What is a keystone species

• A species which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community's organization and survival.

• A common species that has plenty of biomass, yet has a fairly low impact on the community's organization.

• A rare species that has minimal impact on the biomass and on other species in the community.

• A dominant a large proportion of the biomass and which affects many other species.

Smoking addiction is harmful because it produces polycyclic aromatic hydrocarbons, which cause

• reduction in oxygen transport

• increase in blood pressure

• cancer

• retardation of growth of foetus.

Which one of the following pairs is not correctly matched

• Streptomyces - Antibiotic

• Serratia - Drug addiction

• Spirulina - Single cell protein

• Rhizobium - Biofertilizer

Which of the following sets includes all bacterial disease

• Cholera, typhoid, mumps

• Tetanus, tuberculosis, measles

• Malaria, mumps, poliomyelitis

• Diphtheria, leprosy, plague

Acrosome reaction in sperm is triggered by

• capacitation

• release of lysin

• influx of Ca⁺⁺

• release of fertilizin

The binding of antibodies to the antigens to produce a large insoluble complex is known as

• antibody-antigen complex

• agglutination

• immunisation

• suppressor cell reaction.

One of the major difficulties in the biological control of insect pest is that

• the predator develops a preference to other diets and may itself become a pest

• the predator does not always survive when transferred to a new environment

• the method is less effective as compared with the use of insecticides

• the practical difficulty of introducing the predator to specific areas.

The main reason why antibiotics could not solve all the problems of bacteria mediated diseases is

• insensitivity of the individual following prolonged exposure to antibiotics

• inactivation of antibiotics by bacterial enzymes

•  decreased efficiency of the immune system

•  the development of mutant strains resistant to antibiotics.

Which of the following statements is incorrect

• Lichen, an association of fungus and algae is an example of mutualism.
  
  

• Those epiphytes which use other plants for support only and not for water or food supply and are examples of commensalism.

• Sea-anemone on hermit-crab is an example of protocooperation.

• Mutualism, protoocoperation, commensalism cannot be included under symbiosis.

The bacteria which attack dead animals are

• first link of the food chain and are known as primary producers

• second link of the food chain and are herbivorous

• third link of the food chain and are tertiary consumers

• the end of food chain and are decomposers.