Tag: energy flow and loss

• A hunter-gatherer is a human living in a society in which most or all food is obtained by foraging (collecting wild plants and pursuing wild animals).
• The energy required daily by hunter-gatherer humans was 2000 - 4000 kcal.
  
• So, the correct answer is ' 2000 - 4000 kcal'.

Energy flow is the amount of energy that flows from one trophic level to another trophic level in an ecosystem. It is unidirectional. In any given ecosystem, flow of energy occurs through different trophic levels. Producers or plants obtain their energy from the sun by photosynthesis. The primary consumers (herbivores) obtain their energy from the producers. The secondary consumers (carnivores) obtained their energy by using herbivores as a source of food and so on. The energy present at each successive trophic level is 10% of the previous trophic level. Hence, as biomass passes from one trophic level to another, the amount of total energy declines.

In an ecosystem, the ultimate source of energy is sun and solar energy is trapped by photoautotrophs or green plants which then convert it into chemical energy which is stored in carbohydrates. This chemical energy in the form of food is passed on from one organism to another in a food chain in the ecosystem. 

• Bioenergetics is a field in biochemistry and cell biology that concerns energy flow through living systems. 
• This is an active area of biological research that includes the study of the transformation of energy in living organisms and the study of thousands of different cellular processes such as cellular respiration and the many other metabolic and enzymatic processes that lead to production and utilization of energy in forms such as adenosine triphosphate (ATP) molecules. 
• That is, the goal of bioenergetics is to describe how living organisms acquire and transform energy in order to perform biological work. 
• The study of metabolic pathways is thus essential to bioenergetics.
  

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.

Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren't needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. Fat is the body's most concentrated source of energy, providing more than twice as much potential energy as carbohydrate or protein (9 calories per gram versus 4 calories each per gram).

Entropy is the measurement of this disorder in energy, in which heat energy, is not usable, is considered disorganized. Thus, a system with a large amount of usable energy has low entropy, a system with little usable energy has high entropy. Based on the second law of thermodynamics, entropy will continually increase in the universe as energy becomes more and more disorganized.

First law of thermodynamics defines that the energy neither created nor destroyed but can only be transformed. Ecosystem is not accepted by the 1st law of thermodynamics because the energy is created.