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F₂ Generation: The generation produced by interbreeding individuals of an F generation.

The genotype ratio in F₂ generation of monohybrid cross is 1 : 2 : 1.

The % of short character in F₂ generation is 25%

(C) F₁ generation

1. Mendel hypothesised that each character or trait is expressed due to a pair of factors or alleles. 

2. Now these alleles are known as genes. 

3. Gene is made up of a segment of DNA which provide information of protein. 

4. Protein is needed for biochemical process. 

5. If the proteins work efficiently, the traits get expressed in better way. 

6. Thus genes control the traits or characters.

Answer is (C) 1 : 2 : 1

Answer is (A) 1 : 2: 1

The alleles or factors which were named by Mendel are known as Genes

(A) Genes in pairs

If an organism has two copies of the same allele for example TT or tt it is homozygous for that trait.

B) Austria, Monastery garden

(A) Pair of genes

Yes the embryological evidences indicate that frogs have evolved from ancestors of fish.

Correct option is: (b) metacentric

Correct option is: (c) dumbbell-shaped

Correct option is: (a) Heredity

Differences in characters within very closely related groups of organisms are referred to as variations.

1. My grandfather and father- had curling hair. I too have curling hair. So it’s an inherited trait in family. 

2. My mother and I both have long noses which appear similar. It’s another inherited trait. 

3. Eyes of my grandmother, my brother and mine are similar. It’s another inherited trait. 

4. Ear lobes of my father, brother and mine are similar. This is another inherited trait.

Archaeopteryx serves as a connecting link between birds and reptiles. It is the fossil evidence to show that birds have evolved from reptiles.

Mendel chose the pea plant (Pisum sativam) for his breeding experiments for the following reasons. 

1. It is sexually reproducing.

2. Flowers are bisexual. 

3. Predominantly self-pollinated. 

4. Predominantly self-fertilization. 

5. Well developed characters. 

6. Early hybridization. 

7. It is an annual plant. 

8. These plants have short maturity and can produce large number of seeds in a single generation. 

9. Pea plants have short life cycle. 

10. These plants can easy to grow either on the ground or in pots.

(D) Not suitable for crossing

Mendel selected garden pea plant for his experiments as these can be self pollinated.

Pea plant has following advantages. 

1. Well defined characters 

2. Bisexual flowers 

3. Predominently self fertilization

4. Early hybridization 

5. Annual plant.

1. Variations arising during the process of reproduction can be inherited. 
2. Variations may lead to increased survival of the individuals. 
3. Gregor Johann Mendel known as the father of genetics started working on the problem of how variations were passed from one generation to another. 
4. Mendel had chosen 7 pairs of contrasting characters in pea plants for his study: flower colour, flower position, seed colour, seed shape, pod colour, pod shape and stem length. 
5. The Pea plant is an annual plant that contains vitamins A, C, E, K and B and minerals like Ca, Fe, Mn. Mg, P, S and Zn. 
6. Cross-pollinating a pure breed of yellow and green gave all pea seeds in the F₁ generation were yellow.

Variations: Differences in characters within very closely related groups of organisms are referred to as variations. 

(OR) 

Differences among living beings are called variations. 

Ex: 1. 

1. Earlobes in some humans are free and in others attached. 

2. Colour of eyes (cornea) in some people are blue and in others black. 

3. Colour of skin is black or white.

Variation is defined as the change which can be observed at the phenotypic and the genotypic level. There are different causes of variation like due to natural selection, germinal variation, etc. Germinal variation is the variations among the organism due to genetic difference. Horn is the phenotypic character of the cattle whose expression is based on the expression of the gene related to the horns. If the gene of horn gets suppressed in some cattle, then the cattle become hornless.

1. Differences in characters within very closely related groups of organisms are referred to as variations. 

2. Often a new character in a group may lead to variations that are inherited. 

3. If we observe parents and offsprings, there will be some similar features in the offspring of the parents. 

4. At the same time we find differences between parents and offspring in their features. 

5. These differences are an example of variations. 

6. Variations are quite apparent among closely related groups of organisms.

7. If we take roses as an another example, we observe number of varieties in them. 

8. But we can still find some characters similar to all plants. 

9. Thus rose plants have similar physical features, at the same time they have differences in characters like flower colour, number of petals, leaf size, stem, spines, etc. 

10. These differences in features are variations.

In the species of cow the following contrasting variations can be observed: 

1. White coloured – spotted

2. Longhorns – short horns 

3. Height – dwarf 

4. Long-tail – short tail 

5. Elongated face – stunted face 

6. More milk giving – less milk giving, etc.

Mendel selected the following characters on pea plants for his experiment.

They are:

Answer is (B) Pigeon

1. Fossils are evidence of ancient life forms or ancient habitats which have been preserved by natural processes. 

2. Fossil evidence is typically preserved within sediments deposited beneath water and land. 

3. They can be actual remains of once lived such as bones or seeds or even traces of past event such as dinosaurs foot print or ripple marks on a pre-historic shore. 

4. Usually when organisms die, their bodies will be decomposed and lost. 

5. But sometimes the body or at least some parts may be in an environment that does not let it decompose completely.

6. For example if a dead insect get caught in mud, it will not decompose quickly and the mud will eventually harden and retain the impression of the body parts of insect. 

7. All such preserved traces of living organisms are called fossils.

1. Homologous organs are the organs which perform different functions but have similar structure and origin. 

2. For example forelimb of a whale (swimmer), bat (flyer), horse (runner), mole (digger) and man (grasping). 

3. If we carefully observe the anatomy of all these animals, they have a common pattern in the arrangement of bones. 

4. Even though their external form and functions are different, they are similar internally. 

5. Thus it indicates that all the vertebrates have evolved from a common ancestor.

Analogous organs:

Organs that have similar appearance and functions but have different structures and origins. eg.: Wings of butterfly, of a bat and of a bird.

The organs which are similar in appearance and function, but have different structures and origins are called analogous organs, eg.: Wings of butterflies, bats and birds.

Homologous organs: Organs which are structurally similar but functionally different are known as “Homologous organs”. 

Forelimbs of a whale – swimming 

Wings of a bat – flying 

Forelegs of cheetah – running 

Analogous: Organs which are structurally different but functionally similar are known as “Analogous organs”. 

Eg : Wings of a bird – flying 

Wings of a bat – flying

(C) Speciation

(B) Charles Darwin

The change occurring suddenly or spontaneously is Mutation

1. Variations: Differences in characters within closely related groups of organisms are referred to as variations. They result in organisms belonging to a species being different from each other. 
2. Offsprings: The organism or organisms resulting from sexual or asexual reproduction. The product of the reproductive processes of an animal or plant. 
3. Traits: A distinguishing characteristic or quality, typically one belonging to a person or animal.
4. Phenotype: It is the composite of an organism’s observable characteristics or traits such as its morphology, development, etc.
5. Genotype: It Is the genetic makeup of an individual usually with reference to a specific characteristic tinder consideration. 
6. Heterozygous: It refers to have two different alleles for a single trait.

1. Every character or trait is controlled by a pair of factors called genes. 

2. At the time of sexual reproduction, one factor or each trait will pass to the gametes. 

3. By the fussion of male and female gametes zygote will form in which factors from both male and female parents get paired again. 

4. This zygote will develop into seed in the later stages. 

5. Thus parent plants pass on their traits to the seeds.

Augustus Weisemann proved that the bodily changes which may occur due to environment won’t be passed to its offsprings.

1. If the tails of parent rats were cut, their offsprings will have normal tails. 

2. Daughter rats do not contain tails because the bodily changes are not inherited. 

3. So the change would not be passed to their offsprings. 

4. This was proved experimentally by Augustus Weisemann and rejected the theory ‘inheritance of acquired characters’ proposed by Lamarck.

Hydrogen bond binds the nucleotides in a DNA.

Homozygous alleles.

1. False – A typical Mendelian dihybrid ratio of F generation is 9 : 3 : 3 : 1 

2. True 

3. True 

4. True 

5. False – Some of the chromosomes have an elongated knob-like appendages known as satellite 

6. True 

7. True

The dominant trait is axial white flower.

Dihybrid cross is a cross in which inheritance of two pairs of contrasting characters.

Adenine and Guanine

DNA is a large molecule consisting of millions of nucleotides. Hence it is called as polynucleotide.

There are two types of nitrogenous bases in DNA. They are purines (Adenine and Guanine) pyrimidines (Cytosine and Thymine).