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4656 words
- Matt Baker is developing a series of taxonomy charts covering the tree of life. The video presents the third chart in his new series, following the bird and mammal charts, and introduces a combined classification of fish, amphibians, and reptiles.
- Viewer feedback has already changed the bird and mammal charts. Baker showed earlier drafts on YouTube, received comments, and incorporated numerous corrections and additions. He is using the same public-feedback process for the new chart.
- The video is less polished than his usual productions because his animator was unavailable. Siaish, from the YouTube channel Al-Mukana, was traveling, so Baker recorded the walkthrough himself, without his usual animation and editing. He warned viewers that the video would be longer and contain pauses and mistakes.
- Baker intends to limit the tree-of-life series to five charts. He originally planned four but separated mammals and birds after viewers requested dedicated charts for each. Fish, amphibians, and reptiles share one chart because they are generally cold-blooded vertebrates and their evolutionary relationships are easier to illustrate together.
- The mammal chart now includes additional Australian marsupials. Baker added numbats and quolls following viewer suggestions, expanding the representation of marsupial diversity.
- The Afrosoricida section of the mammal chart has been expanded. Baker separated golden moles, tenrecs, and otter shrews into more detailed groups after a viewer pointed out that the order contains three substantially different types of animals.
- Marine mammals now have their own distinguishing colour. Baker changed the colour of sirenians, pinnipeds, otters, and cetaceans to teal, making these groups easier to identify without obscuring their broader evolutionary relationships.
- Species counts may eventually be broken down by family rather than only by order. Viewers requested more detailed counts. Baker agreed that family-level figures could improve the chart but had not decided how to incorporate them.
- Giant ground sloths were added despite Baker's previous restriction on extinct animals. He had intended to concentrate on animals that became extinct within roughly the last 5,000 years, but included giant ground sloths after several viewers requested them. He also considered their importance to the history of palaeontology a justification for making an exception.
- The relationship between domestic horses and wild horses is now represented more cautiously. Baker explained that present-day wild horses are feral descendants of domesticated horses, rather than the direct ancestors of domestic horses. Because the original ancestral species is uncertain and no longer exists, he marked the lineage with a question mark.
- The quagga has been added to the mammal chart. Baker described it as an African subspecies of the plains zebra that became extinct approximately 150 years ago. It had a zebra-like head and a body with more horse-like characteristics.
- The ancestry of the dromedary camel remains uncertain. Baker marked its ancestral species as unknown because the original population is no longer around and its appearance is unclear. He contrasted this with the two-humped camel, for which a wild form still exists.
- Domestic pigs are now connected to the wild boar. Baker added this relationship after viewers requested clearer indications of the wild ancestors of domesticated animals.
- The okapi has been added to the chart. Baker noted that this striped-legged animal is the only living relative of giraffes within the giraffe family apart from giraffes themselves.
- Several missing mammal groups have been restored. These include mouse deer, pronghorns, spiral-horned antelopes, and additional foxes. The additions reflect requests from viewers who noticed gaps in the earlier version.
- Aurochs have been included as the ancestors of domestic cattle. Baker explained that aurochs became extinct around 1627, making them a useful example of an extinct species with a direct connection to familiar domesticated animals.
- River dolphins have been added. Their inclusion further expands the representation of aquatic mammals on the chart.
- Neanderthals now appear on the human evolutionary branch. Baker acknowledged that many extinct Homo species could be included, but he does not intend the mammal chart to become a comprehensive account of human evolution. He added Neanderthals to demonstrate that humans were not the only members of the genus Homo.
- Baker is reconsidering which person should represent modern humans on the mammal chart. His draft used Marie Curie, but he is considering alternatives. He wants a recognisable historical figure represented by a colour photograph rather than another familiar drawing of Charles Darwin.
- The choice of a human portrait is constrained by image-use rights. Baker said he wanted to avoid recently deceased people, such as Jane Goodall, because he understood that families could retain rights over their images for 70 years after death. He is therefore seeking a suitable historical figure whose photograph can be used appropriately.
- All eight living bear species are now represented. Baker acknowledged that his original selection was overly focused on North America and added Asian and South American bears after viewers pointed out the omissions.
- The cat section has been substantially reorganised. Baker divided cats into small cats and big cats, with the latter including members of Panthera and the clouded leopard. He expanded the section after viewers, including himself as a cat enthusiast, felt that the original selection was inadequate.
- A newly recognised cat was added at the last minute. Baker referred to it as the “Tokyo,” while expressing uncertainty about the name. He explained that a species discovery in this context means scientists have determined that a cat population from a particular region is distinct from other members of its genus.
- Baker is still accepting final corrections to the mammal chart. He invited viewers to identify omissions and errors before he considers the chart sufficiently complete.
- The new chart begins with vertebrates within the phylum Chordata. Baker explained that the chart covers vertebrate animals, while the much larger invertebrate portion of the animal kingdom will receive a separate chart.
- An invertebrate chart remains the major unfinished part of the planned animal classification series. It will cover groups such as insects, spiders, molluscs, and other animals outside the vertebrate section. Baker explained that vertebrates receive separate charts partly because they are generally larger and more familiar to people.
- Jawless vertebrates occupy separate classes near the base of the chart. Baker identified lampreys and hagfish as surviving jawless creatures, each represented by its own class. He contrasted their small classes with the much larger classes represented by mammals and birds.
- The evolution of jaws marks a major branching point in the fish classification. After early vertebrates developed jaws, one branch led to cartilaginous fishes, while another led to bony fishes.
- Sharks and rays are grouped separately from bony fishes because their skeletons are largely cartilaginous. Baker explained that their skeletons contain much less bone than those of other fish, with the vertebral column, skull, and a few other bones forming the principal bony structures.
- Rays form a substantial part of the cartilaginous-fish branch. Baker highlighted familiar groups such as stingrays and manta rays, alongside other species with flattened, often circular or diamond-shaped bodies.
- Chimaeras form a third major branch of cartilaginous fishes. Baker explained that their name comes from the mythological chimera, a creature assembled from different animal parts, reflecting their unusual appearance.
- The shark branch contains several distinctive orders. Baker highlighted carpet sharks, bullhead sharks, and hammerhead sharks, using their unusual body shapes to illustrate the diversity within the group.
- The shark chart includes the great white, whale shark, and megamouth shark. Baker identified the great white as the shark most familiar to the general public, described the whale shark as the largest shark, and highlighted the deep-ocean megamouth as another unusual species.
- Baker has not yet completed all the research needed for detailed explanations of every fish group. He described the new chart as an initial overview rather than a definitive deep dive. He plans to investigate individual branches more thoroughly in future videos.
- The chart is intended to be crowdsourced as well as educational. Baker asked viewers with specialist knowledge to identify omitted groups, correct mistakes, and recommend additions. He specifically welcomed feedback from people familiar with sharks and other less familiar parts of the chart.
- Bony fishes divide into lobe-finned and ray-finned lineages. Baker explained that lobe-finned fishes have rounded, fleshy fins, while ray-finned fishes have fins supported by rays. He noted that the ray-finned grouping is now a broader clade containing multiple classes, including the major lineage that leads to mammals, birds, and reptiles.
- The lobe-finned lineage is important because it leads to tetrapods. Baker highlighted this branch in purple, using the colour and layout to emphasise the evolutionary route toward four-limbed vertebrates.
- Several extinct species document the transition toward land-walking vertebrates. Baker acknowledged that fossils show many intermediate stages. He explained that “transitional form” can be misleading because all species descend from earlier organisms and continue to evolve over long periods.
- Tiktaalik is included as a particularly important transitional fossil. Baker described its discovery in the early 2000s as a major find because it represented an animal close to developing four limbs capable of supporting movement on land, although it was not yet fully adapted for that mode of life.
- Tetrapods are defined by their four limbs. Baker explained that the name refers to four feet or limbs and used the group to introduce the split between amphibians and amniotes.
- Amphibians differ from amniotes in their reproductive requirements. Baker explained that amphibians lay their eggs in water and often remain partly aquatic as adults. Frogs and salamanders can move onto land, but their life cycles remain more closely tied to aquatic environments than those of many other vertebrates.
- The amniotic egg enabled vertebrates to reproduce on land. Baker explained that the evolution of specialised egg membranes allowed amniotes to reproduce away from water. He noted that living amniotes either lay eggs on land or, in mammals and a few other cases, give birth to live young.
- The amphibian chart contains three orders, although two dominate the familiar examples. Baker identified frogs, salamanders, and wormlike amphibians as the three principal groups. He contrasted this limited number with the greater diversity of birds, mammals, and fish.
- Salamanders are grouped separately from frogs. Baker explained that salamanders retain tails, whereas adult frogs generally do not. Giant salamanders form a distinct family, while most other salamander families belong to the principal salamander lineage shown on the chart.
- The axolotl is a particularly notable salamander. Baker explained that axolotls retain juvenile characteristics throughout their lives and have exceptional regenerative abilities, including the ability to regrow limbs. He included the species partly because it is familiar to viewers through video games and popular culture.
- Salamanders can resemble lizards but differ in important physical characteristics. Baker noted that salamanders lack scales, tend to be more aquatic, and are generally smaller than the largest lizards.
- Frogs divide into two major groupings on the chart. One contains many familiar ground- and pond-dwelling frogs, while the other includes a wide range of tree frogs and forest-associated species.
- Flying frogs can glide without actually flying. Baker highlighted their webbed feet, which allow them to move through the air for short distances. He used them as an example of the unusual adaptations found among frogs.
- Some frogs have highly distinctive body shapes. Baker pointed out a family whose members have extremely short necks and compact bodies, making them resemble small balls.
- Common European and North American frogs occupy part of the main frog branch. Baker highlighted familiar examples such as the green frog and bullfrog, noting that bullfrogs grow considerably larger.
- Tree frogs include several visually unusual groups. Baker identified poison frogs, glass frogs whose translucent skin reveals internal organs, horned frogs, red-eyed leaf frogs, and familiar tree frogs known for their calls.
- Toads are technically frogs but belong to a distinct family. Baker explained that toads generally spend more time on land, are less dependent on wet environments, and tend to have warty skin. The distinction is therefore a subgroup relationship, not a separation between frogs and an entirely unrelated type of animal.
- Amniotes divide into synapsids and sauropsids. Baker explained that the original distinction relates to skull structure. Synapsids eventually produced mammals, with features including fur and mammary glands, while sauropsids gave rise to reptiles and the lineage containing dinosaurs and birds.
- The reptile section includes lizards and snakes, turtles and tortoises, crocodilians, and the tuatara. Baker initially described three living reptile orders but corrected himself when he remembered the tuatara, a distinctive New Zealand animal placed in a group of its own.
- The tuatara is grouped with lizards in Lepidosauria. Baker explained the name as referring to scaled reptiles, while cautioning that not every scaled reptile belongs to the lizard lineage.
- Dinosaurs are not simply large lizards. Baker noted that although the word dinosaur means “terrible lizard,” scientists now recognise that dinosaurs differ from modern lizards in their body structure and other characteristics.
- Squamates divide into several major lizard and snake lineages. Baker identified skinks, typical lizards, geckos, and a broader branch containing snakes and iguanas as four principal directions on the chart.
- Skinks have elongated, almost tubular bodies. Baker described them as small, smooth-looking reptiles that can resemble salamanders, although they are lizards rather than amphibians.
- Some lizards give birth to live young, while others can reproduce without males. Baker highlighted examples of lizards that produce live offspring and another in which females can lay eggs that develop into genetic clones of themselves.
- Geckos have distinctive eye and climbing adaptations. Baker explained that most geckos lack eyelids and use their tongues to keep their eyes moist. Their specialised feet also allow them to climb walls and other surfaces.
- The branch containing snakes and iguanas includes many venomous reptiles, but not all its members are dangerous. Baker explained that some descendants retain venomous characteristics while others have lost them. He used the group to introduce several of the most familiar and potentially dangerous snakes.
- The Komodo dragon and water monitor are included among the larger lizard groups. Baker identified the Komodo dragon as the largest living lizard species and then moved on to iguanas and related groups.
- Iguanas are often herbivorous and relatively large. Baker also highlighted other members of the broader iguanian grouping, including horned lizards, anoles, and bearded dragons.
- Horned lizards are sometimes called “horny toads” in the United States. Baker clarified that, despite their name and appearance, they are lizards rather than toads.
- Anoles are recognised by their expandable throat displays. Baker pointed out the dewlap, which these lizards extend into a prominent display.
- Bearded dragons are common pet reptiles. Baker also highlighted a frilled lizard that raises the frills around its neck when attempting to deter a potential predator.
- Baker identified a classification error in the snake section. He noticed that the chart placed a suborder inside another suborder, which would be inconsistent with the hierarchy he intended to use. He said the nested group should instead be an infraorder.
- The snake chart includes blind snakes, thread snakes, and five major families of more familiar snakes. Baker identified pythons, boas, vipers, elapids, and colubrids as the principal families in the main snake grouping.
- Elapids include cobras and other snakes with specialised fangs. Baker highlighted the family because it contains several dangerous species, including cobras.
- Colubrids are the largest snake family and include many relatively harmless species. Baker listed garter snakes, grass snakes, and water snakes as familiar examples. He said most members of the family are not dangerous, while acknowledging that some exceptions may exist.
- Pythons and boas include some of the largest snakes. Baker described pythons as among the largest snakes and highlighted the green anaconda as a particularly large boa. He also explained how boa constrictors subdue prey by wrapping around it and squeezing.
- India's “Big Four” snakes were highlighted because of their contribution to snakebite incidents and fatalities. Baker identified the Indian cobra, common krait, Indian saw-scaled viper, and Russell's viper. He noted that the four belong to two families: elapids and vipers.
- Other dangerous snakes are included from several regions. Baker mentioned the king cobra, the African black mamba, and an Australian species he described as having an exceptionally high concentration of deadly venom despite being rare.
- Rattlesnakes, copperheads, and cottonmouths appear in the viper section. Baker explained that rattlesnakes are among Canada's dangerous snakes, particularly in the prairies, and that the United States also has copperheads and cottonmouths, which are sometimes called water moccasins.
- Adders represent another important group of vipers. Baker noted their presence in Europe as he completed the snake section.
- Turtles divide according to how they retract or position their heads. Baker explained that he had previously assumed all turtles could tuck their heads inside their shells. While some turtles retract their necks into the shell, side-neck turtles turn their heads sideways instead.
- Softshell turtles have distinctive snouts, while other familiar groups have hard shells. Baker highlighted sea turtles, snapping turtles, mud turtles, and musk turtles before moving to the broader turtle grouping that also contains tortoises.
- Tortoises are a subgroup of turtles rather than a separate, unrelated category. Baker explained that all tortoises are turtles, but not all turtles are tortoises. Tortoises are primarily land-dwelling, while other turtles are more closely associated with water, rivers, ponds, or aquatic environments.
- Giant tortoises are represented by both species examples and named individual animals. Baker included the Galápagos giant tortoise and another giant tortoise from the Indian Ocean region, while expressing uncertainty about which was the largest.
- Jonathan is featured as an exceptionally long-lived tortoise. Baker identified Jonathan as a specific individual and described him as nearly 200 years old, making him, in Baker's account, the oldest living tetrapod or vertebrate.
- The chart also includes Gus, a tortoise Baker has personally met. Gus lives at a museum in Nova Scotia, where Baker grew up. Baker first encountered him in elementary school, when Gus was approximately 60 or 70 years old, and noted that Gus was now well over 100.
- The turtle chart includes familiar pond turtles from Europe and the Americas. Baker identified a European pond-turtle species and American examples such as pond sliders, painted turtles, and box turtles.
- Archosauria contains crocodilians and dinosaurs. Baker explained that the name means “ruling lizards” and used the branch to show the close evolutionary relationship between crocodiles, dinosaurs, and birds.
- Crocodilians are less diverse in living groups than turtles and squamates. Baker identified crocodiles, alligators, and a smaller group containing gharials and false gharials.
- The shape of the snout can help distinguish alligators from crocodiles. Baker explained the general rule that alligators have broader, U-shaped snouts when viewed from above, while crocodiles tend to have narrower, more pointed, V-shaped snouts.
- The United States has both alligators and crocodiles. Baker noted that the Chinese alligator is the only other living alligator in the world and is critically endangered. He also included caimans within the broader alligator family.
- The crocodile branch includes the Nile crocodile and saltwater crocodile. Baker identified the saltwater crocodile as the largest crocodile and the largest living reptile, and also included a freshwater crocodile.
- Dinosaurs are divided into bird-hipped and reptile-hipped groups. Baker highlighted the counterintuitive fact that birds did not descend from the bird-hipped dinosaurs. That group, which includes Triceratops, is entirely extinct.
- Birds descend from the reptile-hipped dinosaur lineage. Baker divided that lineage into theropods and large, four-legged sauropods. Although both groups included extinct dinosaurs, the theropod branch survives through birds.
- Tyrannosaurus rex is a familiar example of a theropod dinosaur. Baker used it to illustrate the group from which birds ultimately emerged, explaining that the evolutionary route continues from the dinosaur branch to the separate bird chart.
- The fish section resumes with early-diverging bony fish. Baker highlighted sturgeons and paddlefish, the latter named for their prominent paddle-like snouts, before moving to the much larger group of modern bony fishes.
- Most familiar bony fish belong to the teleost lineage. Baker described these fish as having the more complete, conventional-looking skeleton associated with familiar fish, including the skull and bones extending along the body.
- Eels branch off relatively early within the bony-fish classification. Baker clarified that electric eels are not placed with the true eels on his chart but in another lineage.
- Two major branches lead toward carp-like and perch-like fish. Baker used carp and perch as familiar examples of the broad body forms associated with the two branches.
- Catfish and electric eels are grouped within the same broad branch. Baker placed them alongside other distinctive fish lineages, including several popular aquarium groups.
- Tetras and piranhas are closely related groups in the chart. Baker highlighted neon tetras, which are common in home aquariums, as well as piranhas, hatchetfish, and pencilfish.
- Anchovies, sardines, and herrings belong to an important food-fish group. Baker explained that this branch contains species commonly eaten by people, including canned sardines and pickled herring.
- The carp branch includes several common aquarium fish. Baker highlighted danios, rasboras, minnows, and carp, including the zebra danio, which is widely used in scientific research.
- Zebra danios are an important research species. Baker described them as one of the most studied vertebrates and noted that they have even been sent into space as part of early space-program research.
- Goldfish are domesticated fish related to the Prussian carp. Baker explained that selective breeding has produced goldfish with many unusual shapes, large cheeks, and elaborate fins and tails.
- Koi are related to goldfish but are not the same species. Baker said koi descend from common carp and have been bred into many colours and forms. He noted that the long history of selective breeding makes their precise lineage difficult to map in a simple chart.
- The carp branch also includes barbs and the bala shark. Baker mentioned tiger barbs and cherry barbs as familiar aquarium fish, and clarified that the bala shark is not actually a shark despite its name and appearance.
- The true-teleost branch includes many commercially important food fish. Baker highlighted salmon, trout, haddock, and cod as examples of fish commonly caught in the wild or farmed for human consumption.
- Perch-like fish form a large and colourful branch. Baker explained that Percomorpha means “perch-like” and includes many tropical fish familiar to aquarium enthusiasts.
- Clownfish and cichlids are among the aquarium groups in this branch. Baker highlighted clownfish, made famous by Finding Nemo, as well as cichlids and angelfish. He also mentioned Oscar fish as a relatively large fish kept by aquarium enthusiasts.
- Livebearing fish are an exception to the usual egg-laying pattern among fish. Baker identified guppies, platies, and mollies as examples that give birth to live young, making them popular aquarium fish.
- Seahorses, gouramis, and bettas are also represented. Baker included these distinctive and commonly kept aquarium fish within the broader perch-like branch.
- Bettas are commonly sold as starter fish, often in very small containers. Baker said they are popular as introductory pets because they can survive in relatively small amounts of water, relating this to the conditions in which they live naturally.
- Tuna are another commercially important group. Baker highlighted their significance to the food industry as he moved toward the final part of the fish chart.
- The true-perch branch includes several unusual marine fish. Baker pointed out pufferfish, deep-sea anglerfish with their characteristic light-producing appendage, tangs, scorpionfish, and lionfish, alongside familiar perch species sought by recreational anglers.
- Dory from Finding Nemo appears among the tangs. Baker deliberately placed Dory alongside a clownfish because of their friendship in the film. He briefly struggled to remember the name of Nemo's father, Marlin.
- Baker expects the fish, amphibian, and reptile chart to receive further revisions. He acknowledged that he knows less about these groups than some other parts of the tree of life and invited viewers to educate him, correct mistakes, and suggest additions.
- The plants and fungi chart is the remaining major chart awaiting a full presentation. Baker has already produced a fungi video but delayed the plant video while waiting for a new scientific classification of flowering plants.
- The Angiosperm Phylogeny Group published its fifth major classification update, APG 5. Baker explained that the group periodically reviews research, including DNA studies, and revises the evolutionary classification of flowering plants. The previous version was APG 4, which Baker used when making his existing chart.
- The new APG 5 classification requires Baker to redraw parts of the plant chart. He said the update had been published that same week and that he needed to revise the chart before presenting it as current.
- Asterids and rosids are two major groupings of flowering plants. Baker explained that the names reflect familiar flowers: asters and daisies for asterids, and roses for rosids. He considers flowering plants his strongest area of knowledge within the tree-of-life project.
- The largest APG 5 changes affect the rosid branch. Baker explained that rosids include two major subgroups, malvids and fabids, and that the new classification changes the placement of several branches.
- Fabids include roses, oak trees, cucumbers, pumpkins, peas, and beans in Baker's explanation. He associated these plants with nitrogen fixation and used them to illustrate the existing fabid grouping.
- One branch previously grouped with fabids will move to malvids. Baker identified three orders by their initials, C, O, and M, as belonging to the branch that APG 5 relocates. He will need to rearrange the chart to reflect the new classification.
- Grapes have been moved out of rosids into superrosids. Baker explained that superrosids are closely related to rosids but represent a distinct grouping in the updated classification.
- The sandalwood family and another branch are also being repositioned. Baker said they are being removed from the superasterid grouping and moved to a separate branch, requiring further changes to the chart's layout.
- Baker plans to produce a detailed plant-classification video after updating the chart. He indicated that the new classification must be incorporated first, rather than explaining the plant chart using the outdated APG 4 arrangement.
- The Kickstarter campaign is accepting late pledges until the end of October. Baker described pledging as effectively pre-ordering the charts through Kickstarter and said orders would be printed and delivered in time for the holiday season.
- The charts will not appear on Baker's main website, UsefulCharts.com, until January. People who want to receive them during the current year must therefore order through Kickstarter before the late-pledge window closes.
- Baker uses iNaturalist extensively to source photographs for his charts. He emphasised that the videos are not sponsored by iNaturalist, but credited the website and app with helping him find images of the species included in the classification charts.
- iNaturalist provides a public record of species observations. Users can photograph a frog, lizard, bird, mammal, plant, mushroom, or another organism, receive help identifying it, and record where it was observed. Baker explained that these observations provide useful data for scientists studying species distributions.
- Public-domain photographs uploaded to iNaturalist can be reused by educators. Baker thanked contributors who make their images available for public use, explaining that their work helps him create educational charts without having to photograph every species himself.
- Baker plans to attend an iNaturalist community event in Vancouver. The global INAT Together initiative has involved events in cities around the world, with participants gathering to explore nature and use the app. Baker said he intended to attend the following day's event at Hastings Park and invited viewers to join him.