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HSC Module-Blueprint of Life

Extracts from this document...

Introduction

9.3 - Blueprint of Life: 1. Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allows change over many generations: * Outline the impact on the evolution of plants and animals of: * Changes in the physical conditions in the environment: * Changes in the chemical condition in the environment: * Competition for resources: - Evolutionary theory states that all organisms have developed from previous organisms and that all living things have a common ancestor in some initial form of primitive life. - It also states that all organisms are fundamentally similar because their basic chemistry was inherited from this very first organism. - Changes in the Physical Environment: * The Earth has continually changed since life first evolved. * Various changes in sea levels, the splitting of the continents and great changes in climate are just some of the environmental changes that life on Earth have had to cope with, or become extinct. * Changes in the environment force species to either die out, or survive and diversify. * An Example - The Peppered Moth: > Prior to the Industrial Revolution of the late 18th Century, the majority of the Peppered moths were light coloured. They survived better as they could camouflage against the white lichen on the trees. > Post-revolution, the pollution caused the trees to blacken with soot. The trees could no longer hide white moths. The darker variant of the moth was better able to hide, and so the population of the Peppered moth shifted from mainly white to mainly dark. > This is how a change in the environment can affect the evolution of an organism. - Changes in the Chemical Environment: * In the early years of life, the environment on earth was chemically unable to support life as we know it today * An anaerobic atmosphere prevented the growth of any aerobic organisms * However, as organisms evolved special pigments that allowed them to exploit the carbon dioxide in the atmosphere, many organisms appeared. ...read more.

Middle

The combinations of alleles of the gametes will vary across cells and differ from the parent * RANDOM FERTILISATION: When the male and the female mate, the two different gametes randomly fuse. Many different combinations are possible, and this causes variation. * Describe the inheritance of sex-linked genes, and alleles that exhibit codominance and explain why these do not produce simple Mendelian results: - Co-Dominance: * In this case, the two alleles are not dominant over each other * Both alleles are expressed in each others presence * There is no "blending", the alleles do not mix, but simply, both can be seen * An example is roan coloured cattle * If a type of cattle has the gene for red, and white, it would not make a pink cow, but the hairs on the cow would be both red AND white, making an interesting roan colour. * Looking at the cross in the form of a Punnett square, we can see that a cross concerning a codominant trait does not give the simple Mendelian ratio of 3:1 * The cross between the two roan cows of the F1 generation does not give the 3:1 ratio because a heterozygous animal does not give the dominant trait, as would happen in simple dominant-recessive cases. A "heterozygous" animal gives the roan colour, which results in the 1:2:1 ratio. - Incomplete Dominance: * The alleles in this case do not show simple dominance either * In this case, if the both alleles are present, a blending of phenotype will occur * For example if a snapdragon (a flower) has a red a white gene, it will be pink. - Sex-linked Characteristics: * SEX is a genetically determined characteristic * The sex of an individual is determined by a pair of chromosomes called the sex chromosomes; in humans, it is the 23rd pair * For females, both the sex chromosomes are the same. ...read more.

Conclusion

They produce their own BT chemicals, and no longer need to be sprayed * COLD STRAWBERRIES: A gene from a type of salmon that allows it to survive cold temperatures has been isolated, and inserted into a strain of strawberry. This strawberry can survive and grow in cold temperatures. * BACTERIAL INSULIN: Diabetics previously obtained their insulin from animals, esp. pigs. The gene for insulin production, taken from the human pancreas, was placed in to the DNA of a bacterium. This now provides mass production of insulin. - Ethical Issues of Transgenesis: * These technologies help treat diseases and increase food production * Should we be tampering with nature in this way? * Is it right to change living organisms for commercial gain? * Transgenesis disrupts evolutionary relationships between organisms * If a transgenic species was released into the natural environment, it could out-compete the natural organisms * Health-risks and side effects with eating GM foods. * Discuss the potential impact of the use of reproductive technologies on the genetic diversity of species using a named plant and animal example that has been genetically altered: - The main fear behind the use of genetic and reproductive breeding techniques on organisms is that the natural diversity and variation within populations is decreased - E.g. cotton plants. The main crop being grown all over the world is BT cotton. - As more and more farmers shift from natural cotton to BT cotton, there are many disadvantages: * Many natural varieties of cotton will be lost * The species itself becomes vulnerable to extinction. If all cotton grown all over the world is BT, and a disease appears, that kills specifically BT cotton, than there is a risk of cotton becoming an extinct organism - In another case, a population of cattle that have all been fathered by the same bull, through artificial insemination techniques, is at risk of environmental changes - A lack of variation is a major risk factor in extinction of a species. ?? ?? ?? ?? HSC - Stage 6 2 Unit Biology 1 ...read more.

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