Read the following quote and draw an energy pyramid with five trophic levels in the space provided:
"Three hundred fish are needed to support one man for a year. The trout, in turn, must consume 90 000 frogs, that must consume 27 million grasshoppers that live off 1000 tons of grass."
Answers
Answer:
all know that the biggest, fiercest, predators such as tigers and Great White sharks are rare on Earth compared to other organisms. Do you know why? In the early days of discovery in the new field of "animal ecology", a scientist named Charles Elton took the common knowledge that "big fish eat little fish" and turned that into an organizing principle we still use today -- that principle says that plants and animals are organized into trophic or "feeding" chains and food webs of interaction. He also introduced the idea that there is a pyramid of numbers of organisms, where there are for example many plants at the base of the food web, fewer herbivores that graze on those plants, and fewer still predators that eat the herbivores. Thus, Elton knew from observing the world around him that big, fierce creatures were rare, but, he didn't know why. He didn't understand the "mechanism" or explanation for the rarity of top predators in food webs. In this lecture we will uncover that mechanism and answer that question, and we will do so by learning about the nature of the flow of energy in ecosystems. Energy is used up and lost as heat as it moves through ecosystems, and new energy is continually added to the Earth in the form of solar radiation. As we learned in the lecture about Ecosystems, the Earth is an open system in regard to energy, and it is a closed system in regard to the materials such as nutrients that are continually recirculated within and amoung ecosystems.
Both energy and materials are essential to ecosystem structure, function, and composition. You have already been exposed to the basic concepts of nutrient cycles; in this lecture we focus on energy. Note that in terms of the cycling of carbon, "materials" and energy can be inter-converted. For example, we know how many calories (a measure of energy) a gram of certain carbon compounds such as fats or carbohydrates contain.
Autotrophs verses Heterotrophs
As a brief review, we recognize that some organisms are capable of synthesizing organic molecules from inorganic precursors, and of storing biochemical energy in the process. These are called autotrophs, meaning "self-feeding." Autotrophs also are referred to as primary producers. Organisms able to manufacture complex organic molecules from simple inorganic compounds (water, CO2, nutrients) include plants, some protists, and some bacteria. The process by which they do this usually is photosynthesis, and as its name implies, photosynthesis requires light (see Figure 1).
For completeness, we should mention the pathway known as chemosynthesis. Some producer organisms, mostly specialized bacteria, can convert inorganic nutrients to organic compounds without the presence of sunlight. There are several groups of chemosynthetic bacteria in marine and freshwater environments, particularly those rich in sulfur or hydrogen sulfide gas. Like chlorophyll-bearing plants and other organisms capable of photosynthesis, chemosynthetic organisms are autotrophs (see microbes lecture notes for more information). Many organisms can only obtain their energy by feeding on other organisms. These are called heterotrophs. They include consumers of any organism, in any form: plants, animals, microbes, even dead tissue. Heterotrophs also are called consumers.
In this lecture we will begin with a consideration of primary production, and in the next lecture we will examine what happens to this energy as it is conveyed along a food chain.
Why tadex?
Explanation: