♪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***