IB Biology — Unity, Diversity and Form flashcards
10 of 78 cards free to study here · 2 topics · the whole deck is built into Willys
Themes A (Unity and diversity) and B (Form and function) of the IB Biology course from molecules to ecosystems: water, nucleic acids, cells, viruses, classification, evolution, macromolecules, membranes, gas exchange and transport. HL-only content is tagged HL.
Learn deck · part of IB Biology · written against: IB Diploma Programme IB Biology subject guide for first assessment 2025 (themes A–D); SL and HL in one deck, HL-only cards under subtopic tags starting HL. Updated 2026-10-10.
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Blood plasma carries glucose and amino acids in solution, but cholesterol has to travel inside lipoprotein particles. Which property of water explains the difference?Water is polar, so it forms hydrogen bonds and attractions with polar and charged (hydrophilic) solutes and dissolves them. Cholesterol is largely non-polar (hydrophobic), so it is packaged inside lipoproteins whose surface is hydrophilic.Unity and Diversity › Molecules
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How does adhesion differ from cohesion in water, and which one draws water into the narrow spaces of soil and cell walls?Cohesion is hydrogen bonding between water molecules; adhesion is attraction between water and other polar or charged surfaces such as cellulose. Adhesion drives capillary action, pulling water into narrow spaces.Unity and Diversity › Molecules
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A ringed seal and a person lose body heat at very different rates in water at 0 °C. Why does cold water draw heat away faster than cold air, and how does the seal cope?Water has a far higher thermal conductivity than air (roughly 25 times), so heat leaves a warm body quickly. The seal is insulated by a thick layer of blubber.Unity and Diversity › Molecules
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Compared with air, how do the buoyancy and viscosity of water change the problems a swimming animal faces?Water is dense, so its buoyancy supports body weight and less skeletal support is needed; but it is much more viscous, so drag is high and streamlined body shapes are favoured.Unity and Diversity › Molecules
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What kind of bond links one nucleotide to the next in a single strand of DNA or RNA, and which parts of the nucleotides does it join?A covalent phosphodiester link formed by condensation: the phosphate of one nucleotide bonds to the pentose sugar of the next, building the sugar–phosphate backbone with the bases projecting sideways.Unity and Diversity › Molecules
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Why can carbon form such an enormous variety of biological molecules?Each carbon atom forms four covalent bonds, single or double, so carbon atoms can link into chains, branches and rings of any size with many different atoms attached.Form and Function › Molecules
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Amylose, amylopectin and glycogen are all polymers of α-glucose. How do they differ in branching, and why does branching matter?Amylose is unbranched and coils; amylopectin is branched; glycogen is the most highly branched. More branches mean more chain ends, so glucose can be added or released faster.Form and Function › Molecules
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How does the arrangement of cellulose molecules give plant cell walls their strength?β-glucose units alternate in orientation, making straight chains that lie parallel and hydrogen-bond to one another, forming microfibrils with very high tensile strength.Form and Function › Molecules
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What role do glycoproteins play in the ABO blood group system?The A and B antigens are carbohydrate chains on red-cell surface glycoproteins (and glycolipids). Their exact sugar structure decides blood group and is recognised by antibodies of other blood groups.Form and Function › Molecules
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How is a triglyceride formed, and how many water molecules are released?One glycerol joins to three fatty acids by condensation, forming three ester bonds and releasing three molecules of water.Form and Function › Molecules
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About these cards
Review status: Second-reader reviewed, with corrections applied.
Checked against:
- IB Diploma Programme subject guide (topic outline only; no text copied)
- Tag order follows the IB Diploma Programme Biology guide for first assessment 2025 (themes A–D across four levels of organisation).
- OpenStax Biology 2e, consulted as a reference; no text copied.
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