How do fish breathe underwater? Simple explanation

📚 How Fish Breathe Underwater: A Simple Explanation

Fish have a special trick that lets them live underwater: gills. Gills are like our lungs, but they work in the water! They allow fish to take oxygen from the water, which is essential for them to survive. Let's dive into how they work:

• 🌊 Water In, Oxygen Out: Fish open their mouths to take in water. The water then flows over their gills.
• 🧬 Gill Power: Gills are full of tiny blood vessels. These vessels absorb the oxygen dissolved in the water.
• 💨 Waste Out: As the gills take in oxygen, they release carbon dioxide (a waste gas) back into the water.
• 🐟 Moving On: The water, now with less oxygen and more carbon dioxide, exits the fish through openings on the sides of its head.

🧫 The Science Behind It

The amazing process of how fish breathe depends on a principle called diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. In this case, oxygen is more concentrated in the water than in the fish's blood, so it diffuses into the blood through the gills.

🧰 Materials for a Gill Model

• 📦 Empty plastic bottle
• ✂️ Scissors or craft knife (adult supervision required!)
• 🎈 Balloons (2)
• 🥤 Straw
• 💧 Water

🧪 Experiment: Building a Simple Gill Model

This experiment simulates how gills work using a simple model. Remember: always ask an adult for help when using scissors or knives.

1. ✂️ Cut the top and bottom off the plastic bottle.
2. 🎈 Cut the neck off of both balloons. Stretch one balloon over one end of the bottle.
3. 🎈 Insert the straw into the other balloon, and tape it tightly to secure it. Stretch the balloon over the other end of the bottle. This is your 'gill.'
4. 💧 Submerge the bottle (your 'fish') in a container of water.
5. 🌬️ Blow air through the straw. Observe what happens to the water and the 'gill.'

What's happening? When you blow air through the straw (representing the fish breathing), it creates bubbles. The balloon on the end acts as a membrane, allowing 'oxygen' to enter (air in this case) and 'carbon dioxide' to exit.

🤔 Why Can't Humans Breathe Underwater Like Fish?

Our lungs are designed to breathe air, not extract oxygen from water. Human lungs aren't efficient enough to get enough oxygen from the water because water holds much less oxygen than air, and our lungs don't have enough surface area like the fish gills do.

❓ Practice Quiz

1. What are the special body parts fish use to breathe underwater?
2. How does oxygen get from the water into a fish's blood?
3. What gas do fish release back into the water when they breathe?
4. Why can fish breathe underwater, but humans can't?
5. Name one thing that flows to the gills.
6. Name one thing that flows from the gills.
7. How is the function of gills similar to human lungs?