Class 10 Biology

Heredity Questions and Answers

Question 1.

1. What is genetics?
2. Give the common name of the plant on which Mendel performed his experiments.
3. What for did Mendel use the term factors and what are these factors called now?
4. What are genes? Where are the genes located?

Heredity and Evolution, Class 10 question answer

Answer:

1. Genetics: It is the study of genes, genetic variations and laws governing the passage of heredity from generation to generation.
2. Garden Pea, Edible Pea.
3. Factors: They are particulate entities which function as units of inheritance that are transferred from generation to generation without being deleted or lost. The factors are now known as
4. Genes: Genes are units of genetic material that have particular functions in inheritance. They are linear segments of DNA/chromosomes.

Question 2. How do Mendel’s experiments show that the

1. Traits may be dominant or recessive.
2. Traits are inherited independently.

Answer:

Traits are Dominant or Recessive: This can be discovered by performing a monohybrid cross. A between pure round-seeded and pure wrinkled-seeded plants yields only round-seeded plants in the F₁ generation. Self-pollination of F₁ plants yields both round-seeded and wrinkled-seeded plants in the ratio of 3:1. TIIIH to poHHiblo only If (lie allele lor wrinkled seed to present in F₁ generation but is unable to express its effect, Therefore, the trail of wrinkled seed is recessive while the trait of round seed which is expressed in a generation is dominant.

class 10 heredity questions

Independent Inheritance of Traits: This can be found by performing a dihybrid cross. A cross between pure round and yellow seeded (RRYY) Pea plant with pure wrinkled and green seeded (rryy) plant yields rounded and yellow seeded F₁ generation. Self-polIination of F₁ plants gives rise to four types of plants—round yellow (9/16), round green (3/16), wrinkled yellow (3/16) and wrinkled green (1/16). Here round yellow and wrinkled green are parental types. Round green and wrinkled yellow are recombinations which can develop only if the factors for these traits are inherited independently of one another.

Question 3.

1. How many pairs of chromosomes are present in human beings? Out of these how many arc sex chromosomes 7 How many types of sex chromosomes are found in human beings?
2. “The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it”. Draw a flowchart showing the determination of the sex of the newborn to justify the statement.

Answer:

Human beings have 23 pairs of chromosomes. One pair of chromosomes are sex chromosomes or allosomes. In females both the sex chromosomes are similar. They are called XX chromosomes. In males, the two sex chromosomes are different (heteromorphic). One is a normal X chromosome (as found in females). The second is a shorter Y chromosome.

Question 4.

1. What are dominant and recessive traits?
2. “Is it possible that a trait is inherited but may not be expressed in the next generation ?’’ Give a suitable example to justify this statement.

Answer:

Dominant Trait: It is that trait which expresses its effect in both homozygous and heterozygous states, Example TT, Tt.

Recessive Trait: It is that trait which is unable to express its effect in the heterozygous state, i.e., in the presence of its alternate trait. The trait expresses its effect in only the homozygous state, Example tt.

Question 5. If we cross purebred tail (dominant) Pea plants with purebred dwarf (recessive Pea plants) we get Pea plants of F₁ generation. If we now self-cross the Pea plants of the F₁ generation, then we obtain Pen plants of the F₂ generation

1. What do the plants of the F₁ generation look like?
2. What is the ratio of tall plants to dwarf plants in F₂ generation?
3. State the types of plants not found in the F₁ generation but appeared in the F₂ generation, mentioning the reason for the same.
4. What are homologous structures? Give an example. Is it necessary that homologous structures always have common ancestors?

Answer:

1. F₁ Generation. All tall p
2. F₂ Gcncmtlon: 3 tall; I dwarf.
3. Dwarf plant: The trait of dwarfness is recessive and cannot express its effect in the presence of an alternate dominant trait.
4. Homologous Structures, See question 5 above. Homologous structures always have common ancestors,

Question 6.

1. What Is the law of dominance? Explain with an example.
2. What is genetics?
3. What are genes? Where are the genes located?

Answer:

Law of Dominance. Out of the two contrasting factors or alleles of a character if present together as in a hybrid, only one factor called dominant expresses its effect. The other factor called recessive docs not express its effect.

Example Cross a pure tall Rea plant with a pure dwarf Pea plant. All the individuals of the F₁ generation are tall though they carry the factor of dwarfness as well.

Question 7. 

1. What does the F₁ progeny of tall plants with round seeds and short plants with wrinkled seeds look like?
2. What are recessive traits?
3. Mention the type of new combination of plants obtained in F₂ progeny along with their ratio, if F₁ progeny was allowed to self-pollinate.
4. If 1600 plants were obtained in F₂ progeny, write the number of plants having traits
   1. Tall with round seeds
   2. Short with wrinkled seeds. Write the conclusion of the above experiment.

Answer:

1. Round and tall (both the traits are dominant over wrinkled seed and short height).
2. Recessive traits are those traits which are unable to express their effect in the presence of their alternate traits, as in the F₁ generation.
3. New Combinations
   1. Tall and wrinkled seeded = 3/16
   2. Short and round seeded = 3/16
4. Tall with round seeds—1600 x 9/16 = 900
   1. Short with wrinkled seeds—1600 x 1/16 = 100.

Conclusion: The two factors of a character separate independently of the two factors of another character, coming together randomly at the time of fertilization. It is called the law of independent assortment.

Respiratory System Questions And Answers

Question 1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer:

Respiratory System Questions

The advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration

Aquatic organisms obtain oxygen for their respiration from water. Water has about 1% oxygen in a dissolved state. Terrestrial organisms obtain oxygen directly from the air. The oxygen content of air is 21%. So terrestrial organisms are in a favourable position to obtain the required oxygen without too much work.

On the other hand, aquatic animals which extract oxygen from water have to perform more vigorous and rapid breathing to obtain the required oxygen. A fish will breathe 100 times/ min as compared to 14-20/min in humans.

Question 2. What are the different ways in which glucose is oxidized to provide energy in various organisms?
Answer:

The different ways in which glucose is oxidized to provide energy in various organisms

There are three common methods by which glucose is catabolised to release energy-aerobic respiration, lactic acid anaerobic respiration and alcoholic anaerobic respiration.

Respiratory Questions

Aerobic Respiration. Glucose is completely oxidised with oxygen as a terminal oxidant. It yields carbon dioxide and energy. The energy yield is 686 kcal/2870 kJ per mole of glucose. About 38 ATP molecules are formed for storing energy. The process occurs partly in cytoplasm and partly in mitochondria.

Lactic Acid Anaerobic Respiration. Glucose is incompletely catabolised to form two molecules of lactic acid without involving the use of oxygen. It occurs in many bacteria and skeletal muscles during vigorous exercise. Only about 50 kcal/210 kJ of energy is released from which 2 ATP molecules are formed. The process occurs exclusively in the cytoplasm.

Ethyl Alcohol Anaerobic Respiration. A molecule of glucose is catabolised to form two molecules of ethyl alcohol. Two molecules of carbon dioxide are evolved. The energy yield is about 50 kcal/210 kJ, equivalent to 2ATP molecules. Oxygen is not required. Respiration occurs inside the cytoplasm. Mitochondria are not required.

Question 3. How are oxygen and carbon dioxide transported in human beings?
Answer:

Transport of Oxygen. It occurs through blood. 97% of oxygen combines with haemoglobin to form oxyhaemoglobin (Hb₄O₈). The remaining 3% dissolves in blood plasma. In the tissues, oxyhaemoglobin breaks down to release oxygen. The deoxygenated blood travels to the lungs for reoxygenation.

Transport of Carbon Dioxide. Carbon dioxide produced in cellular respiration passes into the blood. 70% of carbon dioxide forms sodium bicarbonate inside the plasma. 23% of carbon dioxide combines with haemoglobin to produce carbaminohaemoglobin. The remaining 7% gets dissolved in blood plasma. Blood-carrying carbon dioxide reaches alveoli where carbon dioxide diffuses into alveolar air.

Question 4. How are the lungs designed in human beings to maximize the area for the exchange of gases?
Answer:

Lungs designed in human beings to maximize the area for the exchange of gases as follows

Human Respiratory System, Class 10 pdf

After entering a lung, each bronchus divides and redivides repeatedly to form segmental bronchi and then each segmental bronchus produces different ranks of bronchioles. The terminal bronchioles form respiratory bronchioles.

The latter form alveolar sacs that are studded with bunches of alveoli. It is estimated that a human lung has about 300 million alveoli. The total alveolar surface of the two lungs is about 80 m2 or roughly 40 times the surface area of the human body. Such a large surface area is most suitable for rapid gaseous exchange between the blood and the alveolar air.