5
Fish
Textbook: Part 1, pp. 22–25
GoalKnow the main features of fish (gills, scales, fins, lateral line, cold blood), and tell aquarium and sea fish apart from sea animals that are not fish.
New words
gill · jabrascale · tangachafin · suzgich
Explanation
Fish are vertebrates adapted to life in water. They take oxygen dissolved in water through their gills. The body is covered with protective scales, and fins and a tail help them swim. The lateral line organ lets a fish sense an approaching animal before seeing it. Fish are cold-blooded: body temperature changes with the water around them. In aquariums people keep guppies, angelfish and cleaner catfish. In the sea live sharks, seahorses and skates. Jellyfish, sea anemones and octopuses are not fish; they are invertebrate sea animals.
Worked examples
A shark and a tiny guppy are both fish: both breathe with gills.
An octopus has no backbone, fins or scales: it is not a fish but a mollusc.
Class activity
“Draw and label a fish”: draw a fish and label head, gill, scale, fin and tail. If you have an aquarium at home, watch what the fish eats.
Practice
1
How do fish breathe in water?
with gills, taking the oxygen dissolved in water
2
What are a fish’s scales for?
They protect the body from predators and make swimming easier.
3
Which is not a fish: shark, jellyfish, angelfish?
jellyfish
4
What does “cold-blooded” mean?
Body temperature changes with the temperature of the surroundings.