Male ejaculates are able to modify female behaviour in advantageous ways, often increasing male fitness. This is particularly beneficial to species where the sperm from the last male takes precedence.
Intrasexual selection (in contrast to intersexual selection) is when members of the same sex (within a species) compete with each other in order to gain opportunities to mate with others, e.g. the male against male competition for females. Because intrasexual selection often involves fighting, species or individuals well adapt for intrasexual selection will have developed better armourments (weapons) than their competition.
It is believed that originally, species reproduced by asexual reproduction. This is where species are able to reproduce through mitosis individually, this means the descendants of the individuals are essentially clones, the only way which variation can occur is through mutations. Asexual reproduction allows for rapid population growth in stable environments (where adaptation through [...]
Fertilisation is an internal process in mammals, the gamete cells however are not fully mature when they leave the gonad (either testicle or ovary) and so continue a process of maturation right up to actual fertilisation, the ovum matures fully when it undergoes its second meiotic division, the process for sperm is as follows:
Spermatogenesis is the biological process whereby spermatogonia (the germ cell) develop into spermatozoa (the mature sperm cells). This process takes place in the seminiferous tubules of the testes; this is the starting point for spermatogenesis. Stem cells adjacent to the inner tubule wall divide, beginning at the walls and proceeding into the innermost part, [...]
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