(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) 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) The amount of biomass produced per unit area over a time period by plants during photosynthesis is defined as the primary productivity. It is expressed as weight or energy. Productivity can be mainly divided into gross primary productivity (GPP) and net primary productivity (NPP). GPP is the rate of production of organic matter during photosynthesis.
Primary productivity is directly proportional to the amount of carbon dioxide, sunlight and water. It is inversely proportional to respiratory losses. NPP = GPP - Respiratory losses (R)
(b) Decomposition is an oxygen consuming process thus it is directly proportional to the concentration of the oxygen in the environment. It is controlled by the chemical composition of detritus and climatic conditions. The decomposition rate decreases when the detritus is rich in lignin and chitin while it is quicker if the detritus contains nitrogen and water-soluble substances such as sugars.
(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.