Mammals, including humans, need dry and empty lungs to breathe properly. When we inhale, small air sacs in our lungs extract oxygen from the air and transport it to our cells.
Fish cannot use mammalian lungs, as they would fill with fluid when submerged underwater, rendering them useless. However, fish still require oxygen to survive. To obtain oxygen from water, they rely on specialized organs called “gills.”
Gills are delicate organs filled with blood vessels. Fish breathe by taking water into their mouths and expelling it through the gill passages. As water flows over the thin walls of the gills, dissolved oxygen enters the bloodstream and is transported to the fish’s cells.
If fish can breathe underwater, why do some marine creatures like dolphins and whales come up to the ocean’s surface? That’s because dolphins and whales are not fish at all! They are mammals, just like humans.
Dolphins and whales share many similarities with humans: they give birth to live young instead of laying eggs, are warm-blooded, and have lungs for breathing air. When a whale or dolphin surfaces, it inhales air through its blowhole, which is located on the top of its head.
Fish facts:
- There are more fish species than the combined total of amphibians, reptiles, birds, and mammals.
- Fish have existed on Earth for over 450 million years.
- The largest fish is the great whale shark, which can grow up to 50 feet in length.
Try It Out
Feeling curious about fish? You can create your own fish companion using recycled materials from around your house.
Start by using an empty dish soap bottle as the fish’s body. Seek assistance from your parents to cut out the fish’s body according to the provided instructions.
Once you have the fish bottle body, let your creativity flow! Challenge yourself to incorporate other recyclable materials to give your fish some unique features.
An old cereal box can be transformed into colorful fins with a little paint. Use old bottle caps as fish eyes! With over 25,000 fish species in the sea to inspire your design, the possibilities are endless.
When you finish, email a picture of your creation to hello@wonderopolis.org and share your aquatic masterpiece made from recycled materials with Wonderopolis:
FAQ
1. How do fish breathe underwater?
Fish breathe underwater through a process called gills. Gills are specialized organs located on the sides of a fish’s head. They are made up of thin filaments that are rich in blood vessels. When a fish opens its mouth, water flows in and passes through the gills. As the water flows over the gills, oxygen is extracted from the water and absorbed into the fish’s bloodstream. At the same time, carbon dioxide, a waste product, is released into the water. This process allows fish to extract oxygen from the water and remove waste gases, enabling them to breathe underwater.
2. Do all fish breathe in the same way?
No, not all fish breathe in the same way. While most fish use gills to extract oxygen from the water, there are some exceptions. For example, lungfish have both gills and lungs, allowing them to breathe in both water and air. Other fish species, such as the mudskipper, have developed the ability to breathe air by using specialized structures called labyrinth organs. These organs allow them to extract oxygen from the air and supplement their gill respiration. Overall, fish have evolved various adaptations to breathe underwater, depending on their habitat and environmental conditions.
3. Can fish breathe in polluted water?
Fish have a remarkable ability to tolerate certain levels of water pollution, but excessive pollution can be harmful to their respiratory system. Pollutants such as chemicals, heavy metals, and toxins can impair the function of a fish’s gills, making it difficult for them to extract oxygen from the water. This can lead to respiratory distress, reduced growth, and even death. Therefore, it is important to maintain clean and healthy aquatic environments to ensure the well-being of fish and other aquatic organisms.
4. How do fish survive in oxygen-depleted water?
Some fish species have adaptations that allow them to survive in oxygen-depleted water. For example, certain species of catfish can breathe atmospheric air using a modified swim bladder, which acts as a lung. These fish are capable of gulping air at the water’s surface and extracting oxygen from it. Additionally, some fish have the ability to tolerate low oxygen levels by reducing their metabolic rate and conserving energy. This allows them to survive in conditions where oxygen availability is limited. However, prolonged exposure to oxygen-depleted water can still be detrimental to fish health and may lead to physiological stress or death.
5. Can fish survive out of water?
Most fish are adapted to live in water and cannot survive for long periods out of the water. However, there are a few exceptions. Lungfish, for example, have the ability to breathe air and can survive for extended periods out of water by burrowing into mud or estivating in a dormant state. Some mudskippers, as mentioned earlier, can also survive short periods out of water by breathing air through their labyrinth organs. However, it’s important to note that these adaptations are specific to certain fish species, and most fish require a constant supply of water to survive.
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