What geographic and weather features affect plant and animal life

The answer is; altitude and temperatures respectively

The higher the altitude, the thinner the atmosphere and the cooler it gets hence  species in these regions are adapted to these altitudes.

Temperature also affects life. Life is less diverse in extreme regions such as the polar regions of earth and deserts like the Sahara. Regions like the equatorial, on the other hand, have abundant  biodiversity.

81 is a composite number.

because the two particles have an equal charge, the charges will cancel out and give the atom an overall charge of 0. so, if at atom has 35 protons in the nucleus, we could expect it to have 35 electrons orbiting that nucleus.