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How do Mendel’s experiments show that traits may be dominant or recessive?

In Mendel's experiment all the F1 generation were tall and no dwarf plant was seen while in F2 generation the dwarf plant reappeared. The experiment showed that 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. Traits like ‘T’ are called dominant traits, while those that behave like ‘t’ are called recessive traits. Thus Mendel's experiment showed that the traits can be dominant or recessive.

4106 Views

A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits– blood group A or O – is dominant? Why or why not?

(i) If A is considered to be dominant over O then the following combinations are possible:
Male: AO and Female: 00

 

A

O

O

AO

00

O

AO

00

(For understanding)
Daughter can be OO and hence have blood group O.

(ii) If O is considered to be dominant over A then the following combinations are possible:
Male: AA and Female: 00 or OA

 

A

A

O

OA

OA

O

OA

OA

O

OA

OA

A

AA

AA

(For understanding)
In this case daughter can be OA and hence have blood group O.
Thus from the information given in the question we cannot ascertain which blood group is dominant as in both cases we can see that the that the daughter can have the blood group O.

1062 Views

How do Mendel’s experiments show that traits are inherited independently?

Mendel took two pairs of alternative expression of two traits of a pea plant and crossed them. The F1 progeny showed only the dominant characteristics among each pair. The F2 progeny had phenotypes similar to parents but also new phenotypes that did not exist in the parents. This indicates that pair of alternate characteristics behave independently of the other pair and are thus inherited independent of each other. 
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How does the creation of variations in a species promote survival?

The variations ensure that the survival of the species as they allow the members of population to adapt to the changing environment and conditions. The species are more suitable to the changed environment . Thus continuity of the species is maintained.
For example, Bacteria variants which can withstand tolerate heat will survive better in a heat wave than variant which cannot heat wave. It proves that creation of variations in a species promote survival.

1657 Views

If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?


Trait B may have arisen earlier as it is present in more members of the population. It must have arisen earlier and has now spread to 60% of the population. Whereas trait A must be new as it has spread to only 10% of the population.
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