Chapter 9 – Heredity and Evolution

1) How are evolution & classification correlated?

Ans – Evolution & classification are correlated because classification (taxonomy) reflects evolutionary relationships among organisms. By grouping species based on common ancestry and shared features, classification systems reveal evolutionary pathways and the diversification of life over time, illustrating how different species have evolved from common ancestors.

2) Is it fair to say according to evolutionary terms which have a “better” body structure among bacteria, spiders, fishes & chimpanzees? Explain!

Ans – In evolutionary terms, we cannot definitively say that one organism has a “better” body design than another because each species is adapted to its specific environment and ecological niche. Bacteria, spiders, fishes, and chimpanzees each possess body designs that are highly effective for their survival and reproduction in their respective habitats.

Evolutionary success is measured by an organism’s ability to survive, reproduce, and pass on its genes, not by a universal standard of “better” design. Therefore, all these organisms are equally well-designed for their particular lifestyles and environments.

3) Define fossilization. Explain the formation of fossils!

Ans – Fossilization is the method by which remains of living organisms are preserved over geological time. They are formed when an organism is buried quickly after death, preventing decay. Over time, minerals infiltrate the remains, replacing organic material and hardening into rock, creating a fossilized replica of the original structure.

4) List the differences between homologous & analogous organs.

Ans – Here are the differences between homologous & analogous organs.

Homologous organs	Analogous organs
They are structurally similar but functionally different.	They are functionally but structurally different.
They have shared ancestry	They have no shared ancestry
Examples include human hands and horses’ forelimbs.	Examples include birds’ and insects’ wings.

5) State the Mendel laws of genetics.

Ans – The 3 Mendel laws of genetics are:

• Law of Segregation: Each organism carries two alleles for each trait, which segregate (separate) during gamete formation, ensuring that each gamete receives only one allele from each pair.
• Law of Independent Assortment: Alleles for different traits are distributed to gametes independently, leading to the random combination of traits in offspring.
• Law of Dominance: In a set of alleles, one allele can hide the expression of the other. The dominant allele is expressed in the phenotype & the recessive allele remains hidden.

6) How does the sex of the baby is decided as a zygote in humans?

Ans – In humans, the sex of the offspring is determined by the sex chromosomes in the sperm and egg. The mother’s egg always contributes an X chromosome, while the father’s sperm contributes either an X or a Y chromosome. If the zygote receives an X from the sperm, it will be female (XX); if it gets a Y, it will be male (XY).

7) How does Mendel’s research prove dominant and recessive traits?

Ans – According to Mendel’s experiments, in a monohybrid cross between tall and dwarf pea plants, the F₁ generation progenies are tall. However, 75% of the pea plants are tall while 25% are dwarf in F₂ generation. This proves whether it’s a dominant or recessive trait.

8) How does Mendel’s research suggest independent inheritance?

Ans – In the F₁ generation, when a round green seed pea plant is crossed with a yellow-seeded wrinkled plant, all the plant progenies have yellow round seeds. However, the wrinkled green and yellow round seeds come in the F₂  generation. It proves the law of inheritance.

9) In asexual reproduction, is geographical isolation a vital factor? Explain.

Ans – In asexual reproduction, geographical isolation is not a major factor because it does not involve the exchange of genetic material between individuals. Offspring are genetically identical to the parent, so isolation does not affect reproduction. Asexual reproduction relies on the organism’s ability to reproduce independently of others.

10) State the basic attributes of inheritance.

Ans – The basic attributes of the mechanism of inheritance are:

• A pair of elements, be they similar or dissimilar, influence each other.
• When an organism has distinct character factors, only one is dominant and the other is recessive.
• During gamete production, two character elements are separated, leaving one factor for that character.
• For two or more pairs of contrasting features, inheritance occurs in a way where one pair is independent of the other.