biology form 4 cell structure and organisation

. The first half of the phase and the changes in these phases are controlled by estrogens and progesterone. The secretion of these hormones occur cyclically because of the cyclic secretions of pituitary gonadotropins in the female. The fertilised ovum in mammals and other higher animals passes thro..

Did You Know? - The cells that make up our body are so small that you would fit over 200 of them on the full stop at the end of this sentence. The word cell is derived from the Latin word cellula which means a little room. It was the British botanist Robert Hooke who, in 1664, w..

Cell Theory - Two German biologists M.J.Schleiden (1838) and Theodore Schwann (1839) proposed the cell theory (or cell doctrine), which unified the ideas prevailing at that period on the organisation in plants and animals. The cell theory states tha..

fig. 19.3 Structure of Chromosomes The terminal end of a chromosome is called as telomere. It is functionally different from the rest of the chromosome. A chromatid may breakup into pieces and the pieces may rejoin, but no segment becomes connected to the telomere. Thus, the telomere show..

A sperm is a haploid male gamete which fuses with the ovum to form the diploid zygot..

Prokaryotic and Eukaryotic Cells - There are two basic types of cells found in living organisms - the prokaryotic cells and the eukaryotic cells. This classification is based on three main features, namely; Organisation of biomembranes Nature of cyt..

Summary - All living organisms are composed of one or more cells. A cell is the structural and functional unit of life. The metabolic reactions in a living organism - can occur only in a delicately balanced environment. Through their unique chemical composition, c..

Properties of Cancer Cells - 1) Cancer cells show uncontrolled mitotic divisions causing unorganised growth 2) Due to uncontrolled growth and division of cells, a tumour (also called Neoplasm is generally formed) 3) Cancer cells are far less adhesiv..

Every organism consists of parts that can be arranged in increasing levels of complexity. Each higher level is more complex than the one below it. The smallest structural unit of matter, both non-living and living are protons, neutrons and electrons. These particles combine in a specific ..

There are basically two types of reproduction - asexual and sexual. This classification is based on the number of parents. Asexual reproduction involves only one parent and the offspring is genetically similar to the parent. Sexual reproduction involves two parents and the offspring has a fusion of..