🤔 Today's Trivia Question:

What Species Can Live Both in Water and on Land?

Correct Answer: A) Amphibians

🐠 Discover the Fascinating Lives of Earth's Vertebrate Species

Amphibians

Red Salamander (Pseudotriton ruber) The red salamander (Pseudotriton ruber) is native to the eastern United States. Amphibians evolved from aquatic tetrapods, which descended from lobe-finned fish, between the Early Devonian Period and the Early Pennsylvanian Subperiod. The term "amphibian," meaning "living a double life," reflects their dual existence, though some species are fully terrestrial or aquatic.

Amphibians comprise three main groups: caecilians, salamanders, and anurans (frogs and toads), totaling over 7,300 species. Many have evolved direct development, bypassing the aquatic larval stage. For example, lungless salamanders and some caecilians and anurans hatch as miniatures of their adult form. Reproductive methods vary, with some species laying eggs in water, on vegetation, or creating foam nests. Notably, marsupial frogs carry eggs in a pouch on their backs.

Fishes

A whale shark (Rhincodon typus) swimming near a snorkeler off the coast of Australia. These enormous fish, which feed on small organisms filtered from the water, pose no danger to humans. Scuba divers and ichthyologists often study these gentle giants in their natural habitats. Whale sharks are an iconic species within marine biology and are celebrated for their impressive size and unique feeding habits.

Fish first appeared around 518 million years ago during the Cambrian Period. Today, there are over 30,000 species in both fresh and saltwater environments. These species range from primitive jawless fish like lampreys and hagfishes to cartilaginous species such as sharks, skates, and rays, and finally to the diverse group of bony fishes.

Fishes exhibit a vast range of sizes, from tiny species less than 10 mm long to whale sharks over 20 meters in length. They inhabit diverse environments, from warm thermal springs to cold Arctic waters and deep ocean trenches. Reproductive strategies also vary widely; many species lay numerous small eggs, which face high mortality rates, while a few species provide parental care or give live birth.

Reptiles

Male Flying Lizard (Draco volans) Reptiles, air-breathing vertebrates, exhibit internal fertilization, amniotic development, and skin covered with scales. Major reptile groups include turtles, tuataras, lizards, snakes, and crocodiles, with over 8,700 species. Evolving from amphibians, reptiles retained several structural characteristics while adapting to diverse environments.

While most reptiles are carnivorous, some, like tortoises, are herbivorous. As cold-blooded animals, they thrive in temperate and tropical regions. Reptiles display varied locomotion, from creeping and swimming to running. They lay large, shelled eggs, with some species providing parental care. Most reptiles are terrestrial, though a few are aquatic.

Birds

Eastern White Pelicans (Pelecanus onocrotalus) Birds, with over 9,600 species, are unique for their feathers. They are warm-blooded vertebrates related to reptiles and possess a four-chambered heart, wings, hard-shelled eggs, and keen vision. Birds are capable of flight, though some species are flightless.

Birds likely evolved from theropod dinosaurs, a group of carnivorous dinosaurs, during the Early Cretaceous period. While most birds care for their young in nests, some species hatch in a well-developed state and can feed themselves or fly immediately. Their diverse adaptations have made birds a highly successful and varied group of animals.

Mammals

Okapi (Okapia johnstoni) Mammals, with about 5,000 species, nourish their young with milk from mammary glands. Distinguished by features such as hair, a lower jaw hinged directly to the skull, and a diaphragm, mammals evolved around 200 million years ago. They range in size from tiny shrews to massive whales.

Mammals are mostly terrestrial, feeding on both animal and vegetable matter, though some are aquatic. They move in various ways, including burrowing, running, flying, or swimming. Most mammals give live birth, with the young developing inside the uterus. Placental mammals have a prolonged developmental period, while marsupials carry undeveloped young in a pouch. Monotremes, like the platypus, lay eggs.