However, human activities generate additional 'greenhouse gases'. Globally, atmospheric concentrations of two of the main greenhouse gases, carbon dioxide (CO2) and methane (CH4) have increased over the last 150 years. Agriculture has played a significant role in this-up to 35% of anthropogenic CH4 comes from animals and their wastes (Monteny et al. 2006).
sperm, sperm cell, spermatozoan, spermatozoon-the male reproductive cell; the male gamete; a sperm is mostly a nucleus surrounded by little other cellular material. egg cell, ovum-the female reproductive cell; the female gamete.
When the sperm has the usual single flagellum (or tail), it is called a spermatozoon and may be described as uniflagellate. The flagellum moves in a whip-like manner, propelling the the sperm towards the egg and uniflagellated sperm are also termed motile sperm.y Dr Ananya Mandal, MD. Sperm is the male reproductive cell in vertebrates. The term is derived from the Greek word sperma meaning seed. Sperm were first observed under a microscope in 1677 by Antonie van Leeuwenhoek who described them as little animals or animalcules.