(a) Write the specific location and the functions of the following cells in human males:
(i) Leydig cells
(ii) Sertoli cells
(iii) Primary spermatocyte
(b) Explain the role of any two accessory glands in human male reproductive system.
(a) (i) Leydig cell are found adjacent to the seminiferous tubules in the testes. They synthesize and secrete testicular hormones called androgens (testosterone).
(ii) Sertoli cells are found in the seminiferous tubules. They act as nurse cell and provide nutrition to the male germ cells.
(iii) Primary spermatocytes are present in the testes. They are diploid cells that are derived from the spermatogonia. They undergo meiotic division to give rise to secondary spermatocyte and thereby male gamete-sperm.
(b) The male accessory glands include the seminal vesicles, prostate gland, and the bulbourethral glands whose secretions constitute the seminal plasma, which provides energy and motility to the sperms until they reach the ovum.
Prostate Gland: It stores and secretes an alkaline, milky fluid known as pre-ejaculate. The purpose of the alkalinity of the semen is to neutralize the acidity of the vaginal tract.
Bulbourethral glands: This gland secretes a viscous secretion during sexual arousal. This fluid helps to lubricate the urethra for easy passage of spermatozoa to pass through, and to help flush out any residual urine or foreign matter.
(a) Name the primates that lived about 15 million years ago. List their characteristic features.
(b) (i) Where was the first man-like animal found?
(ii) Write the order in which Neanderthals, Homo habilis and Homo erectusappeared on earth.
State the brain capacity of each one of them.
(iii) When did modern Homo sapiens appear on this planet?
(a) Explain primary productivity and the factors that influence it.
(b) Describe how do oxygen and chemical composition of detritus control decomposition?
(a) What is El Nino effect? Explain how it accounts for biodiversity loss.
(b) Explain any three measures that you as an individual would take, to reduce environmental pollution.