ScienceAnd Blog

1.  The chemical systems of the Archea and the Bacteria. The prokaryotic cell is a hollow molecule enclosing various sites of specific chemical reactions.
· Ribosomes are involved with protein synthesis, granules acquisition and storage of materials and the nucleoplasm is the information control center.
· Mesosomes are invaginations of the molecule where specific chemical reactions can take place, partially isolated from the hostile external chemical environment.

2.  The chemical systems of the Eukarya. The eukaryotic cell is an advanced chemical system in which the various sites of specific chemical reactions are isolated by their own semi-permeable membrane, from the hostile chemicals in the surrounding cellular material.

	The lysosome is involved with the digestion of bacteria and other foreign bodies.
	The centriole is involved in cell division.
	The mitochondria are the main sources of energy for chemical reactions.
	The endoplasmic reticulum is involved either in protein or lipid synthesis, depending upon their location.
	The Golgi body is involved in moving material across the plasma lemma.
	Vacuoles store metabolic products and water.
	The nucleus is the control center.

3.  Showing how a single trait can be the result of more than one gene.

4.  Structure of the chromosome. The basic unit of the DNA molecule is a chemical compound called a nucleotide that comprises a phosphate [P] attached to a sugar [S] attached to a base [B].

5.  Nucleotides are attached together forming long lines in which the basic links are P to S to P to S etc. In the DNA molecule two of these lines are attached laterally to one another by the bases on one string linking with the bases on the other string. The distribution of the chemical forces involved cause the two strings to twist into the double helix structure commonly shown as a DNA molecule.

6.  Chemical structure of the chromosome bases. The chemical bases form two groups. The pyrimidines include cytosine [C] and thymine [T]; the purines include adenine [A] and Guanine [G]. The chemical properties of the CTAG bases are such that C and G can bond together and A and T can bond together, other links are not possible.

7.  The process of mitosis makes a copy of each chromosome during the division of the cell such that the two new daughter cells that result from cell division contain replicas of the DNA in the original cell. Although the process is remarkably accurate the diagram shows it is chemically quite complicated and errors [mutations] can occur at a number of places in the replication sequence. A phase of relative chemical stability [G1], when the cell is preparing for DNA synthesis is followed by intense metabolic activity [S phase], when DNA replication occurs. This is followed by a phase of growth and expansion [G2]. Finally, the actual formation of the two new daughter cells occurs [M phase].

8.  Meiosis is involved with the making of the sex cells [gametes] by a process of reductive division which reduces the number of chromosomes by half [from a diploid cell to a haploid cell]. Again there are many chemical reactions involved in this sequence, where errors can arise resulting in a mutation.

9.  Protein synthesis, after Percus, 2001. In protein synthesis parts of the DNA produce a chemical string called messenger mRNA which consist of groups of three bases [called a codon] linked laterally. A second kind of RNA [tRNA] present in the cell attaches itself to the mRNA, read the triple code and produces an amino acid. A linear sequence of amino acids is a protein.

10. Species definition using the gamodeme concept. Here four gamodemes [A-D] are present. C and D are adjacent and capable of interbreeding one with the other and as a result show morphological overlap. A is capable of breeding and giving fertile offspring with either C or D but is geographically isolated from these two gamodemes. B is incapable of interbreeding with either A, C or D. Thus two biospecies are present. The first is composed of gamodemes A, C and D, and the second of gamodeme B.

11. Chronospecies definition using the gamodeme concept. Here four paleontological chronospecies are represented. Each chronospecies shows a set amount of trait variation. With time and orthogenetic evolution trait variation gradually changes through the five chronospecies populations. The morphological similarity of each successive population with the previous population indicates they all belong to one genetic [evolutionary] line and a chronospecies can be defined.

12. Styles of evolutionary tempo. The tempo of evolutionary change is dependant on the selection pressure acting upon the population. Higher selection pressure tends to drive evolution more quickly. It is convenient to recognize four different temps of evolution to accommodate sudden [typogenesis], rapid [anagenesis], normal [orthogenesis] or slow [stasigenesis] rates of change.

13. Effects of selection pressure upon survival. From the viewpoint of evolution, selection pressure acts on the life cycle of individuals in the interbreeding population. The critical point is that of sexual maturity. If an organism dies before reaching sexual maturity it cannot pass on its genetic material to offspring. High selection pressure means a large number of individuals will die before reaching sexual maturity.

14. Cartoon of E. B. Ford’s observations. The Ford data on the Marsh Fritillary butterfly colony can be interpreted as a cycle of changing selection pressure: from moderate to high to low to moderate.

15. Phases of cladogenesis. As selection pressure changes and organisms adapt into new environments they eventually comes a time when different types become reproductively isolated from one another, and then they progress along their own evolutionary lines as genetically isolated interbreeding systems. In this way biospecies are formed.

16. Rates of phylogenesis. To accommodate the data observed in the fossil record different rates of species formation are recognized. Rapid changes are evolutionary bursts triggered by very low selection pressure and cause divergence into numerous environmental niches. Normal, simple divergence is essentially dichotomous and evolution that involves a long period of stasis followed by rapid explosive activity is punctuative evolution.

17. Generalized geological time scale showing the evolution of the Primates. Dichotomous evolution of the major primate groups was a phenomenon of the Cenozoic Era. The Miocene Epoch saw numerous evolutionary offshoots of the Dryopithecines, eventually producing the Apes and Homo. The Homo lineage had two major branches; one led to H. neanderthalensis the other to Homo sapiens.

18. The hexagonal web of resource needs

19. Make-up of the core of Eusociety.

20. Southern migration of the tribes based on oral history [mainly after Lye and Murray]. The San [Khoi-Khoi] may represent the first wave of Homo sapiens out of Central Africa. Their geographic area was later greatly restricted by the expansion of other groups. The dates of the Nguni migrations down the East coast are well documented in the historic record. There were no substantial numbers of Bantu in the western part of Cape Province when the Europeans arrive, and it has been reported that they did not intrude into the area until the middle of the last century.

21. Rate of growth of the World population. The population density of Earth has increased rapidly since the Industrial Revolution. The chart shows how many years it took to add a billion people to the living population. Prior to 1800 the entire evolution of H. sapiens was never able to reach large numbers. By 1800 it is estimated there were 1 billion folk alive in the world. It took 130 years for the world population to reach 2 billion but only 30 more years to reach 3 billion. By 2000 about 1 billion people were being added to the world population every eleven years, as global industrial expansion occurred. Estimates for the future suggest that by the end of the present century the global population will be 11 billion. It is highly unlikely that war or pestilence will do much more than delay this development. Only a strategy of population regulation can have any real effect. Data from Haub [1995] based upon Population Reference Bureau estimates from United Nations 1990 and 1994 projections.