Problem 6 - Campbell Biology

Question

Food chains tend to be short because (A) only a single species of herbivore feeds on each plant species. (B) local extinction of a species causes extinction of the other species in its food chain. (C) most of the energy in a trophic level is lost as energy passes to the next higher level. (D) most producers are inedible.

Step-by-Step Solution

Answer

Option C: Most of the energy in a trophic level is lost as energy passes to the next higher level.

Step 1: Understand the Question

The question asks why food chains tend to be short. This relates to ecological principles and the energy transfer between different trophic levels.

Step 2: Analyze Each Option

Review each given option to see which one correctly explains the short length of food chains.

Step 3: Option A: Single Herbivore Species

Option A suggests that each plant species is fed on by only one herbivore species. This is incorrect; often, multiple herbivore species can feed on the same plant species.

Step 4: Option B: Local Extinction Impact

Option B argues that the extinction of one species causes the extinction of others in its food chain. While this can impact food chains, it is not the primary reason food chains are short.

Step 5: Option C: Energy Loss

Option C states that most energy in a trophic level is lost as it passes to the next higher level. This is correct because only about 10% of the energy is transferred to the next level, making long food chains unsustainable.

Step 6: Option D: Inedible Producers

Option D proposes that most producers are inedible. This is not true; many producers are edible and form the base of food chains.

Step 7: Select the Best Answer

The best answer is Option C, as the significant energy loss between trophic levels effectively limits the length of food chains.

Key Concepts

trophic levels

Trophic levels represent different stages in a food chain through which energy flows. At the base, we have the producers, mainly plants, which convert solar energy into chemical energy through photosynthesis. This energy is then passed on to the herbivores, or primary consumers, which eat the plants. Next, the energy moves to the secondary consumers, typically carnivores, which eat the herbivores. Finally, we have the tertiary consumers, which prey on secondary consumers. Each step, or level, in the food chain is called a 'trophic level'.

Trophic levels help us understand the flow of energy within an ecosystem. By studying these levels, we can see how energy decreases as we move up the chain.

energy loss

Energy loss is a crucial factor in determining the length of food chains. In an ecosystem, energy transfer between trophic levels is not 100% efficient. Typically, only about 10% of the energy is passed on to the next level. The rest is lost mainly through metabolic processes as heat. This concept is known as the '10% Rule'.

Because of this significant energy loss, food chains are limited in length. Longer chains would result in even more loss, making it unsustainable for higher trophic levels to obtain enough energy. Consequently, shorter food chains are more common and stable.

• Energy is lost at each level through activities like movement, growth, and reproduction.
• Only a small fraction of the energy is available to the next trophic level.
• This limitation in energy restricts the number of levels in a food chain.

ecological principles

Ecological principles help us understand how ecosystems operate and maintain balance. One key principle is the idea of energy flow, which reveals that energy decreases as it moves up trophic levels. Understanding these principles is essential for grasping why food chains are naturally short.

Another important principle is the interconnectedness of species within an ecosystem. Although local extinctions can affect food chains, energy transfer remains the primary reason for their limited length. Changes at one trophic level can influence the whole chain, leading to shifts in population and ecosystem dynamics. Studying these interactions helps us appreciate the delicate balance within ecosystems.

• Energy flow and energy loss are vital in maintaining ecosystem stability.
• Interconnected food chains form complex food webs.
• Balance in ecosystems is maintained through these intricate relationships.