Notes Class 8th science chapter 1 ajk text book slo based new notes

 Chapter 1: Variations, Heredity & Cell Division

Exercise Based Questions & Answers

Define cell division.

Cell division is the process in which a parent cell divides to form two or more daughter cells.

How is mitosis different from meiosis?

Mitosis produces two identical diploid cells for growth and repair, while meiosis produces four genetically different haploid cells for reproduction.

What is the function of a gene?

A gene is a segment of DNA that contains instructions for making proteins and controlling traits.

Define nucleotides.

Nucleotides are the basic units of DNA and RNA made up of a sugar, phosphate group, and nitrogenous base.

How is prophase in mitosis different from prophase-I in meiosis?

In mitosis, chromosomes condense only, while in prophase-I of meiosis homologous chromosomes pair up and crossing over occurs.

Justify the statement: “Chromosomes are the carriers of DNA and genes.”

Chromosomes are made of DNA, and genes are sections of DNA that carry hereditary information.

Differentiate between haploid and diploid cells.

Haploid cells contain one set of chromosomes (n), while diploid cells contain two sets of chromosomes (2n).

Which type of cell division develops variations in the next generation, mitosis or meiosis? Give reason.

Meiosis develops variations because crossing over and random assortment occur during meiosis, producing genetic diversity.

Differentiate between variations and adaptations.

Variations are differences among individuals of the same species, while adaptations are traits that help organisms survive in their environment.

What factors drive variations among organisms?

Genetic mutations, crossing over, and random assortment of chromosomes are the main factors that cause variations.

What is the relation between chromosomes, DNA, and genes?

Chromosomes are structures made of DNA, and genes are specific parts of DNA that control traits.

What is crossing over?

Crossing over is the exchange of genetic material between homologous chromosomes during meiosis.

Write the effect of crossing over.

Crossing over creates new gene combinations and increases genetic variation in offspring.

SLO’s Based Questions & Answers

What is heredity?

Heredity is the transfer of traits from parents to offspring.

What is variation in biology?

Variation means the differences in traits among individuals of the same species.

What is a gene?

A gene is a unit of heredity that controls a specific characteristic.

What is the role of DNA in heredity?

DNA carries genetic information from parents to offspring.

What is cell division?

Cell division is the process by which a parent cell divides into daughter cells.

What is mitosis?

Mitosis is a type of cell division that produces two identical daughter cells.

What is meiosis?

Meiosis is a type of cell division that reduces chromosome number by half and forms gametes.

What are chromosomes?

Chromosomes are thread-like structures made of DNA that carry genetic information.

What is the significance of variations in a population?

Variations help organisms adapt to environmental changes and support evolution.

What is a dominant trait?

A dominant trait is a trait that appears in offspring even if only one parent passes the allele.