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 12.1-1a Discovery and Hypothesis-Drive Ecology–1 of 2 Figure 12.1-1b 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.

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 12.1-3a Ecology Can Be Studied on Many Levels–1 of 5 Figure 12.1-3b Ecology Can Be Studied on Many Levels–2 of 5 Figure 12.1-3c Ecology Can Be Studied on Many Levels–3 of 5 Figure 12.1-3d Ecology Can Be Studied on Many Levels–4 of 5 Figure 12.1-3e Ecology Can Be Studied on Many Levels–5 of 5 Ecosystem ecology Global ecology

12.1 Organismal ecology Organismal ecology focuses on the ways that organisms adapt to their environments through physiology and behavior. Figure 12.1-3a 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.

12.1 Population ecology Population ecology is concerned with the factors that affect population size, growth, and density. Figure 12.1-3b 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?

Questions in community ecology focus on interactions among species. Figure 12.1-3c 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?

12.1 Ecosystem ecology Ecosystem ecology is concerned with questions of energy flow and chemical cycling. Figure 12.1-3d 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?

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 12.1-3e 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.

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

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

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 12.1-3e Ecology Can Be Studied on Many Levels–5 of 5 Abiotic factors can have a profound effect on the life within an ecosystem.

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 12.2-1b Energy–2 of 3 Figure 12.2-2a Nutrients–1 of 2

12.2 Other important abiotic factors Wind Water availability Figure 12.2-3 Wind Figure 12.2-4a Temperature–1 of 2 Figure 12.2-5a Water–1 of 2 Figure 12.2-6a Fire–1 of 2 Temperature Fire

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

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

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 12.3-1c Energy Flow–3 of 6 Figure 12.3-1d Energy Flow–4 of 6 Figure 12.3-1e Energy Flow–5 of 6

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 12.2-1a Energy–1 of 3 Figure 12.2-5a Water–1 of 2 Active Learning: Opening questions can be done as a 1-minute THINK-PAIR-SHARE activity or as small-group work.

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 12.3-1b Energy Flow–2 of 6 Figure 12.3-1f Energy Flow–6 of 6

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 12.3-1a Energy Flow–1 of 6 At each energy conversion heat is released.

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 9.10-2a A Gallery of Gymnosperms–1 of 5

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 12.3-1a Energy Flow–1 of 6

12.3 Energy availability can be visualized in an ecological pyramid Producers Primary Consumers Secondary Consumers Figure 12.3-3a Ecological Pyramids–1 of 2 Figure 12.3-3b Ecological Pyramids–2 of 2 20,000,000 calories of primary production can support 10 vegetarians or one meat-eater for one day.

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 1.7-2 Evolution: Descent with Modification Active Learning: Opening questions can be done as a 1-minute THINK-PAIR-SHARE activity or as small-group work.