Field
Life
Kinship written in cells, selection, and shared code.
89 entries
Every cell on Earth is kin
All known terrestrial life shares a common ancestor. The evidence is a nested hierarchy of traits plus a shared genetic code.
Heredity is a molecule
DNA is the hereditary material of cellular life. Its double helix stores sequence information that is replicated and transcribed.
Selection writes the fit
Heritable variation plus differential reproduction produces adaptation. This is natural selection.
A tree is built mostly from air
The dry mass of a tree is chiefly cellulose and lignin made from carbon dioxide. The carbon came out of the atmosphere, not out of the soil.
Sharks were swimming before trees stood
Shark-like fishes appear in the fossil record before the earliest trees. Teeth and scales of chondrichthyans predate Archaeopteris.
Birds are dinosaurs
Birds sit inside Dinosauria. They are the living continuation of theropod dinosaurs, not a neighbouring class that merely resembles them.
The whale’s closest living cousin is the hippo
Molecular phylogeny places whales inside the even-toed ungulates, with hippos as their nearest living relatives.
Your mitochondria used to be free
Mitochondria descend from bacteria that took up residence inside another cell. They still carry their own circular genome.
Ants invented farming long before we did
Leafcutter ants grow a fungus on harvested leaves and have done so for tens of millions of years. The fungus is their crop.
A slime can solve a maze
The plasmodium of Physarum polycephalum finds the shortest path through a maze by growing toward food and letting dead ends starve.
Some animals survive the vacuum
Tardigrades in a dried tun state have survived exposure to open space on a satellite, including vacuum and, with some shielding, solar ultraviolet.
Wombat dung is a cube
Bare-nosed wombats produce roughly cubic feces. The corners are formed by a stiff intestine of uneven elasticity, not by a square hole.
A shrimp punch boils the water
The peacock mantis shrimp’s club strike is so fast it cavitates seawater. The bubble collapses and adds a second blow, with a brief temperature of thousands of degrees.
A snap in the ocean is briefly as hot as the sun
The pistol shrimp’s claw collapses a cavitation bubble that reaches about 5,000 K and emits a flash and a crack louder than a gunshot.
A jellyfish can age backwards
Turritopsis dohrnii can revert from a free-swimming medusa to a juvenile polyp, rewriting its life cycle instead of dying after spawning.
A shark can be older than a nation
Eye-lens radiocarbon dates Greenland sharks at lifespans of centuries. One large female was estimated at about 400 years, with a wide uncertainty.
A bird flies an ocean without landing
Satellite-tracked bar-tailed godwits fly nonstop from Alaska to New Zealand, more than 11,000 kilometres, in about eight or nine days.
Some birds sleep while flying
Great frigatebirds sleep in flight, mostly with one hemisphere at a time, for minutes at a stretch, on trips that last weeks.
Bees tell each other where the flowers are
A honey bee’s waggle dance encodes the direction and distance of food. Other bees read it in the dark and fly the route.
A cat cannot taste sugar
Cats lack a working sweet receptor. The Tas1r2 gene that encodes one half of it is a pseudogene in all felids tested.
Every clownfish starts as male
Clownfish are protandrous hermaphrodites. Juveniles mature as males. The dominant fish in a group becomes the female.
A dragon can reproduce alone
Female Komodo dragons can produce viable offspring by parthenogenesis. It has been documented in zoos in females kept without males.
Most of an octopus thinks in its arms
About two thirds of an octopus’s neurons are in the arms, not the central brain. Each arm can organise reaching and touch locally.
Some blood runs blue
Octopuses, horseshoe crabs, and many other animals carry oxygen with copper-based hemocyanin. Oxygenated, it is blue.
Almost none of your genome is genes
About one to two percent of the human genome codes for proteins. The rest is regulatory sequence, introns, and a great deal of repeats.
A mushroom is closer to you than to a rose
Fungi share a more recent common ancestor with animals than either does with plants.
The largest organism is a fungus
A single honey fungus in Oregon, Armillaria ostoyae, occupies on the order of ten square kilometres of forest floor.
A frog freezes and then walks away
The wood frog spends northern winters frozen. Its heart stops, ice forms between its cells, and in spring it thaws and moves.
A living tree is older than the pyramids
At least one Great Basin bristlecone pine alive today germinated before the Great Pyramid was built.
The ocean holds more viruses than the sky holds stars
A standard estimate puts on the order of 10 to the 30 virus particles in the oceans. The observable universe holds on the order of 10 to the 22 or 10 to the 24 stars.
Half of photosynthesis happens in the water
About half of Earth's net primary production — the carbon fixed by photosynthesis — takes place in the ocean.
The platypus lays eggs, makes milk, and carries venom
The platypus is a mammal that lays eggs, feeds its young on milk secreted through the skin, and, in the male, has a venomous spur.
The father gives birth
In seahorses, the male carries the pregnancy. The female deposits eggs in his brood pouch, and he bears them until they are born.
A fish returned from the fossil record
The coelacanth was known as a Cretaceous fossil until a living one was caught off South Africa in 1938. A second species was later found in Indonesia.
A polar bear is not white
The hairs of a polar bear are unpigmented and translucent. The skin underneath is black. The coat looks white because the hairs scatter visible light.
An octopus keeps three hearts
Two branchial hearts pump blood through the gills. A third, the systemic heart, pumps it through the body. During jet swimming the systemic heart pauses.
A beetle fires a boiling spray
The bombardier beetle mixes reactants in a reaction chamber and ejects a pulsed spray of hot quinones, near the boiling point of water.
Eight percent of the genome is old virus
About eight percent of human DNA is the remains of retroviruses that inserted themselves into the germline and were inherited. Nearly all of it is broken.
The fungus steers the ant through its muscles
Ophiocordyceps makes an infected ant climb, bite, and die in a place that suits the fungus. The fungal network surrounds the muscles. It does not fill the brain.
A lungfish sleeps through the drought
When its pool vanishes, an African lungfish burrows, secretes a cocoon of mucus, and estivates. Animals have been watched in that state for many months, and the classical accounts run past a year.
A chameleon changes colour by retuning a crystal
The rapid colour shift is a change in the spacing of guanine crystals in a skin cell, which changes which wavelength they reflect. It is a lattice, not a dye being pumped.
A young albatross does not land for years
After it fledges, a wandering albatross stays at sea continuously for three to seven years before it returns to a colony.
A blue whale’s heart can fall to two beats a minute
A tagged blue whale, diving off California, had a heart rate of four to eight beats a minute at depth, and at moments two. At the surface the same heart reached the high thirties.
A bacterium can be longer than a fly
Thiomargarita magnifica, from Caribbean mangroves, has cells averaging longer than nine millimetres. They are visible without a microscope. The DNA sits in membrane-bound compartments.
The most abundant photosynthetic thing was missed until 1988
Prochlorococcus is a cyanobacterium smaller than a micrometre, and it is the most numerous photosynthetic cell in the ocean. It was described in 1988 because it slipped through the nets.
A whale was still carrying a nineteenth-century harpoon
Bowheads landed in the late twentieth century contained harpoon points of a kind last made in the nineteenth. Lens chemistry puts some of these whales past a hundred years, and a few estimates near two centuries.
A date seed from Masada sprouted
A date seed excavated at Masada, radiocarbon-dated to the first century, was germinated in 2005 and grew like an ordinary date seedling.
A gecko sticks without glue
A gecko’s toe is covered in hundreds of thousands of hairs, split at the tips into still smaller pads. The force holding it to the wall is intermolecular attraction, and the toe lets go by changing its angle.
A cicada spends seventeen years underground, then comes up with all the others
Periodical cicadas live as nymphs below ground for 13 or 17 years, feeding on the sap of roots. Then a whole brood emerges within days, mates, and is gone in weeks.
In some anglerfishes, the male fuses to the female
In certain deep-sea anglerfishes a tiny male bites a female and the tissues join. His blood supply becomes hers. He lives on as a source of sperm, fed by her bloodstream.
A turtle’s shell is its ribs
The carapace is not a house the animal sits in. It is the backbone and the ribs, grown outward and fused into bone the shoulder blades end up inside.
A fish in the Antarctic has no haemoglobin
Icefish have no red blood cells and no haemoglobin. The blood is clear. Oxygen rides in the plasma, and the cold sea holds enough of it for that to work.
A sea slug keeps the chloroplasts of the algae it eats
Elysia takes chloroplasts from its food and holds them inside its own cells, where they go on absorbing light for weeks to months. The slug does not make them, and it does not become a plant.
A Venus flytrap counts to decide whether the meal is real
Two touches on the trigger hairs, within about twenty seconds, shut the trap. Further touches — about five — start the digestive glands. The tally is a series of electrical impulses.
A thousand amoebae can become one crawling thing
When Dictyostelium runs out of bacteria, the separate cells signal, stream together, and assemble into a slug that migrates as a single body. Then some of them die to build a stalk.
A dolphin sleeps with one half of the brain
In slow-wave sleep, dolphins put one hemisphere to sleep at a time. The other stays awake, one eye stays open, and the animal surfaces to breathe.
An Arctic tern flies nearly twice around the Earth in a year
Geolocators on Arctic terns recorded annual trips of about seventy thousand kilometres, and more than eighty thousand for some birds. The circumference of the Earth is forty thousand.
A wild bird recruits people to open a bees’ nest
The greater honeyguide leads honey-hunters to a hive it cannot open, with a call and a flight from tree to tree. The people smoke the bees and break in. The bird eats the wax.
A bird’s breath does not come back the way it went
Air flows through a bird’s lung in one direction, from back to front, both when the bird inhales and when it exhales. The air sacs, not the lungs, are the bellows.
Dragonflies arrive across open ocean, where no larva could have lived
Globe skimmers turn up on islands and ships hundreds of kilometres from the nearest fresh water. Their young can develop only in fresh water. The adults crossed.
A bacterium can have its genome shattered and stitch it back
Deinococcus radiodurans survives acute radiation of thousands of grays, which shatters its chromosomes into hundreds of pieces. It then reassembles them. A few grays kills a person.
An octopus edits its RNA, especially in the nervous system
Cephalopods recode RNA transcripts at tens of thousands of sites, heavily in the nervous system, far beyond what a vertebrate does. The genome says one thing. The message that is read often says another.
A reindeer’s eyes change colour in winter
The mirror behind a reindeer’s retina is gold in summer and deep blue in winter. The shift tracks the months of darkness, and it changes which light is reflected back through the retina.
A Portuguese man-of-war is not one animal
Physalia is a siphonophore: a colony of specialised individuals — the float, the stinging tentacles, the feeding parts, the reproductive parts — budded from one larva and unable to live apart.
An aphid can be born already pregnant
In the summer generations, a female aphid gives live birth to daughters who already contain embryos. A grandmother, a mother, and a granddaughter are nested in one body.
A goose flies over the Himalayas under its own power
Bar-headed geese climb from near sea level to between 4,000 and 6,000 metres in a single day, flapping, often at night, without needing an updraft to do it.
A sponge pushed through a cloth can assemble itself again
Separate the cells of a sponge and, left in seawater, they crawl back together and rebuild a sponge, with the cell types sorted into the right layers.
Bread wheat is three grasses that never came apart
The wheat in a loaf carries three complete ancestral genomes. Two wild hybridisations stacked them, and the plant kept all three instead of choosing.
A dung beetle steers by the Milky Way
On moonless nights, a dung beetle rolls its ball in a straight line by keeping a heading against the band of the Milky Way. Hide the sky and the path curls.
A bird navigates a cave by clicking
The oilbird nests in caves and finds its way in the dark by echolocation. The clicks are slow enough to hear. The system is coarser than a bat's, and it works.
An Antarctic fish stays liquid in water colder than its freezing point
The sea under the ice is about minus 1.9 degrees. The blood of a notothenioid fish would freeze at a higher temperature than that, except for proteins that bind tiny ice crystals and stop them growing.
A locust is a grasshopper that changes its body when the crowd arrives
The desert locust has two forms. Alone, it is a cryptic grasshopper. Crowded, it changes colour, shape, brain and behaviour, and it swarms. Same genes. Different life.
A bee can find the Sun through cloud, by the polarisation of the sky
Sunlight scattered by air is polarised in a pattern that points back to the Sun. A bee can see that pattern, and can steer by it when the Sun itself is behind cloud, so long as some blue sky remains.
An elephant keeps spare copies of the gene that stops a tumour
Elephants carry about twenty copies of TP53, the gene whose protein makes a damaged cell stop or die. Humans have one working copy. Elephants still get cancer. They get less of it than their size predicts.
A salmon finds its river by the smell
Young salmon imprint on the chemistry of their home stream. Years later, coming back from the ocean, they choose that stream by its odour. Block the nose and the choice fails.
A virus was filed as a bacterium because it was big enough to see
Mimivirus is about 0.4 micrometres across, visible in a light microscope, with a genome larger than some bacteria. It was stained, named as a microbe, and only later recognised as a virus that infects amoebae.
A virus can be infected by a smaller virus
Sputnik replicates inside the factory that a giant virus builds in an amoeba. Where Sputnik is present, the giant virus produces fewer and deformed particles. The small one is a parasite of the large one.
A bacterium in an insect can turn males into females
Wolbachia is passed only through eggs. Males are a dead end for it. In different hosts it kills male embryos, lets females reproduce without mating, or converts genetic males into females.
A fungus replaces a cicada's abdomen, and the cicada keeps flying
Massospora consumes the rear of an adult cicada and turns it into a mass of spores. The insect, abdomen gone, continues to fly and to seek mates, and in doing so spreads the fungus.
A caterpillar, eaten hollow, stays to guard the wasp's young
After parasitic wasp larvae chew out of a caterpillar and pupate beside it, the dying caterpillar thrashes at anything that approaches them. Caterpillars that do this lose fewer of the pupae to predators.
A plant with no leaves finds its victim by smell
Dodder seedlings grow toward the volatile chemicals of a host plant. They prefer a tomato to a wheat stalk, and they do it before they have touched either.
A lichen is not two organisms. In many, it is three
For a century a lichen was a fungus farming an alga. In 2016 a second fungus, a yeast, was found living in the cortex of many common lichens, and its abundance tracks how the lichen looks.
An electric eel leaps out of the water to deliver the shock
When a threat is partly out of the water, an electric eel rises, presses its chin against it, and uses the lifted body as the live path of the circuit. The current no longer leaks away through the river.
A mole locates food by the difference between its two nostrils
The common mole's nostrils sample slightly different air. Block one, or cross the scent with tubes, and the animal can no longer turn toward the smell. It was using the difference.
A pit viper sees warm bodies with an organ that is not an eye
The pit between eye and nostril is a pinhole camera for infrared. It forms a crude image of heat, on a membrane, and the brain overlays that image on vision. The molecular sensor is a channel that in you helps feel pain.
A cuttlefish's skin responds to light without the eyes
Chromatophores in cuttlefish skin expand when the skin itself is lit. The response does not require the eyes, or a signal from the brain. The skin has light-sensitive pigments of its own.
A glass sponge coordinates its whole body, and it has no nervous system
Hexactinellid sponges are a syncytium, one continuous cytoplasm. A single electrical impulse crosses the body and stops every feeding chamber at once. There are no neurons to carry it.
A frog swallowed her eggs and gave birth through her mouth
The gastric-brooding frog shut down her stomach acid, swallowed the fertilised eggs, raised the young in her stomach, and opened her mouth to let froglets out. Both species are extinct.
A grove of aspens can be one tree
Quaking aspen spreads by roots that send up new trunks. A stand of thousands of stems, covering hectares, can be a single genetic individual. The famous one in Utah is a forest you can walk through, and it is one plant.