CHAPTER – 9
Heredity and Evolution
Genetics : Branch of science that deals with Heredity and variation.
Heredity : It means the transmission of features/ characters/ traits from one
generation to the next generation.
Variation : The differences among the individuals of a species/ population are
called variations.
MENDEL AND HIS WORK ON INHERITANCE
Gregor Johann Mendel (1822&1884) : Started his experiments on plant
breeding and hybridisation
Mendel fi
was known as Father of Genetics
Plant selected by Mendel : Pisum sativum (garden pea). Mendel used a number
of contrasting characters for garden pea.
TABLE OF CONTRASTING CHARACTERS. (SEVEN PARTS)
CHARACTER DOMINANT RECESSIVE
TRAIT TRAIT
Flower colour Purple White
Flower position Axial Terminal
Seed colour Yellow Green
Seed shape Round Wrinkled
Pod shape Inflated Constricted
Pod colour Green Yellow
Height of plant Tall Dwarf
Seven pairs of contrasting characters in Garden
Pea
Mendels Experiments : Mendel conducted a series of experiments in which he
crossed the pollinated plants to study one character (at a time)
Monohybrid Cross :
Cross between two pea plants with one pair (monohybrid cross) contrasting
characters
Example : Tall / Short Plants.
80 X-Science
,PARENT Tall plant ·Dwarf plant
GENERATION
TT ·tt
GAMETES T T
Tt All tall plants
F1 GENERATION
(first filal generation)
Tt · Tt
SELF POLLINATION
(F1) Tt (F1)
GAMETES
T t T E
TT Tt Tt tt
F2 GENERATION
(Second Final TALL TALL TALL SHORT
Gneration
Phenotypic ratio 3:1
Phenotypic ratio 1:2:1
81 X-Science
, 82 X-Science
Heredity and Evolution
Genetics : Branch of science that deals with Heredity and variation.
Heredity : It means the transmission of features/ characters/ traits from one
generation to the next generation.
Variation : The differences among the individuals of a species/ population are
called variations.
MENDEL AND HIS WORK ON INHERITANCE
Gregor Johann Mendel (1822&1884) : Started his experiments on plant
breeding and hybridisation
Mendel fi
was known as Father of Genetics
Plant selected by Mendel : Pisum sativum (garden pea). Mendel used a number
of contrasting characters for garden pea.
TABLE OF CONTRASTING CHARACTERS. (SEVEN PARTS)
CHARACTER DOMINANT RECESSIVE
TRAIT TRAIT
Flower colour Purple White
Flower position Axial Terminal
Seed colour Yellow Green
Seed shape Round Wrinkled
Pod shape Inflated Constricted
Pod colour Green Yellow
Height of plant Tall Dwarf
Seven pairs of contrasting characters in Garden
Pea
Mendels Experiments : Mendel conducted a series of experiments in which he
crossed the pollinated plants to study one character (at a time)
Monohybrid Cross :
Cross between two pea plants with one pair (monohybrid cross) contrasting
characters
Example : Tall / Short Plants.
80 X-Science
,PARENT Tall plant ·Dwarf plant
GENERATION
TT ·tt
GAMETES T T
Tt All tall plants
F1 GENERATION
(first filal generation)
Tt · Tt
SELF POLLINATION
(F1) Tt (F1)
GAMETES
T t T E
TT Tt Tt tt
F2 GENERATION
(Second Final TALL TALL TALL SHORT
Gneration
Phenotypic ratio 3:1
Phenotypic ratio 1:2:1
81 X-Science
, 82 X-Science
