According to the BBC, about 90 percent of the available energy in any trophic level is lost and becomes unavailable to higher trophic levels. For example, if the green plants in a habitat represent 1000 calories of food per square foot, the herbivores that eat these plants only represent about 100 calories per square foot. The predators that feed on these herbivores only represent about 10 calories per square foot.Know More
In general, the more fertile the habitat, the more trophic levels it can support. Because energy is lost with each trophic level, the BBC explains that the number of possible trophic levels for any ecosystem is limited. Animals of the fourth trophic level only represent about one - one thousandth of the original energy, and by the time the fifth trophic level is reached, only about one - ten thousandth of the original energy remains in the food chain. Commercial farming operations try to minimize these inefficiencies to maximize profits.
Tropic levels lose energy due to several inefficiencies in the system. As noted by BioTopics.co.uk, some of these inefficiencies include the fact that plants and animals use energy during cellular respiration. Additionally, when animals eat food items, they rarely digest them completely, leading to wasted calories.Learn more about Biology
Blood oxygen levels under 90 percent are considered low and warrant immediate medical attention, according to the Mayo Clinic. A dangerous blood oxygen level, also called hypoxemia, occurs when a lower-than-average level of oxygen is circulating from the blood to the cells and tissues of the body. Normal blood oxygen levels are within the 95 to 100 percent range.Full Answer >
A low blood oxygen level, or hypoxemia, is considered anything under 90 percent, notes Mayo Clinic. A normal range is 95 to 100 percent. Blood oxygen level may be measured with a blood test or a pulse oximeter, which clips onto the finger and measures oxygen saturation through estimation.Full Answer >
A pulse oximeter reading of below 90 percent is considered low, reports Mayo Clinic. A pulse oximeter measures oxygen saturation level, which is then used to estimate the amount of oxygen in the blood. Oxygen levels can also be tested using a sample of blood from an artery.Full Answer >
Primary producers, or autotrophs, make up the first trophic level of all food webs. Autotrophs are organisms that produce their own energy from inorganic substances, such as carbon dioxide and water. The primary producers of many food webs are green plants.Full Answer >