Grade 9||Body Structure and Life Process|| Notes

Introduction to Life Processes

Every living thing starts from a single cell (zygote).

• Unicellular organisms (e.g., amoeba) → do all life activities in one cell.
• Multicellular organisms (plants, animals) → cells → tissues → organs → systems.

Life processes: Nutrition, respiration, photosynthesis, circulation, excretion, reproduction – these keep life going. Cell is the basic structural and functional unit of life. Tissue: Group of similar cells doing the same job. Study of tissues = Histology.

Two main types: Plant tissues and Animal tissues.

5.1 Tissues – Plant Tissues (Detailed)

1. Meristematic Tissue (Growing tissue)

Cells that keep dividing → help plant grow. Features: Thin cell walls, big nucleus, dense cytoplasm, no spaces between cells. Location: Growth points. Function: Increase length and thickness.

Sub-types (with diagrams):

• Apical meristem: At tips of roots and shoots → increases height.
• Lateral meristem: Sides of stem/root → increases thickness (girth).
• Intercalary meristem: At base of nodes/leaves → increases length of internodes (e.g., in grasses).

2. Permanent Tissue (Mature, no division)

Cells stop dividing, have fixed shape/size.

A. Simple Permanent Tissues (one type of cells):

• Parenchyma: Thin walls, living, spaces between cells. Stores food, some do photosynthesis (chlorenchyma), helps floating (aerenchyma).
• Collenchyma: Thick corners (living cells). Gives flexibility and support (under skin of stems).
• Sclerenchyma: Very thick walls, dead cells. Gives strength (in stems, seeds, veins).

B. Complex Permanent Tissues (mix of cells – vascular):

• Xylem: Dead cells → transports water + minerals from roots up. Also gives hardness (wood).
• Phloem: Living cells → transports food from leaves to other parts.

C. Special Tissues:

• Glandular: Secretes oils, resins, enzymes (e.g., in Tulasi).
• Lactiferous: Secretes latex (e.g., rubber plant, Poinsettia – white milk when broken).

Animal Tissues (Detailed)

1. Epithelial Tissue (Covering tissue)

Covers body and organs. Functions: Protection, absorption, secretion. Sub-types:

• Squamous (pavement): Flat cells → lining of blood vessels, lungs.
• Cuboidal: Cube-shaped → kidney tubules, glands.
• Columnar: Tall cells → intestine (absorption).
• Glandular: Secretes mucus, enzymes.

2. Muscular Tissue (Movement)

• Skeletal (striated, voluntary): Attached to bones, striped look → walking, running.
• Cardiac (striated, involuntary): Only in heart → heartbeat.
• Smooth (non-striated, involuntary): In stomach, blood vessels → digestion, blood flow.

3. Connective Tissue (Connects & supports)

• Areolar: Loose, under skin.
• Adipose: Fat storage, cushion.
• Bone: Hard, support.
• Cartilage: Flexible (nose, ear).
• Blood: Transport oxygen, nutrients.
• Lymph: Immunity.

4. Nervous Tissue (Control & coordination)

Basic unit: Neuron (dendrites → cell body → axon).

5.2 Human Nervous System

• Central: Brain + Spinal cord.
  • Cerebrum: Thinking, memory, senses.
  • Cerebellum: Balance, coordination.
  • Medulla: Breathing, heartbeat.
• Peripheral: Cranial nerves (12 pairs) + Spinal nerves (31 pairs).
• Reflex action (quick response):

Path: Receptor → Sensory nerve → Spinal cord → Motor nerve → Muscle (e.g., hot object → pull hand).

• Autonomic: Controls automatic actions. Sympathetic (emergency), Parasympathetic (relax).

5.3 Human Glandular (Endocrine) System

The human glandular system (also called the endocrine system) is a group of special glands that produce and release hormones. Hormones are like chemical messengers – they travel through the blood to control many body functions, such as growth, metabolism, sugar level, stress response, and reproduction.

Types of Glands

There are two main types:

• Exocrine glands: Release secretions through tubes (ducts) to the outside or inside body cavities (e.g., sweat glands, salivary glands – for sweat, saliva, digestive juices).
• Endocrine glands: No ducts! They release hormones directly into the blood.
• Mixed glands: Do both (e.g., pancreas – digestive juice through duct + hormones into blood).

Main Endocrine Glands and Their Hormones

Here are the key glands with their location, hormone, and function:

1. Pituitary Gland (Master gland)
   • Location: Base of the brain (pea-sized).
   • Hormones: Growth hormone + many stimulating hormones.
   • Functions: Controls growth, and tells other glands what to do.
   • Problems: Too little → dwarfism; too much → gigantism.

1. Thyroid Gland
   • Location: Front of the neck.
   • Hormone: Thyroxine.
   • Functions: Controls metabolism (how body uses energy), growth.
   • Parathyroid glands (4 small ones behind thyroid): Parathormone – controls calcium in blood/bones.

1. Adrenal Glands
   • Location: On top of each kidney (one on each).
   • Hormones: Adrenaline (for emergency/stress – "fight or flight"), cortisone.
   • Functions: Handle stress, blood pressure, energy in danger.

1. Pancreas (Mixed gland)
   • Location: Behind stomach.
   • Hormones: Insulin (lowers blood sugar), Glucagon (raises blood sugar) – from Islets of Langerhans.
   • Functions: Controls blood glucose level.
   • Problem: Low insulin → Diabetes (high sugar, thirst, frequent urine).

1. Gonads (Sex glands)
   • Testes (in males): Produce testosterone + sperm. → Male features (deep voice, beard).
   • Ovaries (in females): Produce oestrogen, progesterone + eggs. → Female features (breast development, periods).

Overall Diagram of Human Endocrine System

Important Functions of Hormones

• Growth and development.
• Control metabolism and energy.
• Regulate blood sugar and calcium.
• Handle stress and emergencies.
• Develop sexual characteristics and reproduction.

If hormones are too much or too little, it causes diseases (e.g., diabetes, goitre, dwarfism).

This system works slowly but has long-lasting effects (unlike nervous system which is fast).

5.4 Plant Hormones

Plants don't have a nervous system or endocrine glands like animals, but they still need to control growth, respond to the environment, and develop properly. They do this using plant hormones (also called plant growth regulators). These are chemical messengers produced in very small amounts in one part of the plant and transported to another part to cause changes.

Plant hormones are produced mainly in growing areas like shoot tips, root tips, leaves, seeds, and fruits. They help plants respond to light, gravity, touch, water, and stress.

Major Plant Hormones and Their Functions

Here are the most important ones (from your Grade 9 chapter):

1. Auxin
   • Produced at: Shoot tips.
   • Main functions:
     • Cell elongation (makes cells longer → growth).
     • Phototropism (bending towards light).
     • Apical dominance (main shoot grows more than side branches).
     • Root formation.
   • Example: Sunflower turns towards sun due to auxin.

1. Cytokinin
   • Produced at: Root tips, seeds, fruits.
   • Main functions:
     • Promotes cell division.
     • Delays aging of leaves.
     • Breaks seed dormancy.
     • Works with auxin for balanced growth.

1. Gibberellin
   • Produced at: Young leaves, roots, seeds.
   • Main functions:
     • Stem elongation (makes plant taller).
     • Breaks seed/bud dormancy.
     • Promotes flowering and fruit growth.

1. Ethylene (gas hormone)
   • Produced at: Ripening fruits, aging leaves.
   • Main functions:
     • Fruit ripening (turns green to colored, soft).
     • Leaf falling (abscission).
     • Promotes flowering in some plants.

1. Abscisic Acid (ABA) – Stress hormone
   • Produced at: Leaves, stems, green fruits.
   • Main functions:
     • Closes stomata during water shortage (prevents water loss).
     • Seed dormancy (keeps seeds sleeping until good conditions).
     • Stress response (drought, cold).

Summary Diagram of Major Plant Hormones

Uses of Plant Hormones (Practical Applications)

• Tissue culture: Auxin + Cytokinin in right ratio → grow new plants from cells.
• Fruit production: Ethylene for ripening, Gibberellin for bigger fruits.
• Weed control: Synthetic auxins kill broad-leaf weeds.
• Seedless fruits: Hormones help develop fruits without seeds.

Warning: Too much synthetic hormones in fruits/veggies can harm health – that's why natural is better!