10 most difficult biology riddles A list of ten (out of 32) biology related questions that are the most often answered incorrectly Biology quiz Which animal doesn't belong to odd-toed ungulates?Rhinoceros. Odd-toed ungulates include the horse, the tapir, and the rhinoceros.very hard 26% hippopotamushippopotamus26%rhinocerosrhinoceros26%camelcamel15%okapiokapi31%Created by: Paweł Kołodziejczyk. Statistics based on 2868 answers in 2 languages »animals riddles » How deep is the root system of a giant sequoia?4 meters (13 feet). The sequoias root system is wide spreading, but shallow. There is no taproot. A mature sequoia's roots can occupy over 1 acre of earth and contain over 90,000 cubic feet of soil. very hard 32% 4 meters (13 feet)4 meters (13 feet)32%20 meters (60 feet)20 meters (60 feet)15%40 meters (130 feet)40 meters (130 feet)24%80 meters (260 feet)80 meters (260 feet)27%Created by: globalquiz.org. Statistics based on 6456 answers in 4 languages »trees riddles » What was included in the original Pepsi-Cola recipe?Digestive enzyme. Pepsi Cola, first introduced in 1898, was named after pepsin (enzyme) and kola (nuts). In 1931, the company entered bankruptcy and changed hands. The new owners changed the recipe to resemble more Coca-Cola.very hard 36% coke from coalcoke from coal6%saltpetersaltpeter16%digestive enzymedigestive enzyme36%heroinheroin40%Created by: Kasia. Statistics based on 13230 answers in 4 languages »beverages riddles » Where do coast redwoods grow?In the west of the United States. Common names of sequoia sempervirens include coast redwood, coastal redwood and California redwood. It is an evergreen, long-lived, monoecious tree living 1,200–1,800 years or more. This species includes the tallest living trees on Earth. It comes from coastal mountains of Oregon and California. (the west of the USA).hard 47% In Central America onlyIn Central America only15%In the west of the United StatesIn the west of the United States47%in the eastern Brazilin the eastern Brazil15%in the entire North and Central Americain the entire North and Central America21%Created by: Paweł Kołodziejczyk. Statistics based on 6809 answers in 4 languages »plants riddles » What is a Curaçao liqueur flavored with?Orange peel. Curaçao is made of dried peel of Laraha (Citrus aurantium currassuviencis), a citrus too bitter to be edible. The beverage and the plant come from Dutch Curaçao island by the coasts of Venezuela. Feral Laraha evolved from domesticated Seville orange brought to the island by Spanish settlers. Its peel is also used in medicine to treat stomach.hard 49% raspberryraspberry2%orange peelorange peel49%key lime and herbskey lime and herbs31%almondsalmonds16%Created by: smyru. Statistics based on 4171 answers in 2 languages »drinks riddles » Where do gharials live?In the Ganges River. The gharial (Gavialis gangeticus), also known as the gavial, and the fish-eating crocodile, is a crocodilian of the family Gavialidae, native to the northern part of the Indian Subcontinent. It is harmless to humans.hard 50% In the NileIn the Nile12%In the Ganges RiverIn the Ganges River50%In the AmazonIn the Amazon17%In the entire Central Africa (Congo and its tributaries)In the entire Central Africa (Congo and its tributaries)18%Created by: Paweł Kołodziejczyk. Statistics based on 12745 answers in 2 languages »reptiles riddles » Which human organ is the largest?Skin is the largest in size (about 2 square meter) and the heaviest organ, making up about 16% of body weigh. It is composed of 3 layers: epidermis, dermis and hypodermis.hard 51% liverliver43%heartheart3%skinskin51%pancreaspancreas1%Created by: smyru. Statistics based on 2266 answers in 2 languages »medicine riddles » How is the soilless cultivation of plants called?Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite or gravel.hard 52% hydrologyhydrology9%hydroculturehydroculture19%hydroponicshydroponics52%hydrofarminghydrofarming19%Created by: Paweł Kołodziejczyk. Statistics based on 12100 answers in 2 languages »fruits riddles » If you were forced to feast along the tribe of cannibals, which part of the human body should you avoid at most?Brain. Eating your own and closely related species is generally a bad idea, as there are species-specific parasites and germs that might get transmitted. But eating brain, bone marrow, and the spinal cord is particularly dangerous, as you may get deadly prion diseases like kuru. hard 54% heartheart4%musclesmuscles6%liverliver34%brainbrain54%Created by: life-o-holic. Statistics based on 19329 answers in 2 languages »cannibalism riddles » What it is an autotomy?Self amputation (e.g. of a tail). Autotomy (from the Greek auto- "self-" and tome "severing") or self amputation is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude a predator's grasp or to distract the predator and thereby allow escape. The lost body part may be regenerated later.hard 58% eating only one kind of spieces (e.g. the koala is eating leaves of the eucalyptus)eating only one kind of spieces (e.g. the koala is eating leaves of the eucalyptus)10%self amputation (e.g. of a tail)self amputation (e.g. of a tail)58%hunting of its own kindhunting of its own kind21%in-breeding (small gene pool)in-breeding (small gene pool)9%Created by: Paweł Kołodziejczyk. Statistics based on 12553 answers in 4 languages »human anatomy riddles » Play biology quiz and see all the questions.