(a) Explain the basic postulates of Darwinism.
(b) What is genetic erosion? State any two factors responsible for it.
(c) What is meant by biotic potential?
(a) Explain the origin of bread wheat (Triticum aestivum)
(b) Write two differences between;
(i) B cells and T cells (ii) Antibiotics and Interferons
(c) Define organ transplantation. Mention a precaution which must be taken for this procedure.
(a) Triticum aestivum is a cultigen (a plant that has been altered by humans through a process of selective breeding) and as such is only known in cultivation. First domesticated at least 9,000 years ago, its origins have been the subject of intensive botanical and genetic research.
Modern wheat cultivars belong primarily to two species: (1) hexaploid
bread wheat, Triticum aestivum (2n = 42 chromosomes), and (2) tetraploid,
hard or durum-type wheat, T. turgidum.
(b)
i.
B cells | T cells |
Produce antibodies | Do not produce antibodies |
Humoral immunity | Cell-mediated immunity |
Antibiotics | Interferons |
An antibody is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to identify and neutralize pathogens such as bacteria and viruses. |
Interferons (IFNs) are a group of signaling proteins made and released by host cells in response to the presence of several pathogens, such as viruses and also tumor cells. |
Produced by B cells | Produced by virus infected cells |