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AS and A Level: Genetics, Evolution & Biodiversity

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  • Marked by Teachers essays 33
  • Peer Reviewed essays 15
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  1. Marked by a teacher

    Revision notes - origins of life on Earth, chemistry of life

    5 star(s)

    * Life may have evolved in these areas using chemical energy available from vents. Abiogenesis (Urey-Miller) * Life on earth arose from organic molecules existing on the primitive earth (amino acids - basic building blocks of life) Panspermia * Suggests either very primitive organisms or complex organic compounds travelled to earth from space. In each theory, before life could have originate/evolve complex organic compounds first had to be formed. Theories differ in how these precursors formed � shallow oceans (Urey-Miller); formation of chem.

    • Word count: 2113
  2. Marked by a teacher

    An Investigation into the Mitotic Nuclear Division of Allium Sativum Root Tip Cells, and the Relative Duration of Each Phase of this Cellular Cycle

    5 star(s)

    In this investigation, it is believed that the durations of each phase in the process of mitotic nuclear division vary, for the following biological and biochemical reasons. Stage B: Prophase: 20 relative time units Prophase is the cellular cycle stage of mitosis in which chromatin condense into a highly ordered structure called a chromosome (7, 8). Since the genetic material has been duplicated, there are two identical copies of each chromosome in the cell. The other important cellular organelles in the prophase stage are the centrioles (1).

    • Word count: 8293
  3. Marked by a teacher

    Explain how twin and adoption studies attempt to distinguish genetic and environmental factors underlying the onset of schizophrenia within families. Review the studies and discuss two limitations of this.

    5 star(s)

    Monozygotic (MZ) twins have almost identical genomes, while Dizygotic (DZ) twins share only approximately half their genes. However, both usually share the same rearing environment. Thus, if environmental factors entirely explain familial clustering there should be no differences in the concordances between MZ and DZ twins. Conversely, if genetic factors are important, the concordance should be higher among MZ than DZ twins. If genetic factors alone were sufficient determinants, there should be a 100% concordance among MZ twins. In a Finnish study, the heritability of schizophrenia was 83% if first-degree relatives had been diagnosed with the disorder, the remaining 17%

    • Word count: 1708
  4. Marked by a teacher

    The Human Genome Project

    5 star(s)

    This double-helical structure of the DNA molecule was discovered Watson and Crick in 1953, for which they received the Nobel Prize for Chemistry. The bases from each side join in pairs to form the "rungs" of the ladder-specifically, adenine always pairs with thymine, and guanine always pairs with cytosine. The genetic code is specified by the order of adenines, thymines, guanines, and cytosines in the DNA ladder. A particular section of the DNA ladder usually has a unique sequence of base pairs.

    • Word count: 2268
  5. Marked by a teacher

    Too Much Information: Genetic Testing

    5 star(s)

    Some examples of these genetic conditions include Tay-Sach's disease, Bloom syndrome, Deafness, cystic fibrosis, and many other diseases (http://www.einstein.edu/e3front.dll?durki=7158). Although many of these conditions are fatal, the ones that are not can be treated early, even before symptoms develop when possible, or if not treated, at least monitored because of the person's high risk of becoming afflicted. If genetic testing is 95 per cent accurate, which is a reasonable margin of error by any standard, then one in twenty people who take the test will get a false result.

    • Word count: 938
  6. Marked by a teacher

    Compare the Similarities and Differences between Meiosis and Mitosis

    4 star(s)

    These daughter cells are clones to the parent cell. On the other hand, meiosis provides gametes that contain only half the number of chromosome number of an adult cell so that when gametes fuse together in fertilisation, a diploid zygote is formed. Genetic materials in daughter cells of meiosis are slightly different to adult cell due to variation from independent assortment and crossing-over of material. Overview of different phases: Both mitosis and meiosis consists of four main phases: prophase, metaphase, anaphase & telophase.

    • Word count: 629
  7. Marked by a teacher

    Biology Issue Report on GM Foods

    4 star(s)

    These two sets of figures do not necessarily tally but the current population is not currently receiving enough food and rising population is not the only factor in food demand. In addition to population growth and reduced rainfall, soil fertility can be depleted by a lack of access to fertiliser and bad farming practices which reduces the area suitable for crops and pasture. Genetic Modification of Crops ? A Biological Solution One solution in combatting food shortages and ensuring healthy yield is ensuring that crops are chosen for planting which are able to grow with a minimal amount of water.

    • Word count: 2177
  8. Marked by a teacher

    Research Project - Could stems cells provide a cure for diabetes?

    4 star(s)

    Some glycogen or fat is broken down into glucose and some is released back into the bloodstream to keep the sugar levels in the blood at a normal level. Insulin is made my cells called beta cells which are part of the islets - islands of cells - within the pancreas. [11] Type of diabetes: A person with diabetes has a disorder where the glucose quantity in the body is too high. This can be due to the fact the body is not producing enough insulin to help level it, or that the body cells are not responding correctly to the insulin that is produced by the pancreas.

    • Word count: 3595
  9. Marked by a teacher


    4 star(s)

    Mental health is linked to behaviour Mental, social and behavioural health problems could interact and have a large effect on an individual's behaviour and well-being. These following examples could have effects on an individual's behaviour and well being and could cause them to find it very difficult to cope, these are as follows: Substance abuse, violence, and abuses of women and children, health problems such as heart disease, depression, and anxiety. (www.who.int) What is mental illness? A mental illness is a health problem that significantly affects how a person feels, thinks, behaves, and interacts with other people.

    • Word count: 11946
  10. Marked by a teacher

    Evolution. This issue report will aim to address the Theory of Evolution by explaining key concepts and ideas in an informative and unbiased way. It will set forth to describe the theory, by highlighting its main components,

    4 star(s)

    They are convinced that they can draw definite conclusions about the origins of life. There are other rationally sound models that deny the original Theory, branding it incorrect. However, are biologists justified in stating that the Theory is ultimately flawless and cannot be refuted? They have to convince everyone that their exposition of science is valid. Before they can find a solution to their problem, let's go back to basics. Firstly, what is the definition of biological evolution? "...biological evolution is defined as descent with modification from a common ancestor."

    • Word count: 2081
  11. Marked by a teacher

    The Loss of the Lemur: The Road to Extinction

    4 star(s)

    I undertook a visit to Woburn Safari Park, which keeps this sub-species of lemur, in order to find the answers to these questions and visit the very animals facing extinction half way around the world. The Cause Although the problem of the declining lemur population was identified by 1986, the problems in Madagascar are still highly prevalent and affecting the subspecies greatly. There are two main causes for this decline, highlighted during the visit by Adele Clegg, Head of Learning at Woburn Safari Park.

    • Word count: 2074
  12. Marked by a teacher

    Five Kindom vs Three domain classification

    4 star(s)

    Each Kingdom is divided into smaller groups called phyla.Each phylum is divided into classes, each class into orders, and each order into families, each family into genera, and each genus into species. Species represent one type of an organism such as h**o sapiens (species have to be in italics or underlined). Monera Many biologists now divide Monera into the Eubacteria and Archeobacteria (Three division). Monera individuals are single celled and may or may not move. They have a cell wall however they don't have chloroplasts, organelles or a nucleus, they are usually very tiny and are green in colour.

    • Word count: 1014
  13. Marked by a teacher

    Epping Forest Coursework

    4 star(s)

    Samples will be used to identify which brackens have a tall height in relation to its area or variables, which area listed below. The statistical test that I will use to interpret these data is the 'Mann-Whitney U' test. This is used to calculate the medians of the two sets of data collected (one from the light and one from the dark area) and would show if the difference in height between the areas is significant or not. This will be used to measure the strength of the relationship between two variables.

    • Word count: 8458
  14. Marked by a teacher

    Understanding DNA Coursework

    4 star(s)

    The phosphate group PO4H2 negatively charged, and is linked to the pentose sugar. The pentose sugar consists of 5 carbons, the sugar present in RNA is ribose, and deoxyribose sugar is present in DNA. Deoxyribose has one less oxygen in its molecule (refer to Differences between DNA and RNA section). Lastly the nitrogen-containing base consists of 5 types in DNA and RNA. The nitrogen containing bases in DNA are Adenine, Thymine, Guanine and Cytosine (ATGC). However, RNA has the three bases AG AND C, but T is replaced by a different base, only found in RNA; uracil (U).

    • Word count: 1314
  15. Marked by a teacher

    Nature vs. Nurture - And its affect on intelligence, personality, and behavior

    4 star(s)

    Evaluation of Sources Nature vs. nurture has been an oscillating controversy in the field of psychology for many years. Does one inherit genes, or are one's genes affected by the environment? This question has been the focal point in the field of psychology for decades. As more and more case studies are coming out with results, a clearer picture comes into view. The "picture" portrays how the blend of both nature and nurture affects human growth and development. The basis of nature is the principle that people have their personalities engraved inside their genes, which are inherited by their parents.

    • Word count: 3331
  16. Marked by a teacher

    Mitosis and Meiosis, the defining differences.

    4 star(s)

    The cell produces many materials essential for its own growth and for carrying out all its functions. DNA replication occurs during interphase. Mitosis: this is the process of nuclear division Cell division: this is the process of division of the cytoplasm into two daughter cells. Although these are the main stages, many sub stages exists allowing further detail into what happens during the cell cycle. Prophase is the longest stage in Mitosis. The chromosomes become visable as long threads, and start to coil up and become shorter and thicker. During Mitosis in animal cells, the centriole divides and moves to opposite poles of the nucleus.

    • Word count: 1332
  17. Marked by a teacher

    Human Cloning Assignment

    4 star(s)

    Each group of researchers has its own specific technique. The best known is the Roslin technique, and the most effective and most recently developed is the Honolulu technique. The cloning of Dolly has been the most important event in cloning history. Not only did it spark public interest in the subject, but it also proved that the cloning of adult animals could be accomplished. Previously, it was not known if an adult nucleus was still able to produce a completely new animal. Genetic damage and the simple deactivation of genes in cells were both considered possibly irreversible.

    • Word count: 2972
  18. Marked by a teacher

    Pros and Cons of Genetic Engineering

    4 star(s)

    DNA discovery is attributed to the research of three scientists, Francis Crick, Maurice Wilkins, and James Dewey Watson in 1951. They were all later accredited with the Nobel Prize in physiology and medicine in 1962. Viewpoint 1 The possibilities of genetic engineering are endless. Once the power to control the instructions, given to a single cell, are mastered anything can be accomplished. For example, insulin can be created and grown in large quantities by using an inexpensive gene manipulation method of growing a certain bacteria.

    • Word count: 1950
  19. Peer reviewed

    An Investigation into the effect of caffeine on reaction times

    5 star(s)

    Reduced adenosine activity also contributes to increased dopamine activity5, a neurotransmitter which is a precursor in the production of epinephrine6. Together, these effects increase the levels of epinephrine in the brain. ADHD (attention-deficit hyperactivity disorder) is caused by a deficiency in dopamine, and its treatments raise dopamine levels7. This suggests that dopamine also plays a part in attention and concentration. Synapse showing antagonistic action of caffeine on adenosine receptors - http://www.snabonline.com/pupil/mediabank.aspx -> Book artwork with no labels -> Figure 8.57 - 22/10/08 As well as blocking adenosine receptors, caffeine also blocks the removal of cAMP (cyclic adenosine monophospate) from cells.

    • Word count: 4449
  20. Peer reviewed

    Discuss the Impact of Genome Sequences on the Study of Development

    5 star(s)

    Despite it's hazy and undramatic origins the field aquired a recognisble unity by the 1930's. One proposed question was "how do the organisms' genes produce their effect in development?" This lead to the field of developmental genetics, using the genes of an organism to explain it's development. During that period Lillie (1927) Spemann (1938) and Just (1939) said there would be no genetic theory of development until: 1. Genetisists could explain how chromosomes produce different and changing types of cell cytoplasms. 2. Genetisists could explain how genes control the earley stages of development. 3. And explain how complex phenomena, such as the s*x determination mechanisms occur.

    • Word count: 1908
  21. Peer reviewed

    Problem - Maintaining the habitat of the capybara and breeding them for meat.

    4 star(s)

    Water is being abstracted for human usage increasing the threat to freshwater habitats. Efforts to protect wetlands have now produced several international agreements. Another habitat being destroyed is the grasslands, in the past grassland covered about two fifths of the earth's land surface 3.This grassland is being destroyed for agricultural use for growing crops or raising livestock. However, farming has created grassland; the hill pastures of Europe and New Zealand, for example, are a result of deforestation several centuries ago 3.This old pasture has a larger range of plants and vegetation, which nutritionally benefits the capybara and several other animals.

    • Word count: 2865
  22. Peer reviewed

    Brewing. During beer production the sugar in the wort is fermented by the yeast into alcohol. For this purpose yeast fungi of the species Saccharomyces cerevisiae are used.

    4 star(s)

    Yeast is able to utilise these sugars both in the presence of oxygen and when oxygen is excluded. The aerobic breakdown, which produces more energy is called respiration and the anaerobic breakdown, which produces less energy is called fermentation. Of the carbohydrates only sugars are respired or fermented by yeast. An important parameter for distinguishing individual yeast species is their ability to respire or ferment various sugars. Whether a sugar is used aerobically or anaerobically depends principally on the oxygen availability. In the presence of oxygen, yeasts obtain their energy by respiration. When the oxygen is removed metabolism changes to fermentation.

    • Word count: 1451
  23. Peer reviewed

    For each of the animal groups you have chosen, describe the structures involved in the biological process you have named. In each case, describe how these structures function, and explain how they allow each group to survive in their habitat.

    4 star(s)

    This allows the insect to have a high metabolic rate - so they can fly. Insects can also open and close their spiracles which allow them to control water loss and allows insect to live in extremely arid conditions Fish: Fish live in an aquatic environment. As water contains less oxygen than air they have developed a very efficient gas exchange system. Gas exchange takes place at the gills which are specialised structures. They have several adaptations to increase the rate of gas exchange. Gills are thin and covered in lamellae this gives the gills a very large surface area.

    • Word count: 1456
  24. Peer reviewed

    How Zoo's Avoid Inbreeding in a Limited Captive Population

    4 star(s)

    With more time, Inbreeding Depression can occur which is the decline of health and poor vigour of a population. Other factors can effect a population for example, Genetic pollution, uncontrolled hybridization, the bottleneck effect, small Gene pools. The term Line breeding is used by breeders of purebred livestock, where the animals are purposely inbred for planned characteristics and predictable offspring. Inbreeding depression is more likely to occur when populations of animals are breeding with relatives, this causes more homozygosity, with that in effect offspring inherit the recessive alleles of their parents, and Recessive alleles are mainly deleterious, thus giving the effect the name 'Inbreeding Depression'.

    • Word count: 2672
  25. Peer reviewed

    Is there a relationship between the girth of a tree trunk and the percentage cover of lichen?

    4 star(s)

    Only one species of tree shall be examined - sycamore trees. This eradicates any influence that could be made by varying amounts of lichen growing on different species of trees, narrowing down the variables to be controlled. Light intensity cannot be controlled, however it can and will be measured. Measuring light intensity could well indicate whether there is a photosynthesis component involved, which would add detail to the results and subsequent conclusions. It will be measured at each tree using a light meter. Light intensity will be measured at the one meter point on the north mark on all trees.

    • Word count: 2468

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