Fish and Amphibians
Fish breathe with gills; amphibians live on land and water.
About this topic
Fish are cold-blooded vertebrates with gills, scales and fins that live in water; bony fish have a swim bladder, and cartilaginous ones (sharks) do not. Blood passes through a single-loop circulation. Amphibians (frogs, newts) start life in water as gill-breathing larvae and become air-breathing adults with lungs and moist skin.
Gills have many thin filaments full of capillaries, giving a large surface area; water flows over them and oxygen diffuses into blood. Fish are streamlined and use lateral muscles to swim. Amphibians breathe partly through their skin, which must stay moist, so they live near water and are sensitive to pollution, making them good indicators of environmental health.
A frog's life cycle shows metamorphosis: eggs (frogspawn) hatch into tadpoles with gills and tails, which grow legs, lose their tails and develop lungs. The heart changes from two chambers in a fish to three in an amphibian. Fish eggs are laid in water, and many species lay huge numbers because few survive.
Amphibian populations have been declining worldwide because of habitat loss, pollution and a fungal disease. Remember that fish are not cold in the sense of freezing; ectothermic animals rely on the environment for body heat. Whales and dolphins are mammals, not fish.
Key ideas
- Cold-blooded
- Metamorphosis in frogs
- Moist skin
Quick check
Use cases: where Fish and Amphibians helps
- Homework: review the key idea behind Fish and Amphibians before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Fish and Amphibians without notes.
- Visual learning: play with the interactive lab to see how Fish and Amphibians changes when you adjust its inputs.
- Teaching a friend: explain Fish and Amphibians in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Fish and Amphibians?
Fish breathe with gills; amphibians live on land and water.
What will I learn in Fish and Amphibians?
Cold-blooded. Metamorphosis in frogs. Moist skin.
Is Fish and Amphibians part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Fish and Amphibians lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Fish and Amphibians?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.