Extra 30 short-answer questions from Chapter:8 Heredity and Evolution (Class 10 CBSE Science):
What is heredity? How are traits inherited from parents to offspring?
Answer:
Heredity is the transmission of characteristics from parents to offspring through genes.
Traits are inherited through DNA present in chromosomes, which are passed from parents to offspring via gametes.
Differentiate between dominant and recessive traits with examples.
Answer:
Dominant Trait
: Expressed in both heterozygous and homozygous conditions (e.g., Tallness in pea plants, Tt or TT).
Recessive Trait
: Expressed only in homozygous conditions (e.g., Dwarfness in pea plants,
tt
).
State Mendel’s Law of Dominance with an example.
Answer:
In a heterozygous condition, only the dominant allele is expressed, while the recessive allele remains hidden.
Example: A cross between
TT (tall) and
tt
(dwarf)
pea plants results in
Tt (tall)
offspring, as tallness is dominant.
Explain Mendel’s Law of Segregation with an example.
Answer:
During gamete formation, the two alleles of a gene pair separate so that each gamete receives only one allele.
Example: A heterozygous tall plant (Tt) produces gametes with either T or t allele.
What is meant by phenotype and genotype? Give examples.
Answer:
Phenotype
: Physical appearance of an organism (e.g., tall or dwarf).
Genotype
: Genetic constitution of an organism (e.g., TT, Tt, or
tt
).
What is the ratio of F2 generation in a monohybrid cross? Explain with an example.
Answer:
The
phenotypic ratio
is
3:1
, and the
genotypic ratio
is
1:2:1
.
Example: Crossing two heterozygous tall plants (Tt × Tt) gives offspring as
TT (tall), Tt (tall), and
tt
(dwarf)
in a 3:1 ratio.
What is meant by sex determination? How is it decided in humans?
Answer:
Sex determination refers to the biological process that decides whether a baby will be male or female.
Males have
XY chromosomes
, and females have
XX chromosomes
.
A child inherits an
X chromosome from the mother
and either
X or Y from the father
, determining the sex.
Why do sons inherit traits from their mothers and daughters from their fathers?
Answer:
Sons inherit
X-linked traits from their mothers
, as they receive only one X chromosome from their mother and a Y from their father.
Daughters inherit
X-linked traits from both parents
, as they receive an X chromosome from both mother and father.
Define variation. Why is variation important in organisms?
Answer:
Variation
: Differences in traits among individuals of the same species.
Importance:
Helps in survival in changing environments.
Leads to evolution by natural selection.
What are acquired and inherited traits? Give examples.
Answer:
Acquired Traits
: Develop during an organism's lifetime (e.g., bodybuilding).
Inherited Traits
: Passed from parents to offspring through genes (e.g., eye
colour
).
What is evolution? Explain with an example.
Answer:
Evolution is the gradual change in organisms over generations, leading to the formation of new species.
Example:
Giraffes developed long necks
over generations to reach high leaves.
What are homologous organs? Give an example.
Answer:
Homologous organs have the
same structure but different functions
.
Example: Human arm and whale flipper.
What are analogous organs? Give an example.
Answer:
Analogous organs have
different structures but similar functions
.
Example: Wings of birds and butterflies.
What are vestigial organs? Give examples.
Answer:
Vestigial organs are
non-functional remnants of ancestral structures
.
Examples: Appendix in humans, hind limb bones in whales.
How do fossils help in studying evolution?
Answer:
Fossils provide evidence of extinct species and transitional forms, showing how life evolved.
Example:
Archaeopteryx
shows the link between reptiles and birds.
Explain Darwin’s theory of Natural Selection.
Answer:
Organisms with beneficial traits survive and reproduce.
Example:
Giraffes with long necks survived better than those with short necks.
How does genetic drift affect evolution?
Answer:
Genetic drift refers to
random changes in allele frequency
in a population.
It can lead to the
elimination or fixation of traits
over generations.
What is speciation? How does it occur?
Answer:
Speciation
is the formation of new species due to genetic variations and environmental changes.
It occurs due to
natural selection, isolation, and mutations
.
What is the role of reproductive isolation in evolution?
Answer:
It prevents interbreeding between populations, leading to
divergence and formation of new species
.
What is meant by embryological evidence of evolution?
Answer:
Similar early embryonic stages in different species indicate a
common ancestor
.
Example: Human and fish embryos have gill slits in early stages.
What is artificial selection? How is it different from natural selection?
Answer:
Artificial Selection
: Humans selectively breed organisms for desired traits (e.g., high-yield crops).
Natural Selection
: Occurs naturally based on survival advantage.
How does antibiotic resistance in bacteria support evolution?
Answer:
Bacteria that survive antibiotics pass resistant traits to offspring.
Over time, antibiotic-resistant bacteria evolve.
Why is genetic variation necessary for evolution?
Answer:
More variation allows species to
adapt to changing environments
and survive.
How are fossils formed?
Answer:
Fossils form when dead organisms are buried under sediment, and their remains get mineralized.
What are transitional fossils? Give an example.
Answer:
Fossils showing intermediate traits between two groups.
Example:
Archaeopteryx (between reptiles and birds).
How does Lamarck’s theory of evolution differ from Darwin’s?
Answer:
Lamarck
: Traits acquired during life are inherited (disproven).
Darwin
: Evolution occurs by natural selection.
Why do some species go extinct?
Answer:
Due to environmental changes, lack of adaptation, or competition.
Why do humans and chimpanzees have similar DNA?
Answer:
They share a
common ancestor
, leading to 98-99% DNA similarity.
How do living species provide evidence of evolution?
Answer:
Similarities in DNA, homologous organs, and embryology show common ancestry.
What is the significance of human evolution?
Answer:
Shows adaptation from primitive ancestors to modern humans through brain development and bipedalism.
