Science · Class 10
Heredity and Evolution
Mendel's laws, sex determination, speciation, and evolution evidence.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Mendel's work on pea plants established rules of inheritance using dominant and recessive traits.
Heredity transmits traits via genes; evolution explains diversity over time. Covers Mendel's laws, monohybrid cross, sex determination, speciation, and evidence for evolution.
Mendelian Genetics
- Gene: unit of inheritance; alleles are variants
- Dominant (T) masks recessive (t) in heterozygote Tt
- Monohybrid ratio F₂: 3:1 phenotypic; 1:2:1 genotypic
Sex Determination
- Humans: XX female, XY male
- Father's sperm determines sex (X or Y)
- All eggs carry X chromosome
Evolution
- Natural selection: advantageous traits selected
- Homologous organs: same origin, different function
- Fossils and molecular evidence support evolution
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Monohybrid cross
Cross Tt × Tt (tall dominant). F₂ ratio?
- 1Gametes: T and t each
- 2Punnett: TT, Tt, Tt, tt
- 3Phenotype 3 tall : 1 short
Answer
3:1 tall to short
Sex of child
Who determines baby's sex?
- 1Mother gives X only
- 2Father gives X or Y
- 3XY → male; XX → female
Answer
Father's sperm (X or Y)
Key Points to Remember
- ✓ Acquired traits not inherited (Lamarck disproved)
- ✓ Speciation: reproductive isolation
- ✓ Analogous organs: similar function, different origin
Exam Tips
- • Draw Punnett square neatly
- • Distinguish homologous vs analogous
- • Know Mendel's three laws
Practice MCQs — Heredity and Evolution
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Father of genetics: