In the lock-and-key model of enzyme action, the enzyme active site is thought of as .

Rigid and non flexible surface

Explanation:

Enzymes are catalyst that speeds up rate of chemical reactions, they bind to a substrate which are known as reactant substrate to speed up rate of chemical reaction and to unlock the key.

The enzyme is said to be rigid and non flexible fitting perfectly to the surface of the substrate where the reaction takes place. Fitting perfectly enable the enzyme to perform its action on the substrate unlocking the key and activating the action in the molecule.

1: most common garden plants prefer loam — soils with a balance of different-sized mineral particles (approximately 40% sand, 40% silt, and 20% clay) with ample organic matter and pore space. however, some plants grow better in sandy soils, while others are well-adapted to clay soils.

2: available water capacity is the maximum amount of plant available water a soil can provide. it is an indicator of a soil's ability to retain water and make it sufficiently available for plant use. available water capacity is the water held in soil between its field capacity and permanent wilting point.

3: it is the same for all living things (plants and animals). it also includes very tiny organisms that our eyes cannot see. they are known as microorganisms, and include viruses, bacteria and fungi.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".