Marine Biology

1) What is scientific classification of plants and animals?
2) What is a fish?
3) How sharks and fish are different?
4) Are sharks dangerous?
5) Why do sharks bite people?
6) How do fish float and sink?
7) What is plankton?
8) What is algae?
9) What is symbiosis?
10) What are food chains, food webs and feeding pyramids?

What is scientific classification of plants and animals?
When you see a plant or animal you call it by a common name. People in other countries (or even in other states) may call the same plant or animal by a different name. When scientists study plants and animals in different parts of the world they need to know if it is the same animal called by another name in another part of the world. To prevent the confusion of different names for the same plants or animals all scientists use a special scientific name, which is the same all around the world. The scientific name is usually made of ancient Greek or Latin words. The scientific name is made of two names, like your first and last names.

• What is a fish?
A fish a cold-blooded vertebrate that lives in water, has scales, fins, and breathes using gills. There are over 25,000 known fish species in the world.
There are three different groups of fishes:
1) Bony fishes – most fishes (over 25,000 species)
2) Cartilaginous fishes –sharks and rays (over 700 species)
3) Jawless fishes – lampreys and hagfish (about 45 species)

How are sharks and fish different?
A shark is a fish, but a shark is a special kind of fish called a cartilaginous (CAR-tuh-lage-in-us) fish. Another word for shark is elasmobranch (E-LAZ-mo-brank). Elasmobranch means "flexible skeleton". The main difference between a fish and a shark is its skeleton. A shark has no bones. A fish skeleton is made out of hard bones, just like your skeleton. A shark’s skeleton is made out of cartilage (CAR-tuh-lij). Grab your ears and wiggle them. They’re made out of cartilage. Rays are also elasmobranchs, just like sharks.

Are sharks dangerous?
Any animal with sharp teeth can be dangerous, but sharks are usually not dangerous to scuba divers. The chances of being bitten by a shark are so small that we never worry about it.

• Why do sharks bite people?
Sharks don't go looking for people to eat, but once in a while a shark may bite someone. A shark may bite someone to make that person leave his territory. This is just like a strange dog that might try to bite you if you get into his yard. A shark may also bite someone by mistake if it thinks you are its favorite food, like a seal or a sea lion. Either way, a shark usually just takes one bite, swims away, and doesn't try to eat that person. More people are killed by being struck by lightning or bee stings or from falling airplane parts, than attacked by a shark. In fact, in the United States more people are killed by farm pigs each year than by sharks! People are more dangerous to sharks than sharks are to people. Each year people kill about 100,000,000 sharks.

• How do fishes float and sink?
Most fishes have a little balloon inside their bodies, called a swim bladder. The fishes can put air inside their swim bladders, which will make themselves float (positive buoyancy). The fishes can squeeze the air out of the swim bladders, which will make themselves sink (negative buoyancy). The fish easily float underwater (neutral buoyancy) by controlling the amount of air inside their swim bladder. Cartilaginous fishes and jawless fishes do not have swim bladders. If these fishes do not swim they will sink.

• What is plankton?
Plankton (PLANK-ton) are microscopic animals and plants that float and drift in the ocean currents. Animal plankton are called zooplankton (zo-PLANK-tun). Plant plankton are called phytoplantkton (fy-toe- PLANK-ton). Plankton are food for many ocean inhabitants, including coral polyps.

• What is algae?
Algae (AL-gee) are underwater plants that don’t have roots, stems or flowers. There are three different kinds of algae:
red algae, green algae, and brown algae.

• What is symbiosis?
Symbiosis (SIM-be-oh-sis) means "together-living". Symbiosis is about how animals, and plants, live together. Sometimes animals are friends with other animals and help them. Sometimes animals are enemies of other animals and hurt them.

On the coral reef there are many different examples of symbiosis that are helpful or hurtful. Helpful symbiosis is found in coral polyps. Plant cells (zooxanthellae - zo-ZAN-thel-lay) live under the skin of coral polyps. The coral polyps provide the plant cells protection and a place to live. The plant cells provide food for the coral polyps and help the polyps build their limestone skeletons.

A fun symbiosis to watch are the cleaner fish. Fish don’t have hands and arms like you do. They can’t brush their teeth and scratch their backs. When a fish is dirty it looks for a tiny, brightly colored cleaner fish sitting on top of the coral. The bigger fish stops in front of the little fish and the little fish hops on the bigger fish and cleans it off. It’s like an underwater car wash for fish!
Not all symbiosis is helpful to other animals. A harmful symbiosis are parasites. Some of the underwater parasites attach themselves to the fishes and suck the fishes’ blood, like a vampire! This symbiosis is good for the parasite, but bad for the fish.

• What are
food chains, food webs and feeding pyramids?
food chain is a drawing that shows how food (energy) passes from one living thing to another in an ecosystem. Plants and animals are put in a grouping depending on who is eaten by whom. An ocean food chain usually begins with the sun making food for plants (producers), the plants eaten by animals (consumers) and those animals eaten by larger animals. A typical ocean food chain would be the sun producing food in phytoplankton (plant plankton), the plankton eaten by small fishes, the small fishes eaten by bigger fishes, the bigger fishes eaten by sharks, and the sharks eaten by people.

food web is a drawing that shows how all the food chains interact within an ecological community. When a food web is drawn it looks like a spider web with all the lines connecting different plants and animals that eat or get eaten by one another.

feeding pyramid is known as a pyramid of numbers. A pyramid of numbers is the organization of a food chain or food web into different feeding (trophic- TRO-fic) levels. The more numerous producers (plants) form the base of the pyramid. The less numerous consumers (animals) are arranged above the producers. The larger animals are above the smaller animals. Pyramids show the energy transfer from one trophic level to the next, as smaller animals are eaten by larger animals.

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