1. 12.1 Ecology is the study of organisms in their environments
Ecology is the study of how organisms interact with each other and with their environment.
Figure a Discovery and Hypothesis-Drive Ecology–1 of 2
Figure b Discovery and Hypothesis-Drive Ecology–2 of 2
Ecologists make verifiable observations using the discovery approach.
Hypothesis-driven ecology science may be conducted in the field or in the lab.

2. 12.1 Ecology can be studied at many levels
Organismal
ecology
Ecologists work at levels ranging from individual organisms to the planet.
It is convenient to divide ecology into five increasingly comprehensive levels.
Population
ecology
Community
ecology
Figure a Ecology Can Be Studied on Many Levels–1 of 5
Figure b Ecology Can Be Studied on Many Levels–2 of 5
Figure c Ecology Can Be Studied on Many Levels–3 of 5
Figure d Ecology Can Be Studied on Many Levels–4 of 5
Figure e Ecology Can Be Studied on Many Levels–5 of 5
Ecosystem
ecology
Global
ecology

3. 12.1 Organismal ecology
Organismal ecology focuses on the ways that organisms adapt to their environments through physiology and behavior.
Figure a Ecology Can Be Studied on Many Levels–1 of 5
What type of questions might an organismal ecologist ask?
An organism is an individual living being.

4. 12.1 Population ecology
Population ecology is concerned with the factors that affect population size, growth, and density.
Figure b Ecology Can Be Studied on Many Levels–2 of 5
A population is a group
of individuals of the same
species living in the same
place at the same time.
What type of questions might a population ecologist ask?

5. Questions in community ecology focus on interactions among species.
Figure c Ecology Can Be Studied on Many Levels–3 of 5
A community consists of all the populations (of multiple species) living in a particular place.
What type of questions might a community ecologist ask?

6. 12.1 Ecosystem ecology
Ecosystem ecology is concerned with questions of energy flow and chemical cycling.
Figure d Ecology Can Be Studied on Many Levels–4 of 5
An ecosystem is all the life living in a particular area together with all the nonliving components.
What type of questions might an ecosystem ecologist ask?

7. 12.1 Ecology of the biosphere
At a global scale, ecologists can study the influence of energy and matter on organisms across the biosphere.
Figure e Ecology Can Be Studied on Many Levels–5 of 5
What type of questions might an ecologist ask about the biosphere?
The biosphere is the global ecosystem.

8. organismal population community ecosystem
If you were studying a single invasive plant species like Bromus tectorum, commonly known as cheatgrass, and this species’ interaction with rabbitbrush, Chrysothamnus viscidiflorus, and sagebrush, Artemisia tridentata, in rangelands you would be considered a(n) __________ ecologist.
organismal
population
community
ecosystem
Answer: C

9. organismal population community ecosystem
If you were studying a single invasive plant species like Bromus tectorum, commonly known as cheatgrass, and this species’ interaction with rabbitbrush, Chrysothamnus viscidiflorus, and sagebrush, Artemisia tridentata, in rangelands you would be considered a(n) __________ ecologist.
organismal
population
community
ecosystem

10. 12.2 The biosphere includes biotic and abiotic factors
The living organisms of an ecosystem constitute its biotic factors.
The abiotic factors of an ecosystem are its nonliving components.
Figure e Ecology Can Be Studied on Many Levels–5 of 5
Abiotic factors can have a profound effect on the life within an ecosystem.

11. The most important abiotic factor is energy.
12.2 Examples of abiotic factors include the supply of energy and nutrients
The most important abiotic factor is energy.
Most ecosystems on Earth are powered by solar energy via sunlight.
The availability of inorganic nutrients can impact plant growth.
Examples are nitrogen and phosphorous.
Figure b Energy–2 of 3
Figure a Nutrients–1 of 2

12. 12.2 Other important abiotic factors
Wind
Water availability
Figure Wind
Figure a Temperature–1 of 2
Figure a Water–1 of 2
Figure a Fire–1 of 2
Temperature
Fire

13. Ecology is considered the study of the interaction between biotic and abiotic factors. Which of the following is an abiotic factor?
wind
fire
temperature
all of the above
Answer: D

14. Ecology is considered the study of the interaction between biotic and abiotic factors. Which of the following is an abiotic factor?
wind
fire
temperature
all of the above

15. 12.3 Energy flows through ecosystems
Primary producers convert solar energy to chemical energy via photosynthesis.
Primary consumers are herbivores that eat primary producers.
Secondary consumers are carnivores that eat primary consumers.
Figure c Energy Flow–3 of 6
Figure d Energy Flow–4 of 6
Figure e Energy Flow–5 of 6

16. 12.3 Opening Questions: How do abiotic factors shape ecosystems?
How do rainforests differ from deserts in their abiotic factors?
How might those differences result in different biological communities?
Figure a Energy–1 of 3
Figure a Water–1 of 2
Active Learning: Opening questions can be done as a 1-minute THINK-PAIR-SHARE activity or as small-group work.

17. 12.3 Energy flows through ecosystems
Tertiary consumers are top-level predators.
As trophic levels increase, less energy is available at each transfer.
Decomposers are organisms that break down nonliving matter.
Death at any level sends energy to the decomposers.
Figure b Energy Flow–2 of 6
Figure f Energy Flow–6 of 6

18. 12.3 The trophic structure of an ecosystem describes the feeding relationships
TROPHIC LEVEL 4
Tertiary consumers
TROPHIC LEVEL 3
Secondary consumers
TROPHIC LEVEL 2
Primary consumers
TROPHIC LEVEL 1
Primary producers
Decomposers break down nonliving matter.
Energy enters an ecosystem as sunlight.
Figure a Energy Flow–1 of 6
At each energy conversion heat is released.

19. 12.3 Different ecosystems have different rates of primary production
Biomass is the total amount of living material in an ecosystem.
Primary production is a measure of the rate at which solar energy is converted to biomass.
Figure a A Gallery of Gymnosperms–1 of 5

20. 12.3 As energy is passed from one trophic level to the next, most of it is lost as heat
From one trophic level to the next, only around 10% of the energy transfers.
The cumulative loss of energy means that each level of trophic structure can support fewer organisms than the last.
Figure a Energy Flow–1 of 6

21. 12.3 Energy availability can be visualized in an ecological pyramid
Producers
Primary Consumers
Secondary Consumers
Figure a Ecological Pyramids–1 of 2
Figure b Ecological Pyramids–2 of 2
20,000,000 calories of primary production can support 10 vegetarians or one meat-eater for one day.

22. 12.4 Opening Questions: Tiger farming?
Across all human societies the large animals that were domesticated for food were herbivores.
Why don’t we farm tigers?
If you decided you wanted to farm tigers, how much space would you need? Explain.
Figure Evolution: Descent with Modification
Active Learning: Opening questions can be done as a 1-minute THINK-PAIR-SHARE activity or as small-group work.