Microtubules are part of the cytoskeleton and can assemble into bundles, for example, the cortical microtubules, the spindle and the phragmoplast. Discovery: De Robertis and Franchi (1953) reported the presence of microtubules in cell. Ledbetter and Porter (1963) found microtubules in the cytoplasm and termed as “Cytotubule”. Distribution: Fawcett and …

Source of minerals Rocks, ores and gems A rock is a mass of one or more minerals or mineral substances. Some rocks, such as limestone or quartzite, are composed primarily of one mineral – calcite or aragonite in the case of limestone, and quartz in the latter case. Other rocks …

The general theory of evolution is that organisms have changed over time. Usually, natural selection keeps things the way they are. This is stabilizing selection (Figure 17.9a and b, and Figure 17.10). Agouti rabbits are the best adapted rabbits to survive predation, so the agouti allele remains the most common …