1. Reproduction and Variation: Reproduction creates new individuals, often similar to the parents, but with small differences (variations). Asexual reproduction results in very few variations, while sexual reproduction creates more distinct variations. These variations help species survive in different environments.
  2. Accumulation of Variation: Offspring inherit traits from both parents, which form the basis for future generations. As generations reproduce, new variations are created. For example, in asexual reproduction, small differences occur due to errors in DNA copying. Sexual reproduction increases variation.
  3. Heredity: Heredity explains how traits are passed from one generation to the next. Traits may be inherited from both parents, but not always in the same way. For example, humans inherit a mix of traits from both parents, but each offspring will have a unique combination of those traits.
  4. Mendel’s Contributions: Gregor Mendel studied inheritance by experimenting with pea plants. He discovered that traits are inherited through genes, which can be dominant or recessive. For example, tallness (T) is dominant over shortness (t), meaning a plant can be tall even if it only has one tall gene (Tt), but it needs two short genes (tt) to be short.
  5. Dominant and Recessive Traits: Dominant traits are expressed even if only one copy of the gene is present, while recessive traits are only visible if both copies of the gene are recessive. Mendel showed that some traits can be inherited independently, leading to new combinations of traits in the offspring.
  6. How Traits are Expressed: Traits are controlled by genes, which provide instructions to make proteins. For example, a plant’s height depends on a hormone controlled by genes. If the gene for making the hormone is altered, the plant may be short.
  7. Sex Determination: In humans, sex is determined by the chromosomes inherited from parents. Women have two X chromosomes (XX), while men have one X and one Y chromosome (XY). A child inherits one X from the mother, and either an X or Y from the father. If the child gets an X from the father, they are a girl (XX), and if they get a Y, they are a boy (XY).

Key points to remember:

  • Inheritance creates both similarities and differences.
  • Traits can be dominant or recessive.
  • Genetic variation helps organisms survive.
  • Mendel’s experiments explained how traits are inherited and how new trait combinations arise.
  • Sex is determined by specific chromosomes, with the father deciding whether the child will be male or female.

THERE ALL ARE THE NOTES OF CHAPTER 8. AND AFTER SOME TIME YOU GET IMPORTANT QUESTIONS AND DIAGRAMS HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊