Mutualism is the ecological interaction between two or more species where each species benefits.

The unicellular photosynthetic algae, called Zoochlorella live symbiotically in the outer tissues of coelenterates. Algae are photosynthetic and produce oxygen and food beneficial to hosts and in exchange, they obtain materials like carbon- dioxide and nitrogenous wastes released by metabolism of host animals.

In prokaryotes meiosis is absent due to absence of gamete formation.  But genetic recombination occurs through following process:

(i) Transduction

(ii) Transformation

(iii) Conjugation.

In nuclear endosperm the primary endosperm nucleus divides repeatedly without wall formation producing a large number of free nuclei. It is most common type of endosperm.

Chloromycetin or chloramphenicol is obtained from Streptomyces venezuelae.

Graafian follicle develops under influence of FSH of anterior pituitary.  Its follicular cells secrete estrogen. Rising level of estrogen decreases production of FSH, and stimulates secretion of LH. The two cause mature Graafian follicle to release the ovum.

Triticum aestivum is an Indian dwarf wheat. It is endemic to Southern Pakistan and North- western India.

Cytoplasmic inheritance or non- chromosomal inheritance is the passage of traits from parents to offspring through structures present inside cytoplasm of contributing gametes. Genes controlling cytoplasmic inheritance are called plasma genes or extra nuclear genes. They occur in plastids, mitochondria, plasmids. It is usually uniparental. Also, it is known as maternal inheritsnce.

Watson and Crick suggested the double helical structure of DNA. Semiconservative nature of DNA replication was proved by Messelson and Stahl by using heavy isotope of nitrogen (¹⁵N).

DNA polymerase III establishes phosphodiester linkages between the adjacent deoxyribo-nucleoside phosphate in presence of ATP/GTP, TPP and Mg²⁺. It produces a new strand of DNA. DNA polymerase binds nucleotides in 5'-3' direction.

Organophosphate or Malathion kills insects by inhibiting enzyme cholinesterase. It is an organic ester of carbonic acid. Its structure is somewhat similar to acetylcholine and, therefore has strong affinity for the enzyme acetylcholinesterase, and inhibits its activity.

Biosphere is the biologically inhabited part of earth along with its abiotic or physiochemical components. It consists of three sub- divisions, namely, atmosphere, lithosphere and hydrosphere.

(i) Atmosphere refers to the transparent gaseous mantle surrounding the earth.

(ii) Lithosphere refers to the outer solid crust of earth.

(iii) Hydrosphere is liquid mantle of earth.