Gas Exchange in Plants and Animals

• Gas exchange involves taking in oxygen (O₂) and releasing carbon dioxide (CO₂).
• It is essential for respiration in both plants and animals as well as photosynthesis in plants.

Basic Principles of Gas Exchange

• Gases need a moist environment to dissolve in water before diffusing.
• Thin, permeable membranes facilitate easy gas passage.
• A large surface area enhances gas diffusion efficiency.
• A concentration gradient maintains gas flow.

Gas Exchange in Plants

• Plants undergo both respiration and photosynthesis.
• Plants use CO₂ and produce O₂ during photosynthesis.
• Plants use O₂ and release CO₂ during respiration.

Structures Involved in Plant Gas Exchange

• Stomata are pores on leaves that facilitate gas exchange.
• Guard cells regulate the opening and closing of stomata.
• Mesophyll cells contain chloroplasts for photosynthesis.
• The waxy cuticle prevents excessive water loss.
• The upper epidermis is a protective layer with fewer stomata.
• The lower epidermis contains more stomata for gas exchange.
• Vascular bundles transport water (xylem) and nutrients (phloem).
• Chloroplasts are the site of photosynthesis.

Gas Exchange in Animals

• Oxygen diffuses into the body, and CO₂ is expelled.
• Hemoglobin in blood helps transport O₂.

Types of Gas Exchange Systems in Animals

• Integumentary Exchange occurs through the skin, as seen in flatworms, earthworms, and amphibians like frogs and toads.
• Gills are specialized structures in aquatic animals like fish and amphibians.
• Gills use counter-current exchange to absorb O₂ from water.
• The tracheal system in insects involves a network of air tubes (tracheae).
• Air enters through spiracles and reaches body cells in insects.
• Lungs are found in mammals, reptiles, birds, and amphibians.
• Oxygen enters alveoli, diffuses into the blood, and CO₂ is expelled.

Structures for Gas Exchange in Animals

• The nasal cavity warms and moistens air.
• The pharynx is a common passage for air and food.
• The larynx contains vocal cords.
• The trachea is the air passage to lungs.
• Bronchi are large airways leading to lungs.
• Bronchioles are smaller branches of bronchi.
• Alveoli are tiny sacs where gas exchange occurs.
• The diaphragm is a muscle that aids breathing.

Introduction to Animal Nutrition

• Animal nutrition is the process by which animals obtain, process, and digest food.
• Nutrition is essential for survival, growth, reproduction, and maintaining bodily functions.
• Major nutrients include carbohydrates, fats, proteins, fiber, minerals, vitamins, and water.

Major Classes of Nutrients

Carbohydrates

• Carbohydrates are the main energy source for the body.
• They are converted into glucose for immediate energy use.
• Sources include rice, bread, pasta, fruits, and vegetables.

Fats

• Fats provide concentrated energy, support cell functions, and aid in the absorption of fat-soluble vitamins.
• Saturated fats are solid at room temperature, found in animal products, and increase LDL (bad cholesterol).
• Unsaturated fats are liquid at room temperature and found in fish, nuts, and vegetable oils.
• Monounsaturated fats are found in olive oil, nuts, and avocados.
• Polyunsaturated fats include omega-3 and omega-6, found in fatty fish and seeds.
• Trans fats are artificially modified and harmful to health.

Fiber

• Fiber aids digestion, prevents constipation, and slows down nutrient absorption.
• Sources for fiber include vegetables, fruits, whole grains, and legumes.

Proteins

• Proteins are essential for growth, muscle repair, and enzyme and hormone production.
• Sources include meat, fish, eggs, dairy, and legumes.
• Proteins are needed for body development and milk production in pregnant and breastfeeding women.

Minerals

• Minerals support bone health, nerve function, and metabolic processes.
• Calcium supports bone health.
• Iron supports oxygen transport in blood.
• Potassium and sodium support electrolyte balance.

Vitamins

• Vitamins are essential for various bodily functions, including immunity and metabolism.
• Fat-soluble vitamins (A, D, E, K) are stored in fat and require dietary fat for absorption.
• Water-soluble vitamins (B-complex, C) need regular intake as they are not stored in the body.

Water

• Water is essential for digestion, circulation, and temperature regulation.
• The daily water requirement is 2–3 liters per day.
• Water produces cells and body fluids.
• Aids in sweating and cooling.
• Supports metabolic processes.
• Keeps tissues moist.
• Helps remove waste through urine.

Feeding Mechanisms in Animals

• Substrate feeders live on or inside their food source (e.g., earthworms, caterpillars).
• Filter feeders strain small organisms from water (e.g., whales).
• Fluid feeders suck nutrient-rich fluids from a host (e.g., mosquitoes, leeches).
• Bulk feeders consume large pieces of food (e.g., humans, snakes, lions).

Food Processing in the Human Digestive System

Oral Cavity, Pharynx, and Esophagus

• In the mouth, food is chewed and mixed with saliva.
• The pharynx connects the mouth to the esophagus, ensuring food goes to the stomach and not the lungs.
• The esophagus uses peristalsis (muscle contractions) to move food to the stomach.

Stomach

• The stomach stores and mixes food.
• It secretes gastric juice (HCl and enzymes) to break down food.
• Converts food into chyme (semi-liquid form).

Small Intestine

• The duodenum completes digestion of carbs, fats, and proteins.
• The jejunum and ileum absorb nutrients into the bloodstream.
• Villi and microvilli increase absorption surface area.

Accessory Digestive Organs

• The liver produces bile to digest fats.
• The gallbladder stores bile.
• The pancreas secretes digestive enzymes and insulin.

Large Intestine (Colon)

• The large intestine absorbs water and minerals and processes waste.
• It contains beneficial bacteria that aid digestion.

Rectum and Anus

• The rectum stores waste until elimination.
• The anus expels feces from the body.