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.
By 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.here is little cytoplasm in sperm and the head is densely packed with DNA. Sperm is released from the male in a fluid called semen. Semen is alkaline and does not allow the sperm to be completely motile until they reach the female reproductive tract or the vagina which is acidic in pH.