Keeping Time with the Skies — Science STD 8 — Question

In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?

What do you mean by the term menarche?

The use of excessive fertilizers in the fields lead to the deficiency of an important substance in the water of a nearby lake. Name the substance.

Which metal is less reactive: copper or iron?

How do fish indirectly affect seed production in plants near a pond?

What is the relation between 'time-period' and 'frequency' of an oscillating body?

Explain how does a sound making object differ from one that is silent?

Name an antibiotic extracted from fungus (mould). Name the fungus.

Arrange the following stages of development of human body in correct sequence. Foetus, Zygote and Embryo.

Name any harmful product released by the burning of fuels.