Biology - Nutrition, Respiration, Circulatory, Excretion

Explore how energy from food is conserved and converted into chemical energy to fuel metabolism, circulation, digestion, growth, and protein synthesis through proper nutrition.

Explore how living beings obtain food and energy, distinguishing autotrophs that synthesize food from carbon dioxide and water, and heterotrophs that rely on organic nutrients.

Explore autotrophic nutrition through photosynthesis, where plants use sunlight, carbon dioxide, and water with chlorophyll to synthesize glucose, store starch, and release oxygen.

Learn how photosynthesis uses chlorophyll in chloroplasts to absorb light energy, split water, and reduce carbon dioxide to produce oxygen and glucose.

Explore how desert plants adapt photosynthesis to extreme dryness, with shallow fibrous roots, thick water-storing stems, and night-time CO2 uptake via stomata, storing intermediates for daytime use.

Plants obtain CO2 from the atmosphere through stomata on the leaf surface. Guard cells open and close stomatal pores to regulate gas exchange, photosynthesis, and water loss.

Explore how plants acquire water and minerals, including nitrogen, phosphorus, potassium, magnesium, calcium, sodium, molybdenum, and other minerals, and how soil fertilizers support growth, photosynthesis, and healthy leaves.

Explore how plants absorb nitrogen from soil compounds like nitrate, nitrite, and ammonia. Fix atmospheric nitrogen in root nodules with rhizobia to enable protein synthesis and photosynthetic product.

Explore heterotrophic nutrition, including mobile vs stationary food sources, extracellular and intracellular digestion, and consumer types—herbivores, carnivores, omnivores, decomposers, and parasites.

Explore how organisms obtain nutrition, comparing unicellular organisms like amoeba with multicellular organisms that use digestive systems to ingest, digest, absorb, distribute nutrients, and excrete wastes.

Explore how humans obtain nutrition through a four-step digestive process—ingestion, digestion, absorption, and elimination—from mouth to anus, involving stomach, liver, pancreas, gall bladder, and intestines.

Explore ingestion and digestion in humans, from mastication and salivary amylase breaking starch to glucose, through peristalsis and stomach acid with pepsin to absorption in the small intestine.

The liver produces bile to emulsify fats in the small intestine, stored and released by the gall bladder. The pancreas provides enzymes to digest fats, proteins, and starch.

Explore how the small intestine's Wylye projections absorb nutrients into blood vessels to energize body cells, while the large intestine reabsorbs water and minerals for feces elimination.

Explains how glucose is broken down through glycolysis and cellular respiration to release energy as ATP, detailing aerobic and anaerobic pathways, fermentation, and mitochondrial roles.

Explore how respiration in plants uses glucose and oxygen to release energy in mitochondria, contrasting it with photosynthesis and highlighting gas exchange through stomata.

Differentiate respiration from breathing as animals exchange oxygen and carbon dioxide with lungs, gills, or skin, while oxygen enables glucose oxidation to ATP in mitochondria.

Explore how aquatic animals respire using gills that exchange dissolved oxygen for carbon dioxide via diffusion, with gill covers protecting the gills and filaments aiding oxygen uptake and blood flow.

Explain the breathing process in humans, showing how inhalation brings oxygen-rich air into the lungs and exhalation releases carbon dioxide via the rib cage, diaphragm, and chest cavity.

Explore the human respiratory system, from nasal passages and pharynx to trachea, bronchi, and alveoli, and learn how oxygen diffuses into blood and carbon dioxide is expelled.

Explore how transportation in the human body moves nutrients, energy, and gases, highlighting ATP as the energy currency and hemoglobin's role in oxygen and carbon dioxide transport.

Learn how blood circulates via arteries, veins, and capillaries to transport oxygen via hemoglobin, nutrients, and medicines, remove carbon dioxide, defend against infection, and regulate body temperature.

Explore the circulatory system’s muscular pump, driven by cardiac tissue and neural impulses, moving oxygenated blood through arteries and returning deoxygenated blood via veins for gas exchange.

Explore the heart's membranes, including the outer fibrous pericardium and inner serous pericardium, the pericardial cavity with fluid, and the heart layers epicardium, myocardium, and endocardium.

Explore heart chamber anatomy, detailing atria and ventricles, left and right, and septum; compare four-chamber mammals and birds with three-chamber reptiles and amphibians, two-chamber fishes, and octopus and squid hearts.

Explore the heart's four chambers, the right and left atria and ventricles, and the valves tricuspid, mitral, pulmonary, and aortic, and how they ensure unidirectional blood flow.

Explore the heart's conduction system, from the SA node to the AV node, Birkinshaw fibers, and how it coordinates atrial and ventricular contraction.

Explore the circulatory system, or cardiovascular system, and learn how the heart and blood vessels deliver oxygen from the lungs to every cell while removing carbon dioxide.

Explore pulmonary, systemic, and coronary circulation, and how they move oxygenated and deoxygenated blood between lungs, body, and heart; compare single and double circulation.

Explore the double circulatory system in humans, detailing pulmonary and systemic circuits, how the heart and lungs exchange gases, and how oxygenated blood reaches body tissues.

Explore the three blood vessel types: arteries, veins, and capillaries, and how they transport oxygenated and deoxygenated blood through the circulatory system, enabling gas exchange and circulation.

Learn how blood clotting occurs in vessels, detailing how platelets and coagulation factors form a fibrin network to stop bleeding and seal injured vessels, with clot dissolution after healing.

Explore the open, non-pressurized lymphatic system with one-way flow, lymph nodes that filter bacteria, and fluid balance across the body.

Learn what blood pressure is, how systolic and diastolic pressures affect the heart, and how to prevent hypertension and hypotension through diet, exercise, and stress management.