Why this chapter matters for UPSC: Life processes in animals connect to multiple UPSC themes: human nutrition and malnutrition (GS2), animal biodiversity and conservation (GS3 Environment), One Health approach (linking animal and human health), disease vectors (mosquitoes, ticks), and food security (livestock nutrition). Understanding basic physiology also helps with public health questions.

PART 1 — Quick Reference Tables

Life Process Definition Organ System Involved
Nutrition Obtaining and using food for energy and growth Digestive system
Respiration Breaking down food (glucose) to release energy; exchange of gases Respiratory system
Transportation Carrying nutrients, oxygen, and waste through the body Circulatory system
Excretion Removing metabolic waste products from the body Excretory system (kidneys, lungs, skin)
Reproduction Producing offspring to continue the species Reproductive system
Mode of Nutrition Description Examples
Herbivore Eats only plants Cow, deer, elephant, rabbit
Carnivore Eats only animals Tiger, lion, eagle, shark
Omnivore Eats both plants and animals Human, bear, crow, pig
Scavenger Feeds on dead/decaying organisms Vulture, hyena, crow
Parasite Feeds on living host without killing it Tapeworm, louse, leech
Filter feeder Filters small organisms from water Whale shark, flamingo, oyster
Organ Function Key Facts
Mouth Ingestion, mechanical digestion, salivary amylase (starch → maltose) Saliva is slightly alkaline (pH 6.8–7)
Oesophagus Peristaltic movement of food to stomach Muscular tube; no digestion
Stomach Protein digestion (pepsin + HCl); churning Highly acidic (pH 1.5–3.5); mucus lining prevents self-digestion
Small intestine Major site of digestion and absorption Villi and microvilli increase surface area; bile (from liver) emulsifies fats
Large intestine Water absorption; faeces formation Houses gut microbiome
Liver Produces bile; detoxification; glycogen storage Largest organ in the body
Pancreas Produces digestive enzymes and insulin/glucagon Both digestive and endocrine function

PART 2 — Detailed Notes

Key Term

Nutrition in Animals: Animals are heterotrophs — they cannot make their own food and must consume other organisms. The process involves:

  1. Ingestion: Taking food into the body
  2. Digestion: Breaking down complex food molecules into simple, absorbable forms
  3. Absorption: Nutrients pass from small intestine into bloodstream
  4. Assimilation: Absorbed nutrients are used by cells for energy, growth, repair
  5. Egestion: Undigested waste is expelled as faeces

Digestion Types:

  • Mechanical digestion: Physical breakdown (chewing, stomach churning)
  • Chemical digestion: Enzymes break chemical bonds (amylase digests starch; pepsin digests protein; lipase digests fat)

Respiration: The process of releasing energy from food (glucose) using oxygen, producing carbon dioxide and water. All living cells carry out respiration.

  • Aerobic respiration: Glucose + Oxygen → CO₂ + Water + Energy (ATP) — occurs in presence of oxygen
  • Anaerobic respiration: Glucose → Lactic acid or Alcohol + CO₂ + Energy (less energy) — occurs without oxygen (e.g., muscles during intense exercise; yeast in fermentation)

Blood Composition:

  • Red Blood Cells (RBC / Erythrocytes): Carry oxygen via haemoglobin; no nucleus in mature RBCs; produced in bone marrow; lifespan ~120 days
  • White Blood Cells (WBC / Leucocytes): Immune defence; fight infection; includes neutrophils, lymphocytes, monocytes
  • Platelets (Thrombocytes): Blood clotting
  • Plasma: Liquid portion; carries dissolved nutrients, hormones, CO₂, waste products

Excretion: Removal of metabolic waste:

  • Kidneys: Filter blood; produce urine (urea, excess salts, water)
  • Lungs: Exhale CO₂ and water vapour
  • Skin: Sweat (water, salt, urea)
UPSC Connect

One Health — Animal, Human, and Environmental Health

One Health is the concept that human health, animal health, and ecosystem health are inseparable. Endorsed by WHO, FAO, OIE (WOAH — World Organisation for Animal Health), and UNEP.

India's One Health approach is particularly relevant because:

  • Zoonotic diseases (diseases transmitted from animals to humans) account for ~60% of human infectious diseases: Rabies, Nipah virus (Kerala outbreaks 2018, 2023), Avian Influenza (H5N1), Brucellosis, Anthrax, Leptospirosis
  • Antimicrobial Resistance (AMR): Overuse of antibiotics in livestock farming drives resistance — threatens human medicine. India's National Action Plan on AMR (2017–2021) revised; linked to GS2/GS3.
  • Animal Nutrition and Food Security: Quality of livestock feed affects milk/meat production — National Livestock Mission under Ministry of Fisheries, Animal Husbandry and Dairying

Malnutrition and Life Processes:

  • Protein-Energy Malnutrition (PEM): Kwashiorkor (protein deficiency in children — swollen belly, stunting); Marasmus (total calorie deficiency — extreme wasting)
  • Anaemia: Iron deficiency → reduced haemoglobin → less oxygen transport → weakness, fatigue
  • Iodine deficiency: Affects thyroid hormone production → goitre, cretinism in children
  • POSHAN Abhiyaan (National Nutrition Mission, 2018): Targets reduction of stunting, wasting, anaemia, and low birth weight

Conservation — Feeding Habits and Ecosystem Roles:

  • Vultures: Critical scavengers; remove carcasses preventing disease spread; decimated by Diclofenac (veterinary NSAID) → Gyps vulture population collapsed >90%. Diclofenac banned for veterinary use (2006). SAVE (Saving Asia's Vultures from Extinction) programme.
  • Whale Shark: Filter feeder; protected under Wildlife Protection Act 1972; world's largest fish; found along Gujarat and Karnataka coasts. India banned its fishing in 2001.
Explainer

Haemoglobin, Oxygen Transport, and Anaemia

Haemoglobin (Hb) is an iron-containing protein in Red Blood Cells. Each Hb molecule can carry 4 oxygen molecules. In the lungs, oxygen binds to Hb (forming oxyhaemoglobin). In body tissues, oxygen is released and CO₂ is picked up.

Iron Deficiency Anaemia: When dietary iron is insufficient, fewer or smaller RBCs are produced → less haemoglobin → reduced oxygen-carrying capacity → fatigue, pallor, breathlessness.

India's Anaemia burden (NFHS-5, 2019-21):

  • 57% of women aged 15–49 years are anaemic
  • 67% of children aged 6–59 months are anaemic
  • Anaemia causes maternal mortality, poor birth outcomes, reduced labour productivity

Government response:

  • Anaemia Mukt Bharat (AMB) Strategy (2018): 6x6x6 strategy targeting 6 beneficiary groups, 6 interventions, 6 institutional mechanisms. Aims to reduce anaemia by 3 percentage points per year.
  • Fortification of rice, wheat, and oil with iron, folic acid, Vitamin B12 under FSSAI Food Fortification standards

Digestion and Diseases:

  • Peptic ulcer: Stomach lining damaged — often by Helicobacter pylori bacteria (Nobel Prize 2005 — Barry Marshall, Robin Warren, who proved H. pylori causes ulcers by drinking the bacteria)
  • Jaundice: Liver dysfunction → bile pigments in blood → yellowing of skin and eyes
  • Cholera: Vibrio cholerae infects small intestine → excessive fluid secretion → dehydration — spreads through contaminated water (faecal-oral route)
  • Food poisoning: Bacteria (Salmonella, E. coli) or their toxins in food → gastroenteritis. FSSAI regulates food safety.

Exam Strategy

  • Know the difference between nutrition (obtaining food) and digestion (breaking it down). Prelims sometimes conflates them.
  • Aerobic respiration releases MORE energy than anaerobic. Yeast uses anaerobic respiration (fermentation) — producing alcohol and CO₂ — basis of bread making and brewing.
  • Haemoglobin in RBCs transports oxygen. Iron deficiency → anaemia → reduced oxygen transport. Connect with India's anaemia burden (NFHS-5 data).
  • Vultures (scavengers) and Diclofenac: Diclofenac used as veterinary pain-killer caused massive vulture die-off when vultures ate livestock carcasses treated with it. Banned in 2006 for veterinary use. Classic UPSC environment MCQ.
  • One Health concept links animal health, human health, and ecosystem health. Zoonotic diseases (Nipah, Rabies, Avian Flu) are classic One Health examples. WHO, FAO, WOAH (formerly OIE) are the three international bodies promoting One Health.
  • Anaemia Mukt Bharat (2018): Know the "6x6x6" strategy label even if not all details. Ministry of Health and Family Welfare.

Previous Year Questions

Q1. Which of the following led to a dramatic decline in vulture populations in India?
(a) Habitat loss due to deforestation
(b) Use of Diclofenac in veterinary medicine
(c) Hunting by tribal communities
(d) Disease from Avian Influenza

(b) Use of Diclofenac in veterinary medicine

Q2. Anaemia Mukt Bharat Strategy was launched primarily to address:
(a) Malaria-related anaemia in tribal populations
(b) Iron deficiency anaemia across multiple population groups
(c) Vitamin B12 deficiency in elderly persons
(d) Protein deficiency anaemia in children under 5

(b) Iron deficiency anaemia across multiple population groups

Q3. During intense exercise, muscles may resort to anaerobic respiration. Which is the end product of anaerobic respiration in human muscle cells?
(a) Ethanol and carbon dioxide
(b) Lactic acid
(c) Glucose and water
(d) Carbon dioxide and water

(b) Lactic acid