Ecology Review

What is the most likely cause of a harmful algal bloom in a freshwater lake?

• Increased levels of oxygen from aquatic plants

• Excess nutrients like nitrogen and phosphorus from fertilizers

• Decreased sunlight reaching the lake surface

• Introduction of invasive fish species

Harmful algal blooms can affect aquatic ecosystems and human health in several ways. Which of the following are specific impacts of harmful algal blooms?

• They deplete oxygen in water and produce toxins harmful to humans.

• They increase fish populations and improve water quality.

• They reduce sunlight penetration and promote healthy aquatic plants.

• They have no effect on aquatic life or human health.

Which process in the nitrogen cycle is carried out by bacteria and converts atmospheric nitrogen (N₂) into a form usable by plants?

• Nitrification

• Denitrification

• Nitrogen fixation

• Ammonification

Which process removes carbon dioxide from the atmosphere?

• Combustion

• Photosynthesis

• Respiration

• Decomposition

What human activity most often leads to excess nitrogen in ecosystems, potentially causing algal blooms?

• Urban development

• Use of nitrogen-based fertilizers

• Hunting wildlife

• Planting trees

In a food chain, which organisms have the most available energy?

• Tertiary consumers

• Primary consumers

• Producers

• Secondary consumers

What happens to the energy that is not passed on to the next trophic level?

• It is destroyed

• It is converted into sunlight

• It is stored permanently

• It is lost as heat

The arrows in a food chain or food web show the direction of flow.

• energy

• water

• carbon dioxide

• nutrients

Which of the following are examples of producers?

• Algae

• Grass

• Mushroom

• Oak Tree

• Wolf

Using the food web, which two organisms eat phytoplankton and what is their role (what is their title in an energy pyramid) in the food web?

• Krill and scallop (primary consumer only); Herring (primary and secondary consumer)

• Shark and squid (tertiary consumer only); Krill (secondary consumer)

• Scallop and shark (secondary consumer only); Herring (tertiary consumer)

• Herring and squid (primary consumer only); Scallop (secondary consumer)