Section: Freshwater Ecosystems

Skills Worksheet

Active Reading

Section: Freshwater Ecosystems

Read the passage below and answer the questions that follow.

Aquatic ecosystems contain several types of organisms that are grouped by their location and by their adaptations. Three groups of aquatic organisms include plankton, nekton, and benthos. Plankton are the organisms that float near the surface of the water. Two types of plankton are microscopic plants called phytoplankton, and micro- scopic animals called zooplankton. Phytoplankton produce most of the food for an aquatic ecosystem. Nekton are free-swimming organ- isms, such as fish, turtles, and whales. Benthos are bottom-dwelling organisms, such as mussels, worms, and barnacles. Many benthic organisms live attached to hard surfaces. Decomposers, organisms that break down dead organisms, are also a type of aquatic organism.

IDENTIFYING MAIN IDEAS

One reading skill is the ability to identify the main idea of a passage. The main idea is the main focus or key idea. Frequently, a main idea is accompanied by supporting information that offers detailed facts about main ideas.

In the space provided, write the letter of the term or phrase that best completes each statement or best answers each question.

1. How are organisms in an aquatic ecosystem grouped?

1. 
   by size and shape
   
2. 
   by the food they eat
   
3. 
   by how they reproduce
   
4. 
   by location and adaptations
   

2. Where do many benthic organisms live?

1. 
   attached to hard surfaces
   
2. 
   in open water
   
3. 
   near the surface of the water
   
4. 
   attached to benthos
   

3. How many groups of aquatic organisms are discussed in this passage?

1. 
   2 c. 5
   
2. 
   3 d. 4
   

4. Which groups of aquatic organisms are discussed?

1. 
   phytoplankton and zooplankton
   
2. 
   plankton, nekton, and benthos
   
3. 
   plankton, nekton, benthos, and decomposers
   
4. 
   plankton, phytoplankton, zooplankton, nekton, and benthos
   

Active Reading continued

5. Most of the food for an aquatic ecosystem is produced by

1. 
   worms.
   
2. 
   phytoplankton.
   
3. 
   zooplankton.
   
4. 
   fish.
   

VOCABULARY DEVELOPMENT

In the space provided, write the letter of the term that best matches the description.



6. aquatic organisms that float near the surface of the water

7. aquatic organisms that

break down dead organisms

8. microscopic plants

9. microscopic animals

10. aquatic organisms that dwell at the bottom of the water

11. aquatic organisms that are free-swimming

1. 
   phytoplankton
   

2. 
   plankton
   

3. 
   nekton
   

4. 
   benthos
   

5. 
   decomposers
   

6. 
   zooplankton
   

Write “P” on the line in front of each example of plankton, “N” on the line in front of each example of nekton, and “B” on the line in front of each example of benthos.

12. turtles 16. mussels
13. worms 17. barnacles

14. zooplankton

15. fish

18. phytoplankton

19. whales

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Aquatic Ecosystems