The ninth chapter in Science textbook is 'Heredity and Evolution'. The process by which the features of an organism are passed on from one generation to another is called heredity.
Genes
Gene is the functional unit of heredity.
Every gene controls one or several particular characteristic features in living organisms.
Mendel’s work
Gregor Johann Mendel, known as ‘Father of Genetics’, was an Austrian Monk who worked on pea plants to understand the concept of heredity.
His work laid the foundation of modern genetics.
He made three basic laws of inheritance – The Law of Dominance, The Law of Segregation and The Law of Independent Assortment.
Dominant traits
The traits that express themselves in an organism in every possible combination and can be seen are called Dominant traits.
Recessive traits
A trait which is not expressed in the presence of a dominant allele is known as recessive trait.
Genetic variations
The differences in the DNA sequences among every organism leading to the diverse gene pool are called genetic variations.
These differences lead to different/varied physical characters or biochemical pathways.
Speciation
It is the process of formation of a new species from existing ones due to several evolutionary forces like genetic drift, isolation of populations, natural selection, etc.
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Speciation leads to diversity in the ecosystem and the diversity and diversity lead to evolution.
Evolution
Evolution is a tangible change in the heritable characteristics of a population over several generations.
These changes can give rise to a new species or the species might change themselves to become better adapted to the surrounding environment.
The topics discussed in this chapter are as follows:
- Monohybrid and Dihybrid cross
- Inheritance
- Mendel's laws
- Sex determination
- Traits
- Variation
- Human Evolution
Students can view and download the chapter from the link given below.
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NCERT Solutions for Chapter 9: Heredity and Evolution
Also Check
Chapter 1: Chemical Reactions and Equations
Chapter 2: Acids, Bases and Salts
Chapter 3: Metals and Non-Metals
Chapter 4: Carbon and its compounds
Chapter 5: Periodic Classification of Elements
Chapter 6: Life Processes
Chapter 7: Control and Coordination
Chapter 8: How do organisms reproduce?
Chapter 10: Light - Reflection and Refraction
Chapter 11: The Human Eye and the Colourful World
Chapter 12: Electricity
Chapter 13: Magnetic Effects of Electric Current
Chapter 14: Sources of Energy
Chapter 15: Our Environment
Chapter 16: Sustainable Management of Natural Resources
Frequently Asked Questions (FAQs) for Chapter 9: Heredity and Evolution
Name the plant on which Mendel performed his experiments.
Mendel performed his experiments on the plant, Pisum sativum – the garden pea plant.
What is the full form of DNA?
The full form of DNA is Deoxyribonucleic Acid.
Define homologous organs.
Homologous organs are those organs, which have similar origin and basic plan of development, but may or may not differ in their functions. The forelimbs of a human, a bird and a horse are homologous organs.
Name the scientist who gave the theory of evolution.
Charles Darwin
Define species.
Species is a group of organisms which can interbreed among themselves to produce fertile offsprings.
