Zooplankton: They are primary consumers in an aquatic food chain who feeds upon phytoplanktons.

The ecological principle behind the biological control of pest insects is based on the ability of predator to reduce prey population in that habitat

None of these - Plants are autotrophic and are called primary producers because they are self-sufficient to synthesise their own food. Also, there is nothing like secondary producers. 

Given, cytosine=20%
\(\therefore \) Percentage of Guanine=20%
Now according to Chargaff's rule, A+T=100-(G+C)
=> A+T=100-40
\(\therefore \) Percentage of Thymine=percentage of Adenine
 =\(\frac { 60% }{ 2 } \)% = 30%

Vivipary is nourishment and growth of embryo inside the body of the female till it becomes fully formed and delivered. Vivipary provides protection and assured nourishment to the young ones. As the female has a limited space and nourishment, the number of youngones always kept low, e.g., one in humans and cattle, 6-12 in Rabbit and Rat.

Due to self-incompatibility, self-pollination fails to take place. Due to self-incompatibility or self sterility, cross pollination is favoured.

1. Alexander Fleming, while working on Staphylococci bacteria, observed a mould growing in one of the unwashed culture plates, around the mould the bacterium could not grow.
2. He found that it was due to a chemical produced by the mould Penicillium notatum and named the chemical as Penicillin.
3. Its full potential as an antibiotic was established later by Ernst Chain and Howard Florey.

1. If denaturation step is missed, the two strands of DNA will not be separated.
2. The primers will not be able to anneal to the template and hence, no extension of the DNA will take place.

This is because plasmid is a circular DNA molecule. When cut with enzyme, it becomes linear, but does not get fragmented.
Whereas, a linear DNA molecule gets cut into two fragments. Hence, a single DNA band is observed for plasmid while, two DNA bands are observed for linear DNA in agarose gel.

(i) The mucus coating of the gut epithelium is a barrier that traps microbes.
(ii) The hydrochloric acid secreted by gastric glands retards the growth of microbes.
This type of immunity is called innate immunity, which occurs right from birth.

1. The rate of decomposition is regulated by temperature and soil moisture, as they influence the activities of decomposers.
2. The trophic have a warm/hot and humid condition; such a condition is favourable for the decomposers and hence they speed up the process of decomposition.

Survival of the fittest means that those individuals which survive and reproduce successfully in their given environment or habitat, are called fit.
Such individuals produce more progeny (with more fit individuals), than the others who are less-adapted to survive and reproduce in that environment.

(i) The methylated guanosine cap helps in the binding of mRNA to the smaller subunit of ribosome during initiation of translation.
(ii) Poly-A tail has a direct relatioship with the logevity of mRNA.

- No, the son never inherits colour blindness from his father.

- The gene for colour-blindness is present on the x-chromosome, but a son receives Y-chromosome from his father.

- Since a male receives the X-chromosome from his mother, he ihherits the disease from his mother only.

Alleles are polymorphs that differ in their nucleotide sequence resulting in contrasting phenotypic expression. These are the alternative forms of a same gene, e.g. genes for height have two alleles, one for dwarfness (t) and one for tallness (T). Significance of alleles are
(i) A characler may have two or more contrasting phenotypic expression, thus resulting in variation in a population.
(i) These are used in the studies of inheritance.

A - iv; B - iii; C - i; D - ii

Parthenocarpy and apomixis are two different phenomena.
(i) Parthenocarpy is formation of fruit without fertilisation of the ovary; hence they are seedless.
(ii) Apomixis is the phenomenon of formation of seeds without fertilisation apomictic embryos are genetically identical to the female parent.

One male gamete fuses with the female gamete (syngamy) to form the zygote. Another male gamete fuses with the polar nuclei (triple fusion) to form the primary endosperm.

1. Embryo developing from synergid is haploid.
2. Embryo developing from nucellus is diploid.

Cross pollination or xenogamy.

During pregnancy,the corpus luteum secretes large quantity of progesterone,which inhibits maturation of any other follicle or ovulation;hence menstrual cycles are absent.