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Crepuscular, a classification of animals that are active primarily during twilight, making them similar to nocturnal animals. Diurnality, plant or animal behavior characterized by activity during the day and sleeping at night. Cathemeral, a classification of organisms with sporadic and random intervals of activity during the day or night.
A group of muskoxen in Alaska. The biodiversity of tundra is low: 1,700 species of vascular plants and only 48 species of land mammals can be found, although millions of birds migrate there each year for the marshes. [9] There are also a few fish species. There are few species with large populations.
Arctic tundra is the northernmost (and coldest) of European habitats, in extreme northern Scandinavia, Svalbard archipelago, northernmost part of Russia. Some typical animals include reindeer, Arctic fox, brown bear, ermine, lemmings, partridges, snowy owl and many insects. Most tundra animals undergo hibernation during the colder season.
Most eel species are nocturnal, and thus are rarely seen. Sometimes, they are seen living together in holes or "eel pits". Sometimes, they are seen living together in holes or "eel pits". Some eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 m (13,000 ft).
Gymnotus species are nocturnal and mainly feed on aquatic insects, crustaceans, small fish and other small animals, [9] but may also take plant material. [8] Being electric fish, they generate weak electric fields used for navigation, finding prey and communicating with other individuals of their species.
Both plant species and animal species have become endangered. The Aleutian shield fern is a plant species that have been endangered due to caribou tramping and grazing, slumping from growing substrate, and human foot traffic. [9] Animal species that are endangered in the tundra include the Arctic fox, caribou, and polar bears.
Initially, most animals were diurnal, but adaptations that allowed some animals to become nocturnal is what helped contribute to the success of many, especially mammals. [7] This evolutionary movement to nocturnality allowed them to better avoid predators and gain resources with less competition from other animals. [ 8 ]
Found almost exclusively in fresh water (the only exceptions are species that occasionally may visit brackish water to feed), these mostly nocturnal fish are capable of producing electric fields to detect prey, for navigation, communication, and, in the case of the electric eel (Electrophorus electricus), attack and defense. [2]