What are Heredity and Evolution? NCERT Class 10 Science Notes
We have already discussed the previous article on Chapter – 9
Heredity and Evolution from class 10 science, but in this article, we are going in detail.
It deals with the study of heredity and variation
It refers to the phenomenon of inheritance of traits and features from the parents to their offspring’s progeny.
Traits refer to any characteristic that is transformed from parents to the offspring. Eg height and color.
It is the process of development of a new type of living organism from an old one from gradual changes
Variation during Reproduction
It refers to the minnow difference which exists between individuals of same species. Variation arises during the process of reproduction. Offsprings produced by asexual or sexual methods of reproduction assemble each other.
There are two types of reproduction
- A sexual Reproduction
-Variations are fewer.
-It occurs due to small inaccuracies in DNA copying.
- Sexual Reproduction
-Variation is large
-It occurs due to crossing over the separation of chromosomes.
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Mendel’s work of Inheritance
George Johann Mendel (1822 &1884) also known as Father of Genetics has started his experiment on plant breeding and hybridization. He proposed the laws of inheritance in living organisms.
In his experiment, he selected Pisum Satvum and used a number of contrasting characters of garden pea mentioned below in the table
He has chosen Garden pea for his experiment because of the following reasons
– Easy availability of detectable contrasting traits of several characters.
– The plant has a short life span
– Normally allows self-fertilization but cross-fertilization can also be carried out.
– It produces a large number of seeds
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It refers to the cross between two pea plants with one pair of contrasting characters.
Observation of Monohybrid cross
– -All F1 progeny were tall, no medium plant.
– -F2 progeny ¼ were short, ¾ were tall.
– -Phenotypic ratio F2-3:1(3 tall:1 short)
– -Genotypic ratio F2-1:2:3(TT:Tt:tt)
– TT and Tt both are tall plants while tt is a short plant.
– A single copy of T is enough to make the plant tall, while both copies have to be “t” for the plant to be short.
– Characters/ traits like “t” are called dominant trait.
It refers to the cross between two plants having two pairs of contrasting characters.
- Round, yellow: 9
- Round green :3
- Wrinkled yellow:3
- Wrinkled green: 1
– When RRyy was crossed with rrYY in F1 generation all were Rr Yy round and yellow seeds. – Self-pollination of F1 plants gave parental phenotype and two mixtures seeds plant in the ration of 9:3:3:1:1
-Round and Yellow seeds are dominant characters.
-The occurrence of new phenotype combination show all genes for round and yellow seed are inherited independently of each other,
1. Round and yellow seeds are Dominant characters.
2. The occurrence of new phenotype combinations shows that genes for round and yellow seeds are inherited independently of each other.
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