aerobic afterbirth algae alimentary canal amber ameba amino acid amoeba anaconda anaerobic androgynous antibody antigen antitoxin appendage arm armour asexual assimilation atrophy aviary bacteria bacteriology barnacle bile binocular vision bio- biochemistry biodegradable biodiversity biological biological clock biology biomass biome biosphere blind brain breathe breed(v) breed(n) breeding bristle bulb capsule carbohydrate carbon dioxide carnivore cell cellular cellulose central nervous system cervical cholesterol chromosome circulation circulatory class clone cold-blooded conceive conch connective tissue copulate coral reef cornea coronary corpuscle cortex cortisone cowrie crab crawfish crayfish creature cross crossbreed culture decay(v) decay(n) decompose defecate denizen dextrose diaphragm digest digestion digestive DNA dorsal dry rot duct dwarf(n) dwarf(a) ecological ecology ecosystem egg ejaculate embryo embryonic enzyme epidermis evolution evolutionary excrement excrescence excrete excretion exhale extinction faeces family fang fat fatty acid fauna feces feed female(a) female(n) ferment(v) ferment(n) fertile fertility fertilize fission flank flatulence flesh fleshy flightless flora foetal foetus foliage fossil freak freshwater fructose gamete ganglion gene gene pool genera genetic genetic code genetic engineering genetic fingerprinting genetics genome genus gestation gland glandular glucose gluten gonad grass snake grow growth habitat haemoglobin hearing heart hemisphere herbivore hereditary heredity hermaphrodite hibernate histamine homing hormone host impregnate impulse incubate indigenous infected infertile infest ingest inhale inseminate insensate insulin integument intercourse interferon intestine invertebrate involuntary iris jaw jelly kidney krill lactate lactation lactic acid leech leg lesser lichen life life cycle life form ligament limb limpet lipid liver living fossil locomotion lymph lymph node male(a) male(n) mammal mandible mate(n) mate(v) membrane metabolism metabolize metamorphosis microbe microbiology microorganism microscopic migrate migratory miscarriage molar morphology motor mould mouth mucous membrane mucus muscle muscular mutant mutate mutation natural history natural selection nature neck nectar nerve nervous nervous system neural neuro- neurology node nose nostril nucleic acid nucleus nutrient nutriment oesophagus oestrogen olfactory optic organ organic organic chemistry organism orifice ossify osteo- outgrowth ovary overwinter oviduct oviparous ovulate ovum parasite pathogen pedigree pelvic pelvis penile penis pepsin period perspiration perspire photosynthesis phylum pigment pigmentation plankton plasma pollinate postnatal pregnancy pregnant premature prenatal product proliferation propagate protein protoplasm protozoan puberty pulmonary pulp pulsation putrefy putrid red blood cell regurgitate renal reproduce reproduction reproductive respiration respiratory respire retina root rot(v) rot(n) ruff sac saliva salivary gland salivate saltwater scale scallop scaly sebaceous secrete secretion semen sense organ sensory serum sex(n) sex(v) sexless sexual intercourse sheath shell sibling skeletal skeleton skin skull spasm spasmodic species specimen sperm spiderweb spinal cord spine spineless starch stem cell stimulate stimulus strain subject subspecies sucker sucrose sweat(v) sweat(n) sweat gland symbiosis systemic tail taxonomy teeth testosterone test-tube baby tissue trachea tube urethra uric urinate urine variety vector vein venom venomous ventricle vertebra vertebrate vivisection warm-blooded wean wildlife windpipe yolk