1. The ultimate source of energy for most ecosystems is (3):
a. Carbon
b. Oxygen
c. Sunlightd. Water
2. Organisms that directly use energy from the sun to make their own food are called (3):
a. Autotrophsb. Hetertrophs
c. Carnivores
d. Decomposers
3. Which of the following illustrates the correct ordering of trophic levels? (3)
a. Decomposers?carnivores?autotrophs?herbivores
b. Herbivores?autotrophs?carnivores?decomposers
c. Autotrophs?herbivores?carnivores?decomposersd. None of the above
4. Within an ecosystem (3):
a. Energy flows in one direction only and nutrients are recycledb. Energy is recycled and nutrients flow in one direction only
c. Energy and nutrients flow in one direction only
d. Energy and nutrients are both recycled
5. The efficiency of energy transfer from a lower trophic level to the next highest level is roughly (3):
a. 1%
b. 5%
c. 10%d. 50%
e. 80%
6. In aquatic ecosystems, biomass is least at which trophic level? (3)
a. Autotrophs
b. Herbivoresc. Carnivores
7. You are in an area where there are squid, seals and penguins. You are most likely in which ecosystem? (3)
a. Deciduous forest
b. Hot Desert
c. Antarctic Ocean Shored. Grassland
8. You find yourself in an area where there are snakes, hawks and coyotes. Based upon these animal populations, you are most likely in which ecosystem? (3)
a. Deciduous forest
b. Hot Desert
c. Grasslandd. You cannot tell from this information
9. You are in an area where the ground is littered with what appear to be dry, dead leaves. You are most likely in which ecosystem? (3)
a. Deciduous forestb. Hot Desert
c. Grassland
d. You cannot tell from this information
10. This zone has the greatest concentration of plankton in a freshwater lake ecosystem (3):
a. Profundal
b. Littoral
c. LimneticInfo
The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.
Plankton have short life spans — when they die, they fall into the deep-water part of the lake/pond, the profundal zone. This zone is much colder and denser than the other two. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.
Temperature varies in ponds and lakes seasonally. During the summer, the temperature can range from 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottom can be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly. During the spring and fall seasons, there is a mixing of the top and bottom layers, usually due to winds, which results in a uniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake. Of course there are many lakes and ponds that do not freeze during the winter, thus the top layer would be a little warmer.
Infobox
Which two ecosystems are you asking about? An ecosystem can be as large as the Sahara Desert, or as small as a puddle or vernal pool.
Ecosystems are dynamic interactions between plants, animals, and microorganisms and their environment working together as a functional unit.
An ecosystem is generally an area within the natural environment in which physical or abiotic factors of the environment, such as rocks and soil, function together along with interdependent or biotic organisms, such as plants and animals, within the same habitat.
Within each ecosystem, there are habitats which may also vary in size. A habitat is the place where a population lives. A population is a group of living organisms of the same kind living in the same place at the same time. All of the populations interact and form a community. The community of living things interacts with the non-living world around it to form the ecosystem.
For example, a coral reef ecosystem is produced by living animal colonies, found in marine waters containing few nutrients. The accumulation of skeletal material, broken and piled up by wave action and bioeroders, produces formation that supports the living corals and a great variety of other animal and plant life. Reefs grow best in shallow, clear, sunny and agitated waters. They are most commonly found at shallow depths in tropical waters, particularly in the Pacific Ocean.
Coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature. They are under threat from climate change, ocean acidification, commercial fishing, fishing for aquarium fish, overuse of reef resources, and harmful land-use practices. High nutrient levels such as those found in runoff from agricultural areas can harm reefs by encouraging excess algae growth.
Now, compare a coral reef ecosystem to a tundra ecosystem. Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil. The Arctic tundra is a vast area of stark landscape that is frozen for much of the year. The soil there is frozen up to three-feet deep, and it is impossible for trees to grow. Instead, bare and sometimes rocky land can only support low growing plants such as moss, heath, and lichen.
There are two main seasons, winter and summer, in the polar tundra areas. During the winter it is very cold and dark. During the summer, temperatures rise somewhat, and the top layer of the permafrost melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs and streams during the warm months. During the summer, the permafrost thaws just enough to let plants grow and reproduce, but because the ground below this is frozen, the water cannot sink any lower, and so the water forms the lakes and marshes found during the summer months. The coral reef has no true seasons and life progresses continually without starting and stopping as in the tundra ecosystem.
The biodiversity of the tundras is low and there are few species with large populations. Due to the harsh climate of the Arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as oil and uranium. Just as with a coral reef, human activity is causing changes to the tundra. A severe threat to the tundras, specifically to the permafrost, is global warming. The melting of the permafrost in a given area on human time scales in decades or centuries could radically change which species can survive there. Another concern is that about one third of the world's soil-bound carbon is in taiga and tundra areas. When the permafrost melts, it releases carbon in the form of carbon dioxide, a greenhouse gas.
Overall, ecosystems will fail if they do not remain in balance. No community can carry more organisms than its food, water, and shelter can accomodate. Food and territory are often balanced by natural phenomena such as fire, disease, and the number of predators. Each organism has its own niche, or role, to play.
Population is defined as the number of individuals of a particular species. Say we had ants in this ecosystem. Ants obviously would outnumber of the birds because there are like billions of ants in a single colony. If there is a huge population, then there is more diversity and so the population lower in the pyramid will have far more individuals. Also, it takes an incredible about of resources to sustain animals that are larger, in this case, the birds. Lack of resources means less population growth.
15. What might happen to an ecological pyramid of numbers in a forest ecosystem if most of the deer were killed due to hunting by people and disease? (5)Then all those animals that depend on deer as food will suffer, such as the wolves (higher-level organisms). The plants in which the deer feed on would experience a population increase because they don't have an organism to keep them in check.
16. What would happen to an ecosystem if the decomposers disappeared? (5)There would no recycling of nutrients (plants/autotrophs would suffer).
17. Could there be a food chain without herbivores and carnivores? (5)Yes, but without autotrophs, not likely.
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