes or slow down their growth. For
example: penicillin
→ We cannot imagine a world without antibiotics. Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes.
Examples:
Aspergillus niger- citric acid
Acetobacter aceti acetic acid
Clostridium butyricum- butyric acid