Capsules

Muscle Contraction

Muscle shortens because two sets of protein filaments slide past one another, driven by myosin heads that repeatedly attach to actin, pivot, and let…

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Aug 4, 2026

The Major Transitions in Evolution

The proposal that the history of life is punctuated by a small number of events in which independently reproducing entities combined into a larger…

The Sexy Son Hypothesis

The proposal that a female may benefit from choosing an attractive mate even if he provides nothing else, because her sons inherit the attractiveness…

The Seed and Soil Hypothesis

The proposal that cancers spread to particular organs not by accident of circulation but because those tissues are hospitable to them. It was…

The Baldwin Effect

The proposal that behaviours learned during life can steer subsequent genetic evolution, without any Lamarckian inheritance of acquired traits. It…

The Krebs Cycle

The central sequence of reactions by which cells extract energy from food. It runs in nearly every organism that uses oxygen, it is the hub where the…

The Blood-Brain Barrier

A selective barrier separating the brain's blood supply from its tissue, admitting what neurons need and excluding almost everything else. It…

The Cell Cycle

The ordered sequence a cell follows to duplicate itself, controlled by checkpoints that stop it proceeding until the previous stage is complete.…

Group Selection

The proposal that natural selection can act on groups as well as individuals, favouring traits that benefit the group at the individual's expense. It…

Niche Construction

The proposal that organisms do not merely adapt to environments but build them, and that the environments they build become selection pressures for…

The Extended Evolutionary Synthesis

The proposal that evolutionary theory needs restructuring to give causal roles to development, inheritance beyond genes, and organisms shaping their…

The Red Queen Hypothesis

The proposal that organisms must keep evolving simply to maintain their position, because everything they interact with is evolving too. It takes its…

Antagonistic Pleiotropy

The proposal that ageing is caused by genes which help early in life and harm later, and which selection favours anyway because early effects matter…

The Disposable Soma Theory

The proposal that organisms age because it is not worth the energy to maintain a body indefinitely when something will kill it anyway. It explains…

The Free Radical Theory of Ageing

The proposal that ageing is cumulative damage from reactive oxygen species produced by normal metabolism. It dominated ageing research for half a…

Clonal Selection

The immune system generates enormous numbers of cells with randomly assembled receptors, and whichever happen to fit an invader are multiplied. It is…

Nitrogen Fixation

Air is nearly eighty percent nitrogen and almost nothing can use it. Breaking the bond that holds the molecule together is what makes proteins and…

Apoptosis

Cells kill themselves on instruction, following a controlled programme that dismantles them tidily. It builds bodies by removing what is not needed,…

Colour Vision

Colour is not a property of light. It is what the visual system computes from the responses of three receptor types, and the computation is what…

The Drunken Monkey Hypothesis

The proposal that the human attraction to alcohol descends from a primate ancestor's taste for fermenting fruit, in which ethanol signalled ripeness…