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SCIENCEIMPORTANT POINTS FOR CLASS X BOARD EXAMINATION

Phenotypic ratio of the F2progeny in a monohybridcross is 3:1 whereas 9:3:3:1 in a dihybrid cross.

The number of autosomes in a cell of humans is 44.

The theory of natural selection was given by Darwin.

Speciation the formation of new species from pre -existing species.

Emasculation removal of anthers from flowers.

Genetic drift a random change in the frequency ofalleles (genes) occurring by chance.

Only 10% of the energy is transferred from one trophiclevel to the next.

Bio magnification accumulation of non biodegradablechemicals in different trophic levels.

Diamond is the hardest substance in nature. It is anallotrope of carbon.

Covalent bonds between atoms are formed by sharing ofelectrons.

Soaps are sodium/ potassium salts of higher fatty acids.

Alcohol + carboxylic acid give sweet- smellingcompounds called esters.

An acid used as a preservative is acetic acid (CH3COOH).

Catenation- the tendency of carbon to combine withother carbon atoms to form a long chain.

Size of an atom increases down a group while decreases

along a period.Examples of metalloids- B, Si, Ge, As, Sb, Te, Po.

Metallic nature of elements decreases along a period &increases along a group.

Dr. P. N. PATHAK SASARAM, BIHAR