Is cracks in rocks an example of mechanical or chemical weathering?

The bacteria found in soil is usually harmful and measures are taken to remove any traces of microorganisms. true or false

In a classic experiment using pea shape, mendel conducted two separate genetic crosses. in the first cross the parent plants were “true breeding” for pea shape; one had round peas ( r )and the other had wrinkled (r). the first cross produced a filial 1 generation of all round peas. in the second cross, mendel bred plants from the filial 1 generation. this cross produced different results. out of approximately 1000 plants, about 75% were round and 25% were wrinkled.

Why do we perceive objects as retaining their brightness under different lighting levels?