Unit 1: Ecology and Basic Introduction

In a pond ecosystem, fish release ammonia as an excretory product, which is highly toxic. Ammonia can make water unfit for the survival of the fish and other aquatic organisms. However, in nature, the level of ammonia in ponds is generally maintained at low levels.

What helps in maintaining the level of ammonia?

• Ammonia is converted to elemental nitrogen by bacteria present in the root nodules of water plants.

• Ammonia is converted by bacteria into nitrogen compounds that can be consumed by plants.

• The salts in pond water react with ammonia, causing it to settle on the bottom of the pond.

• The leaves of water plants absorb ammonia, removing the toxic substance from the pond water.

The diagram shows the cycling of nitrogen through an ecosystem. If the number of denitrifying bacterial decreased, what direct effect would this have on the ecosystem?

• More nitrogen would be available for leguminous plants.

• Less nitrate ions would be available for assimilation in plants.

• Less nitrogen would be available for fixation by nitrogen-fixing soil bacteria.

• More ammonium ions would be available for nitrification by nitrifying bacteria.

The table lists the roles of different organisms in an aquatic food chain.

Align each organism into its appropriate box in the pyramid to represent the information in the table.

• 1 - aquatic plant

  2 - large mouth bass

  3 - blue gill

  4 - caddisfly larvae

• 1 - caddisfly larvae

  2 - large mouth bass

  3 - blue gill

  4 - aquatic plant

• 1 - aquatic plant

  2 - caddisfly larvae

  3 - bluegill

  4 - large mouth bass

• 1 - large mouth bass

  2 - bluegill

  3 - aquatic plant

  4 - caddisfly larvae

What is the importance of plants in the carbon cycle?

• They convert atmospheric carbon into usable carbon compounds.

• They convert water vapor into liquid water which is released into the soil.

• They decay organic matter in compost heaps and sewage.

• They convert nitrogen into nitrogen gas which is released into the atmosphere.

Carbon is an element that is found in all living organism, so the cycling of carbon through these organisms is essential to sustaining all life. Which process is one way that a living organism is involved in the movement of carbon around the Earth?

• combustion

• decomposition

• denitrification

• transpiration

Answer explanation

As organisms die or are digested - their molecules are again released and reduced to Carbon again.

According to the food web, which of the following organisms can be classified into more than one trophic level? 

• grasshopper
• owl
• rabbit
• frog

Which of the following correctly lists the flow of matter in the food web above?

• plants, animals, nematodes, arthropods

• animals, nematodes, arthropods, plants

• plants, nematodes, arthropods, animals

• nematodes, plants, arthropods, animals

Based on the food web shown above, which of the following is most likely responsible for the rabbit population trend as shown in the graph? 

• increase in amount of grass
• decrease in amount of grass
• overpopulation in squirrel population
• increase in rabbit population

Tell if the item is an abiotic factor or biotic.....

TREE

• Abiotic

• Biotic

Tell if the item is an abiotic factor or biotic.....

Water

• Abiotic

• Biotic