Foundations

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.

Bacteria and archaea have distinct cell-envelope and molecular organizations despite both lacking a membrane-enclosed nucleus.

Phototrophy and chemotrophy describe energy sources; lithotrophy and organotrophy describe electron donors; autotrophy and heterotrophy describe carbon sources.

Viruses depend on host-cell systems for replication.

Fungi are eukaryotic absorptive heterotrophs that secrete enzymes and take up released nutrients.

Protist is a convenient description for diverse eukaryotes outside the familiar animal, plant and fungal categories rather than one natural monophyletic group.

Plant meristems supply dividing cells for growth; apical and lateral meristems contribute to length and girth in the stated vascular-plant model.

Plant growth responds to interacting chemical and environmental signals.

In the sexual seed-plant life cycle, reduced gametophytes participate in pollen-mediated reproduction and ovules develop into seeds following the appropriate fertilization sequence.

Epithelial, connective, muscle and nervous tissues contribute different structural and functional roles in animal organs.

In the neuronal model, voltage-dependent ion conductances create regenerative action potentials followed by refractory behaviour.

Animal embryogenesis includes division of the zygote, tissue rearrangement and differentiation.

Community composition depends on interactions and environmental conditions.

A food web represents multiple feeding connections, including detrital pathways.

Nitrogen fixation converts N₂ toward biologically usable reduced nitrogen; ammonification, nitrification and denitrification transform nitrogen among distinct chemical pools.

Biodiversity includes genetic, species and ecosystem dimensions.

A cohort life table follows individuals born together.

In a fixed density-independent age model, the growth factor λ satisfies Σ_{x≥1}λ^(−x)l_xm_x=1.

A simple internally colonized metapopulation tracks the occupied fraction p of equivalent habitat patches.

Failure to detect a species does not establish absence.

For a collection containing N individuals with N_i in each observed species, the expected species count in a uniformly drawn subset of n individuals without replacement is E[S_n]=Σ_i[1−C(N−N_i,n)/C(N,n)].

A genetic perturbation tests a causal prediction when the intended change and relevant phenotype are measured against appropriate controls.

Ecological levels describe different interacting sets and environments.

Total individuals and individuals per area or volume must be distinguished.