Chapter 9. Chapter 9: Community Ecology

How does matter and energy move through ecological communities?

Interactive Study Guide
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Guiding Question 9.1

How does matter and energy move through ecological communities?

Why You Should Care

Matter can’t be created or destroyed, and in the case of matter in the biosphere, it usually can’t enter or leave. Energy is constantly bombarding the planet as radiation from the Sun, which is then converted to other forms, like chemical energy, through processes like photosynthesis and cellular respiration. So what? First off, ponder this: Every time you breathe in, there’s a good chance you are using at least one molecule of oxygen that has been breathed by just about any human who ever lived. Just now, you could be recycling Julius Caesar’s last breath. The carbon in you has to come from somewhere, too. You may very well have carbon in you that was once part of a Tyrannosaurus. Dinosaurs exhaled CO2, just as we do now, so carbon that was part of their bodies entered the atmosphere. It is quite possible that, after millions of years, one of those carbon dioxide molecules was recently captured out of the atmosphere again by a corn plant by photosynthesis and used to make sugar. If that sugar was then converted into, say, high-fructose corn syrup, you may have just drunk part of a dinosaur in your soda today.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
iIlnXOGiiOdjPDfDuhlEe4/Fii0CmORxxNjGeYXySnYDjbI6NahAA77inVyBuo9owE/ulyhMoQxMzeLonGciH5Jm64BogZ1+1nCK5ax/JwsoczbQLeqt1ul8pIgB7p2lIX/4l/9kWL1pW2W5uMWp68rLAsQINTrp87hNHxvVyfDq+Bp2W9hJylTtrg6c4QPa27cqe795sa9MwE2Gtk0TjatK1m5sn0RUL110aqrPuwB7OTQoUxkWp1Xn8xc8bwnxBxlzLDZOJvY= A simple, linear path starting with a plant (or other photosynthetic organism) that identifies what each organism in the path eats.
D1sI1sIqlxi3sy6xUYPTKbkEZi1UkLoqd9BTnxac74ubdTa+2YOeSpd+ozgLJcexlphsB/KqvzrXCEeTLwS/B1JZpMMrJOdMjlCBHXpi35TI1lmf1PUW83LZqr/ZsoGRRYHAtPqh/cIHlKbFO1+wjVuc8dYUUfYGpTs5s/l2Qhu2MWm3Za3zWPa2ywTcveA6cmG9+8f7SLtbYQE4wRYVwNnYrl3Xr/9YWsr450DOrPWF/V0vbD25lrMgxpzznfpzA0zG9o7tQhI= An organism that eats other organisms to gain energy and nutrients; includes animals, fungi, most bacteria.
k+so7v+06wIYZbz3JPR1yyBT1KZwskdupSv+lncMKWeC+E0HoTiWfomkNdE6UjEFfNT0cXDXGafa5mOm8rk9iGutrn84b0HGn5yrhIGnvFDH9lH6+CpKDva5+gyQnXENnTZOWUaTOEsGDcs7P/lHVDXwAH3iB7lY34z/Karocf/dk0z36dTbR0KKcypT2c1/dQaHvxOyPiK5Pzi1NPGg838xrVuItOtUZupDdSzus5Dols5Ucn5kfKML0u6qlgO1led25OIbPTY= Organisms such as bacteria and fungi that break down organic matter all the way down to constituent atoms or molecules in a form that plants can take back up.
4ffOviIk/XEBE36uz20SRfdKYB5wQll4rcAoPRgEWLmmTGsVsNkbQOZz4sNTD/59A0XEXYkQYIiXcQyczenEUiIvEsh0J7j9vo4LpcIUWmOJ/0rYAR64Z2fkXUhzVibtdxB3o9psoJG9pK4Cd0kEKzF7DHkbdy6rRPIQqHGIsaJ/3shdS+UINn1d6m+EgbbRZ7G9WZ9M86M3lCBr7HTtmrFk1wiTL/JI7LwT/3RFRA0oYYA6719HyRCCaRm9R19woTzeEAx0E2A= The species that are particularly vulnerable to ecosystem perturbations, and that, when we monitor them, can give us advance warning of a problem.
vqY008bnbZTBbiK765Y1Z/XVO0QZaAjTdFRwmxU4VxrDMQG4TGVnUxKf5U8y1Tz1L4g0VBUDryc3UT/iiMwL4bSORBN4oRHjhNS1ZIZdbLMeFzw91huH85dAIzpoLdCbMkhO5XLDFEes4hcfiquWORa4Cegm7UDD5j7h9BRZA1H82rNvsp21wOsYDa0lf5MKHuPoMF+sttvPklr9MxYFslHQFueYa7itezIyO6YjwOo3uWoeDJ4UgqctjPEfApVMtOBbj8F3SEw= All of the organisms in a given area plus the physical environment in which they interact.
46yS1fW9WZjBE+2HNcwllOEvbIYj5yM5btBc/tdGJzG+Q1O2SOOC4Cjb4kZ2LnONk+At5CL+mbcuFx6BeGaBtTF7ZpgRvP/6tez6wKxdt7dJ2GG9uhFN0QhX+S0RGu4czt7T/MeqMMtkT6SvrK3Nt0e711VFwVXMfCObibhbTM++pLvFS8X0IPZuvVF2ZGfCnSbGFrMEsKRQ12NM52qGGUmb/LVM0HKz26AY88QQvRcxijVJt6kR/OR6IAze9p3JoocSiMsHtl8= A measure of the total amount of energy captured via photosynthesis and transferred to organic molecules in an ecosystem.
dgkxW47YEWaITISm03lG5GakvSxIHh3QB+9iAJjsM0uD476pUM8R8gpn+PUfayti+5q0973u+w6JqJFKzSlu5WIYah150CkX1NYAV50lR7LcGBhY//umfza0xw90ud5DsmiBIX5xJhePwCHgxfQG3yJB1lKLlWTABCuN+qFCdvLKCBQ8Pz+qZUdwcDYn0p+OAuN/YoLgOuXfRwJ7VCkgVFknqKdj5w6LxxE1GMuK2YlNYTKtC7gg8MqPCw3jAhvN4YYajz6R894= The study of all the populations (plants, animals, and other species) living and interacting in an area.
0pS0wNDrl4gdWcLWdLCHaliKoUCQ5XmqfAM3+0Yv+G8p8DRoinjAV7Ue6S6OmeAbQJbxVSsWxwWe9QnHmdMlsfzN6GS2+hup0zJU5h1/99jsjBLwyhz2IMhH3NUJU4kkwGG1Scpk+R2VQR7zLvDmcBd157QcrgR/Ycn1hKEqLRiF/AHruzQ6vY9UDdt23lJr24SELw2EaUHZ6lIaDM0dR5d3rsZW52Q/LQaPKcOaqVRiN599zoN3Obt05yKVs/S4Gj7+1SH0xis= Feeding levels in a food chain.
wQNxYlat2C4vzX5AcCyQZ9g3zOGsrSE4NuCxzP/zZu1JkN/bUWMeNll0b44m1P8fNQbGgZ//a/pl0O+PdSz5RxN3Wvxezbn00mytSBEj35x/yjuBup0Wbd4/AHYQyysqgDSD+WkBSRA3VNsz1HCvL6XYbo8fJAUWs+IhkcXzPq2y89P/PAOe2Tpv6H22nn803pYYHOXdQrFK/JIfPZrItxAnSoUCZEPVx3If0T4YQmVi8TwaoJmbGXCjrcdgzcy7k79GdJDC9W4= Consumers (including worms, insects, crabs, etc.) that eat dead organic material.
yq4NJhX7vhBfxUPG56XwjlFrO+RACyhKCRS32XCkFUAvIThM1LecyZ4AgsriadMc6krTXckWmpnIZyEPImGGaTf+KN+F530Bw+wC+UB2v9xj5wWzy9xZepcqY6N7ZfV8bIZT0V5LxLPop9o08nW//b93p960WAbgoiAzwWWxx7m72m6tmodfFL63p+DzrJzHMEjPbuNmUkce4Rns/00khsH2GTpSGaoFPMEpXAEqgDkPB4tLOZ8rc4d9/sp9/Kq9ILpU4ftUr4o= A linkage of all the food chains together that shows the many connections in the community.
ymuxTdJAlKus89FfHKCne9KIQwNENApu+nQVRseI6Nz5A05G1qip0SoKPxGWvRW+I2GH6CddW3rtRNLPJ6V5V8DxrdSIzUwaCOREjhEN6pLYbfjVidJjPK+1SKYzAHWvqlFesckzNfGo8KIoRyAGMrh/YdJ5AM9l2YZhtWqIy/AJois/ZySToHyYz1fw/qyrRQf+RY5FxzRDrpjjttbEfGfzZkRGbFxNQ6qHfODUDJjCA9tp1UI2MlIRExX1ciRfwwFD7YevozU= A photosynthetic organism that captures solar energy directly and uses it to produce its own food (sugar).
x++6HGhniqhlHL/91zfLvkD7EjIYu81LdsDRBRF9kdBPq5K0GoidCK7xF9XdmqK06i8xLIvoPqt2Jc6E5DzlIbnxdce5PcjAWGj6rBNw+CtyksDMLvNteJcHdMCQ0Ya8Fa2WNWVVi3DePtQyEk34ZAVSQxgGi0EinV2upgQ3rB7w6w3FvhJJnDrQHtAVsqJGnPxUV2DnB9GVTrTsEXaudJcznzgBlrvvgqMCZP4UY5zkdT5uCo3/TSN2OQHzRIeJL1/2P7U1P7s= A measure of the amount of energy captured via photosynthesis and actually stored in the photosynthetic organism.
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Infographic 9.1: Food Web

Question 9.1

xiEz8roySLCYU20Vl4U9tadR4LD3x+fYnJlkZUlD4mvmk+JqxkPdgY/+uB7ZlxBN5XDvx80KHp3ESHR0jJvOBON7YH1TgIdUgDIQLd2t4c2YBvgEtO6WjMFaUActVjYNKtCULsuD52JkQ7DjY+bHpm8xtFDJaxU4
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Question 9.2

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Question 9.3

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Question 9.4

rUAhshVm3Z3rdnGjXp0f33EKVWGQ6K5yreWI5pU/svup0Fv1cCCVUNmYPGrG+BhyAk1rZB0TxberQ4E2eS9MMw/iGOT9ztnwuhMTx47xQ8ngn8n6IUs3/aW2DCQxFXKqFX3x4Dli0RGJCLU8jdhk18Oss1F8WDPG6pIP5CX1P3Zu+e2a3rr/B3V6UoN8xXRyLW5ZBlCNBsgh82Slc/odL/+9d01aGxi2KnR7JBWNVGPTJYyOPEySx9dPoOUFDoTOLZljl0DQqugC0gCl0mYwzxjU2e1v2oo/2YIZxIgE6d1w9xwjejHAzJjufwCr1FxXH9r8+RcuLu91FDAflJ9ooNml2q5eMM9WCgSlF6VRwUbMwenvg+XQTCog9zIRpSGJQMLSRJII0O51DBAFz6ZN8XjJATeqCQEUyzjNT/IZASYFeIquJ32j1w==
As we have learned in previous chapters, energy flows through an ecosystem and matter cycles within it. The carnivorous habits of the bladderwort are an example of a link in nutrient cycles, but not of the transfer of energy. Connections in food webs, that is, between trophic levels, are usually considered to involve a transfer of both matter and energy. So, it is up to the beholder to decide whether an organism that consumes without any energy transfer is a true consumer. A safer bet would be to consider this plant a producer.

Question 9.5

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Alligators are the apex predators because, at least as adults, they are generally not preyed upon.
Infographic 9.2 Interactive

Question 9.6

If a species of fish lives on the zooplankton that eat phytoplankton (algae), it would be considered a rUoq2saBs3vge5p6wAffaalGskPQ90UZzdX9z0lc7fiYUbjRDkZz3xEzj6ljpK3f consumer.

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Correct. Algae are photosynthetic and, therefore, producers. The zooplankton that eat them must, therefore, be primary consumers, making their consumers secondary.
Incorrect. Algae are photosynthetic and, therefore, producers. The zooplankton that eat them must, therefore, be primary consumers, making their consumers secondary.

Question 9.7

The level that puts new energy into the food web is the N4AbhTxp2uWLdl/RzZMqoO/FG6yqb80+T/0eJi782vndA8WLdcm6GzFQtwthi9mKknbJY66zfsrGyny4FQ9mEQ==.

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Question 9.8

The trophic level that allows matter to return to the food web is the VtkybwZ901GnXbDNQfMjm3TNY0Q8zl5+drK2cwndJ7tN6gn9zQdQdYDzuH//Y75jI6VAR/Rv0A+2S0R/Ol9aLw==.

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Correct. Decomposers release matter back into the environment to be used by producers. The producers are the trophic level that puts matter into the food web, but the decomposers provide that matter.
Incorrect. Decomposers release matter back into the environment to be used by producers. The producers are the trophic level that puts matter into the food web, but the decomposers provide that matter.

Question 9.9

If only 10% of energy is transferred between each trophic level, and alligators are quaternary predators, how much of the energy captured by producers in the Everglades actually reaches the alligators? UQ5fZt1qNRe3JasDpercent

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Question 9.10

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Question 9.11

Decomposers are typically kOaUtSKOjzQ/2ysvMn+yVFKAAihPlSq05lyjf4X3R3wsDqrjF6O+RAGch1DCB6Kt2ez836VzStIKy2ai96ETHftVI2rlfefBagsD1hQuxk11fNoPfWIhpA==, whereas detritivores are xeVtuJcERR/9zllebVdU3+g4AIoPZVyJ4e64tdgzJWMntEePbFs48WHB624GLwARUcvkvMVv48V/3G/rsjgTN3LmQq0W82RB5IzRmgOhxqj5bp5cS4MThQ==.

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Question 9.12

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All of the energy that moves up the trophic pyramid ultimately came from producers, so it’s true that alligators get their energy indirectly from the Sun.

Question 9.13

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Because only about one-tenth of the energy available from each trophic level is actually transferred to the next one, there is simply not enough energy left to supply trophic levels above 5 or 6. Similarly, matter assimilation is not 100% either, so there is not as much biomass available to make it to higher levels.