TAKS OBJECTIVE 3:TEKS 12 (E)

The student knows that interdependence and interactions occur within an ecosystem. The student is expected to INVESTIGATE and EXPLAIN the interactions in an ecosystem including food chains, food webs, and food pyramids.

Energy Flow in Ecosystems

Energy and matter flow through ecosystems. Solar energy drives ecosystems; food webs are limited by the amount of energy that can be transferred between levels.

**Energy**Energy in an ecosystem originally in an ecosystem originally comes from the suncomes from the sun

**Energy flows through Ecosystems **Energy flows through Ecosystems from from producers to consumersproducers to consumers

Producers (make food)Producers (make food)Consumers (use food by Consumers (use food by

eating eating producers or other producers or other consumers)consumers)

Photosynthesis

Producer Primary Consumer

Secondary consumer

Tertiary consumer

Decomposer

Heat lost through respiration

Heat lost through respiration

Heat lost through respiration

Heat lost through respiration Nutrients

returned to environment

Wheat Mouse Snake Owl

WHO EATS WHAT???A food chain, above, shows one path the energy can take. A food web, below, is a collection of several food chains, linked together.

ARROWS SHOW FLOW OF ENERGY!!!!

A food (or energy) pyramid is another way to represent this information. •The pyramid gets its shape from the fact that the greatest amount of energy in the ecosystem is stored in the producers. (There is more grass than mice, and there are more mice than snakes.) •There are very few tertiary consumers in ecosystems because it takes a lot of energy feed one.

Toxins (poisons) can build up in the food chain. They are the least concentrated in the producers, but can build up in the bodies of animals as they feed. The higher an animal is on the energy pyramid, the more poison he has consumed.

TAKS PRACTICE

The diagram to the right is intended to show relationships in an ecosystem. What do the arrows represent?A The direction of population migrationB Differences in dietary habitsC Progressively smaller organismsD The direction of energy flow

Remember, energy flows from the producers to the primary consumers to the secondary consumers, to the tertiary consumers in webs, chains, and pyramids.

Which organisms in this food web can be described as both primary and secondary consumers?

F HawksG WeaselsH RaccoonsJ Mice

The diagram represents different levels of a marine food pyramid. Between which two levels is the greatest amount of energy transferred?A R and QB S and RC T and SD U and T

Remember, radiant energy from the sun is stored as chemical energy in plants. They contain the most energy in the ecosystem.

4 In this food web, the bacteria probably function as — A producersB herbivoresC decomposers D carnivores

Remember, bacteria can be decomposers. Also, anything that appears to be eating other dead organisms in the ecosystem is a decomposer.

5. Which of these groups of organisms would most likely have accumulated the largest concentration of a long-lasting chemical pollutant in their bodies?A PhytoplanktonB ZooplanktonC Lake troutD Gulls

Remember, toxins present in small amounts on the producers, are concentrated as they pass from lower energy levels to higher ones. They become concentrated in the carnivores at the top of the food chain.

As matter and energy move from grasses to coyotes, the amount of As matter and energy move from grasses to coyotes, the amount of available energy _____.available energy _____.

AA always decreases and population size always increases always decreases and population size always increasesBB always increases and population size always decreases always increases and population size always decreasesCC always decreases but population size may increase or always decreases but population size may increase or decreasedecreaseDD increases or decreases but population size remains the increases or decreases but population size remains the samesame

Referring to Figure 3-1, the relationship between cats and mice could best be described as _____.

A predator-prey C parasite-hostB scavenger-carrion D consumer-producer

Within the above ecosystem, several interactions occur between different organisms. A food chain is illustrated in order to show a series of interactions and energy flow. Specifically, the coyotes would be considered _____.

A herbivoresB third-order consumersC second-order consumersD decomposers

Which of the following food chains Which of the following food chains correctly shows the path of matter and correctly shows the path of matter and

energy through an ecosystem?energy through an ecosystem?

A deer · bear · grass

B seeds · bear · chipmunk

C grass · deer · bear

D chipmunk · seeds · deer

A manufacturing plant is located on the banks of a A manufacturing plant is located on the banks of a river. One day, toxic chemicals from the plant river. One day, toxic chemicals from the plant accidentally spilled into the river. Fish absorbed accidentally spilled into the river. Fish absorbed some of these chemicals into their bodies. Later, a some of these chemicals into their bodies. Later, a hawk living near the river is found to have the hawk living near the river is found to have the same toxic chemicals in its system. Which same toxic chemicals in its system. Which statement best explains why?statement best explains why?

A The chemicals entered the air.B The chemicals entered the food chain.C The chemicals were contagious.D The chemicals are commonly found in the

environment.

EXPLANATION

ECOSYSTEM: all the animals and plants found in one place, and the way they all live togetherNiche-Animal’s role in the ecosystem. Types of niches:

•Herbivore-eats only plants/producers, •Omnivore-eats both plants and animals, •Carnivore-eats consumers only (meat), •Predator-hunter•Prey-what is being hunted,•Decomposer-usually fungus or bacteria that eat dead material and returns nutrients to the environment (may not be

included in food webs and pyramids).

ESSENTIAL VOCABULARY CONT’D

Producer: usually a green plant that produces its own food by photosynthesis

Consumer: primary- the organism that eats the producer secondary- the organism that eats or derives

nutrients from the first-order consumerBiomass- the total weight of the organisms in a trophic level Autotroph- organisms that produce their own food. Heterotroph- organisms that eat producers; they search for

their own food. Food chain- A food chain almost always begins with a green

plant (producer) which is eaten by an animal (consumer). The arrow means 'is eaten by', and shows the flow of matter and energy along the food chain. There are no decomposers in a food chain.

Food web- a network of interrelated food chains in a given area

Trophic Level- A trophic level is each level in a food chain. Matter is always 'lost' as heat energy at each trophic level.