Monoterpenes ester are called pyrethroids

occur in leaves and flower of chrysanthemum species show very striking insecticidal activity

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#Id: 9554

#XL - T Zoology

Alfred Russel Wallace - Who was collecting specimens in the Malay Archipelago, had independently conceived of natural selection

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#Id: 9555

#XL - T Zoology

Populational change is Darwin’s hypothesis that evolution occurs by changes in the proportions (frequencies) of different variant kinds of individuals within a population.

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#Id: 9556

#XL - T Zoology

TLS Online TPP Program

#Id: 9557

#XL - T Zoology

Where, though, do these hereditary variations come from?

This was the great gap in Darwin’s theory, and he never filled it. The problem was serious because, according to the prevailing belief in blending inheritance, variation should decrease, not increase.

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#XL - T Zoology

Orthogenesis - “Straight-line evolution,” held that the variation that arises is directed toward fixed goals.

So that a species evolves in a predetermined direction by some kind of internal drive, without the aid of natural selection.

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#Id: 9559

#XL - T Zoology

Mutationist - Theories were advanced by some geneticists who observed that discretely different new phenotypes can arise by a process of mutation.