what is the basis for energy in most ecosystems? how much energy is kept as you go up a energy pyramid or a food chain?why?

Primary producers—usually plants and other photosynthesizers—are the gateway for energy to enter food webs.

Productivity is the rate at which energy is added to the bodies of a group of organisms—such as primary producers—in the form of biomass.

Gross productivity is the overall rate of energy capture. Net productivity is lower, adjusted for energy used by organisms in respiration/metabolism.

Energy transfer between trophic levels is inefficient. Only about 10% of the net productivity of one level ends up as net productivity at the next level.

Ecological pyramids are visual representations of energy flow, biomass accumulation, and number of individuals at different trophic levels.

Introduction

Have you ever wondered what would happen if all the plants on Earth disappeared—along with other photosynthesizers, like algae and bacteria?

Well, our beautiful planet would definitely look barren and sad. We would also lose our main source of oxygen, that important stuff we breathe and rely on for metabolism. Carbon dioxide would no longer be cleaned out of the air, and—as it trapped heat—Earth might warm up fast. And, perhaps most problematic, almost every living thing on Earth would eventually run out of food and die.

Why would this be the case? In almost all ecosystems, photosynthesizers are the only "gateway" for energy to flow into food webs—networks of organisms that eat one another. If photosynthesizers were removed, the flow of energy would be cut off, and the other organisms would run out of food. In this way, photosynthesizers lay the foundation for every light-receiving ecosystem.

Producers are the energy gateway

Plants, algae, and photosynthetic bacteria act as producers. Producers are autotrophs, or self-feeding organisms, that make their own organic molecules from carbon dioxide. Photoautotrophs, like plants, use light energy to build sugars out of carbon dioxide. The energy is stored in the chemical bonds of the molecules, which are used as fuel and building material by the plant.

The energy stored in organic molecules can be passed to other organisms in the ecosystem when those organisms eat plants or other organisms that have previously eaten plants. In this way, all the consumers—or heterotrophs, other-feeding organisms—of an ecosystem rely on the ecosystem's producers for energy. Consumers include herbivores, carnivores, and decomposers.

with mrs. linde, nora reveals her insensitivity and lack of shame about the forgery she committed. she implies that mrs. linde has obviously aged since they last met 10 years earlier, which accounts for nora’s inability to recognize her old friend. although nora seems sympathetic to mrs. linde’s plight, she can’t seem to control herself from boasting about her three children, her husband’s recent promotion, and how good she feels to finally have some money to spend. in a way, she seems to be flaunting her good fortune in front of mrs. linde who, deprived of all these benefits, has come to ask nora for . it is also through her interactions with mrs. linde that we realize something deeper lies under nora’s seemingly childish exterior. she reveals the secret of her forgery to mrs. linde and seems to see herself as quite resourceful for having done it.

in the company of dr. rank, nora is freer than she is with her own husband. she openly laughs with joy at knowing that all the other bank employees will be under her husband’s control. she offers dr. rank a macaroon, apparently forgetting that he knows she is forbidden to eat them. she then quickly covers for herself by claiming that mrs. linde brought them. nora seems much more assertive and free with these other characters, as well as unabashedly willing to scheme, lie, and justify her transgressions as altruistic.  

krogstad provides an interesting parallel to nora. like nora, he too is guilty of committing forgery, for which torvald condemns him and decides to fire him. although krogstad is a man and nora a woman, their crimes of forgery unite them. in fact, krogstad might represent what nora would be like if she were a man and were not strictly scrupulous like her husband is. for example, she tells mrs. linde that "a barrister's profession is such an uncertain thing, especially if he won't undertake unsavoury cases; and naturally torvald has never been willing to do that." perhaps nora would have delved into the unsavory, given how opposite she is to her husband. krogstad's is also the only harsh voice of reality that nora is forced to hear, and that is because he blackmails her for her regaining his job at the bank. finally, torvald’s reaction to krogstad’s forgery seems to foreshadow his harsh and cold reaction to nora’s forgery.