Biology
Chapter 18 Introduction to Ecology
Notes Outline
Section 18-1 Introduction to Ecology
Objectives
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Identify a key theme in ecology.
Describe an example showing the effects of interdependence upon organisms in their environment.
Identify the importance of models to ecology.
State the five different levels of organization at which ecology can be studied.
A. Introduction to Ecology
1. _______________________ is the study of the interactions between organisms and the
_______________________ and _______________________ components of their environment.
B. Interdependence: A Key Theme in Ecology
2. The field of ecology was not named until ____________; however, ecological information and
understanding has been crucial to ______________________.
3. _______________________ was developed about _____________ to ____________ years ago.
4. Our early ancestors were _________________________________________.
a. They obtained all their food by hunting _________________________ and gathering
__________________, __________________, _________________, and ______________.
b. Their survival was dependent on __________________________________________ about
their environment.
5. Though most humans today do not survive as hunter-gatherers, they _____________________ with the
environment and other organisms ___________________________________.
C. Organisms and Their Environments
6. Species interact with both ________________________ and their ___________________ environment.
7. This interconnectedness is called ___________________________________________.
D. Effects of Interdependence
8. Because of this interdependence, ___________________________ can affect ____________________
in an ecosystem.
9. Example – after a season of high _______________________ production, the cases of
______________________________ in humans increases
E. Ecological Models
10. Since ecology is extremely _______________________ and difficult to study, scientists use ecological
__________________________ to represent and describe components of an ecological system.
11. Models may be _______________________, ______________________, or ______________________.
12. Models help scientists understand environmental interactions and make _________________________
about possible changes.
13. Though models may be useful, ecological models are _________________________ because they
cannot ____________________________________________________________ in a real environment.
F. Levels of Organization
14. Ecologists recognize a ________________________________________________ in the environment:
_______________________, _______________________, ________________________,
_______________________, and _______________________.
15. Each level has _______________________ properties that result from interactions between its
components.
16. Levels of Organization
G. The Biosphere
17. The broadest, most inclusive level of organization is the _______________________, the volume of
Earth and its atmosphere that supports life.
18. If Earth were the size of an ______________________, the biosphere would only be as thick as the
________________________________.
19. Many organisms are found within a few ______________________ of the surface of the land or oceans.
H. Ecosystems
20. The biosphere is composed of smaller units called _________________________.
21. An ecosystem includes all of the _________________________ and the ______________________
environment found in a particular place.
I. Communities, Populations, and Organisms
22. A ___________________________ includes all the interacting organisms living in an area.
23. Below the community level of organization is the __________________________ level.
a. A population includes all the members of a _____________________ that live in one place at one time.
b. The simplest level of organization in ecology is the _______________________.
*** Assignment: Answer the 18-1 Section Review questions #1-9 page 362.
Section 18-2 Ecology of Organisms
Objectives
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Compare abiotic factors with biotic factors, and list two examples of each.
Describe two mechanisms that allow organisms to survive in a changing environment.
Explain the concept of the niche.
A. Introduction
1. The place where an organism lives is its _______________________.
B. Ecosystem Components
2. Ecologists separate factors that influence an organism into two types: _____________________ and
________________________ factors.
a. The _____________________ components of the environment are called biotic factors.
b. The _____________________ components, called abiotic factors, are the physical and
chemical characteristics of the environment.
c. Examples of abiotic factors include _______________________, ____________________,
________________, _________________________ (saltiness), ____________________
concentration, amount of _______________________, availability of __________________,
and __________________________.
d. Abiotic factors are not ____________________. They vary from place to place and over
________________.
C. Organisms in a Changing Environment
3. Each organism is able to survive within a ______________________ range of environmental conditions.
4. For example, an organism may be able to function only within a specific ________________________ range
which can be determined by measuring how _______________________ it performs at different
temperatures.
5. A graph of performance versus values of an environmental variable, such as temperature, is called a
____________________________________.
6. An organism can survive and function in conditions _________________________ its optimal range, but its
performance is greatly _________________________.
7. An organism cannot survive under conditions that fall _________________________ its tolerance limits.
8. An organism’s range may be determined by _____________________________ factors, such as pH,
temperature, or salinity.
D. Acclimation
9. Some organisms can ________________________ their tolerance to abiotic factors through the process of
__________________________.
E. Control of Internal Conditions
10. Environments _________________________ in temperature, light, moisture, salinity, and other chemical
factors. There are two ways organisms deal with these change in their environment:
a. _______________________________ are organism that do not regulate their internal conditions;
they _____________________ as their external environment ______________________.
b. _______________________________ are organisms that use energy to _____________________
some of their internal conditions within the optimal range over a wide variety of environmental
conditions.
F. Escape from Unsuitable Conditions
11. Some species can survive unfavorable environmental conditions by escaping from them
_____________________. For example, desert animals usually hide ______________________ or in the
__________________ during the hottest part of the day, or they are active at ___________________ when
the temperatures are much lower.
12. A long-term strategy is to enter a state of ___________________ activity, called ______________________,
during periods of unfavorable conditions like ________________ or ___________________. For example,
bears __________________ in winter.
13. Another strategy is to ______________________ to a more favorable habitat, called __________________.
For example, birds spend spring and summer in ______________________ climates and migrate to
____________________ climates in the fall.
G. The Niche
14. Species do not use or occupy all parts of their ______________________ at once.
15. The specific role, or way of life, of a species within its environment is its _______________________.
16. The niche includes the ______________________________________ that the species can tolerate, the
________________________ it uses, the _______________________ by which it obtains resources, the
______________________________ it has, its ________________________________, and all other
___________________________ with its environment.
17. ________________________ are species with _________________ niches, like the
______________________ that is found across much of the United States.
18. ________________________ are species that have __________________ niches, like the ______________
of Australia.
19. Some species occupy __________________________ niche within a lifetime. For example, a
______________________ eats the leaves of plants, but as an adult ____________________, it feeds on
nectar.
*** Assignment: Answer the 18-2 Section Review questions #1-8 page 365.
Section 18-3 Energy Transfer
Objectives
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Summarize the role of producers in an ecosystem.
Identify several kinds of consumers in an ecosystem.
Explain the important role of decomposers in an ecosystem.
Compare the concept of a food chain with that of a food web.
Explain why ecosystems usually contain only a few trophic levels.
A. Introduction
1. All organisms need ___________________ to carry out essential functions, such as growth, movement,
maintenance and repair, and reproduction.
2. In an ecosystem, energy flows from the ________________ to autotrophs, then to organisms that eat
the ____________________, and then to organisms that feed on other organisms, _________________.
3. The amount of energy an ecosystem receives and the amount that is transferred from organisms to
organism affect the ecosystem ______________________.
B. Producers
4. Most ___________________ are ________________________ and make ____________________ by
using energy from the sun.
5. Some autotrophic ____________________ do not use sunlight as an energy source; instead, they carry
out _______________________.
6. Chemosynthesis uses energy stored in ___________________ compounds to produce carbohydrates.
C. Measuring Productivity
7. ___________________________________ is the rate at which producers in an ecosystem capture the
energy of sunlight by producing organic compounds.
a. Photosynthetic producers use _______________ and ________________________ to make
___________________, an energy-rich molecule.
b. This sugar is used for ______________________________, ______________________ and
________________, and _____________________ or _________________________.
8. The organic material produced in an ecosystem is called _____________________.
9. The rate at which biomass is produced is called the _____________________________________.
10. Although __________________________ account for only about _____% of earth’s surface, they
account for almost _____% of the world’s primary productivity.
11. Variations in three factors – ____________________, ______________________, and
__________________ – account for most of the variation in productivity in ___________________
ecosystems.
12. In ____________________ ecosystems, productivity is usually determined by only two factors:
_____________________ and availability of ______________________.
D. Consumers
13. Consumers _______________________________ by eating other organisms and include herbivores,
omnivores, carnivores, detritivores, and decomposers.
a. Herbivores eat _______________________.
b. Carnivores eat other __________________________.
c. _______________________ eat both producers and consumers.
d. Detritivores feed on _________________________________ matter and ____________________.
e. Decomposers _________________________ matter and release nutrients back into the ecosystem.
E. Energy Flow
14. When one organism eats another, energy is ______________________.
15. As a result, energy ___________________ through an ecosystem, moving from producers to consumers.
16. An organism’s trophic level indicates its position in a sequence of energy transfers.
a. Producers are the ________________ trophic level.
b. Herbivores belong to the _________________ trophic level and are referred to as
______________________ consumers.
c. Carnivores belong to the ________________ trophic level and are referred to as
______________________ consumers.
F. Food Chains and Webs
17. A ___________________________ is a ___________________ pathway of feeding relationships among
organisms in an ecosystem that results in energy transfer.
18. A _______________________ showing all paths of energy transfer is a ________________________.
G. Energy Transfer
19. Ecosystems contain only a few trophic levels because there is a _____________________ of energy
transfer between each level.
20. Only about _____% of the total energy consumed in one trophic level is available in the next trophic
level.
H. Limitations of Trophic Levels
22. Because only 10% of the energy available at one trophic level is transferred to the next trophic level,
there is ________________________________ in the top level to support more levels.
23. Organisms at the lowest trophic level are usually much more ________________________ than
organisms at the highest trophic level.
*** Assignment: Answer the 18-3 Section Review questions #1-9 page 369.
18-4 Ecosystem Recycling
Objectives
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List four major biogeochemical cycles.
Summarize three important processes in the water cycle.
Outline the major steps in the carbon cycle.
Describe the role of decomposers in the nitrogen cycle.
Summarize the major steps of the phosphorus cycle.
A. Introduction
1. As energy and matter flow through an ecosystem, matter must be ___________________ and
____________________.
2. Substances such as water, carbon, nitrogen, calcium, and phosphorus each pass between the living and
nonliving worlds through ______________________________ cycles.
3. A biogeochemical cycle is the _________________________ of substances through living organisms
from or to the environment.
B. The Water Cycle
4. Water is crucial to __________________.
5. Cells contain ____ to ____ percent water, and water provides the environment in which of life’s
________________________________ occur.
6. ____________________ of the available water on Earth is trapped within living things at any given time.
7. Most of Earth’s water is found in _______________________________, such as lakes, rivers, streams,
and oceans.
8. There is also water in the ______________________ and below the _____________________.
9. Water in the soil or in underground formations of porous rock is known as ________________________.
10. The movement of water between the bodies of water, the atmosphere, and the ground is known as the
_________________________.
11. Key processes in the water cycle are ________________________, _________________________, and
__________________________.
12. Evaporation adds ___________________________ to the atmosphere.
13. _______________ causes water to evaporate from bodies of water, from the soil, and from living things.
14. The process by which water evaporates from the leaves of plants is called _______________________.
15. Transpiration causes plants to take in water through their __________________.
16. Animals drink water or obtain it from their _________________, and they release water when they
________________, ________________, or _________________.
17. Water leaves the atmosphere through ________________________.
18. The amount of water the atmosphere can hold depends on abiotic factors, such as _________________
and ______________________________.
19. Once the atmosphere becomes ________________________ with water vapor, precipitation occurs in
the form of ________________, _______________, _________________, _________________, or
__________________.
C. The Carbon Cycle
20. _________________________ and ________________________ are the two main steps in the carbon
cycle.
a. Plants and other autotrophs use atmospheric carbon dioxide to produce ______________________.
b. Carbohydrates are broken down in cellular respiration to release ____________________________.
c. ___________________________ release carbon dioxide when they break down organic compounds.
21. In the last _____ years, the concentration of atmospheric carbon dioxide has risen more than ____%.
22. Humans contribute to this increase by burning _______________________ and other organic matter.
D. The Nitrogen Cycle
23. All living things need nitrogen to make ____________________ and _________________________.
24. Nitrogen-fixing ____________________ are important in the nitrogen cycle because they change
nitrogen gas into a usable form of nitrogen (nitrates) for plants.
25. These bacteria live in the __________________ and inside swellings on the __________________ of
some plants, such as beans, peas, clover, and alfalfa.
26. Decomposers break down dead organisms, urine, and dung and release the nitrogen they contain as
_______________________ which becomes _________________________ in the soil.
27. This process, called ________________________, makes nitrogen available to other organisms again.
28. Soil bacteria convert ammonium to nitrites and nitrates through a process called __________________.
29. ______________________ occurs when anaerobic bacteria break down nitrates and release nitrogen
gas into the atmosphere.
E. The Phosphorus Cycle
30. In the phosphorus cycle, phosphorus moves from phosphate deposited in _______________, to the
______________, to living organisms, and finally to the _________________.
*** Assignment: Answer the 18-4 Section Review questions #1-8 page 374.