10 most difficult biology riddles A list of ten (out of 34) 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 24% hippopotamushippopotamus26%rhinocerosrhinoceros24%camelcamel14%okapiokapi34%Created by: Paweł Kołodziejczyk. Statistics based on 4283 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 30% 4 meters (13 feet)4 meters (13 feet)30%20 meters (60 feet)20 meters (60 feet)16%40 meters (130 feet)40 meters (130 feet)26%80 meters (260 feet)80 meters (260 feet)27%Created by: globalquiz.org. Statistics based on 8018 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 33% coke from coalcoke from coal6%saltpetersaltpeter16%digestive enzymedigestive enzyme33%heroinheroin44%Created by: Kasia. Statistics based on 17159 answers in 4 languages »beverages riddles » Which protein causes blood to clot?Fibrinogen. In order to reduce the loss of blood and facilitate the recovery of the blood vessel at the site of the injury, a blood clot is formed. It is made up of platelets and dissolved plasma protein-fibrogen. By the substance released by the blood-thrombin plate, fibrogen changes into fibrin, which creates a dense network at the site of injury.very hard 35% fibrinogenfibrinogen35%fibrinfibrin30%myosinmyosin12%pepsinpepsin21%Created by: pawnik. Statistics based on 3600 answers in 2 languages »blood riddles » To which superfamily do ants belong?Wasps. It might be surprising, but ants form part of wasp superfamily. They are closer related to wasps and hornets than bees and bumblebees, that appear to be so much similar.very hard 36% BeesBees22%HornetsHornets19%WaspsWasps36%BumblebeesBumblebees22%Created by: fitjaco93. Statistics based on 2491 answers in 2 languages »insects 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 42% raspberryraspberry3%orange peelorange peel42%key lime and herbskey lime and herbs36%almondsalmonds17%Created by: smyru. Statistics based on 10788 answers in 2 languages »drinks 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 44% In Central America onlyIn Central America only16%In the west of the United StatesIn the west of the United States44%in the eastern Brazilin the eastern Brazil17%in the entire North and Central Americain the entire North and Central America21%Created by: Paweł Kołodziejczyk. Statistics based on 9474 answers in 4 languages »plants 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 48% In the NileIn the Nile13%In the Ganges RiverIn the Ganges River48%In the AmazonIn the Amazon18%In the entire Central Africa (Congo and its tributaries)In the entire Central Africa (Congo and its tributaries)19%Created by: Paweł Kołodziejczyk. Statistics based on 17671 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 49% liverliver44%heartheart3%skinskin49%pancreaspancreas2%Created by: smyru. Statistics based on 4938 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 50% hydrologyhydrology9%hydroculturehydroculture18%hydroponicshydroponics50%hydrofarminghydrofarming21%Created by: Paweł Kołodziejczyk. Statistics based on 16563 answers in 2 languages »crops riddles » Play biology quiz and see all the questions.