You might have played the game called “animal, vegetable, mineral”. One player thinks of an object or organism and the other players ask questions to try to guess what it is – starting with this simple classification. But nature isn’t this simple. There are dozens of groups of living species that are neither plants nor animals.
We tend to think of plants as organisms that stand still and use photosynthesis to produce energy from sunlight and make their own organic molecules from the soil. And we see animals as creatures that move and feed on other organisms to obtain the energy and molecules they need.
But many organisms challenge those descriptions. The Venus flytrap, despite being a plant, feeds on other organisms – and some of its parts move faster than its unfortunate animal prey. Many groups of animals do not move and live attached to a surface for most of their life, including sponges, corals, mussels and barnacles to name a few. It’s still relatively easy to say whether these creatures are plants or animals. But there are other organisms whose nature is more mystifying. Here are a few of the most intriguing creatures who defy our simple categories.
Hungry sea anemones
Sea anemones are technically animals, but they look so much like plants that they are named after a group of flowers. Even Aristotle, the ancient Greek who produced one of the world’s first systems for categorising life, was puzzled by them. He classified anemones as “zoophytes”, organisms bearing traits of both groups.
The truth is that they are animals because they can (very slowly) move and feed on other unsuspecting organisms that get trapped in their tentacles. In fact, sea anemones belong to a group of animals called cnidarians, which also includes jellyfish. Interestingly, there are even components of their nervous system that are the same as humans’, although their anatomy is very different.
To make things even more confusing, there is a cnidarian called the “Venus flytrap sea anemone” that completely looks the part. It is a brilliant example of convergent evolution, where unrelated organisms independently evolve similar adaptations (for example, the wings of birds and bats). In this case, it is an animal that looks like a plant that imitates a carnivorous plant that feeds like an animal.
Leafy sea slugs
Chlorophyll is the green pigment in plant cells that enables photosynthesis to happen, and is one of the defining traits of plants. But some animals use a very clever trick: they steal those solar-powered factories and use them to their benefit, a process aptly named kleptoplasty. The gorgeous sea slug Elysia chlorotica was once described as “a leaf that crawls”. They can borrow chloroplasts from its algal snacks, sucking them with a structure that pretty much looks like a straw, pushing the concept of veganism to the limit. These sea slugs have specialised cells that can keep those chloroplasts for months. What’s more, they also use the stolen chlorophyll for camouflage. The blue dragon slug, Pteraeolidia ianthina, can go a step further. Instead of keeping chloroplasts from is food, is able to enslave whole algal cells.
Science news in pictures
Science news in pictures
1/20 'Tiny vampires' existed millions of years ago
Scientists have discovered that microscopic 'vampire' amoebae existed hundreds of millions of years ago, and they may have been some of the first predators on Earth. By examining ancient fossils with an electron microscope, paleobiologist Susannah Porter from UC Santa Barbara discovered tiny holes which may have been drilled by vampiric microbes. The tiny creatures are believed to be the ancestors of modern Vampyrellidae amoebae, and punctured holes in their prey before sucking out the contents of their cells
2/20 Kepler 62f
An Earth-like planet orbiting a star 1,200 light years away could have conditions suitable for life, say scientists. Kepler 62f is about 40 per cent larger than the Earth and may possess surface oceans. It is the outermost of five planets circling a star that is smaller and cooler than the sun discovered by the American space agency Nasa's Kepler space telescope in 2013
3/20 Vegetables grow well in soil from Mars
Scientists have taken a leaf out of the script of The Martian by showing how easy it would be to grow your own veg on the Red Planet. In the hit Ridley Scott film, a stranded astronaut played by Matt Damon uses his botanical skills to cultivate potatoes. Now his success has been emulated by researchers in the Netherlands who harvested tomatoes, peas, rye, rocket, radish and cress raised on simulated Martian soil supplied by Nasa
4/20 Ancient Roman 'leisure complex' unearthed in Jerusalem
An ancient Roman estate complete with its own wine press and bathhouse has been unearthed in Jerusalem. A series of buildings dating back at least 1,600 years were discovered underneath the city's famous Schneller Orphanage which operated on the site from 1860 until the end of the Second World War, when it was turned into an army base. The ruins were discovered by archaeologists from the Israel Antiquities Authority who were excavating the site ahead of building new flats for the city's Orthodox Jewish community
5/20 Scientists discover possible new species of deep-sea octopus nicknamed 'Casper'
Scientists believe they may have found a new species of octopus likened in appearance to Casper, the friendly cartoon ghost. Researchers with the US National Oceanic and Atmospheric Administration made the discovery by chance as they searched the seabed on an unrelated mission collecting geological samples. Teams were operating an unmanned submarine on the Pacific Ocean floor at depths of more than four kilometres (two-and-a-half miles) in the Hawaiian Islands when they spotted the unusual creature
6/20 Black hole captured eating a star then vomiting it back out
Astronomers have captured a black hole eating a star and then sicking a bit of it back up for the first time ever. The scientists tracked a star about as big as our sun as it was pulled from its normal path and into that of a supermassive black hole before being eaten up. They then saw a high-speed flare get thrust out, escaping from the rim of the black hole. Scientists have seen black holes killing and swallowing stars. And the jets have been seen before.But a new study shows the first time that they have captured the hot flare that comes out just afterwards. And the flare and then swallowed star have not been linked together before
7/20 'Male and female brains' aren't real
Brains cannot be categorised into female and male, according to the first study to look at sex differences in the whole brain. Specific parts of the brain do show sex differences, but individual brains rarely have all “male” traits or all “female” traits. Some characteristics are more common in women, while some are more common in men, and some are common in both men and women, according to the study
8/20 Dog-sized horned dinosaur fossil found shows east-west evolutionary divide in North America
A British scientist has uncovered the fossil of a dog-sized horned dinosaur that roamed eastern North America up to 100 million years ago. The fragment of jaw bone provides evidence of an east-west divide in the evolution of dinosaurs on the North American continent. During the Late Cretaceous period, 66 to 100 million years ago, the land mass was split into two continents by a shallow sea. This sea, the Western Interior Seaway, ran from the Gulf of Mexico to the Arctic Ocean. Dinosaurs living in the western continent, called Laramidia, were similar to those found in Asia
9/20 Asteroid to skim past Earth on Halloween 2015
A huge asteroid is set to skim by Earth on Halloween, just three weeks after it was first spotted. The rock is travelling through space at 78,000 miles per hour, and will fly past the Earth at a distance of only 300,000 miles – only slightly further away than our moon, and easily close enough for Nasa to class it a potentially hazardous object. The asteroid is bigger than a skyscraper
10/20 Life on Earth appeared hundreds of millions of years earlier than previously thought
Life may have come to earth 4.1 billion years ago, hundreds of millions of years earlier than we knew. The discovery, made using graphite that was trapped in ancient crystals, could mean that life began "almost instantaneously" after the Earth was formed. The researchers behind it have described the discovery as “a potentially transformational scientific advance”. Previously, life on Earth was understood to have begun when the inner solar system was hit by a massive bombardment from space, which also formed the moon's craters
11/20 Earth could be at risk of meteor impacts
Earth could be in danger as our galaxy throws out comets that could hurtle towards us and wipe us out, scientists have warned. Scientists have previously presumed that we are in a relatively safe period for meteor impacts, which are linked with the journey of our sun and its planets, including Earth, through the Milky Way. But some orbits might be more upset than we know, and there is evidence of recent activity, which could mean that we are passing through another meteor shower. Showers of meteors periodically pass through the area where the Earth is, as gravitational disturbances upset the Oort Cloud, which is a shell of icy objects on the edge of the solar system. They happen on a 26-million year cycle, scientists have said, which coincide with mass extinctions over the last 260-million years
12/20 Genetically-engineered, extra-muscular dogs
Chinese scientists have created genetically-engineered, extra-muscular dogs, after editing the genes of the animals for the first time. The scientists create beagles that have double the amount of muscle mass by deleting a certain gene, reports the MIT Technology Review. The mutant dogs have “more muscles and are expected to have stronger running ability, which is good for hunting, police (military) applications”, Liangxue Lai, one of the researchers on the project. Now the team hope to go on to create other modified dogs, including those that are engineered to have human diseases like muscular dystrophy or Parkinson’s. Since dogs’ anatomy is similar to those of humans’, intentionally creating dogs with certain human genetic traits could allow scientists to further understand how they occur
13/20 Nasa confirms Mars water discovery
Nasa has announced that it has found evidence of flowing water on Mars. Scientists have long speculated that Recurring Slope Lineae — or dark patches — on Mars were made up of briny water but the new findings prove that those patches are caused by liquid water, which it has established by finding hydrated salts.
14/20 Bees in the Rocky Mountains are evolving shorter tongues
With warmer summers, flowers in the Rockies have become shallower and more suited to shorter-tongued bees
15/20 The majority of the UK public believe in aliens
The titular alien character from 2011's 'Paul' - a poll has found the majority of the public in Britain, Germany and the US believe that intelligent life is out there in the universe
16/20 Researchers discover 'lost world' of arctic dinosaurs
Scientists say that the new dinosaur, known as Ugrunaaluk kuukpikensis, “challenges everything we thought about a dinosaur’s physiology”. Florida State University professor of biological science Greg Erickson said: “It creates this natural question. How did they survive up here?”
17/20 Scientists find exactly what human corpses smell like
New research has become the first to isolate the particular scent of human death, describing the various chemicals that are emitted by corpses in an attempt to help find them in the future. The researchers hope that the findings are the first step towards working on a synthetic smell that could train cadaver dogs to be able to more accurately find human bodies, or to eventually developing electronic devices that can look for the scent themselves.
18/20 The Syrian civil war has caused the first ever withdrawal from the 'doomsday bank'
Researchers in the Middle East have asked for seeds including those of wheat, barley and grasses, all of which are chosen because especially resistant to dry conditions. It is the first withdrawal from the bank, which was built in 2008. Those researchers would normally request the seeds from a bank in Aleppo. But that centre has been damaged by the war — while some of its functions continue, and its cold storage still works, it has been unable to provide the seeds that are needed by the rest of the Middle East, as it once did.
19/20 A team of filmmakers in the US have made the first ever scale model of the Solar System in a Nevada desert
Illustrations of the Earth and moon show the two to be quite close together, Mr Overstreet said. This is inaccurate, the reason being that these images are not to scale.
20/20 Academics claim a full bladder makes for a better liar
People lie more convincingly if they have a full bladder, according to research by academics at California State University. Iris Blandón-Gitlin's team asked 22 students to lie to a panel of interviewers. Half were given 700ml to drink before the interview and the other half, just 50ml. The students with the full bladders showed fewer signs that they were lying and their untrue answers were longer and more detailed, meaning interviewers were less able to detect that they were telling porkies. PM David Cameron has previously attested to giving speeches on a full bladder.
Creatures that are not animals or plants are often informally called protists. Many in this category are in the habit of robbing plastids from algae or subjugating other single-celled organisms. These include dinoflagellates, ciliates and foraminiferans. In this way, all these organisms are able to use an animal-like behaviour (eating other organisms) to acquire plant-like traits (photosynthesis), getting a higher return from their sunbathing sessions than their peers.
Algae are mostly aquatic organisms that we often think of as single-celled lifeforms that appear as a kind of growth or slime on top of bodies of water in a range of colours. But there are also multicellular types of algae that look far more like plants – even though they often don’t have roots or leaves as we traditionally think about them. Even though they have evolved separately, algae are like plants in that they don’t move and can photosynthesise.
If you have been to a beach, you most likely have run or swam into the sea lettuce Ulva, which despite its name is not a vegetable but a green alga. Nori seaweed is commonly used in Japanese cuisine to wrap delicious bits of sushi and rice – and red dulse is a snack in Ireland and Iceland that some claim tastes like bacon when fried. But in spite of their plantlike appearances and animal-like tastes, nori and dulse are scrumptious red algae. Another example is kelp, which forms astonishing massive underwater forests – some specimens reach the impressive length of 80 metres – and is also a key ingredient in many Asian meals. Despite its size, kelp belongs to the brown algae, and is unrelated to plants.
Mushrooms are often treated like vegetables but fungi (which includes yeast and mould) are actually closer to animals than plants, and form an entirely separate kingdom. Like plants, they do not move, but they also don’t perform photosynthesis. Instead their source of molecules and energy are other organisms. But instead of “hunting” them like animals, they either grow on top of them (soil, trees, human feet) or on top of decaying dead organisms (dead bark, dead animals, your bread). Due to their close evolutionary relationship to animals, eating a portabello mushroom in a bun is much closer to eating a hamburger than other veggie substitutes.
What’s more, they can grow much bigger than any plant (or animal, for that matter), with the individual heads all part of one giant organism spread out underground. The humungous honey fungus, Armillaria, is allegedly able to cover up to nine square kilometres of forest, weigh up to 35,000 tons and live up to 2,400 years. These fungi are agents of a major forest pest, the “white rot” root disease, which slowly kills numerous trees.
Nature is diverse, beautiful and complicated, always defying simple definitions. Human perception can be easily deceived by the intricacy of live beings. But none of this complexity impedes us from making delicious food out of almost every organism we encounter.
This article first appeared on The Conversation (theconversation.com). Jordi Paps is a lecturer, school of biological sciences, at the University of EssexReuse content