1) Fossil fuels were formed a very long time ago from plants and animals that were buried and with time changes into oil, coal and natural gas. They are essentially not part of the carbon cycle. However when man burns fossil fuels, they upset the balance of CO2 concentration in the cycle as they released a lot of amount of CO2 in the atmosphere. With the abundance of CO2 in the atmosphere, all are not used for the photosynthesis and respiration sustained by the cycle.
The excess CO2 contributes to the greenhouse effect, a condition where more heat is trap in the earth because of too many CO2 in the atmosphere. As a result, global warming occurs (Gautier, 2008, pp. 78-79). 2) All four species of lizards that are closely related can become separate species because of the process of active radiation. In an island, these four lizards may live and utilize in different microenvironments of different habitats. There is a rapid speciation of these lizards proceeding to the phenotypic adaptation to divergent environments.
According to Darwin in 1842, phenotypes of species ‘fit’ the divergent environments that they inhabit, and hence that species have “been taken and modified for different ends” (qtd Schluter, 2000, pp. 10-12). 3). The DNA (chromatins) are not visible in the interphase because by then they are still uncoiled, diffused and disorganized in the nucleus. What happens at this time is that genetic information is transcribed to produce RNA. They appear as dots or grains or thin long strands. However to facilitate separation of DNA, chromosomes are duplicated in the S phase.
To prepare for mitosis, the chromosomes condense; condensin (an elongated complex of several proteins) mediates then binds and circles DNA into a single chromatid at multiple spots, twisting the chromatin into a variety of shorter and thicker coils and loops. This made the DNA visible in the microscope (Hartl & Jones, 2005, pp. 75-76). 4). The four daughter cells produced in meiosis are unique resulting from a variation of two processes known as independent segregation of the chromosomes and crossing-over.
In the independent segregation at the end of Meiosis I, two very different intermediate cells are produced. Crossing-over then takes place in meiosis I which affords time and opportunity for the random exchange of information from homologous pairs of chromosomes resulting to the unique combination of alleles. These are the reasons why four daughter cells have completely different set of genetic information (Hartl & Jones, 2005, p. 115).
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