Fishes are what type of animals

Fish have developed special senses, too. Because water transmits sounds, disperses chemicals, and conducts electricity better than air, fish rely less on their vision and more on their hearing, taste, and smell. Many can detect motion in the water using a special row of scales with sensors known as the lateral line. Others can find their prey and even navigate by detecting electrical charges. One reason fish are so diverse is that 70 percent of the planet is covered in water.

The animals in this group live in a variety of habitats ranging from coral reefs and kelp forests to rivers, streams, and the open ocean. Another is that fish are very old on the evolutionary scale. According to fossil records, they have been on Earth for more than million years! The total number of living fish species—about 32,— is greater than the total of all other vertebrate species amphibians, reptiles, birds, and mammals combined.

From the National Geographic book, Animal Encyclopedia , Watch this water-spitting fish identify human faces, get rewards. All rights reserved. Therefore, scientists have to use careful wording when defining a fish. There are two generally accepted scientific definitions of a fish:. Notice that neither of these definitions mention skeletal features.

Both definitions include fishes with skeletons made of bone like tuna and fishes with skeletons made of cartilage like sharks. This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password.

Main menu About this Site Table of Contents. Home Biological Fish What is a Fish? What is a Fish? Fish and Fishes Fish are aquatic vertebrate animals that have gills but lack limbs with digits, like fingers or toes. Defining a Fish Defining a fish is difficult because the term fish includes a very wide range of aquatic animals. Voice of the Sea. Table 4. Terms and definitions of words used to describe fish Term Definition Poikilothermic An animal whose temperature adjusts with the outside temperature.

Aquatic Living in the water, either seawater or freshwater. Chordate Animals with notochords. Gills Organs for gas exchange. Most fishes breathe with gills.

Scales Thin plates that cover the thin skin of fish. Fins If fish have appendages, they are thin, flat moveable fan-like parts. Further Investigations. Table of Contents: What is a Fish? Activity: Draw a Fish. Activity: What is a Fish? Special Features:. Further Investigations: What is a Fish? Representative Image:. Further Investigations: What is an Invertebrate? Question Set: What is a Mammal? There are more than 32, species of fish, which is more than all of the mammals, birds, reptiles and amphibians combined.

So what makes fish different from other animals? Fish are unique in that they have a combination of gills and fins and that they live only in the water. While some invertebrates and amphibians have gills, some mammals and amphibians have fins and lots of animals live in water, only fish have the combination of all three attributes. Just like almost every other animal on the planet, fish have brains.

They are all invertebrates. It is widely accepted that fish can and do feel pain. Fish brains have neurons called nociceptors which detect intense pressure, temperature changes and caustic chemicals. Fish produce the same opioids innate painkillers as mammals do in response to injury. If they were aware that fish feel pain just like rabbits do, perhaps they would think twice. However, science is increasingly demonstrating that fish are sentient and emotional beings.

Just like other animals, fish respond to painful events with changes in their behaviour and physiology. Fish learn to avoid things that cause them harm, which helps them to survive. Goldfish have been shown to remember the exact colours and locations of specific feeding tubes up to a year after exposure. Fish may not be capable of experiencing the range of feelings that humans and some non-human animals do, such as anger, joy, worry, amusement and disgust.

Some people might assume that animals are medium-sized four-legged creatures, as those are the animals that they are most familiar with. They may not know that the animal kingdom spans all sorts of animals, including marine life like fish. Another reason why people may think that fish are not animals is because of the Catholic doctrine which states that Catholics must abstain from eating meat on Fridays, but that they can eat fish.

When we look at the history of how fish came to be considered not meat, we can see that this is influenced by both religion and language. The Catholic Church defines meat as the flesh of warm-blooded animals. The real reason why some Catholics avoid meat on Fridays stems from the Biblical tales of how Jesus fasted for 40 days and how he died on a Friday.