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Species originate discontinuously withou...

Species originate discontinuously without intermediate forms according to

A

Lamarck

B

de Vries

C

Darwin

D

Haeckel

Text Solution

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The correct Answer is:
B
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Knowledge Check

  • If the axes are rotated through an angle 45^(@) in the positive direction without changing the origin, then the coordinates of the point (sqrt(2),4) in the old system are

    A
    `(1-2sqrt(2),1+2sqrt(2))`
    B
    `(1+2sqrt(2), 1-2sqrt(2))`
    C
    `(2sqrt(2), sqrt(2))`
    D
    `(sqrt(2),2)`

  • There are no intermediate stages in the course of evolution according to

    A
    Use and disuse theory
    B
    Natural selection theory
    C
    Mutation theory
    D
    Modern synthetic theory

  • Statement (A): According to wave nature of light the radiant energy spreads out continuously in the form of wave. Statement (B): According to particle nature it behaves as a particle and is localized at a point in space.

    A
    Only A is correct
    B
    Only B is correct
    C
    Both A, B are false
    D
    Both A, B are true

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    The products of bond breaking, shown below, are not stable, and cannot be isolated for prolonged study. Such species are referred to as reactive intermediate, and are belived to be transient intermediates in many reactions. The general structures and names of four such intermediates are, Charged Intermediates Uncharged Intermediates Carbocations (called carbonium ions in the older literature) are electrophiles and carbananions are nucleophiles. Carbenes have only a valence shell sextet of electrons and are therefore electron deficient. In this sense they are elecrophiles, but the non-bonding electron pair also gives carbenes nucleophilic character. As a rule, the electrophilic character dominates carbene reactivity. Carbon radicals have only seven valence electrons, and may be considered electron deficient, however, they do not in general bond to nucleophilic electron pair, so their chemistry exhibits differences from that of conventional electrophiles. Radical intermediates are often called free radicals. Intermediates are in general stabilised with conjugation, electron donating and electron with drawing groups. Which of the following is relatively an unstable intermediate compared to rest ?

    The products of bond breaking, shown below, are not stable, and cannot be isolated for prolonged study. Such species are referred to as reactive intermediate, and are belived to be transient intermediates in many reactions. The general structures and names of four such intermediates are, Charged Intermediates Uncharged Intermediates Carbocations (called carbonium ions in the older literature) are electrophiles and carbananions are nucleophiles. Carbenes have only a valence shell sextet of electrons and are therefore electron deficient. In this sense they are elecrophiles, but the non-bonding electron pair also gives carbenes nucleophilic character. As a rule, the electrophilic character dominates carbene reactivity. Carbon radicals have only seven valence electrons, and may be considered electron deficient, however, they do not in general bond to nucleophilic electron pair, so their chemistry exhibits differences from that of conventional electrophiles. Radical intermediates are often called free radicals. Intermediates are in general stabilised with conjugation, electron donating and electron with drawing groups. Which of the following carbo cations is more stable?

    The no.of intermediate formed in the following conversion is

    The no.of intermediate formed in the following conversion is

    In the conversion of alkyne to trans -alkene by birch reduction using alkali metals (such as Na or K) in liquid NH_3 and alcohol (MeOH or EtOH), The mechanism takes place in the formation of intermediate species in the following sequence:

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