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Understanding Ecosystems and Population Dynamics

Explore the interactions between species and their environment, population density calculations, food chains, trophic levels, carrying capacity, and more in ecosystems. Learn about habitats, niches, biotic factors, and energy pyramids.

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Understanding Ecosystems and Population Dynamics

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  1. 1. An example of a biotic factor is • The number of worms in the soil • The amount of leaf liter (dead leaves) in the soil • The pH of the soil • Both A and B

  2. The interaction between the different species in an area and their physical surroundings is called • a community • a population • an ecosystem • a biosphere

  3. 3. A forest has 9,000 trees in an area of 10 square miles. What is the population density for the trees in this forest? • 90 trees-mi2 • 90 trees/mi2 • 900 trees-mi2 • 900 trees/mi2 • 90,000 trees-mi2 • 90,000 trees/mi2

  4. To calculate population density divide the population size by the area. Population Density = Population size / Area A population of 9,000 trees in an area of 10 mi2 has a density of 900 trees/ mi2. The unit for the population of trees in this forest is trees / mi2 pronounced trees per square mile because the formula involved dividing the trees by the area.

  5. A full description of an organism’s role in an ecosystem, that includes its position in the food web and how it interacts with other species is its • habitat • niche • biotic capacity • abiotic capacity

  6. Organisms that can produce their own food, using sunlight or in a few cases certain chemical compounds, are called • producers • autotrophs • heterotrophs • A and B • A and C

  7. 6. An example of a chemosynthetic organism is • a yeast cell that is able to ferment grapes to produce alcohol • a bacteria found in hydrothermal vents that is able to produce organic food molecules using the energy found in certain volcanic compounds • both A and B • neither A nor B

  8. Which of the following words in synonymous with the word “consumer”? • Autotroph • Herbivore • Scavenger • Heterotroph

  9. The diet of a bear includes both meat and vegetation such as berries and bulbs. With this type of diet, bears are classified as • Carnivores • Scavengers • Omnivores • Herbivores • Detritivores

  10. A trophic level is • a step in a food chain. • the amount of sunlight present in an ecosystem • the average temperature in an ecosystem • the average amount of precipitation in an ecosystem

  11. A food chain (or web) forms an energy pyramid, in which the widest part of the pyramid with the greatest amount of stored energy and biomass is • a top consumer • an autotroph • an herbivore • a decomposer

  12. 11. A food chain in a pond begins with algae that are eaten by mayfly nymphs which serve as food for sunfish which are then consumed by great blue heron. (algae  mayfly nymph  sunfish  great blue heron ) If this pond becomes contaminated with mercury, which organism would likely become most contaminated with this toxin? • The algae • The mayfly nymph • The sunfish • The great blue heron

  13. 12. If you compared the amount of mercury in a tuna (a larger fish that is higher on the food chain) to that in a herring (a smaller plankton-eating fish) it would likely have A. A greater total amount of mercury B. A higher concentration (grams of mercury per pound of body mass) C. Both A and B D. Neither A nor B

  14. Review: Remember that food chains form energy pyramids with less biomass for each level you move up the food chain. (More algae is needed to feed the mayfly nymphs etc.) This pattern is due to the 2nd Law of Thermodynamics that states that in any energy conversion, some energy will be “degraded” into less useful heat energy. Therefore, the top consumer generally has the greatest concentration of toxins, since the same amount of toxin is present in a smaller quantity of biomass. The top consumer has had to consume a greater amount of food from the lower levels.

  15. 13. The carrying capacity for the rabbit population is • 3 • 4 • 30 • 60 • 65

  16. 14. Which of the following could cause an increase in the carrying capacity of the rabbit population? • An increase in the supply of food • An increase in the birth rate • Both A and B • Neither A nor B

  17. 15. The initial phase of a logistic growth graph shows • an exponential increase in the population • a steep linear increase • a decline in population • a gradual linear increase

  18. Organisms generally reproduce at a rate that would allow for exponential growth. The carrying capacity of a population is caused by the factors that limit its growth (food supply, predators etc.) The carrying capacity is not a fixed quantity. If the limiting factors change than the carrying capacity will also change.

  19. 16. Which type of species would have an advantage if there is an unstable environment? • Generalist • Specialist

  20. D • C • D • B • D • B • D • C • A • B • D • C • D • A • A • A

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