Class 10 Heredity and Evolution Mind Map for Science Board Exam 2026

Class 10 Heredity and Evolution: With the Class 10 Science board exam 2026 scheduled on 25 February, students are now in the most crucial phase of revision. The chapter Heredity and Evolution is concept-based and frequently asked in exams through definitions, reasoning questions, genetic crosses, and case-based problems. 

To support quick and effective last-minute revision, this mind map–based explanation helps you connect key concepts like DNA, variation, Mendel’s laws, genetic crosses, and sex determination in a clear and organised manner, making revision faster and more confident. 

For a clearer understanding, students can also watch the Heredity and Evolution Mind Map on the Physics Wallah Foundation YouTube Channel. This mind map explains all important terminology in the easiest possible way and is designed to boost Class 10 Science board exam preparation.

Class 10 Heredity and Evolution Mind Map Series

The chapter Heredity and Evolution is an important part of the Class 10 Science syllabus and often carries a significant weight in board exams. However, many students find it tricky because of genetics terms, Mendel’s crosses, and concepts that are connected to each other. To make learning easier and revision more effective before exams, a simple and organised approach can really help.

Also Watch: Easy Explanation of Class 10 Heredity and Evolution Mind Map Series Life Processes in 40 Minutes

This mind map video presents the entire chapter in a clear and connected format, making concepts easy to grasp and helping students revise quickly and confidently for exams.

Heredity, DNA and Variation

Heredity is the process of passing characteristics (traits) from parents to their offspring, or from one generation to the next. In sexual reproduction, a new individual receives half of its DNA from the male parent and half from the female parent, which is why children often resemble their parents.

DNA (Deoxyribonucleic acid) is a thread-like structure inside the cell's nucleus. It contains the information that determines an organism's characters, such as eye colour, hair pattern, height, blood group, and earlobe attachment. This genetic information, passed on during reproduction, is the essence of heredity.

However, individuals within the same species are not identical. For instance, human eye colour varies (e.g., black, brown, green, blue), and earlobes can be either free (detached) or attached (fused). These differences in characters among individuals of a species are called variations. 

The study of heredity and variation is known as Genetics, a term coined by William Bateson. Gregor Johann Mendel is celebrated as the "Father of Genetics."

2-Minute Quick Recap

This quick recap helps students revise the most important points of Heredity and Evolution in just 2 minutes, making it ideal for last-minute board exam revision.

• Core Definition: Heredity = transfer of traits from parents to offspring through DNA

• Important Diagram: Monohybrid cross (TT × tt)

• One-Line Summary: Dominant allele masks the expression of the recessive allele

• Must-Remember Fact: Gregor Mendel is known as the Father of Genetics

Importance of Variation

Variations are crucial for the survival and evolution of a species and are a frequently asked examination topic in the 10th Class Science Board exam.

Cause of Variation: Variations primarily arise from changes or errors that occur during DNA replication when a new organism is formed. An altered DNA sequence can change a character, leading to a variation.

Benefits of Variation:

• Adaptation: Variations help organisms adapt and survive in changing environmental conditions.

• Formation of New Characters: Altered DNA can introduce entirely new traits into a population.

• Evolution: Over long periods, the accumulation of beneficial variations drives the evolution of new species.

Types of Traits

Traits are broadly classified based on whether they are inherited from parents or developed during life.

Inherited vs. Acquired Traits

Characters, or traits, can be classified into two main types. This distinction is important for examinations.

Some Important Terminology in Genetics

Understanding the following basic terms is essential for studying genetic crosses. For Clear Understanding of These Terms You can watch Mind Map Series for Class 10th at Physics Wallah Foundation Youtube Channel 

• DNA (Deoxyribonucleic Acid): The genetic information carrier, DNA, is found in the nucleus and can be very long when uncoiled (approximately 2.2 meters in a single human cell)

• Gene: A specific segment of DNA that contains the code for a particular character, such as eye color or blood group. The human genome has about 20,000-22,000 genes.

• Chromatin vs. Chromosome: These are different organizational states of the same DNA molecule.

• Chromatin: The uncoiled, spread-out state of DNA in a non-dividing cell.

• Chromosome: The condensed, tightly coiled, rod-shaped structure of DNA during cell division, allowing for orderly separation.

• Haploid vs. Diploid Cells: Refers to the number of chromosome sets.

• Diploid (2n): Cells with two copies of each chromosome (one from each parent). Most human body cells are diploid.

• Haploid (n): Cells with a single copy of each chromosome. Human gametes (sperm and egg cells) are haploid.

• Allele: Different versions or variants of a single gene. (Memory Tip: Think of a gene as a car model, and alleles as its different versions, like manual or automatic transmission.)

• Dominant Allele: The "stronger" allele that expresses its trait even if only one copy is present. Represented by a capital letter (e.g., T for tallness).

• Recessive Allele: The "weaker" allele that expresses its trait only when two copies are present. It is masked by a dominant allele. Represented by a lowercase letter (e.g., t for dwarfness).

• Homozygous Dominant: An individual has two identical dominant alleles for a trait.

• Genotype: TT

• Phenotype (Expression): Dominant trait expressed (e.g., a tall plant).

• Homozygous Recessive: An individual has two identical recessive alleles for a trait.

• Genotype: tt

• Phenotype (Expression): Recessive trait expressed (e.g., a dwarf plant).

• Heterozygous (or Hybrid): An individual has one dominant and one recessive allele.

• Genotype: Tt

• Phenotype (Expression): The dominant allele masks the recessive one, so the dominant trait is expressed (e.g., a tall plant).

• Phenotype: The observable physical appearance or expressed characteristic of an organism.

• Example: A plant being "Tall" or "Dwarf".

• Genotype: The specific genetic makeup or combination of alleles an organism possesses for a trait.

• Example: The gene combination being TT, Tt, or tt. For example, a tall plant may be TT or Tt, while a dwarf plant is always tt.

Mendel's Experiments with Pea Plants

Gregor Mendel, the "Father of Genetics," established inheritance laws through experiments on garden pea plants (Pisum sativum).

Reasons for Choosing the Pea Plant (An Important Exam Question):

1. Short Life Cycle: Grows and produces results quickly.

2. Controlled Pollination: Allows for both self-pollination and cross-pollination.

3. Multiple Offspring: Produces a large number of seeds (offspring), providing statistical data.

4. Clear Contrasting Characters: Exhibits several easily distinguishable traits with opposing forms.

Mendel's Seven Contrasting Characters in Pea Plants:

To know this in more easy way you can watch the Mind Map Series for Class 10th for Heredity and Evolution Chapter

Memory Tricks & Mnemonics (For Quick Recall)

This section helps Class 10 students remember genetic terms, symbols, and ratios quickly during exams by using simple associations and shortcuts, reducing confusion and saving time while answering heredity and evolution questions.

• TT–Tt–tt → Tall–Tall–Dwarf genotypes

• Capital letter = Dominant, small letter = Recessive

• 3:1 → “3 Tall : 1 Dwarf” (Monohybrid F2)

Mendel’s Law of Inheritance - Monohybrid Cross and the Law of Dominance

A monohybrid cross studies the inheritance of a single character (e.g., plant height).

Mendel's Experiment:

1. Parental (P) Generation: Mendel crossed a purebred Tall plant (TT) with a purebred Dwarf plant (tt).

2. Gamete Formation: The tall plant produced T gametes; the dwarf plant produced t gametes.

3. First Filial (F1) Generation: All offspring were Tt, resulting in all F1 plants being Tall. This observation led to Mendel's Law of Dominance: When two different alleles for a trait are present (heterozygous condition), only the dominant allele expresses itself in the phenotype.

Self-Crossing the F1 Generation: Mendel allowed F1 plants (Tt) to self-pollinate.

• Second Filial (F2) Generation: This cross produced offspring with:

• Phenotypic Ratio: 3 Tall : 1 Dwarf (3:1 ratio).

• Genotypic Ratio: 1 TT : 2 Tt : 1 tt (1:2:1 ratio), meaning 1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive.

The Dihybrid Cross

A dihybrid cross studies the inheritance of two characters at the same time.

Mendel's Experiment:

• Mendel crossed plants with Round, Yellow seeds (dominant) with plants having Wrinkled, Green seeds (recessive).

• The F2 generation showed not only parental combinations but also new combinations (e.g., Round, Green and Wrinkled, Yellow seeds).

• The resulting phenotypic ratio in the F2 generation of a dihybrid cross is 9:3:3:1.

• 9 with both dominant traits (Round, Yellow)

• 3 with one dominant, one recessive (Round, Green)

• 3 with the other dominant and recessive (Wrinkled, Yellow)

• 1 with both recessive traits (Wrinkled, Green)

Sex Determination

Sex determination is the biological mechanism by which an organism develops as male or female, varying across species.

Environmental Sex Determination

In some animals, the environment influences sex.

1. Temperature-Dependent Sex Determination (Reptiles): In turtles and crocodiles, egg incubation temperature determines sex. For turtles, high temperatures yield females; low temperatures yield males.

2. Sex Change in Response to Environment (Snails): Some snails can change their sex based on environmental conditions.

Human Sex Determination

Human sex determination is a critical topic, often examined by justifying: "The sex of the baby is dependent on the male parent."

The Genetic Basis of Sex in Humans:

1. Chromosomes: Humans have 23 pairs of chromosomes, with the final pair being sex chromosomes.

2. Sex Chromosome Variation: Females are XX; Males are XY.

Mechanism of Determination:

Sex is determined at fertilization by the type of sperm fertilizing the egg.

• Gamete Production in Females (Mother): Females (XX) produce eggs containing only an X chromosome.

• Gamete Production in Males (Father): Males (XY) produce two sperm types: 50% carry an X chromosome, 50% carry a Y chromosome.

• Fertilization and Outcome: An X-sperm fertilizing an egg results in XX (female); a Y-sperm results in XY (male). Thus, the father's sperm determines the child's sex.

Smart Revision Tips for Class 10 Science Board Exam

Using the right revision strategy helps students retain concepts better, avoid mistakes, and score higher in the Class 10 Science board exam.

• Revise in short cycles (20–30 minutes)

• Focus on high-weightage topics like Mendel’s crosses

• Practice active recall of ratios and definitions

• Solve previous year questions

• Use timed practice for genetic numericals

Common Mistakes Students Make in Heredity and Evolution Chapter

Many Class 10 students lose easy marks in this chapter due to conceptual confusion, careless presentation, and poor exam-time strategy.

• Confusing genotype and phenotype

• Skipping diagrams or not labelling them properly

• Writing incomplete definitions in 1–2 mark questions

• Ignoring NCERT-based statements

• Poor time management in genetic cross questions