Biology: Botany and Zoology
Biology splits into Botany and Zoology, and UPCATET mixes recall (classification, terminology) with reasoning (crosses, physiological cause–effect, ecological pyramids).
Botany
Photosynthesis: the light reactions on thylakoid membranes generate ATP and NADPH; the Calvin cycle in the stroma fixes CO₂ through RuBisCO, using 3 ATP and 2 NADPH per CO₂. C₄ plants concentrate CO₂ in bundle-sheath cells and suppress photorespiration. Xylem carries water and minerals upward; phloem translocates sucrose in any direction. Transpiration pull, root pressure and the cohesion–tension mechanism explain water movement.
Zoology
Digestion, circulation, respiration, excretion, nervous and endocrine coordination, reproduction and genetics. In the human heart the pulmonary artery carries deoxygenated blood and the pulmonary vein oxygenated blood - the reverse of the systemic rule. In the nephron, filtration occurs in the glomerulus, reabsorption in the proximal tubule, and ADH controls water reabsorption in the collecting duct.
Worked example
Cross AaBb × AaBb with independent assortment. Each parent produces four gametes (AB, Ab, aB, ab) in equal proportion, so the Punnett square has 16 cells. Phenotypes segregate 9:3:3:1, and the double recessive aabb occupies one cell, i.e. 1/16 = 6.25%. For Aa × Aa alone the genotypic ratio is 1:2:1 while the phenotypic ratio is 3:1 - examiners exploit exactly this confusion.
Traps
Quoting 9:3:3:1 for a single gene; mixing mitosis (two diploid cells) with meiosis (four haploid cells); saying arteries always carry oxygenated blood; reversing xylem and phloem; confusing the sites of light and dark reactions.