Wednesday, November 29, 2006

Hanging Gardens of Babylon

The Hanging Gardens of Babylon and the walls of Babylon were considered one of the Seven Wonders of the World. They were both supposedly built by Nebuchadnezzar II around 600 BC.
The lush Hanging Gardens are extensively documented by Greek historians such as Strabo and Diodorus Siculus, but otherwise there is little evidence for their existence. In fact, there are no Babylonian records of any such gardens having existed. Some evidence gathered at the excavation of the palace at Babylon has accrued, but does not completely substantiate what look like fanciful descriptions. Through the ages, the location may have been confused with gardens that existed at Nineveh, since tablets from there clearly show gardens. Writings on these tablets describe the possible use of something similar to an Archimedes' screw as a process of raising the water to the required height.

Sunday, November 26, 2006

Conjoined twins

Conjoined twins, are monozygotic twins, whose bodies are joined together at birth. This occurs where the single zygote of identical twins fails to separate completely, and the zygote starts to split after day 13 following fertilization. This condition occurs in about 1 in 50,000 human pregnancies. Most conjoined twins are now evaluated for surgery to attempt to separate them into separate functional bodies. The degree of difficulty rises if a vital organ or structure is shared between twins, such as brain, heart or liver.

A chimera is an ordinary person or animal except that some of his or her parts actually came from his or her twin. A chimera may arise either from identical twin fetuses,or from dizygotic fetuses, which can be identified by chromosomal comparisons from various parts of the body. The number of cells derived from each fetus can vary from one part of the body to another, and often leads to characteristic mosaicism skin colouration in human chimeras. A chimera may be a hermaphrodite, composed of cells from a male twin and a female twin.

Sunday, November 19, 2006

Psychology of education

Educational psychology is the study of how humans learn in educational settings, the effectiveness of educational interventions, the psychology of teaching, and the social psychology of schools as organizations. Although the terms "educational psychology" and "school psychology" are often used interchangeably, researchers and theorists are likely to be identified as educational psychologists, whereas practitioners in schools or school-related settings are identified as school psychologists.
Educational psychology is concerned with the processes of educational attainment among the general population and sub-populations such as gifted children and those subject to specific disabilities.Educational psychology can in part be understood through its relationship with other disciplines. It is informed primarily by psychology, bearing a relationship to that discipline analogous to the relationship between medicine and biology.

Thursday, November 09, 2006

Identical twins

Identical twins occur when a single egg is fertilized to form one zygote which then divides into two separate embryos. This is not considered to be a hereditary trait, but rather an anomaly that occurs in birthing at a rate of about 1:150 births worldwide, regardless of ethnic background. The two embryos develop into fetuses sharing the same womb. When one egg is fertilized by one sperm cell, and then divides and separates, two identical cells will result. Depending on the stage at which the zygote divides, identical twins may share the same amnion, which can cause complications in pregnancy.

For example, the umbilical cords of monoamniotic twins can become entangled, reducing or interrupting the blood supply to the developing fetus. About 50% of mono-mono twins die from umbilical cord entanglement. Monochorionic twins, sharing one placenta, usually also share the placental blood supply. These twins may develop such that blood passes disproportionately from one twin to the other through connecting blood vessels within their shared placenta, leading to twin-to-twin transfusion syndrome.

Thursday, November 02, 2006


Genetics is the science of genes, heredity, and the variation of organisms. The word genetics was first suggested to describe the study of inheritance and the science of variation by the prominent British scientist William Bateson in a personal letter to Adam Sedgwick, dated April 18, 1905. Bateson first used the term genetics publicly at the Third International Conference on Genetics London, England in 1906.

Heredity and variations form the basis of genetics. Humans applied knowledge of genetics in prehistory with the domestication and breeding of plants and animals. In modern research, genetics provides important tools for the investigation of the function of a particular gene, e.g., analysis of genetic interactions. Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA (deoxyribonucleic acid) molecules.

Genes encode the information necessary for synthesizing the amino-acid sequences in proteins, which in turn play a large role in determining the final phenotype, or physical appearance, of the organism. In diploid organisms, a dominant allele on one chromosome will mask the expression of a recessive gene on the other.The phrase to code for is often used to mean a gene contains the instructions about how to build a particular protein, as in the gene codes for the protein. The one gene, one protein concept is now known to be simplistic. For example, a single gene may produce multiple products, depending on how its transcription is regulated. Genes code for the nucleotide sequences in mRNA, tRNA and rRNA, required for protein synthesis.