Added requirement for sexual reproduction

Sexual reproduction has the obvious cellular complexities of meiosis and fertilization. Beyond these, however, are practical considerations of how to bring male and female and subsequently egg and sperm together for fertilization. We list some of nature’s solutions to this problem in the following:

Bringing male and female–eggs and sperm together.

Have students note that sea urchins simply eject sperm and eggs into sea water. This is a very inefficient way of achieving fertilization. (Many eggs don’t get fertilized.) Most species have developed means of in creasing the efficiently. Salmon make “nests” into which eggs and sperm are deposited. See:

Frogs and toads–the male clasps the female and deposits sperm on the eggs as they are extruded by the female: See:

Mammals, birds, insects and many others, the male ejects sperm into the female’s body (copulation).

Courtship

A female becoming receptive to being fertilized frequently involves an elaborate courtship ritual. See examples:

Pheromones

Scientists have discovered that in insects of many species, the female emits a chemical substance, called a pheromone, that attracts males of the same species so that successful mating and reproduction occurs.