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1. August Weisemann, tested the theory of “Inheritance of acquired characters”proposed by Lamarck by an experiment on rats. 

2. He removed tails of parental rats. 

3. He observed its offsprings which have normal tails. 

4. He has done it again for twenty two generations but still offsprings are normal with tails. 

5. He proved that the bodily changes are not inherited. So they won’t be passed to its offspring. 

6. Thus he disproved the theory of “Inheritance of acquired characters”.

1. Law of inheritance of acquired characters was proposed by Jean Baptist Lamarck. 

2. He thought that the characters acquired by an organism in its life time are passed to its offsprings. 

3. He thought that at same point of time in the history, the size of giraffe was equal to that of deer. 

4. Due to shortage of food material on the ground and lower branches of trees giraffes started stretching their necks. 

5. Because of continuous usage of neck, after several generations giraffes obtained longer necks. 

6. Such characters that are developed during the lifetime of an organism are called acquired characters.

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

2. Variations develop during reproduction in organisms. 

3. Variations are passed from parent to offspring through heredity. 

4. Beneficial variations are selected by the nature in evolution. 

5. Variations increase the survival chance of the organisms. 

6. These variations help the organisms to adapt to their environments. 

7. For example, green colour in the beetles is a variation that gave a survival advantage to the beetles as they cannot be seen by the crows. 

8. Some variations do not help organisms to survive. For example, colour variation occurs in red beetles and some blue beetles are produced instead of red beetles as they are eaten by crows easily.

Regarding his experiments with pea plants, Mendel hypothesised that

1. Characters were carried as traits and an organism always carried a pair of factors for a character. 

2. The distinguishing traits of the same character were present in the population of an organism. 

3. The traits shown by the pea plants must be in the seeds that produced them. 

4. The seeds must have obtained by the traits from the parent plants.

His assumptions made to explain his observations are:

 Assumption 1: 

Every pea plant has two ‘factors’ which are responsible for producing a particular property or trait. 

Assumption 2: 

During reproduction one ‘factor’ from each parent is taken to form a new pair in the progeny. 

Assumption 3: 

One of these will always dominate the other if mixed together.

Laws made from his experiments: 

1. Law of Dominance: Among a pair of alleles for a character, only one expresses itself in the first generation as one of the allele is dominant over the other. 

2. Law of Segregation: Every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy of only one of these to its offspring. 

3. Law of Independent Assortment: In the inheritance of more than one pair of characters the factors for each pair of characters assorts independently of the other pairs.

1. evolution 

2. heredity 

3. Round, wrinkled, yellow, green 

4. 100 

5. dominant

a) Pure breed: These are the plants that expresses a selected character over several generations. Such plants according to Mendel were pure breed for that character. 

b) Phenotype: The characters which can be seen is known as phenotype. We cannot determine the internal factors by phenotype. It tells about only the dominating char-acters which express externally. The phenotype ratio in monohybrid cross is 3 : 1. 

c) Genotype: The genetic make up of an individual is known as genotype. Genotype itself is the indication of internal factors. It tells about both dominant and recessive characters present within. The genotype ratio in monohybrid cross is 1 : 2: 1. 

d) Alleles: Alleles are corresponding pairs of genes located at specific positions in chromosomes. Together they determine the genotype of their host organism. Every individual possesses a pair of alleles for any particular trait and that each parent passes a rondomly selected copy of only one of these to an offspring. The offspring then receives its own pair of alleles for that trait one each from both parents.

(D) All the above

(C) Palaeontology

(B) Existing man

B) Not useful for digestive system

(B) Fossil evidences

The vitamins present in pea plant are ‘A, C, E, K and B’.

The determining agent responsible for each trait is called a factor.

F₃ generation represents the offsprings produced from the individuals of F₂ generation.

(C) Galapagos

B) Dominant, Recessive

(D) All the above

The detailed structure of DNA was discovered by Francis Crick and James Waston.

D) 1 – c, 2 – a, 3 – b

Answer is (C) Uracil

According to Darwin’s theory of natural selection, nature only selects or decides which organism should survive or perish in nature. This is the meaning of survival of the fittest.

(C) iii and iv

Allosomes or Sex chromosomes. They are xx (girls) and xy (boys).

Answer is (C) Both

Answer is (C) RNA

A) All variations in a species have equal chance of survival

1. The chromosome which determine the sex of a person is called sex chromosome. 

2. The two types of sex chromosomes are X chromosome and Y chromosome. 

3. Sex chromosomes in male is XY. 

4. Sex chromosomes in female is XX.

Macroevolution: Macroevolution generally refers to evolution above the species level.

Some of the evidences of evolution are 

1. Homologous and analogous organs 

2. Evidences from embryology and 

3. Evidences from fossils.

I. Homologous and analogous organs : 

1. Organs which have common fundamental anatomical plan and similar embryonic origin, whatever varied functions they may perform are regarded as homologous organs. 

2. For example forelimb of a whale, wing of bat, leg of leopord, claw of mole and hand of man. 

3. They indicate that all the vertebrates are evolved from common ancestor. 

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

5. For example wings of bats and wings of birds. 

6. The designs of the two wings, their structure and components are different but they looksimilar because they have a common use for flying but their origin is not common. 

II. Evidences from embryology: 

1. There are remarkable similarities in the embryos of different animals from fish to man. 

2. The resemblance is so close that at an early stage even an experienced embryologist would find difficulty to distinguish one embryo from the other. 

3. This strengthens the view of the existence of a common ancestor from which all these have evolved. 

III. Evidences from fossils: 

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

2. Palaeontologists determine the age of fossils by using carbon dating method.

3. These fossils provide evidences of presence of extinct animals like dinosaurs and how the evolution occurred on the earth, etc.

Microevolution: Evolutionary change within a species or small group of organisms, especially over a short period.

Acquired characters: The characters that are developed during the lifetime of an organism are called acquired characters.

Dominant gene: Gene that produces the same phenotype in the organism whether or not its allele is identical.

The law of segregation states that every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy of only one of these to its offspring.

1. Pure breed is that expresses the selected character over several generations. 

2. A pure breed will have both the factors of the same type. 

3. It means all the pure breeds are homozygous. 

4. All the gamates produced by them will have same type of factor. 

5. Pure breed on self pollination will give pure breed again.

1. F generation or first filial is the offspring of first generation parents. 

2. Cross pollination of pure breeds will give F generation.

3. All the individuals produced in F generation are heterozygous. 

4. Only the dominant characters are expressed in this generation.

Correct option is A) Nature selects desirable characters

Change in the frequency of genes in small populations is known as genetic drift.

1. Variations which are useful are retained, while those which are harmful are removed. 

2. In a population where there is a struggle, the “fittest” will be survived. 

3. Nature favours only useful variations. 

4. Each species tends to produce large number of offspring. 

5. They compete with each other for food, space, mating and other species. 

6. In this struggle for existence, only the fittest can survive. This is called survival of the fittest. 

7. Over long period of time this leads to formation of new species.

1. Nature favours only useful variations. 

2. Each species tends to produce a large number of offspring.

3. They compete with each other for food, space, mating and other species. 

4. In this struggle for existence only the fittest can survive. 

5. When cat tries to catch some rats, the rats which can run fast and hide in its hole can survive and which is slow can become prey for the cat. 

6. When we spray some insecticide on insects, most of them will die but few which can withstand that chemical will escape. 

7. When a pest attacks our garden plants, most of them may die but Which can withstand the pest can survive. 

8. When the dog tries to catch chickens, the chickens which will run fast and escape can survive but the slower ones will become food for the dog.

(D) Archeopteryx