Saturday, December 11, 2010

♪biology form 5...chapter 6:variation note♫

after final exam we have one more month to finish school.so the teachers taught us some form 5 chapter.for biology we learn variation.skip the long intro.here is the note that i take while the teacher mr fazlie is teaching....

definition of variation:
diff which exist between living organism as a resultof their genotypes(genetic) &/@ their environment

importance:
to withstand harsh environmental conditions

examples:
height,weight,blood group,tounge rolling,eye color,sex

type of variation:

  • continuos 
  • discontinuous
continuos:
-diff were slight
-dtrmined by many genes &/@ enviromental influence
-bell-shaped,normal distribution curve
-e.g:height and weight

discontinuous:
-the diff are discrete(separate)&(clear cut)
-dtrmined by queles of one,two @ only a few genes
-not influenced by environmental factor
-e.g:blood group,tounge rolling,gender,ear lobe shape

compare n contrast between continuous and discontinuous

sim:both refer to diff in inherited traits that exist among members of species

diff:
continuous:have no distinct categories into which individual can be placed
                :tend to be quantitative
                :are controlled by a large number of genes
                :are significantly affected by the environment

discontinuous:have distinct categories into which individual can be placed
                    :tend to be qualitative
                   :are controlled by one or a small number of genes
                   :are largely unaffected by the environment

Causes of variation:
causes:
-both genetic and enviromental
-plenotype=genetic factor and environmental factor

genetic-sexual-independent assortment
                     -crossing over
                     -random fertilisation
environmental-mutation-gene mutation
                                   -chromosomal mutation

finished***

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