Chapter 2: Influences on Development: Heredity and Environment
🌟 Chapter Overview
Welcome to Chapter 2 of your PSTET CDP journey! This chapter explores one of the most fundamental questions in child development: What makes us who we are? Is it our genes or our surroundings? As a teacher, understanding these influences helps you appreciate why each child is unique and how you can create an environment that nurtures every learner's potential.
| Section | Topic | PSTET Weightage |
|---|---|---|
| 2.1 | Concept of Heredity: Mechanisms and Transmission | High |
| 2.2 | Concept of Environment: Types and Impact | High |
| 2.3 | Interactionism: The Nature vs. Nurture Debate | Very High |
2.1 Concept of Heredity: The Biological Blueprint
🎯 Learning Objectives
After studying this section, you will be able to:
Explain the mechanisms of heredity including genes and chromosomes
Identify what traits and characteristics are transmitted through heredity
Understand common genetic disorders and their educational implications
What is Heredity?
Heredity refers to the transmission of physical and psychological characteristics from parents to offspring through genes. It is the biological endowment that children receive at conception, which serves as the foundation for all subsequent development .
📌 PSTET Key Point: Heredity provides the POTENTIAL for development; it sets the upper and lower limits within which development can occur.
The Mechanisms of Genetic Transmission
🔬 Understanding the Basics: Cells to Chromosomes
┌─────────────────────────────────────────────────────────────┐ │ HIERARCHY OF HEREDITY │ ├─────────────────────────────────────────────────────────────┤ │ │ │ CELL │ │ └── Contains NUCLEUS │ │ └── Contains CHROMOSOMES (46 in humans) │ │ └── Made of DNA (deoxyribonucleic acid) │ │ └── Contains GENES (20,000-25,000) │ │ └── Units of heredity │ │ │ └─────────────────────────────────────────────────────────────┘
Chromosomes: The Carriers of Heredity
At the moment of conception, every child receives 46 chromosomes—23 from the mother and 23 from the father. These chromosomes are arranged in 23 pairs .
| Chromosome Type | Description | Function |
|---|---|---|
| Autosomes | First 22 pairs | Carry genetic information for most body characteristics |
| Sex Chromosomes | 23rd pair (XX or XY) | Determine the sex of the child |
Mother always contributes X chromosome
Father can contribute X (results in female child - XX) or Y (results in male child - XY)
FATHER'S contribution determines the sex of the child
Genes: The Functional Units
Genes are segments of DNA that serve as the basic units of heredity. Each gene contains instructions for specific traits .
GENETIC TERMINOLOGY FOR PSTET: ┌─────────────────────────────────────────────────────────────┐ │ • GENOTYPE: The genetic makeup of an individual │ │ (The hidden potential - what genes say) │ │ │ │ • PHENOTYPE: The observable characteristics │ │ (What actually expresses - what we see) │ │ │ │ • ALLELES: Alternative forms of the same gene │ │ (e.g., gene for eye color - blue allele, brown allele) │ └─────────────────────────────────────────────────────────────┘
Principles of Genetic Inheritance
1. Mendelian Inheritance: Dominant and Recessive Traits
Gregor Mendel's classical principles explain how traits are passed from parents to offspring .
| Type of Trait | Definition | Example |
|---|---|---|
| Dominant | Expressed even when only one allele is present | Brown eyes, curly hair, dimples |
| Recessive | Expressed only when both alleles are identical | Blue eyes, straight hair, attached earlobes |
PSTET Application: A child may inherit the genotype for a trait but not show it in the phenotype if it is recessive.
2. Exceptions to Mendelian Inheritance
| Exception Type | Description | Example |
|---|---|---|
| Additivity | Both alleles contribute to the trait | Blood type (A, B, AB, O) |
| Polygenetic Inheritance | Multiple genes influence one trait | Height, intelligence, skin color |
| Sex-Linked Characteristics | Genes located on sex chromosomes | Hemophilia, red-green color blindness |
What is Transmitted Through Heredity?
🧬 Physical Traits
| Category | Specific Traits |
|---|---|
| Basic Features | Height, weight, body structure, skin color |
| Facial Features | Eye color, hair color and texture, nose shape |
| Biological Factors | Blood type, metabolic rate, hormone levels |
| Health Predispositions | Susceptibility to certain diseases, allergies |
🧠 Psychological and Intellectual Traits
| Trait | Heritability Evidence |
|---|---|
| Intelligence/Cognitive Ability | Moderately heritable; genetic factors play increasing role with age |
| Temperament | Basic emotional and behavioral styles show genetic influence |
| Personality Traits | Traits like shyness, sociability have genetic components |
| Talents and Abilities | Musical, artistic, mathematical aptitudes may run in families |
⚠️ Important for Teachers: Heritability does NOT mean immutability! Genetic potential requires environmental support to be realized.
Genetic Disorders and Educational Implications
Understanding genetic disorders helps teachers provide appropriate support .
Recessive Gene Disorders (require two recessive alleles)
Dominant Gene Disorders (single dominant allele sufficient)
Chromosomal Abnormalities
A. Autosomal Nondisjunctions
B. Sex Chromosome Nondisjunctions
Structural Abnormalities
📝 PSTET Practice Question
Q1. A child has difficulty with spatial tasks, left-right discrimination, and shows lower Performance IQ than Verbal IQ but has normal intelligence. This pattern is characteristic of:
a) Down Syndrome
b) Turner Syndrome
c) Klinefelter Syndrome
d) Fragile X Syndrome
2.2 Concept of Environment: The Nurturing Context
🎯 Learning Objectives
After studying this section, you will be able to:
Identify and explain the different types of environment
Understand how various environmental factors influence development
Apply this knowledge to create supportive classroom environments
What is Environment?
Environment refers to all external conditions and influences that affect the development of an individual from conception onward. It encompasses everything outside the organism that interacts with it .
📌 PSTET Key Point: Environment provides the OPPORTUNITY for genetic potential to be realized.
The Epigenome: Where Heredity and Environment Meet
Recent research has discovered that genes are not fixed as once thought. The epigenome (meaning "above the genes") consists of chemicals that can turn genes on and off—like the operating system of a computer .
┌─────────────────────────────────────────────────────────────┐ │ THE EPIGENOME │ ├─────────────────────────────────────────────────────────────┤ │ │ │ Positive Environmental Factors: │ │ • Health │ │ • Quality learning experiences │ │ • Supportive, loving relationships │ │ ↓ │ │ Turn ON genetic potential │ │ │ │ Negative Environmental Factors: │ │ • Toxic substances │ │ • Poor health practices │ │ • Lack of quality experiences │ │ • Stressors │ │ ↓ │ │ Cause harm across development domains │ │ │ └─────────────────────────────────────────────────────────────┘ [citation:5]
Types of Environment
Environmental influences can be categorized in multiple ways. For PSTET, understand these classifications:
1. Based on Timing
| Type | Definition | Examples |
|---|---|---|
| Prenatal Environment | Conditions in the womb before birth | Maternal nutrition, maternal illness, drugs, toxins |
| Natal Environment | Conditions during birth | Anoxia (oxygen deprivation), birth injuries, prematurity |
| Postnatal Environment | Conditions after birth | Family, school, community, nutrition |
2. Based on Proximity
┌─────────────────────────────────────────────────────────────┐ │ BRONFENBRENNER'S ECOLOGICAL MODEL │ │ (for reference) │ ├─────────────────────────────────────────────────────────────┤ │ │ │ ┌─────────────────────────────────────────────────────┐ │ │ │ MACROSYSTEM (Distal) │ │ │ │ ┌─────────────────────────────────────────────┐ │ │ │ │ │ EXOSYSTEM │ │ │ │ │ │ ┌─────────────────────────────────────┐ │ │ │ │ │ │ │ MESOSYSTEM │ │ │ │ │ │ │ │ ┌─────────────────────────────┐ │ │ │ │ │ │ │ │ │ MICROSYSTEM (Proximal) │ │ │ │ │ │ │ │ │ │ • Family │ │ │ │ │ │ │ │ │ │ • School │ │ │ │ │ │ │ │ │ │ • Peers │ │ │ │ │ │ │ │ │ │ • Neighborhood │ │ │ │ │ │ │ │ │ └─────────────────────────────┘ │ │ │ │ │ │ │ │ • Family-School interaction │ │ │ │ │ │ │ └─────────────────────────────────────┘ │ │ │ │ │ │ • Parent's workplace │ │ │ │ │ │ • Community services │ │ │ │ │ └─────────────────────────────────────────────┘ │ │ │ │ • Cultural values │ │ │ │ • Laws and policies │ │ │ │ • Socioeconomic conditions │ │ │ └─────────────────────────────────────────────────────┘ │ │ │ │ PROXIMAL = Direct, immediate contact │ │ DISTAL = Indirect, broader influence │ └─────────────────────────────────────────────────────────────┘
3. Comprehensive Classification of Environments
| Environment Type | Components | Examples |
|---|---|---|
| Physical Environment | Natural and built surroundings | Climate, housing, classroom physical setup, playground |
| Social Environment | People and relationships | Family, peers, teachers, community members |
| Cultural Environment | Beliefs, values, traditions | Language, customs, religious practices, gender roles |
| Psychological Environment | Emotional climate, attitudes | Family emotional tone, classroom atmosphere, expectations |
Detailed Analysis of Environmental Types
🏠 A. Physical Environment
Definition: The material conditions and surroundings in which a child lives and develops.
| Subtype | Components | Developmental Impact |
|---|---|---|
| Home Environment | Space, lighting, ventilation, safety, resources | Affects physical health, cognitive stimulation, sense of security |
| School Environment | Classroom arrangement, facilities, learning materials | Influences attention, engagement, learning outcomes |
| Neighborhood | Parks, recreational areas, safety, pollution | Affects play opportunities, physical activity, exposure to toxins |
| Nutritional Environment | Food quality and quantity | Critical for brain development, physical growth, energy for learning |
PSTET Application: A well-ventilated, well-lit classroom with age-appropriate furniture and learning materials enhances learning.
👨👩👧👦 B. Social Environment
Definition: The network of human relationships and interactions surrounding the child .
| Social Agent | Role | Developmental Influence |
|---|---|---|
| Family | Primary socialization agent | Attachment, language, values, basic skills |
| Peers | Equal-status relationships | Social skills, cooperation, identity |
| Teachers | Formal educators and guides | Academic learning, self-concept, aspirations |
| Community | Wider social network | Sense of belonging, cultural identity |
Research Finding: The Home Observation for Measurement of the Environment (HOME) inventory shows significant association with ALL developmental domains—linguistic, motor, cognitive, and social-behavioral .
🌍 C. Cultural Environment
Definition: The shared beliefs, values, customs, and practices of a group .
| Cultural Element | Examples | Impact on Development |
|---|---|---|
| Language | Mother tongue, dialect | Shapes thought, identity, learning |
| Values | Individualism vs. collectivism | Influences self-concept, goals |
| Practices | Child-rearing customs, rituals | Affects daily experiences |
| Gender Roles | Expectations for males/females | Shapes behavior, opportunities |
Research Example: Parenting practices differ by social class—middle-class families often use "concerted cultivation" (adult-driven activities, encouraging self-expression), while working-class families may emphasize "natural growth" (more independent play, clearer adult-child boundaries) .
💭 D. Psychological Environment
Definition: The emotional and attitudinal climate surrounding the child.
| Aspect | Description | Developmental Impact |
|---|---|---|
| Emotional Climate | Warmth vs. hostility, support vs. criticism | Affects emotional security, self-esteem |
| Expectations | Beliefs about child's potential | Self-fulfilling prophecy |
| Stress Level | Chronic vs. manageable stress | Toxic stress harms brain development |
| Parental Mental Health | Parents' psychological well-being | Influences quality of interaction |
Critical Finding: Lower emotional and cognitive support mediates the negative effect of lower socioeconomic status on children's cognitive performance .
Environmental Risk Factors
Prenatal Environmental Risks
| Risk Factor | Potential Effects |
|---|---|
| Maternal Malnutrition | Low birth weight, impaired brain development |
| Maternal Illness (TORCH) | Toxoplasmosis, Rubella, CMV, Herpes—can cause birth defects |
| Drugs | Thalidomide (limb deformities), alcohol (Fetal Alcohol Syndrome), nicotine |
| Chemical Toxins | PCBs linked to lower IQ |
| Radiation | Cognitive impairments |
Natal Environmental Risks
Postnatal Environmental Risks
📝 PSTET Practice Question
Q2. According to recent research, which environmental factor shows significant association with ALL developmental domains (linguistic, motor, cognitive, and social-behavioral)?
a) Parental education level
b) Home environment (HOME inventory)
c) Neighborhood safety
d) Peer group quality
Answer: b) Home environment (HOME inventory)
2.3 Interactionism: The Nature vs. Nurture Debate
🎯 Learning Objectives
After studying this section, you will be able to:
Trace the historical nature vs. nurture debate
Explain the modern interactionist perspective
Understand how heredity and environment work together
The Historical Debate
For years, psychologists argued about which affected growth and development more—heredity or environment. This argument was called nature versus nurture .
┌─────────────────────────────────────────────────────────────┐ │ HISTORICAL POSITIONS IN THE DEBATE │ ├─────────────────────────────────────────────────────────────┤ │ │ │ NATURE POSITION (Heredity) │ │ • Development is determined by genetic factors │ │ • "Biology is destiny" │ │ • Advocates: Francis Galton, Arnold Gesell │ │ │ │ NURTURE POSITION (Environment) │ │ • Development is shaped by experience │ │ • "Tabula rasa" (blank slate) │ │ • Advocates: John Locke, John Watson, B.F. Skinner │ │ │ └─────────────────────────────────────────────────────────────┘
Why the Debate is Resolved: Interactionism
Modern experts agree that heredity and environment work together—they are not separate forces but interact continuously throughout development .
📌 PSTET Key Point: There is NO way to study environment separate from heredity because the environment has to act upon the genes.
How Heredity and Environment Interact
1. Range of Reaction
Heredity sets a range of possible outcomes, and environment determines where within that range the individual falls.
HEREDITY SETS THE RANGE
──────────────────────
Upper Limit (Genetic Potential)
↑
┌───────────┼───────────┐
│ │ │
Enriched Average Deprived
Environment Environment Environment
│ │ │
↓ ↓ ↓
┌─────────┐ ┌─────────┐ ┌─────────┐
│ Optimal │ │ Average │ │ Minimum │
│Outcome │ │Outcome │ │Outcome │
└─────────┘ └─────────┘ └─────────┘
↓
Lower Limit (Genetic Potential)2. Canalization
Some traits are strongly canalized (buffered against environmental influence), while others are more plastic.
| Canalization Level | Description | Examples |
|---|---|---|
| Strongly Canalized | Develop similarly across environments | Walking, basic language acquisition |
| Weakly Canalized | Highly influenced by environment | Intelligence, academic achievement |
3. Genotype-Environment Interactions
Three ways genotypes and environments correlate:
| Type | Description | Example |
|---|---|---|
| Passive | Parents provide both genes and environment | Musically gifted parents create music-rich home |
| Evocative | Child's genetic traits evoke responses from others | Cheerful infant receives more social interaction |
| Active | Child seeks environments matching genetic tendencies | Sociable child seeks out friends |
Modern Research Evidence
Recent studies using advanced methods reveal the complexity of heredity-environment interplay .
Key Findings from the 2025 NIH Study
A study of 391 seven-year-old children examined genetic factors (polygenic score for educational attainment) and environmental factors (HOME inventory) across multiple developmental domains .
| Domain | Environmental Influence (HOME) | Genetic Influence (PGS for EA) |
|---|---|---|
| Linguistic | Significant | Not significant |
| Motor | Significant | Not significant |
| Cognitive | Significant | Significant |
| Social-Behavioral | Significant | Not significant |
Interpretation: The home environment influences ALL domains, while genetic factors specifically influence cognitive function. The study identified two orthogonal dimensions—one associated with environmental factors, one with genetic factors .
Examples of Heredity-Environment Interaction
| Trait | Heredity Role | Environment Role | Interaction Example |
|---|---|---|---|
| Height | Sets potential range | Nutrition determines actual height achieved | Tall genes + poor nutrition = average height |
| Intelligence | Provides potential | Quality of stimulation determines realization | High genetic potential + enriched environment = high achievement |
| Temperament | Basic style inherited | Parenting shapes expression | Shy child + supportive environment = confident adult |
| Athletic Ability | Body type inherited | Training develops skill | Flexible body + gymnastics training = gymnast |
The Teacher's Role: Optimizing the Interaction
As a teacher, you cannot change a child's heredity, but you can optimize the environment to help each child reach their potential.
┌─────────────────────────────────────────────────────────────┐ │ TEACHER'S ROLE IN INTERACTION │ ├─────────────────────────────────────────────────────────────┤ │ │ │ HEREDITY (Fixed) ENVIRONMENT (Modifiable) │ │ ────────────────── ───────────────────── │ │ • Genetic potential • Classroom climate │ │ • Inborn temperament • Teaching strategies │ │ • Physical characteristics • Learning materials │ │ • Cognitive potential • Peer interactions │ │ ↓ ↓ │ │ └───────────────┐ ┌───────────────┘ │ │ ↓ ↓ │ │ ┌─────────────────────┐ │ │ │ OPTIMAL CHILD │ │ │ │ DEVELOPMENT │ │ │ └─────────────────────┘ │ │ │ │ TEACHER'S JOB: Create environment that helps every │ │ child reach their unique genetic potential │ └─────────────────────────────────────────────────────────────┘
Practical Classroom Applications
| Hereditary Factor | Environmental Modification |
|---|---|
| Varying cognitive abilities | Differentiated instruction; multiple learning modalities |
| Different temperaments | Flexible classroom management; individual support |
| Learning disabilities | Specialized interventions; accommodations |
| Giftedness | Enrichment activities; advanced materials |
| Physical differences | Accessible classroom; adapted activities |
🔑 Key Principles for PSTET
Heredity provides potential, environment determines realization
Genes and environment interact continuously throughout development
The same environment affects different children differently (due to genetic differences)
The same genetic makeup expresses differently in different environments
Teachers cannot change heredity but CAN optimize environment
📝 PSTET Practice Question
Q3. Which statement BEST represents the modern interactionist view of development?
a) Heredity determines intelligence, regardless of environment
b) Environment alone shapes who we become
c) Heredity and environment interact dynamically throughout development
d) Heredity matters in infancy, environment matters later
Answer: c) Heredity and environment interact dynamically throughout development
🔑 Chapter Summary for PSTET Revision
┌─────────────────────────────────────────────────────────────┐ │ CHAPTER 2: QUICK REVISION │ ├─────────────────────────────────────────────────────────────┤ │ │ │ HEREDITY (Nature) │ │ ┌─────────────────────────────────────────────────────┐ │ │ │ • Mechanism: 46 chromosomes (23 from each parent) │ │ │ │ • Genes = units of heredity │ │ │ │ • Genotype = genetic makeup │ │ │ │ • Phenotype = observable traits │ │ │ │ • Transmits: physical traits, intelligence │ │ │ │ potential, temperament │ │ │ └─────────────────────────────────────────────────────┘ │ │ │ │ ENVIRONMENT (Nurture) │ │ ┌─────────────────────────────────────────────────────┐ │ │ │ TYPES: │ │ │ │ • Physical: surroundings, nutrition │ │ │ │ • Social: family, peers, teachers │ │ │ │ • Cultural: values, language, traditions │ │ │ │ • Psychological: emotional climate, expectations │ │ │ │ • Prenatal/Natal/Postnatal │ │ │ └─────────────────────────────────────────────────────┘ │ │ │ │ INTERACTION (Modern View) │ │ ┌─────────────────────────────────────────────────────┐ │ │ │ • Heredity + Environment work TOGETHER │ │ │ │ • Heredity sets RANGE, environment determines │ │ │ │ actual outcome │ │ │ │ • Epigenome: environment turns genes on/off │ │ │ │ • Research shows BOTH influence development │ │ │ └─────────────────────────────────────────────────────┘ │ │ │ │ MNEMONIC: "G-P-E-I" │ │ G - Genes provide potential │ │ P - Phenotype shows expression │ │ E - Environment shapes realization │ │ I - Interaction is continuous │ └─────────────────────────────────────────────────────────────┘
✅ Self-Assessment Checklist
Tick (✓) when you can confidently:
Explain the mechanism of heredity (chromosomes, genes)
Distinguish between genotype and phenotype
Describe dominant, recessive, and sex-linked inheritance
Identify common genetic disorders and their educational implications
List and explain the four types of environment
Describe prenatal, natal, and postnatal environmental risks
Explain the modern interactionist perspective
Provide examples of heredity-environment interaction
Apply this knowledge to classroom situations
Answer PSTET-level questions on this chapter
📝 Practice Questions for PSTET
Q4. A child receives 23 chromosomes from mother and 23 from father at conception. The sex of the child is determined by:
a) Mother's X chromosome only
b) Father's contribution (X or Y chromosome)
c) Both parents equally
d) Environmental factors after conception
Answer: b) Father's contribution
Q5. A student with Turner Syndrome (45, XO) is likely to need support in which area?
a) Verbal comprehension
b) Social interaction
c) Visual-spatial skills
d) Memory
Answer: c) Visual-spatial skills
Q6. Research using the HOME inventory shows that the home environment significantly influences:
a) Only cognitive development
b) Only social development
c) All developmental domains (linguistic, motor, cognitive, social)
d) Only physical development
Answer: c) All developmental domains
📚 References for Further Reading
National Institutes of Health. (2025). Environmental and Genetic Influences on Developmental Outcomes. PMC
Illinois State University. Basis of Behavior: Genetic Influences
G-W Online Textbooks. Child Development: Early Stages Through Age 12
Cambridge University Press. Handbook of Environment in Human Development
National Institute of Open Schooling. Growth and Development
Next Chapter Preview: Chapter 3 - The Social World of Children: Socialization Processes
We will explore how family, peers, and teachers shape children's social development and understanding of the world.
