Life Processes in Living Organisms Part 2Class 10 Science Part 2 Chapter 3 Notes – Maharashtra Board

Summary: Life Processes in Living Organisms Part 2

Excretion is the removal of metabolic wastes from the body. The human excretory system includes kidneys (filter blood), ureters (transport urine), urinary bladder (store urine), and urethra (expel urine). Kidneys filter about 180 liters of fluid daily from blood; most is reabsorbed, leaving about 1-2 liters of urine. This maintains water balance and removes nitrogenous wastes like urea. The liver also excretes bile containing bilirubin (from hemoglobin breakdown). The lungs excrete CO₂ and water vapor.

Movement requires coordination between the skeletal system (bones and cartilage), muscular system (muscles), and nervous system (coordination). Bones provide structure and protection; joints allow movement. Muscles contract due to nerve signals and use ATP energy. Antagonistic muscles work in pairs—when one contracts, the other relaxes. In plants, movement occurs through growth responses called tropisms (toward light, gravity, or touch) mediated by hormones like auxins.

Reproduction creates new organisms. Asexual reproduction (mitosis) produces genetically identical offspring from one parent—fast and efficient but no variation. Sexual reproduction (meiosis and fertilization) combines genetic material from two parents, creating genetic diversity. In animals, the reproductive system produces gametes (sperm in males, eggs in females) and delivers them for fertilization. In plants, flowers are reproductive structures; pollen carries male gametes, ovules contain female gametes. Seeds and fruits result from sexual reproduction.

Key points to remember

• Excretion removes metabolic wastes; different from egestion (removal of undigested food) and secretion (release of useful substances).
• Kidneys contain ~1 million nephrons; each filters blood and forms urine. Process: filtration (small molecules), reabsorption (useful molecules), secretion (remove extra ions).
• Nephron structure: Bowman's capsule (filtration), proximal convoluted tubule (reabsorption), loop of Henle (water reabsorption), distal convoluted tubule (ion regulation), collecting duct (final urine formation).
• Glomerular filtration: high pressure in capillaries forces small molecules (glucose, urea, water, salts) into Bowman's capsule; large molecules (proteins, RBCs) stay in blood.
• Selective reabsorption: useful molecules (glucose, amino acids) and some water/ions reabsorbed back into blood in proximal tubule and loop of Henle.
• ADH (antidiuretic hormone) increases water reabsorption when body is dehydrated; more dilute urine is produced when ADH levels are low.
• Skeletal system: 206 bones in adults; provides structure, protection, movement lever, mineral storage (calcium, phosphorus), blood cell production.
• Joints: immovable (skull), slightly movable (vertebrae), freely movable (shoulder, knee). Movable joints have cartilage, synovial fluid for lubrication, and ligaments for support.
• Muscles work in pairs: agonist (contracts to move body part), antagonist (opposes agonist). Example: biceps contracts to bend arm; triceps contracts to straighten arm.
• Muscle contraction: nerve signal releases acetylcholine; calcium released in muscle cell; myosin heads pull actin filaments (sliding filament theory); ATP provides energy for contraction and relaxation.
• Asexual reproduction: mitosis produces two genetically identical daughter cells. Seen in bacteria (binary fission), plants (vegetative reproduction), some animals (budding, fission).
• Sexual reproduction: meiosis produces haploid gametes (half the chromosomes); fertilization restores diploid chromosome number.
• Male reproductive system: testes (produce sperm), epididymis (store sperm), vas deferens (transport), prostate/seminal vesicles (produce seminal fluid), penis (copulation).
• Female reproductive system: ovaries (produce eggs), fallopian tube (transport egg), uterus (develop fetus), cervix, vagina (copulation and birth).
• Menstrual cycle: ~28 days. Follicular phase (egg matures), ovulation (egg released), luteal phase (uterus prepared), menstruation (uterine lining shed if no fertilization).
• Fertilization: sperm penetrates egg; nuclei fuse; zygote forms and begins mitotic divisions to become embryo.
• In plants, flowers: stamens (male, produce pollen), carpels (female, produce ovules). Pollination: pollen reaches stigma; pollen tube grows to ovule; fertilization occurs.
• Seeds contain embryo plant and stored nutrients. Fruits develop from ovary and aid seed dispersal.

Life Processes in Living Organisms Part 2 – Notes

1. Excretion and kidney function

• Excretion removes nitrogenous wastes (urea from protein metabolism) and maintains water/ion balance.
• Kidney has outer cortex and inner medulla. Medulla contains pyramids where most urine formation occurs.
• Filtration in Bowman's capsule: blood pressure forces water, glucose, amino acids, urea, ions through capillary wall; large proteins and RBCs blocked.
• Proximal convoluted tubule: selective reabsorption of glucose, amino acids, vitamins, and some water/ions via active transport; some urea remains.
• Loop of Henle: descending limb permeable to water, impermeable to salts (water leaves); ascending limb impermeable to water, permeable to salts (salts leave); creates osmotic gradient.
• Distal convoluted tubule: further regulation of water and ions under hormonal control (aldosterone, ADH).
• Collecting duct: final water reabsorption controlled by ADH; urine flows to ureter.

2. Movement: skeletal and muscular systems

• Skeleton: 206 bones (adults), cartilage, ligaments. Functions: structure, protection, movement, mineral storage, blood cell production.
• Bone composition: matrix (collagen—flexibility, minerals—hardness) and osteocytes (living bone cells).
• Cartilage: flexible connective tissue. In joints: prevents bone rubbing. In ears, nose: structural support. No blood vessels—nutrients from diffusion.
• Joints: synovial fluid lubricates, cartilage cushions, tendons attach muscle to bone, ligaments connect bones.
• Muscles: bundles of muscle fibers (cells). Each fiber contains myofibrils with thick filaments (myosin) and thin filaments (actin).
• Sliding filament model: myosin heads pull actin toward center; muscle shortens. ATP hydrolysis provides energy; calcium triggers contraction.
• Antagonistic muscles: agonist contracts to create movement; antagonist relaxes and then contracts to reverse movement. Energy required for both actions.

3. Asexual and sexual reproduction

• Asexual reproduction: one parent produces offspring via mitosis. Offspring genetically identical to parent. Fast, efficient, no energy for mate finding.
• Drawbacks of asexual: no genetic variation, no adaptation to changing environment, population vulnerable to disease.
• Binary fission (bacteria): DNA replicates, cell elongates, septum forms, two identical cells produced.
• Vegetative reproduction (plants): new plants from runners (strawberry), tubers (potato), fragmentation (some plants).
• Budding (yeast, hydra): small outgrowth develops into new organism, then detaches.
• Sexual reproduction: meiosis produces haploid gametes (n); fusion of gametes restores diploid (2n). Genetic recombination creates variation.
• Meiosis: two divisions (Meiosis I, Meiosis II) producing four haploid cells. Crossing over (exchange of genetic material) increases variation.

4. Human male reproductive system

• Testes (gonads): produce sperm via spermatogenesis. Mature at puberty, produce millions of sperm daily, survive ~48-72 hours.
• Sperm structure: head (nucleus, acrosome), midpiece (mitochondria for energy), tail (flagellum for movement).
• Epididymis: coiled tube where sperm mature and are stored.
• Vas deferens: muscular duct transporting sperm during ejaculation.
• Seminal vesicles: secrete fructose (energy) and proteins (nourish sperm).
• Prostate gland: secretes alkaline fluid (neutralizes acidic vagina), prostaglandins (help sperm movement).
• Cowper's glands: secrete lubricating fluid before ejaculation.
• Semen: mixture of sperm and secretions from accessory glands. Normal volume: 2-5 mL; 40-300 million sperm per mL.

5. Human female reproductive system and menstrual cycle

• Ovaries (gonads): produce eggs (ova) via oogenesis. Contain primordial follicles; each month, one matures.
• Egg structure: nucleus (genetic material), cytoplasm (nutrients), zona pellucida (protective layer), corona radiata (follicle cells).
• Fallopian tube: site of fertilization. Cilia and peristalsis move egg toward uterus.
• Uterus: thick muscular wall (myometrium), vascular inner lining (endometrium). Site of fetal development.
• Menstrual cycle (~28 days): Follicular phase (days 1-13): FSH stimulates follicle growth, estrogen rises. Ovulation (day 14): LH surge triggers egg release. Luteal phase (days 15-28): progesterone from corpus luteum prepares uterus. Menstruation (days 1-5): if no fertilization, hormone levels drop, endometrium sheds.
• Hormones: FSH (follicle stimulation), LH (ovulation trigger), estrogen (follicle development, endometrium growth), progesterone (endometrium maintenance, pregnancy).

Formulas at a glance

Key terms

Life Processes in Living Organisms Part 2 – Flashcards

Read the question, answer it in your head, then tap the card to check. 20 cards.

Life Processes in Living Organisms Part 2 – MCQ Quiz

15 questions. Tap an option — you will see at once if it is right and why.

How to study Life Processes in Living Organisms Part 2

⏱ About 5 hours over 3-4 days

1. Day 1 — Kidney and excretion
   Master nephron parts and urine formation: ultrafiltration, selective reabsorption.
2. Day 2 — Homeostasis and endocrine
   Learn ADH, insulin/glucagon, negative feedback, hypothalamus.
3. Day 3 — Nervous system
   Study action potentials, synapses, reflex arcs, myelin conduction.
4. Day 4 — Integration and practice
   Complete flashcards and quiz. Draw action potential graphs.

✍️ Diagrams to practise

• Nephron showing filtration and reabsorption in each region
• Action potential graph with resting, depolarization, repolarization phases
• Synapse with neurotransmitter molecules
• Reflex arc pathway showing rapid response
• Feedback loops for ADH and insulin/glucagon regulation