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Class 10:Heredity and Evolution

🌐 Translate / অনুবাদ / अनुवाद :

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যেকোনো ভাষায় এটি অনুবাদ করতে, ডানদিকে তিনটি লাইনে ক্লিক করুন এবং তারপর অনুবাদ করুন!

इसे किसी भी भाषा में अनुवाद करने के लिए दाहिनी ओर तीन पंक्तियों पर क्लिक करें और फिर अनुवाद करें!

これを任意の言語に翻訳するには、右側の 3 本線をクリックして翻訳してください.

Pour traduire cela dans n'importe quelle langue, cliquez sur les trois lignes à droite puis traduisez !

Heredity and Evolution

Available Only on Study Saathi!

Have you ever wondered why you look like your parents but not exactly identical to them? Why do some people have blue eyes while others have brown? The answer lies in the microscopic codes inside us: Genes.

This chapter explores the passing of traits from parents to offspring (Heredity) and how life changes over millions of years (Evolution).

Part 1: Heredity

Heredity is the passing of traits (like eye color, height, or shape of leaves) from parents to offspring. This happens via genes located on chromosomes.

🔑 Key Terms You Must Know

Traits Characteristics inherited from parents (e.g., Tall vs Dwarf).
Genes Segments of DNA that control specific traits.
Alleles Different forms of a single gene (e.g., 'T' for tall and 't' for dwarf are alleles of the height gene).
  • Dominant Trait: The trait that appears in the first generation (e.g., Tall plant). usually denoted by Capital letters (TT or Tt).
  • Recessive Trait: The trait that is hidden in the first generation but may reappear later. usually denoted by small letters (tt).
  • Variation: Differences between individuals of the same species. This is necessary for adaptation.

Part 2: Mendel's Experiments

Gregor Mendel, known as the "Father of Genetics," experimented on pea plants and discovered the basic rules of heredity.

Mendel's Three Laws:

  1. Law of Dominance: In a pair of contrasting traits, only the dominant trait is expressed in the F1 generation.
  2. Law of Segregation: Two alleles of a trait separate during gamete formation and unite randomly at fertilization.
  3. Law of Independent Assortment: Traits are inherited independently of each other (if genes are on different chromosomes).
📷 Click here to View Diagram: Mendel's 7 Pea Traits

Part 3: Evolution

Evolution is the process by which living organisms change over generations. It explains how simple life forms gave rise to complex ones.

Darwin's Theory of Natural Selection

Charles Darwin proposed that nature "selects" the fittest individuals. The key points are:

  • Organisms produce more offspring than can survive.
  • Variations exist within a population.
  • Only those with traits suited to the environment survive and reproduce ("Survival of the Fittest").

Part 4: Evidence of Evolution

How do we know evolution actually happened? We have proof!

1. Fossils Preserved remains of ancient organisms found in rocks. They show us how life forms have changed over time.
2. Homologous Organs Same structure, Different function.
Example: Forelimbs of humans, bats, and whales all have similar bone structures but are used for holding, flying, and swimming. This proves we share a Common Ancestor.
3. Analogous Organs Different structure, Same function.
Example: Wings of bats (skin) and insects (membrane). They evolved separately to solve the same problem (flight).
4. Vestigial Organs Organs with no apparent function in the current body.
Example: Human appendix.
📷 Click here to View Diagram: Homologous vs Analogous Organs

📝 Quick Tips for WBBSE Exams

  • Monohybrid Cross Ratio: 3:1 (Phenotype), 1:2:1 (Genotype).
  • Dihybrid Cross Ratio: 9:3:3:1 (Phenotype).
  • Examples matter: Always use examples like "Antibiotic resistance in bacteria" as modern evidence of evolution.
  • Draw Diagrams: Practice drawing the sex determination flowchart (XX-XY) and the crosses.

Final Thought: Heredity gives the blueprint, Evolution rewrites it over time. Both together tell the story of life's journey on Earth.

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