Class 10 Biology Notes

Chapter 1: Homeostasis

Introduction

Homeostasis is the maintenance of internal environment of the body within narrow limits. It involves regulation of:

• Body temperature
• Blood glucose concentration
• Water balance
• pH of blood

Osmoregulation

Regulation of water and salt content in blood.

• Too much water: More urine production (dilute)
• Too little water: Less urine production (concentrated)

Thermoregulation

Body temperature maintained at 37°C.

• Hot: Sweating, vasodilation
• Cold: Shivering, vasoconstriction

Excretory System

Kidneys filter blood and remove waste.

• Kidneys: Filter blood, produce urine
• Ureters: Carry urine to bladder
• Bladder: Stores urine
• Urethra: Removes urine from body

Nephron

Functional unit of kidney.

1. Glomerular Filtration: Blood filtered at Bowman's capsule
2. Selective Reabsorption: Useful substances reabsorbed
3. Urine Formation: Waste excreted

Chapter 2: Coordination and Control

Nervous System

Fast response system using electrical impulses.

Central Nervous System (CNS)

• Brain: Control center
• Spinal Cord: Reflex actions

Peripheral Nervous System (PNS)

• Somatic: Voluntary actions
• Autonomic: Involuntary actions

Neuron Structure

• Cell Body: Contains nucleus
• Dendrites: Receive signals
• Axon: Carries signal
• Myelin Sheath: Insulates axon

Synapse

Junction between two neurons. Neurotransmitters carry signal across.

Reflex Action

Rapid, automatic response to stimulus.

Endocrine System

Slow response system using hormones.

Major Glands

• Pituitary: Master gland
• Thyroid: Metabolism, growth
• Pancreas: Insulin, glucagon (blood sugar)
• Adrenal: Fight or flight
• Gonads: Sex hormones

Chapter 3: Support and Movement

Skeletal System

Provides framework, protection, and enables movement.

Types of Bones

• Long Bones: Femur, humerus
• Short Bones: Carpals, tarsals
• Flat Bones: Skull, ribs
• Irregular Bones: Vertebrae

Bone Structure

• Compact Bone: Outer layer, hard
• Spongy Bone: Inner layer, contains marrow
• Bone Marrow: Red (blood cells) and yellow (fat)

Joints

• Ball and Socket: Hip, shoulder (all directions)
• Hinge: Knee, elbow (one plane)
• Pivot: Neck (rotation)
• Gliding: Wrist, ankle

Muscles

3 types: Skeletal (voluntary), Cardiac (heart), Smooth (involuntary).

Muscle Contraction

Actin and myosin filaments slide past each other (sliding filament theory).

Chapter 4: Inheritance

Genetics

Study of heredity and variation.

Key Terms

• Gene: Unit of heredity
• Allele: Different forms of a gene
• Genotype: Genetic makeup
• Phenotype: Physical appearance
• Homozygous: Same alleles (AA, aa)
• Heterozygous: Different alleles (Aa)

Mendel's Laws

Law of Dominance

In heterozygote, dominant allele masks recessive.

Law of Segregation

Alleles separate during gamete formation.

Law of Independent Assortment

Genes on different chromosomes assort independently.

Mendelian Ratio

• Monohybrid: 3:1 (dominant:recessive)
• Dihybrid: 9:3:3:1

Sex Determination

Genetic Disorders

• Down Syndrome: Extra chromosome 21
• Hemophilia: Blood clotting disorder (X-linked)
• Color Blindness: X-linked recessive

Chapter 5: Evolution

Theory of Evolution

Life on Earth has changed over time through gradual modifications.

Evidence of Evolution

• Fossils: Remains in rocks
• Comparative Anatomy: Homologous structures
• Embryology: Similar embryonic development
• Biochemistry: Common genetic code

Natural Selection

Darwin's theory: Organisms best adapted to environment survive and reproduce.

Speciation

Formation of new species from existing ones.

Human Evolution

1. Australopithecus
2. Homo habilis
3. Homo erectus
4. Homo neanderthalensis
5. Homo sapiens (Modern humans)

Chapter 6: Ecosystem

Ecosystem Components

Biotic (Living)

• Producers: Plants (photosynthesis)
• Consumers: Herbivores, carnivores, omnivores
• Decomposers: Fungi, bacteria

Abiotic (Non-Living)

• Sunlight
• Water
• Temperature
• Soil

Food Chain and Web

Energy flows from producers → primary consumers → secondary consumers → tertiary consumers.

Energy Flow

Biogeochemical Cycles

Carbon Cycle

• Photosynthesis: CO₂ → Organic compounds
• Respiration: Organic compounds → CO₂
• Decomposition: Releases carbon

Nitrogen Cycle

• Nitrogen fixation: N₂ → NH₃
• Nitrification: NH₃ → NO₂⁻ → NO₃⁻
• Denitrification: NO₃⁻ → N₂

Chapter 7: Biotechnology

Introduction

Use of living organisms or their products for human welfare.

Applications

1. Fermentation

• Bread making (yeast)
• Yogurt production (bacteria)
• Alcohol production

2. Genetic Engineering

• DNA Cloning: Copying genes
• PCR: Polymerase Chain Reaction
• Gene Therapy: Treating genetic diseases

3. Recombinant DNA Technology

Combining DNA from different sources.

Genetically Modified Organisms (GMOs)

• Plants: Pest-resistant, herbicide-tolerant
• Animals: Growth hormones
• Bacteria: Insulin production

Cloning

Creating genetically identical copy of an organism.