Q1. Define Heredity. Explain the mechanism of Hereditary changes?
i. Heredity is defined as the transfer of biological characters from one generation to another via genes
ii. The mechanism of heredity is as follows
a) Heredity changes occur due to genetic variation
b) During fusion of male and female gametes, the offspring always has recombined genes of both the parents. These offspring’s thus show some characters of either of the parents.
c) Sometimes sudden changes known as mutations occur in the genes. A change in the position of even a single nucleotide can cause either a minor effect or a considerable changes in the characters of an individual.
d) If these changes (mutation) occur in DNA of germ line cells then, these changes would be inherited to the next generation.
Q2. How are the hereditary changes responsible for evolution?
i. Evolution is gradual change occurring in living organisms over a long duration.
ii. Sudden heredity changes may occur in the genes of an individual resulting in genetic variations.
iii. These genetic variations are responsible for the formation of new species
iv. According to Darwin's theory, organisms with favorable or beneficial variations survive in competition and are selected by nature whereas the others with non-favourable are eliminated.
v. This leads to formation of new species due to specific changes in specific characters accumulated through several generations in selected organisms.
Q3. Write a note on 'transcription'.
i. Transcription is the process of synthesis of mRNA from DNA. It takes place in the presence of RNA polymerase.
ii. During transcription, mRNA is produced as per the sequence of nucleotides present on the DNA.
iii. This mRNA sequence is always complementary to the DNA strand that is used for its synthesis.
iv. The thymine in DNA molecule is replaced by uracil in RNA, during the process of transcription.
Q4. Explain in detail the process of translation.
Translation is the process of synthesis of proteins after transcription of DNA to RNA. It is carried out in the following manner:
i. mRNA formed in the nucleus during transcription moves in the cytoplasm, carrying the coded message by DNA.
ii. Each mRNA contains codes for amino acids in the form of triplet codons.
iii. As per the message on mRNA, amino acids are supplied by the tRNA, which has an anticodon (complementary sequence) to the codon on mRNA.
iv. The amino acids supplied by tRNA are bound together by peptide bonds with the help of rRNA
v. The process continues as the ribosome moves along the entire length of the mRNA by the distance of one triplet codon, also known as translocation. Many chains of amino acids come together to form complex proteins.
Q5. Write a short note on evolution.
i. Evolution is defined as the gradual change occurring in living organisms over a long duration.
ii. It is a slow-going process through which development of organisms is achieved.
iii. Evolution is thus the formation of new species due to changes in specific characters of living organisms.
iv. Changes in these specific characters get accumulated over several generations of living organisms in response to natural selection.
v. It may occur due to speciation - geographical or reproductive isolation, mutation etc.
Q6. Explain the process of formation of complex proteins.
i. Around 3.5 billion years ago, it is speculated that life was non-existent on earth.
ii. In the beginning, only simple elements may have been present in the oceans.
iii. Simple organic and inorganic compounds may have been formed by these simple elements.
iv. These simple compounds may have eventually resulted in the formation of complex compounds like proteins and nucleic acids.
v. The process of formation of complex proteins from simple elements may have occurred over a long period of several years.
Q7. Explain with suitable examples importance of anatomical evidences in evolution.
i. Anatomical evidences are the similarities in the structures of bones and joints of animals that provide proof of evolution.
ii. The hand of human, foreleg of cat, flipper of whale and forelimbs of bat appear different morphologically.
iii. Also, the function of these structures is different in different animals.
iv. However, there is a similarity in the structure of bones and bony joints in the organs of these animals.
v. These similarities indicate that the animals evolved from a common ancestor.
Q8, Define fossil. Explain importance of fossils as proof of evolution.
i. Remnants and impressions of organisms that remain preserved underground are called as Fossils.
ii. Carbon consumption of animals and plants stops after death and only the decaying processes of C-14 takes place continuously.
iii. In dead plants and animals with time, the ratio of C-14 to C-12 changes constantly as C-12 is non-radioactive
iv. The time passed since the death can be calculated by carbon dating i.e. by measuring the radioactivity of C-14 and ratio of C-14 to C-12 present in the remains of the dead organism.
v. Thus, study of fossils is an important aspect of evolution since, it can be used in paleontology and anthropology for determining the age of fossils.
Q9. Write a short note on connecting link.
i. Connecting links are some plants or animals that show morphological characters by which they can be related to two different groups of organisms
ii. Peripatus is the connecting link between two different groups annelids and arthropods. It shows annelid-like characters such as segmented body, thin cuticle and parapodia-like organs. It also shows arthropod-like characters such as tracheal respiration and open circulatory system.
iii. The duck-billed platypus is a connecting link between mammals and reptiles. II shows similarity with mammals due to the presence of mammary glands and hairs. It lays eggs like reptiles.
iv. Lungfishes are connecting links between fishes and amphibians. The lungfish performs respiration with lungs even though it is a fish.
Q10. Write a short note on embryology.
i. Embryology is a branch of biology that deals with the study of different stages of development of embryo.
ii. As the developing embryo grows there is increase in complexity from differentiation of the cells into specialized tissues to form specific organs.
iii. Embryology helps us to comparatively study the developmental stages of various animals.
iv. Embryos of different vertebrates appear similar during the initial stages and these similarities decrease gradually as the embryo develops.
Q11. Explain the theory of evolution and mention the proof supporting the theory
i. According to the theory evolution the first living material (protoplasm) was formed in the ocean
ii. In the course of time unicellular organisms were formed
iii. Larger and more complex organisms were formed due to slow and gradual changes that occurred in the unicellular organisms.
iv. Through evolution, plants and animals progressively developed from their ancestors that had different structural and functional organization.
v. The proof supporting the theory of evolution arc as follows:
a) Morphological evidence: It is based on the similarity of size, shape or structure' of organs among a group of organisms proving that they evolved from the same ancestor.
b) Anatomical evidence: It is based on the similarities in the structure of bones and bony joints in the organs of animals.
c) Vestigial organs: It is based on the theory that some useless organs are degenerated or underdeveloped due to non-functionality through several years.
d) Paleontological evidence: It is based on the study of remnants and impressions of organisms that remain preserved underground as fossils.
e) Connecting links: It is related to some plants or animals that show morphological characters by which they, can be related to two different groups of organisms.
f) Embryological evidence: It arises from comparative study of embryological developmental stages of various vertebrates.
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