Food chains and food webs：练习题

Which of the following describes the role of a secondary consumer in a food web?

Why is it generally more energy efficient for the human population to eat crop plants directly rather than eating livestock that have been fed on the same crops?

What is the principal source of energy input to most biological systems on Earth?

Which statement explains why the transfer of energy from one trophic level to the next is often not efficient?

If a top predator is overharvested from an ecosystem by humans, what is the most likely immediate effect on the food web?

Explain why a pyramid of biomass is generally considered a more accurate representation of the energy available at each trophic level than a pyramid of numbers.

Explain, in terms of energy loss at each trophic level, why it is more energy efficient for the human population to consume crop plants directly rather than consuming livestock that have been fed on the same crops.

A student draws a food web for a forest ecosystem. Describe how the introduction of a new, highly efficient secondary consumer might affect the population size of the producers and the tertiary consumers in the web.

A marine ecosystem consists of phytoplankton, krill, small fish, and leopard seals. The leopard seals feed on both krill and small fish, while both krill and small fish feed on phytoplankton.
(a) Identify the producers in this food web and describe their role in terms of energy flow.
(b) Explain the potential impact on the population of leopard seals and krill if human overharvesting significantly reduces the number of small fish in the area.

Ecological pyramids are used to represent the relationships between organisms in a food chain. Consider a food chain consisting of one large oak tree, \(2000\) aphids, and \(50\) ladybirds.
(a) Explain why a pyramid of numbers for this specific food chain would have an unusual shape compared to a pyramid of biomass.
(b) Discuss the advantages of using a pyramid of energy to represent an ecosystem rather than a pyramid of numbers or biomass.
(c) Explain why it is more energy efficient for humans to eat crop plants directly rather than feeding the crops to livestock and then eating the livestock.