Foundations

Shared ancestry and independent similarity are different explanations.

Bacteria, archaea and eukaryotes differ in important cellular organization.

Vascular plants move water and organic solutes through different transport tissues.

Diffusion across exchange surfaces and bulk transport serve different roles.

Membrane electrical changes and synapses connect neural cells.

Animal hormones influence cells that possess appropriate response machinery.

Kidney tubules modify filtered fluid through selective transport.

Simple growth equations expose assumptions about density dependence.

Interaction categories describe effects on participating populations.

Production is a flow over time, whereas biomass is a standing amount.

Repeated samples can estimate a population under explicit sampling assumptions.

Barrier and recognition mechanisms cooperate with antigen-specific responses.

The placement of meiosis and fertilization differs among life cycles.

Regulated cell states, division and spatial organization produce multicellular form.

An ion's equilibrium potential balances its chemical and electrical driving terms.

Eukaryotic protein abundance depends on synthesis and degradation.

In representative animal apoptosis pathways, activated initiator caspases promote an execution cascade that cleaves cellular targets.

Base-excision repair begins when a glycosylase removes a recognized damaged base, leaving a site that is processed and restored by DNA synthesis and ligation.

End joining can restore continuity of a double-strand-broken DNA molecule without using a long homologous donor template.

Sensory receptors convert appropriate physical or chemical stimuli into changes in cellular electrical signalling.

The experimental unit is the entity independently assigned to a treatment in a specified design.

In the mammalian nephron model, selective tubular transport modifies filtered fluid.

Vasopressin released from the posterior pituitary can increase collecting-duct water permeability through aquaporin insertion.

In the vertebrate thyroid-axis example, hypothalamic signals stimulate pituitary hormone release, which stimulates the thyroid.

In the mammalian model, pancreatic insulin and glucagon coordinate nutrient use and storage with blood-glucose availability.

Gases diffuse across respiratory surfaces down their own partial-pressure gradients.

Mammalian ventilation moves air when respiratory-muscle action changes thoracic volume and pressure.

Coordinated electrical activation drives atrial and ventricular contractions.

Myosin interaction with actin converts ATP-dependent molecular cycling into force.

In the vertebrate digestive example, signals coordinate secretion, motility and delivery of material between compartments.