148 Fun Facts About Zoology

Which flightless bird is the largest and heaviest bird alive today?

The ostrich cannot fly, but it can sprint at about 70 km/h, and a kick from its two-toed foot is powerful enough to kill a lion.

What are animals called when outside heat, not their own, sets their body temperature?

Ectotherms, such as frogs and lizards, rely on outside heat to set body temperature, which lets them run on very economical metabolic rates; endotherms like mammals generate their own heat.

What is the largest land mammal by weight?

The African elephant is the largest land mammal: bush elephant bulls average around six tonnes, and their huge ears, far bigger than an Asian elephant's, work as radiators that shed body heat.

Which seasonal dormancy, marked by low body temperature, slow breathing and a slow metabolism, lets many animals overwinter?

Hibernation was long reserved for deep sleepers such as rodents, but bears are now counted too: their bodies stay above 30 °C while their metabolism falls to a quarter of normal.

On an insect, which body section carries all six legs and the wings?

The thorax is the insect's engine room: the whole section is specialised for movement, and it holds the muscles that drive the legs and wings.

What is the moulting process called when an insect or crab sheds its inelastic exoskeleton in order to grow?

Ecdysis leaves the animal pale, soft and easy prey until its new skin hardens; the soft-shell crabs on a menu are simply crabs caught just after moulting.

What mimicry involves two or more unpalatable species evolving to resemble each other?

Müllerian mimicry spreads the cost of teaching predators: a bird sickened by one species then avoids every look-alike. Fritz Müller proposed it in 1878 after studying tropical butterflies.

Jellyfish, sea anemones and corals, radially symmetrical animals armed with stinging cells, make up which phylum?

Cnidaria are armed with stinging cells, each a capsule holding a coiled thread that shoots out in a few microseconds when prey brushes against it, drilling in with its barbs to deliver venom.

Insects that undergo 'complete metamorphosis' pass through which four life stages?

Egg, larva, pupa, adult: inside the pupa most of the larva's body is broken down and the adult is built from clusters of cells set aside for the job, which is how a caterpillar comes out as a butterfly.

Which animal has the longest known lifespan of any vertebrate?

The Greenland shark is the longest-lived vertebrate known: 2016 radiocarbon dating of eye lenses put one female at roughly 400 years (at least 272), and the species matures at around age 150.

Marsupials are primarily characterized by what reproductive trait?

Undeveloped young reared in a pouch: a newborn kangaroo, about 2 cm long, blind and hairless, hauls itself through its mother's fur to the pouch with its forelimbs, unaided.

Which of these animals has the strongest bite force recorded?

The saltwater crocodile's bite was measured at 16,414 newtons, the highest recorded for any living animal and over three times a spotted hyena's; bite force rises with body size, and this is the largest crocodilian.

Which seabird's yearly commute to the Antarctic is the longest migration of any bird?

The Arctic tern's round trip came to about 70,000 km a year in a tracking study published in 2010; rather than fly straight, they ride the prevailing winds, heading home in a giant S up the middle of the Atlantic.

Which sensory ability allows bats and dolphins to navigate and hunt in darkness or murky waters?

Echolocation in bats was proved by a Harvard undergraduate, Donald Griffin, who showed they emit ultrasonic calls and steer by the echoes, solving a puzzle left by Spallanzani's bat experiments in the 18th century.

Sea sponges, sessile filter feeders with no organ systems, belong to which animal phylum?

Porifera means 'pore bearer': sponges keep a constant flow of water through their porous bodies to feed, breathe and remove waste, and have no true tissues or organs.

The harmless scarlet kingsnake is a Batesian mimic, copying the red, yellow and black bands of which venomous species?

The coral snake's warning bands protect its mimic only where the real thing lives: field tests found that predators attack kingsnake look-alikes freely in places with no coral snakes.

Which term describes animals whose young are nourished by the mother's body before live birth?

Viviparous birth is no mammal monopoly: bearing live young has evolved independently more than 150 times among vertebrates, most often in lizards and snakes.

Seals, sea lions, and walruses belong to which group of marine mammals?

Pinnipeds are no kin of whales: they are carnivorans descended from land-living ancestors, in the same doglike branch of the order as bears, weasels and raccoons.

Which mammal holds the record for the deepest dive?

Cuvier's beaked whale has been tracked to 2,992 metres, and one stayed under for 222 minutes; down there it hunts squid in total darkness, sucking them into its mouth.

Which bird is known for laying the largest egg relative to its body size?

A kiwi is about the size of a chicken, yet one egg can reach 20% of the female's weight; its huge yolk means the chick hatches feathered and mobile, and is never fed by its parents.

Mammals take their name from which feature, shared by every species in the class?

Milk glands gave mammals their name, from the Latin mamma, 'breast': even the egg-laying platypus, which has no nipples, feeds its young on milk.

What term describes the hollow bones of birds that open into their respiratory system?

Pneumatic bones are air-filled and braced inside by struts; soaring birds have the most, while divers such as penguins and loons have none, since solid bones make it easier to stay under water.

Which insect undergoes incomplete metamorphosis?

A grasshopper skips the pupa: it hatches as a wingless miniature of the adult and moults several times, looking more like the finished insect after each one.

What specialized sensory organ do fish use to detect vibrations and pressure changes in the water?

The lateral line lets fish feel their neighbours: in a classic experiment, blindfolded saithe kept their place in a school, but lost it once their lateral lines were cut as well.

What do you call the study of where species live, across space and geological time?

Biogeography owes much to Alfred Russel Wallace, who noticed in Indonesia that Asian animals give way to Australian ones across a single narrow strait.

Lizards and snakes together make up which order of reptiles?

Squamata is the largest reptile order, and its snakes are in effect lizards that lost their legs over evolutionary time: pythons and boas still carry tiny spurs, the remnants of hind limbs.

Which branch of zoology studies how animals behave, often in the wild?

Ethology treats behaviour as something natural selection has shaped, much as it shaped the body, and asks what survival value each behaviour has.

Which branch of zoology is devoted to reptiles and amphibians?

Herpetology takes its name from the Greek for 'creeping animal': the field is thought to be a holdover from the old habit of classing everything that creeps together.

Whose work on anatomy went largely unchallenged in Europe until the 16th century?

Galen's anatomy, based largely on dissecting pigs and Barbary macaques, was taken as authoritative for some 1,300 years until Andreas Vesalius's De humani corporis fabrica (1543) corrected it from human dissection.

Sharks, rays and chimaeras make up which class of fishes?

Chondrichthyes have skeletons of cartilage, with only the teeth and sometimes the vertebrae hardened, so a whole body fossilises only under special conditions and most fossil sharks are just teeth.

Aristotle spent two years studying marine animals on which Greek island, the home of the poet Sappho?

On Lesbos, Aristotle studied the sea life of a sheltered lagoon so closely that parts of his zoology were not bettered for some two thousand years, until the 19th century.

Which 17th-century microscopist first observed bacteria, calling them 'animalcules'?

Antonie van Leeuwenhoek was a Delft draper, not a trained scholar: he made his own single-lens microscopes and from the 1670s sent the Royal Society reports of 'animalcules' no one had seen before.

Whose 4,500-page Historia animalium appeared in four volumes between 1551 and 1558?

Conrad Gessner, a Swiss naturalist from Zurich, compiled Historia animalium (1551–1558), a 4,500-page encyclopedia of animals that earned him the title of a founder of modern zoology; a fifth volume on snakes appeared in 1587.

Which teacher of Thomas Aquinas wrote commentaries on nearly all of Aristotle's works, animals included?

Albertus Magnus did more than paraphrase Aristotle: he added 'digressions' reporting his own observations, and in 1941 the Church named him patron saint of natural scientists.

Which group of insects is the largest order in the animal kingdom, with hundreds of thousands of known species?

Beetles are so numerous that the biologist J. B. S. Haldane, asked what nature revealed about its Creator, is said to have replied: an inordinate fondness for beetles.

Which explorer-naturalist, namesake of a cold Pacific current, laid foundations for ecology?

Alexander von Humboldt spent 1799 to 1804 in Spanish America, measuring land, weather and living things as he went; on the volcano Chimborazo he climbed higher than any European was known to have gone.

Which pair worked out the double-helix structure of DNA in 1953?

Watson and Crick drew on X-ray data from Rosalind Franklin's lab, including Photograph 51, an image of DNA that was shown to Watson without her knowledge.

Which ship carried Charles Darwin on the five-year voyage that shaped his theory of natural selection?

HMS Beagle was away for nearly five years, and Darwin used his time ashore to collect the plants, animals and fossils that became the evidence for his theory.

Which edition of Systema Naturae is the starting point of zoological nomenclature?

The first edition had classified whales as fishes; by the 10th, Linnaeus had moved them into the mammals.

In a binomial name such as Panthera leo, what does the first word identify?

The genus comes first, so close relatives share a first name: the lion is Panthera leo, the tiger Panthera tigris, and the leopard and jaguar are Panthera too.

Which group of mammals, including the platypus and echidnas, lays eggs?

Monotremes, the platypus and four echidna species, are the only egg-laying mammals; females have no teats and secrete milk through patches of skin for the hatchlings to lap.

Which micro-animals, nicknamed water bears, have survived exposure to outer space?

Tardigrades, dried into a dormant 'tun' state, orbited on the 2007 FOTON-M3 mission exposed to open space; the vacuum proved no problem for them, and they revived once they were given water again.

Which animal has three hearts, two of them dedicated to pumping blood through its gills?

An octopus has three hearts, one for the body and one for each gill; for all that plumbing it gets about mostly by crawling on its arms, jetting off backwards only when alarmed.

Which bird's hunting dive is said to make it the fastest animal on Earth?

The peregrine falcon hunts other birds on the wing: it climbs above them, folds into a dive that can pass 320 km/h, and strikes them in mid-air.

Which salamander normally reaches sexual maturity without undergoing metamorphosis?

The axolotl, native to lakes near Mexico City, keeps its feathery external gills and stays aquatic as a sexually mature adult, a condition called neoteny; injected thyroid hormone can force it to metamorphose.

Which burrowing African rodent was the first mammal found to be eusocial?

The naked mole-rat was identified as eusocial by Jennifer Jarvis in 1981: colonies of up to 300 have a single breeding queen, and the other females are reproductively suppressed, as in ant and termite colonies.

What does a honey bee's waggle dance tell its hive-mates?

Where to find food: the angle of the dancer's waggle run from straight up gives the direction relative to the sun, and the length of the run gives the distance.

Who studied imprinting in goslings, which bond with the first moving object seen after hatching?

Konrad Lorenz showed that greylag goslings imprint on the first moving object they see in the hours after hatching; hand-reared goslings famously followed him around as their 'mother'.

Which German zoologist coined the terms ecology, phylum and phylogeny?

Ernst Haeckel coined all three, but he is best known for a slogan, 'ontogeny recapitulates phylogeny': his since-disproven claim that a growing embryo replays the evolutionary history of its species.

Which French naturalist established extinction as a scientific fact?

Georges Cuvier's 1796 comparison of mammoth and living elephant bones showed that species could vanish; he rejected evolution, favouring repeated catastrophes such as floods that wiped out earlier faunas.

The Wallace Line runs through the strait between Bali and which island?

Lombok and Bali sit only a short hop apart, but the strait between them is a deep-water channel that stayed open sea when ancient sea levels fell, so land animals could not simply walk across.

Which English biologist, nicknamed 'Darwin's Bulldog', gave the Wallace Line its name?

Thomas Henry Huxley named the line in 1868 while studying how gamebirds are spread across the islands; he earned the 'Bulldog' nickname for his vigorous public defence of Darwin's theory.

The first living coelacanth specimen was found in December 1938 off which country's coast?

Off South Africa, a trawler netted the fish in 1938 and museum curator Marjorie Courtenay-Latimer saw it was something special: coelacanths were thought to have died out with the dinosaurs, 66 million years earlier.

Which striped animal of the Congo rainforest is the giraffe's only living relative?

The okapi's striped legs make it look like a zebra's cousin, but its long tongue and short, skin-covered horns mark it as a short-necked relative of the giraffe.

Which flexible rod of cells supports the body of a vertebrate embryo before the backbone forms?

The notochord gives the chordates their name: in animals with no bones, muscles pull against this semi-flexible rod to swim, while in vertebrates the growing backbone surrounds and largely replaces it.

Insects, spiders and crustaceans all belong to which phylum, which holds more than three-quarters of all known animal species?

Arthropoda are named for their jointed limbs; their hard outer skeleton cannot stretch, so every member of the phylum has to shed it and grow a new one in order to get bigger.

Snails, clams and cephalopods belong to which phylum, the second-largest of all?

Mollusca take their name from the Latin for 'soft', yet most species guard that soft body with a shell of calcium carbonate, laid down by a fold of tissue called the mantle.

Adult starfish are built on a five-part plan, but their larvae show which kind of body symmetry?

Bilateral symmetry is the original plan: echinoderms descend from two-sided ancestors, and the five-part body of a starfish or sea urchin only takes shape later, as the larva transforms.

Earthworms and leeches are segmented worms of which phylum?

Annelida are the 'little ring' worms: each ring is a segment with its own muscles, and an earthworm crawls by squeezing and stretching them in waves that ripple down its body.

Thomas Hunt Morgan's genetics work turned which animal into a major model organism?

Morgan began breeding the fruit fly Drosophila melanogaster around 1908 in his Columbia 'Fly Room'; his lab showed that genes sit on chromosomes, earning him the 1933 Nobel Prize.

Which limbless, worm-shaped amphibians make up the order Gymnophiona?

Caecilians take their name from the Latin for 'blind'; in at least one species the brooding mother grows a fatty outer layer of skin, which her young peel off with special teeth and eat.

Which animal, at roughly two grams, is regarded as the smallest living mammal by mass?

The Etruscan shrew is regarded as the smallest mammal by mass; Thailand's bumblebee bat weighs about the same but is shorter, so it takes the title by body length.

Which crustacean strikes with an acceleration of over 10,000 g?

The mantis shrimp's club accelerates at over 10,000 g to about 23 m/s, so prey is hit twice: by the club and by the collapsing cavitation bubbles; aquarists call them 'thumb splitters'.

The 'immortal jellyfish' Turritopsis dohrnii can revert from adult to which stage?

When injured or starved, the adult medusa of Turritopsis dohrnii shrinks, settles and turns back into a polyp, its cells switching type to rebuild the younger body, a cycle it can in theory repeat without end.

Among emperor penguins, which parent incubates the egg through about two months of Antarctic winter?

The male emperor penguin balances the egg on his feet under a fold of skin through about two months of Antarctic winter, eating nothing, while the female returns to the sea to feed.

Which eel-shaped jawless fish defends itself by releasing copious slime?

The hagfish's slime swells almost instantly in seawater and clogs an attacker's gills: predators filmed biting one let go at once and backed away, choking.

Despite the name, the electric eel is a member of which order of South American fishes?

The electric eel is one of the knifefishes, closer kin to catfish and carp than to true eels; it is also an obligate air-breather that must surface regularly to gulp air.

Which python is generally ranked the world's longest snake?

The reticulated python is generally ranked the longest snake: a captive one named Medusa measured 7.67 metres in 2011, though the stockier green anaconda outweighs it.

Which spider is the largest in the world by mass?

The Goliath birdeater is the heaviest spider known, yet despite the name it seldom eats birds: its usual meals are insects, worms and the odd mouse or lizard.

Which insect ejects a near-boiling, foul-smelling chemical spray with a loud pop?

The bombardier beetle mixes hydroquinones and hydrogen peroxide in an abdominal chamber lined with catalase and peroxidase enzymes; the reaction heats the spray to about 100 °C and forces it out with an audible pop.

In the main taxonomic ranks, which level sits between order and genus?

Family sits between order and genus, and animal families are easy to spot: under the zoological code their names must end in -idae, as in Canidae, the dog family.

What do taxonomists call the one specimen chosen to carry a newly described species' name?

The holotype is the name-bearer: however later studies redraw a species' boundaries, its scientific name goes, by definition, with that one specimen.

In which year was the International Commission on Zoological Nomenclature founded?

The International Commission on Zoological Nomenclature was founded in 1895 at the Third International Congress of Zoology in Leiden; it publishes the Code that governs animal names and rules on disputed cases.

Bat wings and whale flippers built from the same ancestral forelimb are examples of what?

Homologous structures were named by the anatomist Richard Owen in 1843, who saw in them a shared plan, not a shared ancestor; it was Darwin who later explained them as inherited from a common ancestor.

Bird, bat and pterosaur wings arose separately yet do the same job, an example of which evolutionary process?

Convergent evolution is the name for it: powered flight arose three separate times among vertebrates, in pterosaurs, birds and bats, each time by reshaping the forelimb in a different way.

Who articulated the biological species concept in 1942?

Ernst Mayr defined a species as a group that breeds only within itself, in Systematics and the Origin of Species; the idea grew out of his expeditions to New Guinea, where he studied how its birds vary from place to place.

Dian Fossey studied mountain gorillas for nearly two decades in which country?

Fossey pitched two tents in Rwanda's Virunga mountains in 1967 and named the camp Karisoke; she studied and defended the gorillas there until her murder in 1985.

Which substrate molecule do fireflies oxidise to produce light?

Luciferin is the fuel and the enzyme luciferase the match: oxidation leaves the molecule in an excited state, and it sheds the extra energy as light. Different glowing creatures use quite different luciferins.

What is the developmental delay insects use to sit out recurring harsh seasons?

Diapause is a programmed arrest of development triggered in advance by cues such as day length, unlike quiescence, a direct response to bad conditions; monarch butterflies overwinter in reproductive diapause.

Dormancy during hot, dry summer months, as in some snails and lungfish, is called what?

Aestivation comes from Latin aestas, 'summer': African lungfish seal themselves in mucus cocoons in dried mud, and land snails seal their shells with a mucus epiphragm until rains return.

Squid and cuttlefish change colour using pigment-bearing cells called what?

Chromatophores in a cuttlefish are tiny elastic sacs of pigment stretched open by muscles, so the animal can change its colour in an instant.

Which branch of zoology is devoted to the study of fish?

Ichthyology counts the Swede Peter Artedi as its father: a gifted classifier of fishes, he drowned in an Amsterdam canal in 1735, aged just 30.

What is the branch of zoology devoted to molluscs called?

Malacology takes its name from the Greek malakos, 'soft', after the soft-bodied animals it studies; it has a medical side too, tracking the molluscs that spread the parasitic disease schistosomiasis.

Insect exoskeletons and squid beaks are built mainly from which tough polymer?

Chitin, a polymer of the sugar N-acetylglucosamine, builds the outer skeletons of insects and crabs and also the cell walls of fungi, so a crab shell and a mushroom share the same building material.

A male narwhal's spiralled tusk, up to 3 m long, is actually an overgrown what?

The narwhal's tusk is a left canine tooth that grows in a spiral through the upper lip; packed with millions of nerve endings, it responds to changes in the saltiness of the water around it.

Which deep-sea animal has eyes about 27 cm across, among the largest of any animal ever measured?

The colossal squid's huge eyes are thought to be an early-warning system: in the dark of the deep sea they could pick out an approaching sperm whale from more than 100 metres away.

Which species is the largest living frog or toad?

The Goliath frog can top 3 kg and 32 cm in body length, yet it starts out ordinary: its tadpoles are the same size as an average frog's, and simply keep growing.

Jonathan, the oldest known tortoise, reached which Atlantic island in 1882?

Saint Helena received Jonathan in 1882 already fully grown, at about 50, which is how his hatching is dated to around 1832; that puts him past 190, older than any other tortoise on record.

Which Arctic species may be the longest-lived of all mammals, passing 200 years?

The bowhead whale may live more than 200 years: stone harpoon tips and a 19th-century bomb lance have been cut out of whales caught in modern times, and chemical dating of their eye lenses backs the estimate.

Ming, found off Iceland and later aged at 507 years, was what kind of animal?

A clam, an ocean quahog: Ming was named for the Chinese dynasty in power when it hatched, and died in 2006 when researchers, unaware of its age, froze it with the rest of their catch.

Why is horseshoe crab blood bright blue?

Its oxygen carrier is copper-based hemocyanin, not iron-based hemoglobin; the blood's cells also clot around bacteria, which is why it is harvested to safety-test vaccines and injectable drugs.

Tiktaalik, a lobe-finned fish with tetrapod features, lived in which period, nicknamed the Age of Fishes?

Devonian rocks in Arctic Canada yielded Tiktaalik, a fish with a neck, shoulders and sturdy wrist bones that could prop itself up in the shallows, some 375 million years ago.

Every Archaeopteryx fossil found so far comes from limestone quarries near Solnhofen in which country?

Germany's Solnhofen limestone splits into smooth slabs that were quarried for lithographic printing, and the fossils turned up in the quarries: hence the species name Archaeopteryx lithographica.

Bombykol, the first pheromone to be chemically characterised, is released by which insect?

The silkworm moth female releases bombykol to draw in mates, and it sets the flightless males off into a fluttering dance; Adolf Butenandt worked out its structure in 1959.

Where on its body does a male platypus deliver its painful venom?

A spur on each hind foot injects venom that males make mainly in the breeding season, which suggests it is a weapon against rival males; in people the pain is excruciating but not lethal.

An anglerfish's lure is a modified version of which body part?

A dorsal fin ray, the foremost one, has moved onto the head as a fishing rod tipped with bait; in deep-sea anglerfish the bait glows, lit by bacteria living inside it.

What is the term for the blood-only diet of vampire bats?

Hematophagy is the whole diet of just three bat species, the only mammals that live on blood alone; they lap it up instead of sucking, and a protein in their saliva named draculin keeps it flowing.

Which wader makes the longest known non-stop flights of any bird, crossing the Pacific from Alaska without landing?

Bar-tailed godwits ride tailwinds across the open Pacific: one tagged female flew 11,680 km from Alaska to New Zealand in eight days in 2007, and tagged birds have since gone farther.

The giant Gippsland earthworm, typically about a metre long, lives wild in only which country?

Australia is its only home, in a small patch of clay soils in Gippsland, Victoria, where hatchlings emerge from their egg capsules already about 20 cm long.

Earthworms have no lungs or gills, so by what route does oxygen reach their blood?

Through their damp skin, which glands keep coated in mucus: oxygen crossing it is picked up by haemoglobin that floats dissolved in the blood plasma.

Giant tube worms, mouthless animals fed by bacteria living inside them, cluster around which seabed features?

Hydrothermal vents pour out the hydrogen sulfide that the worms' internal bacteria turn into nourishment; nobody had seen the animals until a 1977 expedition to the Galápagos Rift.

The common earthworm Lumbricus terrestris is sold to North American anglers as bait under which name?

Nightcrawler is the trade name, often 'Canadian nightcrawler', because the large majority of those sold as fishing bait are gathered in southern Ontario.

Having no teeth, an earthworm grinds its food with swallowed grit inside which muscular organ?

Gizzard muscles squeeze each mouthful against sand grains the worm has swallowed, grinding it to a fine paste, the same trick birds manage with pebbles.

Which belt-shaped glandular swelling near an adult earthworm's front end secretes the cocoon for its eggs?

Clitellum is the pale saddle visible on a mature worm; after mating it secretes a ring that the worm backs out of, and the ends seal into an onion-shaped cocoon.

Which tiny bristle-like hairs on nearly every segment let an earthworm anchor part of its body as it crawls?

Setae grip the burrow wall so one stretch of the worm holds fast while the rest reaches forward; special ones on the underside even pin mating worms together.

Earthworm blood stays confined inside vessels for its whole circuit, an arrangement known by which term?

Closed circulation means the blood never spills out to bathe the organs; in an earthworm, paired aortic arches act as simple hearts to keep it moving.

Which natural anticoagulant in a medicinal leech's saliva keeps blood flowing freely from the bite?

Hirudin blocks thrombin, the enzyme that makes blood clot; John Berry Haycraft discovered it in 1884, and it went on to inspire a line of clot-preventing drugs.

Marine bristle worms such as ragworms swim and crawl using which paired fleshy flaps on each body segment?

Parapodia work as paddles and, in many species, as gills too, since their rich blood supply makes them the worm's main breathing surface.

Nearly all animal phyla first appear in the fossil record in which burst of evolution over 500 million years ago?

Cambrian explosion rocks hold the first appearances of practically every animal phylum, all within a geological eyeblink of some 13 to 25 million years.

Which of these sea creatures belongs to the phylum Echinodermata alongside starfish and brittle stars?

Sea cucumber is the odd-looking member: it breathes through branching 'cloacal trees' in its rear end and sifts sediment with tube feet reshaped into tentacles around its mouth.

Tapeworms and flukes belong to Platyhelminthes, a phylum of animals known by which common name?

Flatworms have no lungs, gills or blood vessels, which is exactly why they are flat: every cell must lie close enough to the surface for oxygen to reach it by diffusion.

Snails and slugs make up which class of animals?

Gastropoda holds an estimated 65,000 to 80,000 living species, and each one twists its body through 180 degrees as it develops, a contortion known as torsion.

Starfish extend and retract their hundreds of tube feet using which network of fluid-filled canals?

Water vascular system canals shift fluid into or out of each tube foot to stretch or shorten it, and the same plumbing helps the animal breathe, feed and sense its surroundings.

The phylum Ctenophora consists of which sea animals, the largest creatures that swim by beating cilia?

Comb jellies row themselves along with eight bands of beating cilia and snare prey with sticky cells called colloblasts, a weapon found in no other animal.

What name is given to the fluid-filled body cavity, lined with mesoderm, that surrounds the gut in many animals?

Coelom fluid absorbs shocks and lets the gut and other organs move and grow freely; in many soft-bodied animals it also stiffens the body as a liquid skeleton.

Caenorhabditis elegans, the first animal to have its whole genome sequenced, belongs to which phylum?

Nematoda gave science a millimetre-long laboratory star: the same worm was also the first animal to have the wiring of its nervous system mapped, all 302 neurons of it.

Which many-legged animals of the phylum Onychophora catch prey by squirting jets of sticky slime?

Velvet worms, named for their velvety skin, glue down other small creatures with the slime before eating them, and some species even give birth to live young.

Which sea animals of the phylum Brachiopoda resemble clams but carry their two valves on top and bottom?

Lamp shells take their name from valves shaped like pottery oil lamps; they were more varied than clams and their kin in Palaeozoic seas but never recovered from the end-Permian mass extinction.

Spiders, ticks, mites and harvestmen belong to which class of mostly eight-legged animals?

Arachnida members carry four pairs of legs on a two-part body, and none has the antennae or wings that mark out an insect.

Which small swarming animals of the Southern Ocean are the main food of baleen whales such as the blue whale?

Krill take their name from a Norwegian word for small fry, yet the Antarctic species alone adds up to an estimated 379 million tonnes of living animal.

Which many-legged animals carry two pairs of legs on most of their body segments?

Millipedes are named for a thousand feet, yet no species was known to reach that total until Eumillipes persephone turned up in 2020 with more than 1,300 legs.

Which eight-legged predators glow a vivid blue-green under ultraviolet light because of chemicals in their cuticle?

Scorpions fluoresce so reliably that a hand-held ultraviolet lamp is the standard tool for surveying them at night, and the glow grows stronger each time one sheds its skin.

Which armoured sea animals, fossils spanning almost 270 million years, vanished in the end-Permian extinction?

Trilobites were among the earliest jointed-legged animals in the fossil record, with over 22,000 species described, yet only a handful were left when the end came.

Which sea creature holds the record leg span among all jointed-legged animals, about 3.7 metres from claw to claw?

Japanese spider crab bodies stay modest, about 40 cm across, because the shell stops growing at maturity while the legs keep on lengthening.

A spider draws out its silk through which organs, usually found on the underside of its abdomen?

Spinnerets let a spider combine several filaments into different silks for webs, egg cases, wrapping prey and even ballooning through the air on a thread.

Insects have no lungs and instead take in air through which small openings in the exoskeleton?

Spiracles lead into branching air tubes that reach the tissues directly, and a flying insect can widen or narrow them to balance its oxygen supply against water loss.

Which fluid, the insect counterpart of blood, fills the body cavity and washes directly over the organs?

Hemolymph surrounds every cell in an insect's body, but it carries little oxygen, because air reaches the tissues through a separate set of tubes.

The compound eye of a fly or dragonfly is built from many repeating optical units known as what?

Ommatidia each supply one picture element, so the eye sees a mosaic; a Drosophila eye packs 700 to 750 of them into a neat repeating pattern.

Which physiologist's work with salivating dogs revealed how animals learn to link a neutral signal with food?

Ivan Pavlov won his 1904 Nobel Prize for work on digestion, not learning; the discovery that made him a household name grew out of those same dog experiments.

Whose 1960 sighting of chimpanzees fishing for termites with grass stalks showed humans are not the only toolmakers?

Jane Goodall had no university degree when Louis Leakey sent her to Gombe; she also watched chimps strip the leaves from twigs to make better probes, the beginnings of toolmaking.

Monarch butterflies from eastern North America fly each autumn to overwinter in the mountains of which country?

Mexico is the journey's end, yet no butterfly makes the round trip: the southbound generation lives about eight times longer than its parents, and its descendants fly north in relays.

Zoologists call an animal such as the mule deer crepuscular when it is mainly active at which times?

Dawn and dusk activity is thought to be mainly a way of dodging predators that hunt in full darkness or full sun; the word comes from the Latin for twilight.

The phrase 'pecking order' comes from a 1920s study of the dominance ranking among which animals?

Chickens settle rank by pecking, as Thorleif Schjelderup-Ebbe described in 1921, and a stable ranking suits the whole flock: fewer challenges leave more resources for laying eggs.

Which horse of the early 1900s seemed to do arithmetic but was really reading his trainer's unwitting body language?

Clever Hans tapped out answers with a hoof until psychologist Oskar Pfungst showed in 1907 that he was right only when he could see a questioner who already knew the answer.

B. F. Skinner taught rats to press levers for rewards, a form of learning known as what?

Operant conditioning shapes behaviour through its consequences, reward making an action more frequent and punishment less; Skinner disliked the label 'Skinner box' for his apparatus.

A cuckoo laying its egg in another bird's nest, leaving the hosts to raise the chick, is practising what?

Brood parasitism has set off an arms race: hosts learn to spot and eject foreign eggs, so the intruder's eggs have evolved to mimic theirs ever more closely.

Sterile worker bees raising a queen's offspring instead of their own are a classic case of which evolutionary idea?

Kin selection solves a puzzle that troubled Charles Darwin: workers that never breed can pass on their genes all the same by helping a mother who shares them.

Male black grouse gather to strut and fight for visiting females at a communal display ground known as what?

Lek comes from a Swedish word for play, though the contest is serious: females tour the gathering to choose a mate, and in black grouse they prefer the most aggressive fighters.

Which naturalist formalised the two-part Latin names that scientists give to every animal species?

Carl Linnaeus, remembered as the father of modern taxonomy, carried a botanical name himself: the surname was taken from a giant lime tree that grew on the homestead.

Along with the common chimpanzee, which ape of the Congo Basin is the closest living relative of humans?

Bonobo and chimpanzee ranges are kept apart by the Congo River, a barrier that neither ape swims well enough to cross.

The giant panda was confirmed as a true bear in 1985 after a long debate over its likeness to which other animals?

Raccoons share enough features with the animal to have kept the question open for decades, and the name panda first belonged to the red panda, described some 40 years earlier.

DNA and fossil evidence show that whales and dolphins have which land mammals as their closest living relatives?

Hippos and whales descend from a shared semi-aquatic ancestor and parted ways about 55 million years ago; until 1909 naturalists had grouped hippos with pigs because of their molars.

Modern classification places birds within which group of dinosaurs, the lineage that included Tyrannosaurus?

Theropods count every living bird among their number, which makes birds the only dinosaurs alive; the group first appeared in the Late Triassic, about 231 million years ago.

Rabbits, hares and pikas resemble rodents but belong to which separate order of mammals?

Lagomorpha members are told apart from rodents by their teeth: a rabbit has four upper incisors where a rat or squirrel has only two, and all of them keep growing for life.

Which reptile resembles a lizard but is the sole survivor of an order that flourished in the age of dinosaurs?

Tuatara live only in New Zealand, and their order was once the world's dominant group of small reptiles before it dwindled away everywhere else.

In deuterostomes such as starfish and humans, the embryo's first opening, the blastopore, becomes which body part?

Anus first, mouth second is the rule that names the group: 'deuterostome' is Greek for 'second mouth', because the gut tunnels through the embryo to open the mouth later.

A scientific name such as Rattus rattus, in which both parts are spelled identically, is known as what?

Tautonym names are welcome in zoology, hence Bison bison and Gorilla gorilla, but the botanical code bans them outright, so no plant can carry one.

Because it leaves out birds, the traditional class Reptilia is an example of which kind of incomplete group?

Paraphyletic groups keep an ancestor but drop some of its descendants; the zoologist Willi Hennig coined the term with cases like the reptiles in mind.