Do NOW… How do we (humans) get “energy”? What’s the name of the process? What do we need energy for?

Section 5.3- Energy Flow in Ecosystems

The Importance of Energy All organisms need energy for growth, movement, maintenance, repair, and reproduction. In an ecosystem, energy flows SUN Autotrophs Heterotrophs With respects to energy, the Earth is an open system. But it cannot exchange matter. 3

A) Autotrophs A groups of organisms that can use the energy in sunlight to convert water and carbon dioxide into glucose (food) process of PHOTOSYNTHESIS Autotrophs are also called Producers because they produce all of the food that they need and heterotrophs use. Without autotrophs, there would be no life on this planet. Examples: Plants and Algae (and some bacteria and protists) 4

Autotrophic Organisms 5

Specialized Autotrophs Chemotrophs (Chemoautotrophs) Autotrophs that get their energy from inorganic substances, such as salt, to make carbohydrates Live deep down in the ocean where there is no sunlight, near hydrothermal vents Example: Bacteria, Deep Sea Worms 6

B) Heterotrophs Organisms that do not make their own food Another term for Heterotroph is a consumer because they consume other organisms in order to get their energy. Examples: Rabbits, Deer, Mushrooms, Bears, Vultures, Shrimp 7

Heterotrophs 8

Classification of Heterotrophs Detrivores (Scavengers)- feed on the tissue of dead/dying organisms examples: vultures, crows, shrimp Herbivores- eat ONLY plants; examples: cows, elephants, giraffes, zebras Carnivores- eat ONLY meat (animals); examples: lions, tigers,sharks, killer whales, seals Omnivores- eat both plants and other animals; examples: bears, humans, racoons, wasps Decomposers- absorb dead material and break it down into simple nutrients or fertilizers; examples: bacteria, mushrooms, earthworms, dung beetle

Heterotrophic Organisms

C) Transfer of Energy When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not metabolized- broken down) When a lion eats a zebra, it does not get all of the energy from the zebra (some of it is lost as heat) 11

Energy flows from producers to consumers The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate 10% Law: Only 10% of the energy from one trophic level is transferred to the next level 12

What happens to the other 90%? Used by the organism for growth, movement, homeostasis (maintain a stable internal environment), reproduction During metabolism, some energy is transformed into heat 13

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1.) Trophic Levels Energy moves from one organism to another when it is eaten Each step in this transfer of energy is known as a trophic level. The main trophic levels are producers, consumers, and decomposers. Most ecosystems have only 3-4 trophic levels Organisms in the lowest trophic level are usually much more abundant than those in the higher trophic levels. 15

Example: Trophic Levels 16

2.) Ecological Pyramid An ecological pyramid shows the relationship between consumers and producers at different trophic (energy) levels in an ecosystem Shows the relative amounts of energy or matter contained at each trophic level The Pyramid shows which level has the most energy and has the highest number of organisms 17

Ecological Pyramid 18

3.) Food Chains The energy flow from one trophic level to the other can be displayed as a food chain A food chain is simple, direct, and linear. It is a single pathway of feeding relationships. It involves one organism at each trophic level Primary Consumers – eat autotrophs (producers); herbivores Secondary Consumers – eat the primary consumers Tertiary Consumers – eat the secondary consumers Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment 19

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4.) Food Web Most organisms eat more than JUST one organism When more organisms are involved it is known as a FOOD WEB (shows all of the feeding relationships within an ecosystem) Food webs are more complex and involve lots of organisms 21

The arrow points to the organism that RECEIVES the energy. Notice the direction the arrow points  the arrow points in the direction of the energy transfer, NOT “what ate what” The arrow points to the organism that RECEIVES the energy. 22

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D) Species are Connected to Ecosystems Biodiversity affects the stability of ecosystems Humans depend on healthy ecosystems to ensure a healthy planet that has balanced cycles. “Everything depends upon everything”. When one species disappears, the entire ecosystem is affected. Food chains and symbiotic relationships are affected. Some species are so critical to the functioning of an ecosystem that they are called keystone species.

The Sea Otter Sea otters eat sea urchins. In the 18oos, sea otters were hunted for their fur to near extinction in the Pacific Northwest. The sea urchin pop rose and began to eat all of the kelp in the area. With no kelp many other species started to die from starvation. In 1937, a small group of surviving sea otters were found and protected. They were reintroduced to the area. The kelp beds regenerated as the otters ate the sea urchins.