Class 10 Science Chapter 8 HOTS Questions - Heredity and Evolution

Q1: What is heredity, and how does it relate to the passing of traits from one generation to another?
Ans: Heredity refers to the process by which traits or characteristics are passed down from one generation to the next. It involves the transfer of genetic information from parents to offspring through genes, which are the functional units of heredity. Genes carry instructions that determine specific traits in living organisms, and these traits are inherited by the offspring.

Q2: Explain the concept of dominant and recessive traits using an example.
Ans: Dominant traits are those that express themselves when present in an organism, and they can be seen in the individual's physical appearance. For instance, in Mendel's experiments with pea plants, the tall trait was dominant over the short trait. Recessive traits, on the other hand, are present in an organism's genetic makeup but are not visible when a dominant allele is present. An example would be the recessive trait for short height in pea plants.

Q3: What is the difference between a monohybrid cross and a dihybrid cross?
Ans: A monohybrid cross involves considering only one trait while crossing two organisms. The resulting F2 generation follows a monohybrid ratio, such as the 3:1 ratio observed when crossing a tall pea plant (TT) with a dwarf pea plant (tt). A dihybrid cross, however, considers two different traits during the crossing process. In the F2 generation of a dihybrid cross, a 9:3:3:1 ratio of four combinations of traits is observed, as seen in the example of round and green peas crossed with wrinkled and yellow peas.

Q4: Explain Mendel's Law of Dominance with an example.
Ans: Mendel's Law of Dominance states that a gene has two contrasting alleles, and one of these alleles, known as the dominant allele, always expresses itself in the organism's phenotype. For instance, when crossing pea plants with a dominant allele for green pod color (GG) and a recessive allele for yellow pod color (gg), all the F1 generation plants will have green pea pods, as the green pod color is dominant.

Q5: What is sex determination, and how does it work in humans?
Ans: Sex determination is the process of determining an individual's sex based on genetic composition. In humans, the presence or absence of a Y chromosome determines the sex. A combination of XX chromosomes results in a female, while XY chromosomes lead to a male. An ovum always contains an X chromosome. If the ovum fuses with a Y-containing sperm, a male child is born, and if it fuses with an X-containing sperm, a female child is born.

Q6: Define genetic variations and explain how they contribute to the diversity in a population.
Ans: Genetic variations are differences in DNA sequences among organisms, leading to a diverse gene pool. These variations result in different physical traits or biochemical pathways. Genetic variations play a crucial role in population diversity. Over time, these variations can accumulate and contribute to the evolution of a population, allowing individuals to adapt to changing environments.

Q7: What is natural selection, and how does it shape a population?
Ans: Natural selection is a process by which favorable traits within a population are selected, leading to the survival and reproduction of individuals with these traits. Environmental conditions apply pressure on all species, and those that are better adapted to the changing conditions are more likely to survive and reproduce. This process gradually leads to the propagation of traits that are advantageous in a given environment.

Q8: Explain the concept of genetic drift and its impact on genetic variation.
Ans: Genetic drift refers to random fluctuations in gene variants within a small population. It can lead to the disappearance of a gene variant from a population, reducing genetic variation. This phenomenon occurs due to chance events rather than selection pressures. Genetic drift can have a significant impact on small populations, causing gene frequencies to change over generations.

Q9: What is speciation, and how does it contribute to the diversity of life forms?
Ans: Speciation is the process by which new species form from existing ones due to various evolutionary forces like genetic drift, natural selection, and isolation of populations. Speciation increases biodiversity by creating distinct groups of organisms with unique traits and characteristics. This diversity contributes to the overall complexity and richness of ecosystems.

Q10: Who is Charles Darwin, and what is his contribution to the understanding of evolution?
Ans: Charles Darwin, often referred to as the "Father of Evolution," was an English naturalist and biologist. He conducted a five-year expedition on the ship HMS Beagle to the Galapagos Islands, which led him to develop his theory of evolution. In 1859, he published the book "On the Origin of Species," detailing his theory of evolution by natural selection. This theory revolutionized our understanding of how species change over time and adapt to their environments.