-adapted combination of inheritable characters, give rise to the next generation. Simply stated, organisms best adapted to their environment will survive to pass on their genes to the nest generation. Beneficial variations, therefore, help the organism to survive, so the beneficial trait gets passed on to the next generation. Adaptation is a key to survival and an organism can adapt in many ways. There are many types of adaptation such as structural adaptation which includes size, shape, and composition, behavioral adaptation which concern activities and responses to the organism's environment, and functional adaptation which include the physiological changes and activities of an organism.
             However, survival is only one characteristic of natural selection. Sexual attractiveness is a very important component of selection, so much so that biologists use the term sexual selection when they talk about this subset of natural selection.
             Sexual selection is natural selection operating on factors that contribute to an organism's mating success. Traits that are a liability to survival can evolve when the sexual attractiveness of a trait outweighs the liability incurred for survival. A male who lives a short time, but produces many offspring is much more successful than a long lived one that produces few. The former's genes will eventually dominate the gene pool of his species. In many species, especially polygynous species where only a few males monopolize all the females, sexual selection has caused males to compete against other males for mates. The competition can be either direct
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