Class 10 Science Part 2 Chapter 1: Heredity and Evolution – Maharashtra Board

This chapter delves into the basic principles of heredity, the process of evolution, and how traits are inherited across generations. It's a crucial topic in understanding how life on Earth adapts and changes over time, as per the Maharashtra Board Class 10 Science curriculum.

🧬 What is Heredity?

Heredity is the process by which traits are passed from parents to offspring through genes. These traits may be physical, behavioral, or physiological.

Important Terms

• Gene: A unit of heredity made of DNA.
• Chromosome: Thread-like structures carrying genes.
• Allele: Alternative form of a gene.
• Genotype: Genetic constitution of an organism.
• Phenotype: Observable traits or characteristics.

Mendel's Experiments

Gregor Mendel conducted experiments on pea plants and discovered the basic principles of inheritance:

• Law of Dominance
• Law of Segregation
• Law of Independent Assortment

Monohybrid Cross

Involves one pair of contrasting traits (e.g., tall vs. short). The F1 generation shows only the dominant trait, while the F2 generation shows a 3:1 ratio.

Dihybrid Cross

Involves two pairs of traits. The F2 generation follows a 9:3:3:1 phenotypic ratio.

🧬 Sex Determination

Humans have XX (female) and XY (male) chromosomes. The sex of the offspring depends on the father's contribution (X or Y chromosome).

🌍 What is Evolution?

Evolution is the gradual change in organisms over generations. It explains the diversity of life on Earth.

Key Concepts

• Speciation: Formation of new species from existing ones.
• Natural Selection: Organisms best suited to the environment survive and reproduce.
• Fossils: Evidence of ancient life forms preserved in rocks.
• Homologous Organs: Same structure but different functions (e.g., human hand and bat wing).
• Analogous Organs: Different structure but same function (e.g., bird wing and insect wing).

🧪 Evidence of Evolution

• Fossil records
• Comparative anatomy
• Embryological similarities
• Molecular biology

📘 Exam Tips

• Remember Mendel’s laws with examples.
• Draw and practice Punnett squares.
• Understand differences between homologous and analogous organs.
• Learn evolutionary evidence types thoroughly.

🔗 You May Also Like

• Class 10 Science Chapter 9: Carbon Compounds – Notes
• Class 10 Science Chapter 10: Space Missions – Notes
• All Class 10 Science Notes
• Kumarbharati English Textbook Solutions
• Class 10 English Paper Pattern

❓ Frequently Asked Questions