1. Biochemistry (Level 3)
2. Chemical biology
3. Molecular biology (Level 3)
4. Biomolecule
5. Alkaloid
   1. Caffeine
   2. Cocaine
   3. Morphine
   4. Nicotine
6. Biological pigment
   1. Carotenoid
   2. Chlorophyll
   3. Melanin
7. Carbohydrate (Level 3)
   1. Sugars
      1. Fructose
      2. Glucose
      3. Lactose
   2. Polysaccharides
      1. Cellulose
      2. Chitin
      3. Glycogen
      4. Starch
8. Hormone (Level 3)
   1. Dopamine
   2. Adrenaline
   3. Estrogen
   4. Insulin
   5. Oxytocin
   6. Plant hormone
   7. Testosterone
9. Lipid (Level 3)
   1. Steroid
      1. Cholesterol
   2. Fat
   3. Fatty acid
10. Nucleic acid
    1. DNA (Level 3)
    2. RNA (Level 3)
11. Protein (Level 3)
    1. Amino acid
    2. Enzyme
    3. Hemoglobin
    4. Protein as nutrient

1. Ecology (Level 2)
2. Biodiversity (Level 3)
3. Biome
4. Biosphere
5. Competition (biology)
6. Ecological niche
7. Ecosystem (Level 3)
8. Endangered species
9. Extinction (Level 3)
10. Extremophile
11. Habitat
12. Invasive species
13. Parasitism
14. Population
15. Sustainability
16. Symbiosis
17. Wildlife conservation

This section contains 4 articles.

1. Zoology (Level 3)
2. Animal (Level 2)
3. Animal coloration
   1. Camouflage

This section contains 14 articles.

1. Ethology
2. Intelligence (Level 3)
3. Sleep (Level 3)
   1. Hibernation
4. Animal locomotion
   1. Bipedalism
5. Animal migration
6. Carnivore
   1. Predation
   2. Scavenger
7. Herbivore
   1. Grazing
8. Instinct
9. Sociality

1. Bilateria
2. Chordate
3. Invertebrate

1. Cnidaria
2. Coral
3. Jellyfish

1. Echinoderm
2. Sea cucumber
3. Sea urchin
4. Starfish

1. Mollusca (Level 3)
2. Clam
   1. Mussel
   2. Oyster
   3. Scallop
3. Octopus
4. Squid
5. Conch
6. Slug
   1. Snail

1. Sponge

1. Arachnid
2. Mite
3. Pseudoscorpion
4. Scorpion
5. Spider
   1. Tarantula
6. Tick

1. Crustacean (Level 3)
2. Crab
3. Crayfish
4. Decapod
5. Krill
6. Lobster
7. Malacostraca
8. Ostracod
9. Shrimp
10. Woodlouse

1. Hexapoda
2. Springtail
3. Insect (Level 3)
   1. Pterygota
4. Cockroach
5. Earwig
6. Flea
7. Louse
   1. Body louse
8. Mantis
9. Phasmatodea
10. Termite

This section contains 5 articles.

1. Beetle
2. Coccinellidae
3. Dung beetle
4. Firefly
5. Weevil

This section contains 10 articles.

1. Fly
2. Common fruit fly
3. Black fly
4. Botfly
5. Crane fly
6. Calliphoridae
7. Tabanidae
8. Housefly
9. Mosquito
10. Tsetse fly

This section contains 7 articles.

1. Hemiptera
2. Cicada
3. Bed bug
4. Leafhopper
5. Aphid
6. Scale insect
7. Whitefly

This section contains 10 articles.

1. Hymenoptera
2. Ant
   1. Fire ant
   2. Carpenter ant
3. Bee
   1. Bumblebee
   2. Africanized bee
   3. Western honey bee
4. Wasp
   1. Hornet

This section contains 8 articles.

1. Lepidoptera
2. Butterfly
3. Bombyx mori
4. Geometer moth
5. Lymantria dispar dispar
6. Moth
7. Pieris brassicae
8. Swallowtail butterfly

This section contains 3 articles.

1. Odonata
2. Damselfly
3. Dragonfly

This section contains 6 articles.

1. Orthoptera
2. Cricket (insect)
3. Grasshopper
4. Mole cricket
5. Locust
6. Tettigoniidae

1. Trilobite

This section contains 3 articles.

1. Myriapoda
   1. Centipede
   2. Millipede

This section contains 3 articles.

1. Chelicerata
2. Eurypterid
3. Xiphosura

This section contains 3 articles.

1. Nematode
   1. Caenorhabditis elegans
2. Tardigrade

This section contains 5 articles.

1. Annelid
   1. Earthworm
   2. Leech
   3. Polychaete
2. Bryozoa

This section contains 2 articles.

1. Flatworm
   1. Cestoda

1. Agnatha
2. Hagfish
3. Lamprey
4. Ostracoderm

1. Fish (Level 3)
2. Coral reef fish
3. Deep-sea fish
4. Chondrichthyes
5. Acanthodii
6. Osteichthyes
   1. Actinopterygii
   2. Sarcopterygii
      1. Coelacanth
      2. Lungfish
7. Placoderm
8. Anglerfish
9. Arapaima
10. Chimaera
11. Eel
12. Electric eel
13. Flying fish
14. Milkfish
15. Northern pike
16. Oarfish
17. Mullet
18. Ophidiiformes
19. Scorpaeniformes
20. Stickleback

This section contains 6 articles.

1. Batomorphi
2. Stingray
3. Manta ray
4. Skate
5. Sawfish
6. Electric ray

This section contains 30 articles.

1. Perciformes
2. Barracuda
3. Cichlid
   1. Tilapia
4. Cyprinodontiformes
   1. Guppy
5. Flatfish
   1. Flounder
   2. Halibut
   3. Plaice
   4. Turbot
6. Gadidae
   1. Alaska pollock
   2. Cod
   3. Haddock
7. Goby
8. Mackerel
9. Marlin
10. Mahi-mahi
11. Serranidae
    1. European seabass
    2. Grouper
12. Seahorse
13. Siamese fighting fish
14. Swordfish
15. Perch
16. Remora
17. Tetraodontiformes
    1. Ocean sunfish
    2. Tetraodontidae
18. Tuna
19. Wrasse

This section contains 2 articles.

1. Characiformes
2. Piranha

This section contains 2 articles.

1. Bichir
2. Sturgeon

This section contains 5 articles.

1. Anchovy
2. Herring
3. Ilish
4. Sardine
5. Sprat

This section contains 4 articles.

1. Cypriniformes
   1. Carp
   2. Goldfish
   3. Koi

This section contains 2 articles.

1. Galaxiidae
2. Smelt

This section contains 3 articles.

1. Salmonidae
2. Salmon
3. Trout

This section contains 6 articles.

1. Shark
2. Great white shark
3. Hammerhead shark
4. Tiger shark
5. Nurse shark
6. Whale shark

This section contains 2 articles.

1. Catfish
2. Loricariidae

1. Amphibian (Level 3)
2. Caecilian
3. Salamander
   1. Newt
4. Frog
   1. Hylidae
   2. Leptodactylidae
   3. True toad
   4. True frog
      1. American bullfrog

1. Reptile (Level 3)
2. Crocodilia
   1. Alligator
   2. Caiman
   3. Crocodile
3. Lizard
   1. Chameleon
   2. Gecko
   3. Gila monster
   4. Green iguana
   5. Horned lizard
   6. Komodo dragon
   7. Skink
4. Snake
   1. Eastern copperhead
   2. Agkistrodon piscivorus
   3. Boidae
   4. Coral snake
   5. Garter snake
   6. Sea snake
   7. Mamba
   8. Naja
   9. Rattlesnake
   10. Adder
5. Tuatara
6. Turtle
   1. Alligator snapping turtle
   2. Box turtle
   3. Common snapping turtle
   4. Painted turtle
   5. Red-eared slider
   6. Sea turtle
   7. Tortoise
      1. Galápagos tortoise

This section contains 13 articles.

1. Dinosaur (Level 3)
   1. Allosaurus
   2. Apatosaurus
   3. Diplodocus
   4. Iguanodon
   5. Stegosaurus
   6. Triceratops
   7. Tyrannosaurus
   8. Velociraptor
2. Plesiosaur
3. Pterosaur
4. Synapsida
   1. Dimetrodon

This section contains 5 articles.

1. Bird (Level 3)
2. Seabird
3. Bird of prey
4. Palaeognathae
5. Archaeopteryx

This section contains 9 articles.

1. Accipiter
2. Eagle
   1. Golden eagle
3. Falcon
   1. Peregrine falcon
4. New World vulture
5. Old World vulture
6. Osprey
7. Secretarybird

This section contains 4 articles.

1. Duck
   1. Mallard
2. Goose
3. Swan

This section contains 2 articles.

1. Hummingbird
2. Swift

This section contains 1 article.

1. Nightjar

This section contains 4 articles.

1. Auk
2. Gull
3. Sandpiper
4. Tern

This section contains 4 articles.

1. Heron
2. Ibis
3. Shoebill
4. Stork

This section contains 4 articles.

1. Columbidae
   1. Dodo
   2. Passenger pigeon
   3. Rock dove

This section contains 3 articles.

1. River kingfisher
2. Hornbill
3. Hoopoe

This section contains 3 articles.

1. Cuckoo
2. Hoatzin
3. Turaco

This section contains 8 articles.

1. Galliformes
2. Chicken (Level 3)
3. Grouse
4. Guineafowl
5. Peafowl
6. Common pheasant
7. Common quail
8. Domestic turkey

This section contains 1 article.

1. Loon

This section contains 4 articles.

1. Gruiformes
2. Crane (bird)
3. Bustard
4. Rail

This section contains 2 articles.

1. Passerine
2. Songbird

This section contains 8 articles.

1. Bird-of-paradise
2. Corvidae
   1. Corvus
      1. Common raven
   2. Eurasian magpie
3. Honeyeater
4. Lyrebird
5. Shrike

This section contains 22 articles.

1. Bulbul
2. Cardinalidae
3. Finch
4. Icterid
5. Lark
6. Mockingbird
7. New World warbler
8. Old World flycatcher
   1. European robin
   2. Common nightingale
9. Ploceidae
10. Old World sparrow
    1. House sparrow
11. Starling
    1. Common myna
    2. Common starling
12. Sunbird
13. Swallow
14. Tit
15. Thrush
    1. American robin
16. Wren

This section contains 3 articles.

1. Antbird
2. Ovenbird (family)
3. Tyrant flycatcher

This section contains 5 articles.

1. Cormorant
2. Darter
3. Frigatebird
4. Pelican
5. Sulidae

This section contains 1 article.

1. Flamingo

This section contains 3 articles.

1. Honeyguide
2. Toucan
3. Woodpecker

This section contains 2 articles.

1. Procellariiformes
2. Albatross

This section contains 4 articles.

1. Parrot
2. Ara
3. Budgerigar
4. Cockatoo

This section contains 6 articles.

1. Cassowary
2. Emu
3. Kiwi
4. Moa
5. Common ostrich
6. Rhea

This section contains 1 article.

1. Penguin

This section contains 3 articles.

1. Owl
   1. Eurasian eagle-owl
   2. Barn owl

This section contains 1 article.

1. Tinamou

This section contains 2 articles.

1. Trogon
2. Resplendent quetzal

1. Mammal (Level 3)
2. Aardvark
3. Armadillo
4. Hyrax
5. Pangolin
6. Sirenia

This section contains 5 articles.

1. Bat
2. Megabat
3. Microbat
4. Pteropus
5. Vampire bat

This section contains 36 articles.

1. Carnivora
2. Bear
   1. Brown bear
   2. Giant panda
   3. Polar bear
3. Canidae
   1. Dog (Level 3)
      1. Dingo
   2. Coyote
   3. Fox
   4. Jackal
   5. Wolf
4. Felidae
   1. Cat (Level 3)
   2. Cheetah
   3. Cougar
   4. Jaguar
   5. Leopard
   6. Lion
   7. Lynx
   8. Smilodon
   9. Snow leopard
   10. Tiger
5. Hyena
6. Mongoose
7. Mustelidae
   1. European badger
   2. Honey badger
   3. Marten
   4. Otter
   5. Sea otter
   6. Stoat
   7. Weasel
   8. Wolverine
8. Procyonidae
9. Skunk

This section contains 8 articles.

1. Cetacea
2. Whale
3. Blue whale
4. Dolphin
5. Humpback whale
6. Orca
7. Porpoise
8. Sperm whale

This section contains 1 article.

1. Hedgehog

This section contains 38 articles.

1. Artiodactyl
2. Ruminant
3. Alpaca
4. Bovidae
   1. African buffalo
   2. American bison
   3. Antelope
   4. Aurochs
   5. Capra
   6. Cattle (Level 3)
   7. Gazelle
   8. Gaur
   9. Goat
   10. Impala
   11. Muskox
   12. Sheep (Level 3)
   13. Water buffalo
   14. Wildebeest
   15. European bison
   16. Yak
5. Camel
   1. Bactrian camel
   2. Dromedary
6. Deer
   1. Elk
   2. Moose
   3. Red deer
   4. Reindeer
7. Llama
8. Giraffe
9. Guanaco
10. Hippopotamus
11. Peccary
12. Pronghorn
13. Sus (genus)
    1. Pig (Level 3)
    2. Wild boar
14. Vicuña

This section contains 3 articles.

1. Lagomorpha
2. Hare
3. Rabbit

This section contains 8 articles.

1. Marsupial
2. Diprotodontia
   1. Kangaroo
   2. Koala
3. Dasyuromorphia
   1. Tasmanian devil
4. Opossum
5. Peramelemorphia

This section contains 3 articles.

1. Monotreme
2. Echidna
3. Platypus

This section contains 7 articles.

1. Perissodactyla
2. Donkey
3. Equidae
4. Horse (Level 3)
5. Rhinoceros
6. Tapir
7. Zebra

This section contains 2 articles.

1. Anteater
2. Sloth

This section contains 4 articles.

1. Pinniped
2. Eared seal
3. Earless seal
4. Walrus

This section contains 22 articles.

1. Primate (Level 3)
2. Monkey
3. Ape
   1. Pan (genus)
      1. Chimpanzee
      2. Bonobo
   2. Gibbon
   3. Gorilla
   4. Orangutan
   5. Human (Level 1)
4. New World monkey
   1. Capuchin monkey
   2. Spider monkey
5. Old World monkey
   1. Baboon
   2. Macaque
   3. Rhesus macaque
6. Strepsirrhini
   1. Slow loris
   2. Galago
   3. Lemur
7. Tarsier

This section contains 3 articles.

1. Proboscidea
2. Elephant
3. Mammoth

This section contains 15 articles.

1. Rodent (Level 3)
2. Capybara
3. Nutria
4. Beaver
5. Dormouse
6. Guinea pig
7. Hamster
8. Marmot
9. Mouse
10. Muridae
11. Muskrat
12. Porcupine
13. Rat
    1. Brown rat
14. Squirrel

This section contains 2 articles.

1. Shrew
   1. Mole (animal)

This section contains 1 article.

1. Siamese cat

This section contains 3 articles.

1. American Brahman
2. Hereford cattle
3. Holstein Friesian

This section contains 6 articles.

1. Gun dog
2. Herding dog
3. Hound
4. Mastiff
5. Spitz
6. Terrier

This section contains 5 articles.

1. Arabian horse
2. Andalusian horse
3. Friesian horse
4. Thoroughbred
5. Pony

This section contains 1 article.

1. Mule

This section contains 1 article.

1. Merino

This section contains 3 articles.

1. Green algae
2. Charophyta
3. Chlorophyta

This section contains 5 articles.

1. Bryophyte
2. Hornwort
3. Marchantiophyta
4. Moss
   1. Sphagnum

This section contains 4 articles.

1. Pteridophyte
2. Fern
   1. Equisetum
3. Lycophyte

This section contains 13 articles.

1. Gymnosperm
2. Cycad
3. Ginkgo biloba

Pinophyta (conifers) (10 articles)

1. Conifer
2. Cedrus
3. Cupressus
4. Douglas fir
5. Fir
6. Juniper
7. Pine
8. Podocarpus
9. Sequoioideae
10. Spruce

1. Monocotyledon
2. Alismatales
   1. Araceae
      1. Anthurium
      2. Philodendron
      3. Taro
3. Arecaceae
   1. Coconut
   2. Date palm
4. Asparagales
   1. Agave
   2. Allium
      1. Garlic
      2. Leek
      3. Onion
   3. Aloe
   4. Amaryllis
   5. Asparagus
   6. Gladiolus
   7. Iridaceae
      1. Iris
      2. Saffron
   8. Lily of the valley
   9. Narcissus
   10. Orchid
       1. Vanilla
   11. Yucca
5. Pontederia crassipes
6. Yam
7. Liliales
   1. Alstroemeria
   2. Colchicum
   3. Liliaceae
      1. Lilium
      2. Tulip
8. Pandanales
   1. Pandanus
9. Zingiberales
   1. Arrowroot
   2. Banana
      1. Cooking banana
   3. Canna
   4. Cardamom
   5. Ginger
   6. Heliconia

This section contains 20 articles.

1. Bromeliaceae
   1. Puya
   2. Spanish moss
   3. Pineapple
2. Cyperaceae
3. Juncus
4. Poaceae
   1. Bamboo
   2. Barley
   3. Maize (Level 3)
   4. Millet
   5. Oat
   6. Rice (Level 3)
      1. Oryza sativa
   7. Rye
   8. Sorghum
   9. Sugarcane
   10. Wheat (Level 3)
       1. Common wheat
5. Typha

1. Eudicots

This section contains 10 articles.

1. Apiaceae
   1. Anise
   2. Carrot
   3. Celery
   4. Cumin
   5. Fennel
   6. Parsley
   7. Parsnip
2. Ginseng
3. Hedera

This section contains 14 articles.

1. Asteraceae
   1. Artichoke
   2. Bellis perennis
   3. Chicory
   4. Chrysanthemum
   5. Cirsium
   6. Dahlia
   7. Lettuce
   8. Solidago
   9. Helianthus
   10. Sonchus
   11. Tagetes
   12. Taraxacum
2. Campanulaceae

This section contains 18 articles.

1. Brassicaceae
   1. Arabidopsis thaliana
   2. Brassica oleracea
      1. Broccoli
      2. Cabbage
      3. Cauliflower
      4. Collard (plant)
      5. Kale
      6. Kohlrabi
   3. Chinese cabbage
   4. Eruca vesicaria
   5. Horseradish
   6. Radish
      1. Daikon
   7. Rapeseed
   8. Rutabaga
   9. Tropaeolum
   10. Turnip
2. Papaya

This section contains 8 articles.

1. Amaranthaceae
   1. Amaranth
   2. Beetroot
   3. Chard
   4. Spinach
   5. Sugar beet
   6. Quinoa
2. Cactus
3. Buckwheat

This section contains 7 articles.

1. Cucurbitaceae
   1. Cucumis melo
   2. Cucumber
   3. Cucurbita
      1. Pumpkin
      2. Zucchini
   4. Watermelon

This section contains 12 articles.

1. Brazil nut
2. Diospyros
3. Ericaceae
   1. Blueberry
   2. Cranberry
   3. Rhododendron
      1. Azalea
4. Theaceae
   1. Camellia
5. Impatiens
6. Kiwifruit
7. Primulaceae

This section contains 14 articles.

1. Fabaceae
   1. Bean
   2. Chickpea
   3. Green bean
   4. Lentil
   5. Lima bean
   6. Liquorice
   7. Mimosa
   8. Pea
   9. Peanut
   10. Phaseolus vulgaris
   11. Soybean (Level 3)
   12. Tamarind
   13. Vicia faba

This section contains 9 articles.

1. Alder
2. Beech
3. Birch
4. Chestnut
5. Hazelnut
6. Hickory
7. Oak
8. Pecan
9. Walnut

This section contains 11 articles.

1. Lamiaceae
   1. Basil
   2. Lavandula
   3. Mentha
   4. Salvia
   5. Thyme
2. Oleaceae
   1. Fraxinus
   2. Olive
3. Sesame
4. Verbena

This section contains 7 articles.

1. Euphorbiaceae
   1. Cassava
   2. Poinsettia
2. Flax
3. Hypericum
4. Viola
5. Willow

This section contains 6 articles.

1. Henna
2. Myrtaceae
   1. Clove
   2. Eucalyptus
   3. Guava
3. Pomegranate

This section contains 20 articles.

1. Cannabis
2. Elm
3. Moraceae
   1. Breadfruit
   2. Ficus sycomorus
   3. Fig
   4. Jackfruit
   5. Morus
4. Rosaceae
   1. Almond
   2. Apple
   3. Apricot
   4. Blackberry
   5. Cherry
   6. Peach
   7. Pear
   8. Plum
   9. Raspberry
   10. Rose
   11. Strawberry

This section contains 12 articles.

1. Citrus
   1. Grapefruit
   2. Kumquat
   3. Lemon
   4. Lime
   5. Orange
   6. Mandarin orange
2. Cashew
3. Lychee
4. Mahogany
5. Mango
6. Maple

This section contains 7 articles.

1. Solanaceae
   1. Bell pepper
   2. Chili pepper
   3. Eggplant
   4. Potato (Level 3)
   5. Tomato
2. Sweet potato

This section contains 14 articles.

1. Cornus
2. Gentianales
   1. Apocynaceae
   2. Rubiaceae
      1. Gardenia
3. Malvaceae
   1. Adansonia
   2. Durian
   3. Okra
4. Proteales
   1. Proteaceae
      1. Macadamia
   2. Nelumbo
   3. Platanus
5. Blackcurrant
6. Grape

1. Fungus (Level 3)
2. Mushroom
3. Yeast
   1. Saccharomyces cerevisiae
4. Ascomycota
5. Basidiomycota
6. Zygomycota

This section contains 6 articles.

1. Agaricus
2. Boletus edulis
3. Chanterelle
4. Pleurotus ostreatus
5. Shiitake
6. Truffle

This section contains 2 articles.

1. Amanita muscaria
2. Amanita phalloides

1. Eukaryote (Level 3)
2. Plankton
3. Protist
4. Paramecium
5. Prokaryote
   1. Archaea (Level 3)
   2. Bacteria (Level 3)
      1. Cyanobacteria
      2. Escherichia coli
      3. Salmonella
      4. Staphylococcus aureus
6. Rhizaria
7. Excavata
   1. Euglenozoa
8. Algae (Level 3)
   1. Red algae
   2. Seaweed
9. Chromalveolata
   1. Stramenopile
      1. Brown algae
         1. Kelp
      2. Diatom
   2. Haptophyte
   3. Cryptomonad
   4. Alveolate
      1. Dinoflagellate
10. Lichen
11. Amoebozoa
12. Slime mold

1. Health (Level 3)
   1. Mental health (Level 3)
2. Nutrition (Level 3)
   1. Diet
   2. Dietary supplement
   3. Food group
   4. Hunger
   5. Malnutrition
   6. Vitamin
3. Hygiene (Level 3)
   1. Bathing
   2. Feminine hygiene
   3. Oral hygiene
   4. Shaving
4. Physical fitness
   1. Body mass index
   2. Exercise (Level 3)
   3. Obesity (Level 3)
   4. Weight loss
5. Ageing (Level 3)
6. Breastfeeding
7. Fertilisation
   1. Infertility
8. Occupational safety and health
   1. Personal protective equipment
9. Stress (biology)