Page 311 - ABCTE Study Guide_Neat

D primary producers.

Answer

The correct answer is D. Primary producers are the first link in the food chain (and the first level of the
food web). A plant is a good example of an autotroph—it uses photosynthesis to produce its own
nourishment. The energy created by the plant travels up the food chain until it reaches the top predator
level.

Seasonal Cycles

Within many ecosystems outside of the tropics, the flow of energy changes dramatically throughout the
year. Winter represents the highest stress time for many organisms; most plants either die or become
dormant, while animals either migrate, hibernate, or deal with the harsh conditions. Nutrients are still
available in dormant or even dead plants but often the plants are buried under snow or are very scarce.
Some species will switch diets, while others will live off of fat reserves built up during the warmer seasons
and feed very little.

As the daylight begins to lengthen in springtime, increased sunlight is available. Soil temperatures warm
and plants begin moving stored nutrients from the roots to the branches to supply buds and developing
stems and leaves. Seeds lying dormant can begin to germinate, and food for primary consumers becomes
abundant again. Many organisms, such as deer, time the birth of their young to coincide with peak
vegetation growth in late spring.

Summer and fall are critical times for hibernating and nonhibernating organisms to obtain sufficient energy
to recover from winter stress, breed, raise young, and gain fat levels needed to survive the next winter.

In some animals, such as elk, insufficient fall preparation creates a much lower chance of surviving the
winter. Some will not breed in the fall because their nutritional level is so poor. The length of daylight
hours drives migration patterns of many birds, but as global temperatures have increased so have soil
temperatures and vegetation emergence. Insect emergence is beginning to occur before some migratory
species move through; The peak availability of food is no longer in synch with the hatching of young.

Question

How might the energy pyramid look if it showed the actual number of organisms in an ecosystem instead
of the amount of energy available to each?

A It would look essentially the same.