"Fish" Main groups of animals PPT courseware 5

"Fish" Main groups of animals PPT courseware 5

learning target

1. Outline the main characteristics of fish.

2. Pay attention to the relationship between fish and human life.

Vertebrate: An animal with a backbone made of vertebrae

Fish are the most diverse group of vertebrates, accounting for more than half of all vertebrate species. According to the living environment, they can be divided into freshwater fish and ocean fish. There are also many kinds of fish in our country.

Types of freshwater fish

Silver carp: It has a lighter body color and is also called silver carp. It moves in the upper layers of the water and feeds on diatoms, green algae and other phytoplankton.

Bighead carp: It has a large head, also known as "fat-headed fish". Its back is dark black with irregular black spots. It is commonly known as silver carp. It lives in the middle and upper layers of the water and feeds on water fleas and other zooplankton.

Grass carp: The body color is greenish-yellow. It lives in the middle and lower layers of the water and on the shores with many aquatic plants. It mainly feeds on aquatic plants.

Black carp: The body color is blue-black. It lives in the middle and lower layers of the water and mainly feeds on molluscs such as snails and clams.

2. Saltwater fish

Pomfret: The body is slightly diamond-shaped, the head is small, the dorsal and anal fins are long, and the tail fin is forked.

Grouper: Distributed in tropical and subtropical warm water waters, it has a larger head and its body color is similar to the color of the surrounding rocks. The larvae are female fish, and when they develop to a certain stage, they can transform into male fish.

Sharks: At the top of the marine food chain, they come in different sizes. Sharks include whale sharks, the largest fish, dwarf dogfish as small as your hand, and ferocious great white sharks.

Hairtail fish: The body is band-shaped, the mouth is large, the dorsal fin is long, almost as long as the back, it is relatively fierce, and it feeds on fish and molluscs.

Flounder: Lives on the bottom of the sea. The eyes of adult fish move to the same side of the body, and the side of the body without eyes faces the bottom of the sea.

Observation and thinking [observe the appearance and movement of fish]

(1) What are the characteristics of the fish’s appearance? What significance does it have to the fish’s aquatic life?

Answer: The body of fish is divided into head, trunk and tail; most of them have flat sides, which is helpful for overcoming the resistance of water.

(2) Touch the surface of the fish with your hands and see what it feels like. Talk about your opinions.

Answer: There are scales and mucus on the surface of fish, which can not only protect the body but also help overcome the resistance of water.

(3) Observe the movement of fish. Fish only rely on their fins for locomotion. Is this a comprehensive statement?

Answer: Not comprehensive. Fish have a spine in their body, and the muscles attached to the spine can generate power for movement. Fish complete swimming movements through the swing of the trunk and tail and the coordinated action of the fins.

(4) After the water flows into the fish mouth, where does it flow out? What are the changes in the dissolved gas composition between the inflowing water and the outflowing water?

After water flows into the fish's mouth, it flows out from the rear edge of the gill cover.

Compared with the outgoing water, the inflowing water contains less dissolved oxygen and more carbon dioxide.

(5) What characteristics of fish gills are crucial for it to breathe in water? Analyze the reasons why fish cannot live without water.

The gills are fan-shaped; there are multiple gill lamellae; the filaments of each gill lamellae are many and thin.

Characteristics of fish gills adapted to breathing in water

The gills are bright red and contain abundant blood vessels. Each gill is composed of many and thin gill filaments. When in the water, the gill filaments expand to expand the contact area with the water, which is beneficial for the fish to breathe in the water.

When the fish leaves the water, the gill filaments stick together. The four gills cover each other, reducing the contact area with the air and making the air dry. Suffocate fish to death.

Main characteristics of fish

live in water

The body surface is often covered with scales

Breathe with gills

Swims through the swing of the tail and trunk and the coordinated action of the fins

Class exercises

Multiple choice questions

1. Which of the following belong to the four major fish species ( )

A. Herring, grass carp, hairtail, silver pomfret B. Silver carp, bighead carp, shark, grass carp

C. Hairtail, carp, crucian carp, yellow croaker D. Herring, grass carp, silver carp, bighead carp

2. What is the difference between the water flowing in from the fish mouth and the water flowing out from the rear edge of the gill cover ( )

A. The latter has more carbon dioxide, while the former has more oxygen.

B. The latter has more carbon dioxide and the former has less oxygen.

C. Both have the same amount of carbon dioxide

D. The former has more carbon dioxide and the latter has less oxygen.

3. The following animals that are not fish are ( )

A. Crucian carp B. Goldfish C. Whale D. Herring

4. The reason why crucian carp feels sticky when you hold it in your hand is ( )

A. With scales B. With water C. With mucus D. The body is spindle-shaped

Observe and think

1. What are the characteristics of the fish’s appearance? What is the purpose of such a feature?

2. How many parts can the body of a fish be divided into?

3. What is on the body surface of fish? What effect does this have on the life of the fish?

4. What are the locomotor organs of fish?

5. Which parts of fish have the most developed muscles? Are there any structures related to fish movement?

(1) Movement of fish

When a fish swims, it mainly relies on the left and right swings of its trunk and tail to stir up the water flow to generate forward momentum.

When a fish is moving, its pectoral fins and pelvic fins play a role in maintaining the balance of the fish body, and the tail fin plays a role in determining the direction of the fish's movement.

Explore: Fish Breathing

1. Observe the fish in the water tank and pay attention to why the fish’s mouth and the rear edge of the gill cover do not open or close at the same time?

2. Use a straw to absorb some ink, slowly drip the ink in front of the fish's mouth, and observe the flow of the ink. Where does this ink come from? What does this mean?

3. What characteristics of fish gills are crucial for it to breathe in water? Fish die soon after leaving the water. Why?

Summary

Characteristics of fish suitable for life in water:

It breathes with gills, has a streamlined body shape, is covered with scales, has mucus, and has lateral lines. It swims through the swing of its tail and trunk and the coordinated action of its fins.

Choose one

When swimming, fish mainly rely on ( ) to maintain balance, rely on ( ) to maintain forward direction, and rely on ( ) to generate forward momentum.

A. Pectoral fin B. Pelvic fin C. Caudal fin

D. Left and right swing of tail and trunk

Use your brain

1. Why do people often put some aquatic plants in fish tanks?

2. In ponds with a lot of algae, it is common to see fish floating on their heads at dawn or even jumping out of the water. After dawn, the fish stop floating on their heads. Think about it, what does this mean?

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