MCQ
The earth like other planets formed from:
- AAggregates of uranium.
- BCloud of gas and dust.
- CDivision of pre-existing planets.
- DCollisions of meteorites.
Explanation:
Approximately 4.6 billion years ago, the solar system was a cloud of dust and gas known as a solar nebula. Gravity collapsed the material in itself as it began to spin, forming the sun in the center of the nebula.
With the rise of the sun, the remaining material began to clump up. Small particles drew together, bound by the force of gravity, into larger particles. The solar wind swept away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky materials to create smaller terrestrial worlds like Earth.
So, earth like other planets formed from cloud of gas and dust.
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$II.$ The population growth rate $r$ is inversely related to generation time
$III.$ The housefly, which has a short life span and produces a large number of eggs, could be considered as a ' $K$ ' selected species
$IV.$ Under a particular set of selection pressures, organisms evolve towards the most efficient reproductive strategies
$V.$ Life history traits of organisms have evolved in relation to the constraints imposed by biotic and abiotic factors in their habitat Select the combination of correct statements
$(1)$ medical termination of pregnancy $(MTP)$ during first trimester is generally safe
$(2)$ generally chances of conception are nil until mother breast feeds the infant upto two years
$(3)$ intrauterine devices like copper $T$ are effective contraceptives
$(4)$ contraception pills may be taken upto one week after coitus to prevent conception.
Which two of the above statements are correct?