fish

how do fish breathe

In order to absorb oxygen from the water, fish use gills ( Figure 1.2). Gills take dissolved oxygen from water as the water flows over the surface of the gill. Gills help a fish breathe.

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characteristics of fish

What exactly is a fish? You probably think the answer is obvious. You may say that a fish is an animal that swims in the ocean or a lake, using fins. But as we saw with the mudskipper, not all fish spend all their time in water. So how do scientists define fish? Some characteristics of fish include: 1. They are ectothermic, meaning their temperature depends on the temperature of their environment. Ectother- mic animals are cold-blooded in that they cannot raise their body temperature on their own. This is unlike humans, whose temperature is controlled from inside the body. 2. They are covered with scales. 3. They have two sets of paired fins and several unpaired fins. 4. They also have a streamlined body that allows them to swim rapidly. Fish are aquatic vertebrates, meaning they have backbones. They became a dominant form of sea life and eventually evolved into land vertebrates. There are three classes of fish: Class Agnatha (the jawless fish), Class Chondrichthyes (the cartilaginous fish), and Class Osteichthyes (the bony fish). All have the characteristics of fish in common, though there are differences unique to each class.

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exceptions to common fish traits

There are exceptions to many of these fish traits. For example, tuna, swordfish, and some species of shark show some warm-blooded adaptations and are able to raise their body temperature significantly above that of the water around them. Some species of fish have a slower, more maneuverable swimming style, like eels and rays ( Figure 1.4). Body shape and the arrangement of fins are highly variable, and the surface of the skin may be naked, as in moray eels, or covered with scales. Scales can be of a variety of different types.

why fish are important

How are fish important? Of course, they are used as food ( Figure 1.5). In fact, people all over the world either catch fish in the wild or farm them in much the same way as cattle or chickens. Farming fish is known as aquaculture. Fish are also caught for recreation to display in the home or in a public aquarium.

how big are fish

Fish range in size from the 65-foot, 75,000 pound whale shark ( Figure 1.3) to the stout infantfish, which is about 0.33 inches (8.4 mm), and the Paedocypris progenetica carp species of the Indonesian island of Sumatra, which is about 0.31 inches (7.9 mm) long, making it also the smallest known vertebrate animal. The second-largest fish is the basking shark, which grows to about 40 feet and 8,000 pounds. Both of the large sharks may look ferocious, and would probably scare anyone who comes across one in the water, but both species are filter-feeders, and feed on tiny fish and plankton. The tiny carp species is unique in that it has the appearance of larvae, with a reduced skeleton lacking a cranium, which leaves the brain unprotected by bone. The fish lives in dark acidic waters, having a pH of 3. Keep in mind that whales are not fish, they are mammals.

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how do fish reproduce

Fish reproduce sexually. They lay eggs that can be fertilized either inside or outside of the body. In most fish, the eggs develop outside of the mothers body. In the majority of these species, fertilization also takes place outside the mothers body. The male and female fish release their gametes into the surrounding water, where fertilization occurs. Female fish release very high numbers of eggs to increase the chances of fertilization.

instructional diagrams

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questions

whales are the biggest fish.

a. true

-->  b. false

some fish can live on land for short periods.

-->  a. true

b. false

ectothermy is a characteristic of fish? what is ectothermy?

a) being cold-blooded.

b) not being able to raise body temperature without help.

c) being dependent on the environment to maintain body temperature.

-->  d) all of the above

what is a unique characteristic of some cartilaginous fish?

a) they are not endothermic.

-->  b) they have very flexible pectoral fins.

c) they reproduce asexually.

d) all of the above

what is a unique characteristic of tuna and swordfish?

a) they are not covered with scales.

-->  b) they are able to raise their body temperature above that of the surrounding

c) they breathe using either gills or lungs.

d) all of the above

what do the two biggest fish have in common?

a) both are fierce rulers of their habitat.

-->  b) both are filter feeders.

c) both are ferocious carnivores.

d) all of the above

what is significant about the smallest vertebrate?

-->  a) it does not have a cranium.

b) it is not a true fish.

c) it does not use gills to breathe.

d) it does not have fins.

diagram questions

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