Crossing over is a method of variation
The number of bacteria present in milk that is refrigerated is likely to be lower than milk that is not, because the temperature of the refrigerator is likely to be a lower temperature than the optimum for the bacteria. This prevents the enzymes from working effectively (though they are not denatured) and the bacteria are less able to multiply
Predator prey relationship, is just basically when the predator eats the prey. Like for example if cheetah eats the zebras, through time zebras can become less of a population. But then think of this, if there was NO prey zebras could over populate and there may not be enough places for them to live or enough food. Hope that helped...
Autotrophs can produce their own food
Passive transport is the movement of biochemicals and other atomic or molecular substances across cell membranes without need of energy input. On the other hand, active transport <span>is the movement of molecules across a cell membrane from a region of their lower concentration to a region of their higher concentration which needs energy input. </span>
