S phase The synthesis phase of the cell cycle; the portion of interphase during which DNA is

replicated.

SA (sinoatrial) node

The pacemaker of the heart, located in the wall of the right atrium. At the base of the

wall separating the two atria is another patch of nodal tissue called the atrioventricular

node (AV).

sac fungi

Members of the phylum Ascomycetes, these range in size and complexity from unicellular yeasts to minute leafspot fungi to elaborate cup fungi and morels. About half of the sac

fungi live with algae in the mutualistic associations called lichens.

saccule A chamber in the vestibule behind the oval

window that participates in the sense of balance.

salivary amylase A salivary gland enzyme that hydrolyzes starch.

salivary glands

salt

saltatory conduction

saprobe

scarcomere

sarcoplasmic reticulum

saturated fatty acid

savanna

scaffolding protein

scanning electron microscope (SEM)

schizocoelous

Schwann cells

scion

sclera

sclereid

sclerenchyma cell

scrotum

scutellum

seascape

second law of thermodynamics

second messenger

secondary cell wall

secondary compound

secondary consumer

secondary growth

secondary immune response

secondary oocyte

secondary plant body

secondary production

secondary structure

secondary succession

secretion

secretory phase

sedimentary rock

seed

seed coat

seedless vascular plants

segmentation genes

segment-polarity genes

selection coefficient

selective channels

selective permeability

self-incompatibility

semelparity

semen

semicircular canals

semiconservative model

semilunar valve

seminal vesicle

seminiferous tubules

sensation

sensitive period

sensory adaptation

sensory division

sensory input

sensory neuron sensory reception sensory receptor

sensory transduction sepal septa

sequential hermaphroditism

serotonin seta

sex chromosomes sex-linked gene

sexual dimorphism sexual reproduction

sexual selection shared derived character shared primitive character

shoot system short-day plant

short-term memory sickle-cell disease

sieve plate

sieve-tube members sign stimulus

signal signal peptide

signal recognition particle (SRP)

signal-transduction pathway

signature sequences simple epithelium single nucleotide

polymorphisms (SNPs) single-lens eye

single-strand binding protein

sink habitat sinuses

sister chromatids skeletal muscle

sliding-filament model slow block to polyspermy

slow muscle fibers small intestine small nuclear

ribonucleoprotein (snRNP) smooth ER

smooth muscle snowball Earth social behavior

sociobiology

sodium-potassium pump solute

solution solvent

somatic cell somatic nervous system

somites soredia

sori source habitat

Southern blotting specialized transduction

speciation species

species diversity species richness species selection

species-area curve specific epithet

specific heat spectrophotometer

spermatheca spermatogenesis

spermatozoon sphincter

spinal nerve spiral cleavage

spiral valve spliceosome spongocoel

spontaneous generation sporangium

spore spore mother cells

sporophylls sporophyte

sporopollenin sporozoites squamata squamous stability

stabilizing selection stamen

standard metabolic rate (SMR) stapes starch

statocyst statolith

stele stem cell

stenohaline stereoisomer

steroids sticky end

stigma stipe stock stoma

stomata

Stramenopila stratified epithelium

stress-induced proteins strict aerobe

strict anaerobe stroke volume

stroma stromatolite

structural formula structural isomers

style substance P

substrate substrate-feeders

substrate-level phosphorylation

sugar sink sugar source

sulfhydryl group summation

supporting cell suppressor T cell (TS) suprachiasmatic nuclei

(SCN) surface tension

survivorship curve suspension-feede

sustainable agriculture sustainable development

swim bladder

symbiont symbiosis

sympathetic division sympatric speciation

symplast synapomorphies

synapse synapsids synapsis

synaptic cleft synaptic terminal synaptic vesicles

syngamy systematics

systemic acquired resistance (SAR)

systemic circulation systole