ICSE Class 10 Biology Mid-Term 2026: Important Questions & Chapters to Revise Before the Exam

Biology questions in the ICSE Class 10 Mid-Term Exam can test more than definitions and factual recall. You may need to interpret diagrams, explain biological processes, solve genetic crosses and apply concepts to unfamiliar situations. Revising important processes and practising different question formats can help you build greater confidence before the exam.

For focused revision, PW’s ICSE Class 10 Biology Mid-Term Marathon 2026 covers Cell Structure and Chromosome, Cell Cycle and Cell Division, Genetics, Plant Physiology, and the Circulatory System. The session brings together concept explanations, previous-year questions, specimen-paper questions and competency-focused questions to help you revise the prescribed topics and practise applying your knowledge.

Important ICSE Class 10 Biology Chapters to Revise

Before solving the questions, revise the concepts covered in the PW Mid-Term Marathon. Pay special attention to terms, sequences, diagrams, experiments, and biological processes that can be tested in different question formats.

Cell Structure and Chromosome

Revise the difference between chromatin and chromosome, along with the basic concepts of DNA, RNA, and nucleotides.

• Chromatin: The loose form of genetic material present in the nucleus.

• Chromosome: The condensed form of chromatin seen during cell division.

• DNA and RNA: Nucleic acids made up of nucleotides.

• Nucleotide: The basic building unit of DNA and RNA.

• RNA: Ribonucleic Acid, described in the session as a single-stranded polymer.

Diagram-based questions on chromatin and chromosome structure are also important to practise.

Cell Cycle and Cell Division

The cell cycle and different types of cell division are important areas for revision.

• Interphase: G1 → S → G2

• G1 phase: Growth of the cell.

• S phase: DNA synthesis.

• G2 phase: Growth and preparation for cell division.

• Mitosis: Important for growth and repair.

• Meiosis: Associated with the formation of reproductive cells.

• Cytokinesis: Division of the cytoplasm after nuclear division.

• Cleavage furrow: The inward depression through which cytokinesis occurs in an animal cell.

• Synapsis and crossing over: Important processes associated with meiosis.

Genetics

Genetics involves several terms and crosses that you should be able to explain and apply.

• Gene: A unit associated with a particular characteristic.

• Allele: An alternative form of a gene, such as R and r.

• Genotype: The genetic constitution or combination of alleles.

• Phenotype: The observable characteristics expressed by an organism.

• Monohybrid cross: A cross involving one pair of contrasting characteristics.

• Dihybrid cross: A cross involving two characteristics simultaneously.

• Mutation: A sudden change in the gene sequence.

For the dihybrid cross discussed in the marathon, revise the allele combinations RY, Ry, rY, and ry for seed shape and seed colour.

Plant Physiology

The marathon focuses on transpiration and the potometer experiment.

Revise:

• Purpose of a potometer

• Role of the capillary tube

• Role of the air bubble

• Initial marking of the air bubble

• Movement of the bubble during transpiration

• Measurement of the distance travelled by the bubble

• Ganong's potometer

• Reservoir and water-tight arrangement

Also revise the role of ATP, ADP, NADP, and NADPH as discussed in relation to photosynthesis.

Circulatory System

The Circulatory System section includes blood circulation, tissue fluid, and the lymphatic system.

Key points to revise include:

• An adult has approximately 5 litres of blood.

• Pulmonary circulation begins from the right ventricle.

• The pulmonary artery carries deoxygenated, carbon-dioxide-rich blood towards the lungs.

• Blood plasma forms tissue fluid around body cells.

• Cells obtain oxygen and other required substances from tissue fluid and release waste products into it.

• Some tissue fluid returns to the blood capillaries.

• Excess tissue fluid enters lymphatic vessels and becomes lymph.

• Lymph nodes are associated with lymphatic vessels.

ICSE Class 10 Biology: 3, 5 & 7-Mark Important Questions

Most Important 3-Marker Questions

1. Differentiate between chromatin and chromosome.

Answer:

Chromatin is the loose form of genetic material present in the nucleus. During cell division, chromatin becomes condensed and forms chromosomes.

Therefore:

• Chromatin: Loose form of genetic material.

• Chromosome: Condensed form of chromatin during cell division.

2. Explain the three stages of interphase and write them in the correct sequence.

Answer:

Interphase consists of three stages:

• G1 phase: The cell undergoes growth.

• S phase: DNA synthesis takes place.

• G2 phase: The cell continues to grow and prepares for cell division.

The correct sequence is:

G1 → S → G2

3. Why is mitosis responsible for the healing of an injury?

Answer:

An injury damages cells and tissues. New cells are required to replace the damaged cells. Mitosis produces new cells and helps in the growth and repair of tissues.

Therefore, healing of an injury occurs due to mitotic cell division.

4. What is an allele? Explain with a suitable example.

Answer:

An allele is an alternative form of a gene. For example, R and r can represent two alternative alleles of a gene.

5. What is pulmonary circulation? From where does it begin?

Answer:

Pulmonary circulation is the circulation of blood between the heart and lungs. It begins from the right ventricle.

The right ventricle pumps deoxygenated, carbon-dioxide-rich blood into the pulmonary artery, which carries it towards the lungs.

Most Important 5-Marker Questions

1. Explain the structure of DNA and RNA, including the role of nucleotides.

Answer:

DNA and RNA are nucleic acids, and their basic building units are called nucleotides.

• A nucleotide is the basic building unit of DNA and RNA.

• DNA contains nucleotides arranged to form its structure.

• RNA stands for Ribonucleic Acid.

• RNA is described in the session as a single-stranded polymer.

• Both DNA and RNA are made up of nucleotides.

Thus, nucleotides form the basic units from which these nucleic acids are made.

2. Explain the stages of the cell cycle, including G1, S, and G2 phases.

Answer:

The cell cycle includes interphase followed by cell division. Interphase has three stages:

1. G1 phase: The cell undergoes growth.

2. S phase: DNA synthesis takes place.

3. G2 phase: The cell continues growing and prepares for division.

The sequence is:

G1 → S → G2 → Cell Division

After interphase, the cell undergoes cell division. The session discusses mitosis and meiosis as two types of cell division.

3. Explain cytokinesis in an animal cell.

Answer:

Cytokinesis is the division of the cytoplasm after nuclear division.

In an animal cell, cytokinesis occurs through the formation of an inward depression called a cleavage furrow. The furrow gradually deepens until the cell divides into two daughter cells.

Thus, cytokinesis completes the division of the cell after nuclear division.

4. Explain a dihybrid cross involving seed shape and seed colour.

Answer:

A dihybrid cross considers two characteristics at the same time.

The session uses:

• R/r for seed shape

• Y/y for seed colour

The cross discussed is between round yellow and wrinkled green seeds.

During gamete formation, the alleles can combine in different ways. The four gamete combinations discussed are:

RY, Ry, rY, ry

These gametes can combine during fertilisation to produce different combinations of the two characteristics in the offspring.

5. Describe Ganong's potometer experiment used to demonstrate transpiration.

Answer:

Ganong's potometer is used to demonstrate water loss associated with transpiration.

The experiment involves:

• Fitting a twig into the apparatus.

• Keeping the apparatus water-tight.

• Connecting a capillary tube to the setup.

• Providing a reservoir of water.

• Introducing an air bubble into the capillary tube.

• Marking the initial position of the bubble.

• Allowing transpiration to take place.

As water is lost from the twig through transpiration, the air bubble moves forward in the capillary tube. The distance travelled by the bubble can then be measured.

Most Important 7-Marker Questions

1. Explain the complete sequence of the cell cycle and cell division.

Answer:

The cell cycle begins with interphase, which consists of three stages:

G1 → S → G2

• G1 phase: The cell grows.

• S phase: DNA synthesis takes place.

• G2 phase: The cell continues growing and prepares for cell division.

After interphase, the cell undergoes cell division. The two types discussed in the session are mitosis and meiosis.

In an animal cell, nuclear division is followed by cytokinesis. During cytokinesis, an inward cleavage furrow develops in the cell membrane. The furrow deepens and eventually divides the cytoplasm into two daughter cells.

Mitosis is particularly important for growth and repair, including the healing of injuries.

2. Explain a dihybrid cross involving seed shape and seed colour.

Answer:

A dihybrid cross involves two characteristics simultaneously.

For the example discussed in the marathon:

• R/r represents seed shape.

• Y/y represents seed colour.

• The parental combination is round yellow × wrinkled green.

During gamete formation, the two pairs of alleles can combine to produce four possible gamete combinations:

RY, Ry, rY, ry

These gametes combine during fertilisation and produce different possible allele combinations in the offspring.

The cross therefore helps explain how two characteristics can be considered together and how different combinations may appear in the offspring.

3. Describe the Ganong's potometer experiment in detail to demonstrate transpiration.

Answer:

A potometer is used to study water uptake associated with transpiration.

The experiment can be described as follows:

1. A suitable twig is fitted into the potometer.

2. The apparatus is made water-tight.

3. A capillary tube is connected to the setup.

4. Water is introduced into the apparatus.

5. An air bubble is introduced into the capillary tube.

6. The initial position of the bubble is marked.

7. The setup is left so that transpiration can occur.

8. Water is lost from the plant through transpiration.

9. The air bubble moves forward in the capillary tube.

10. The distance travelled by the bubble is measured.

The movement of the air bubble provides a way to study water movement associated with transpiration.

4. Explain pulmonary circulation in detail.

Answer:

Pulmonary circulation involves the movement of blood between the heart and lungs.

• It begins at the right ventricle.

• The right ventricle pumps deoxygenated, carbon-dioxide-rich blood.

• This blood enters the pulmonary artery.

• The pulmonary artery carries the blood towards the lungs.

• In the lungs, the blood undergoes the process associated with gaseous exchange.

• The blood then returns towards the heart as part of the pulmonary circulation.

Thus, pulmonary circulation connects the heart and lungs and is involved in the movement of blood for gaseous exchange.

5. Explain the formation of tissue fluid and its relationship with the lymphatic system.

Answer:

Blood plasma forms tissue fluid around the body cells. This fluid acts as the medium through which substances are exchanged between the blood and cells.

Body cells:

• Obtain oxygen and other required substances from tissue fluid.

• Release waste products into the tissue fluid.

After this exchange:

• Some tissue fluid returns to the blood capillaries.

• The excess tissue fluid cannot all return directly to the blood.

• It enters the lymphatic vessels.

• This excess fluid becomes lymph.

• Lymph nodes are associated with the lymphatic vessels.

Therefore, the lymphatic system helps in handling excess tissue fluid and returning it towards the circulation.

6. Explain mutation as discussed in the marathon and mention the role of radiation.

Answer:

A mutation is a sudden change in the gene sequence.

The session discusses radiation as a factor that can cause changes in gene sequences. X-rays and gamma rays are specifically mentioned in this context.

A change in the gene sequence can therefore result in a mutation. Understanding mutation helps explain how changes can occur in genetic material.

Note: For more important questions and a deeper understanding of the concepts covered here, watch the PW Class 10 Mid-Term Marathon video and revise along with the explanations.

How Does the PW Mid-Term Marathon Help With Biology Revision?

The PW ICSE Class 10 Biology Mid-Term Marathon brings important concepts and question types together so you can revise the chapters covered in the session without limiting your preparation to textbook reading. You can use the marathon to:

• Revise Key Biological Concepts: Go through important topics such as cell division, genetics, transpiration, and circulation and refresh concepts that you may have forgotten.

• Practise Different Question Types: Work through questions based on definitions, differences, explanations, experiments, diagrams, and applications.

• Strengthen Diagram-Based Preparation: Revise areas such as chromatin, chromosomes, cell division, and the potometer experiment where diagrams can support your answers.

• Understand Biological Processes: Follow sequences such as G1 → S → G2, cytokinesis, pulmonary circulation, and the movement of tissue fluid.

• Identify Topics That Need More Revision: Use your mistakes in questions to identify concepts, terms, processes, or experiments that need another round of revision.

The marathon can therefore be used alongside your regular chapter revision to check whether you can recall important concepts and explain them in exam-style questions.