The sun, the moon, stars, planets and other objects that we see in the sky are called heavenly bodies or celestial objects. Those celestial bodies which emit heat and light of their own are called stars. The stars appear to move from east to west due to the rotation of the earth from west to east.
Class VIII Science
A flower develops on a branch from a bud. A flower is the reproductive part of the plant. A stalk called the pedicel attaches the flower to the branch. The upper swollen end of the pedicel is called ‘thalamus’. Thalamus bears floral parts like – Sepals, Petals, Stamens and Pistil (carpel).
Reproduction, Asexual Reproduction, Budding, Buds, Binary Fission, Sexual Reproduction, Male reproductive organs, Sperms, Male gametes, Female Reproductive organ, ova (eggs), Female gamete, Fertilization, Internal Fertilization, External Fertilization, Zygote, Embryo, Foetus, I.V.F. ( In vitro fertilization), Test tube babies, Oviparous animals, Viviparous animals, Metamorphosis, Tadpole (larva), Cloning, Dolly Sheep
Coal- It is a hard stone like black coloured solid fossil fuel. It is used for cooking food. Steam based railway engine used coal to produce steam for running pistons. In thermal power plants, coal is used to generate electricity. Different industries use coal as a fuel. Petroleum (Petra-Rock; oleum=oil)-Petrol and diesel like oils are obtained from petroleum. Petroleum is formed by the carbonization of fossils of animals and tiny plants like planktons. It is found in between the layers of impervious rocks inside the earth. It is found at a depth of few kilometers to few hundred kilometers. Petroleum is a dark oily liquid. It has unpleasant odour. It is a mixture of different hydrocarbons.
The percentage of nitrogen in the atmosphere is 78 %. Nitrogen is very essential for living organisms as it is a constituent of proteins, vitamins, Chlorophylls, nucleic acids like D.N.A and R.N.A. The atmospheric nitrogen cannot be taken directly by plants and animals. Certain bacteria and Cynobacteria (blue green algae) fix the atmospheric nitrogen in the soil in form of nitrogenous compounds. In factories when chemical fertilizers are prepared and also during lightening, nitrogen is fixed in nitrogenous compounds.
The period during which the human body undergoes various changes leading to reproductive maturity is called adolescence. It is called as a period of storm and stress in life. The need is to understand it as normal growth and development process.
The light coming out of a torch is a beam of light. The beam of light is made up of light rays. Simply, a narrow beam of light is called as ray. When a light ray falls on a reflective surface like mirror, it gets reflected in other direction with some angle.