Growth in plants and animals its types

Definition:
               Growth is the biological process in which the number of cells increases or the increase in size and weight.Growth occurs in both plants and animals.It is permanent .
Types:
        There are two types of Growth:

1.  Indeterminate Growth (open growth)
2. Determinate Growth.    (closed growth)

Indeterminate Growth:
                                   In this type of growth the organism size continuously increases as long as they live.This type of growth mostly occur in plants.Because plants have the capacity for the indeterminate growth due the presence of perpetual embryonic tissues called  meristems  or the meristematic tissues.

Determinate Growth :
                                 The type of growth occur in mostly animals in which they cease growing after reaching a certain size.this type of growth mostly occurs in animals.

Alkyl Halides introduction Chemistry

Alkyl Halide Introduction:

                             Alkyl halid are the compounds in which a halogen atom has been substituted for a hydrogen stom  in alkanes.

              They have general formula .
                                                             R----X

            where R=alkyle group.
            and X =F,Cl,Br,I.

The alkyl halide are classified as primery, secondary,or tertiary depending upon wether the halogen atom is attached to a primery ,secondary or tertiary Carbon atom.Alkyle halide are the most useful organic compounds.they frequently used to introduce alkyl groups into organic molecules

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Historical background of clissification of lelements (XII Notes)

                 After Delton Atomic theory the following well known scientists did valuable contribution in the Classification of elements.

Lavoisier.
Dobereiner.
Newland.
Mendeleev.
Moseley.


Lavoisier Classification of elements:


    In 1789 Lavoisier classified 25 to 30 elements in two groups"Metals and non metals"


   * Metals:
              
              Metals are those elements whose oxide and hydroxide are basic in nature,have low ionization potential,
low electron effinity,low electro negativity and high electro positivity.they are good conductor of electricity.
They Malleable,ductile and have a metallic lustre.Most of the metals are exist in solid state.


   *Non Metals:

               The non metals are those elements whose oxides and hydroxides are acidic in nature.Non metals have high
ionization potentials,high electron efinity,high electro negativity and low electropositivity.They are bad conductor of Heat and electricity.
  This classification failed because there are some elements which are called metalloids.
These elements act as a metal as well as non metals.For example. Graphite and silicon has high melting and boiling point but low densities like non metals.Elements having some properties like metals while some properties like non metals are called metalloids.Thus this classification was rejected.