Science Class 10 - Heredity And-Evolution Notes

Heredity and Evolution

Welcome to the chapter on Heredity and Evolution for Class 10. In this chapter, you will learn how traits are passed from parents to offspring, how variations arise, and how evolution shapes the diversity of life on Earth. By the end of this chapter, you will understand the basic principles of heredity, the role of genes, and the process of evolution.

Key Concepts

• Heredity: The passing of traits from parents to offspring.
• Genes: Units of heredity made up of DNA.
• Variation: Differences among individuals of a species.
• Evolution: The gradual change in living organisms over generations.

Heredity: How Traits are Passed On

Heredity is the reason why children look like their parents. Traits such as eye color, hair type, and height are inherited from parents through genes.

• Each parent gives half of their genes to their child.
• Genes are found on chromosomes inside the cell nucleus.
• Gregor Mendel is known as the "Father of Genetics" for his experiments with pea plants.

Mendel’s Laws of Inheritance

• Law of Dominance: Some traits are dominant and mask the effect of others (recessive traits).
• Law of Segregation: Each individual has two copies of each gene, but only one is passed to offspring.
• Law of Independent Assortment: Genes for different traits are inherited independently.

Variation and Its Importance

Variation means differences between individuals. Variations can be inherited (passed from parents) or acquired (developed during life).

• Inherited variations are due to genes.
• Acquired variations are due to environment or habits.
• Variation is important for evolution and survival of species.

Sex Determination in Humans

The sex of a baby is determined by the combination of sex chromosomes inherited from the parents.

• Females have XX chromosomes; males have XY chromosomes.
• The father’s sperm decides the sex of the child.

Evolution: Change Over Time

Evolution is the process by which living things change over long periods of time. It explains the diversity of life on Earth.

• Charles Darwin explained evolution by natural selection.
• Fossils provide evidence for evolution.
• Similarities in body structure and DNA show common ancestry.

Practice Questions

1. What is heredity?
2. Who is known as the Father of Genetics?
3. What is the difference between inherited and acquired traits?
4. How is the sex of a child determined in humans?
5. What is evolution?

Challenge Yourself

• Explain Mendel’s experiment with pea plants in your own words.
• List two examples of inherited traits and two examples of acquired traits.
• Describe how fossils support the theory of evolution.

Did You Know?

• Humans share about 98% of their DNA with chimpanzees!
• The study of heredity is called genetics.

Glossary

• Trait: A feature or characteristic, like eye color or height.
• Gene: A unit of heredity that controls a trait.
• Chromosome: A structure in cells that contains genes.
• Fossil: The remains or impression of a living thing from the past.
• Natural Selection: The process by which better-adapted organisms survive and reproduce.

Answers to Practice Questions

1. Heredity is the passing of traits from parents to offspring.
2. Gregor Mendel.
3. Inherited traits are passed from parents through genes; acquired traits are developed during life.
4. By the combination of sex chromosomes (XX for girls, XY for boys) inherited from parents.
5. Evolution is the gradual change in living organisms over generations.

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Understanding heredity and evolution helps us know how life changes and adapts over time!