Biosphere and Energy

1.2 The Biosphere and Energy

All activities require a source of energy – a fuel (ex. Need a supply of wood to sustain a campfire; need gas in the tank to reach a destination by car; to migrate successfully, hummingbirds need to burn fat that is stored in their tissues.

In each example, fuel is different – wood for campfire, gasoline for car, and nectar stored as fat for the hummingbirds.


3 sources of energy are the same since they come from the same source – solar energy that has been converted to and stored as chemical energy.


Solar energy is energy from the Sun, and given off by nuclear reactions in the Sun


Some organisms in the biosphere trap solar energy and use it to make food, which is then used by all organisms to fuel activity and growth.


Enormous amount of energy reaches Earth from the Sun.


At the same time, there is a never-ending loss of energy from the earth.


Energy is lost as heat when it spreads back out from Earth’s surface, beyond Earth’s atmosphere.


Earth’s atmosphere is able to trap some of the heat, warming the atmosphere and making Earth habitable.


Matter is used over and over as it moves through Earth’s four spheres.

Nutrients may change form or take millions of years to complete their cycle, but no matter is lost as they move through Earth’s four spheres.


Photosynthesis and the Sun’s Energy


Chlorophyll and Photosynthesis


Conversion of solar energy to chemical energy, in the form of food, is important to life for two reasons; first, the Sun will continue to supply Earth with energy for billions of years. Second, many organisms on Earth, including plants, algae, and some bacteria, contain chlorophyll, which allows the biosphere to harvest some of this reliable solar energy


Chlorophyll is central player in photosynthesis, a process that is crucial to life on Earth


Chlorophyll is a pigment that gives leavers their green colour.


Photo means light, synthesis means putting together.


Photosynthesis refers to putting something together using light.


Photosynthesis puts together carbon, hydrogen, and oxygen to make sugar glucose.


Photosynthesis – a process that changes solar energy into chemical energy


Trophic Levels


Matter and energy are transferred between trophic levels within the biosphere.


Trophic level is a category of organisms that is defined by hoe the organisms gain energy (ex. Primary producers and consumers).


Primary producers are organisms that can make their own food, such as plants.


Consumers are organisms that cannot make their own food and must eat other organisms to get the matter and energy they need to survive.


Primary consumers are at first trophic level, primary consumers is at second trophic level, secondary consumers eat primary consumers to obtain energy, and at the third trophic level, and tertiary consumers – which feed on secondary consumers to obtain energy – are at the fourth trophic level.


Herbivores are organisms that only eat plants (ex. Grasshopper).


Consumers that eat other animals are carnivores (ex. Hawk).
Consumers that eat both plants and other animal are called omnivores.
Both energy and matter, including nutrients, move through the trophic levels of this food chain.
All levels of food chain linked to decomposers, which move nutrients in the decaying. bodies and wastes of producers and consumers back to the abiotic parts of the ecosystem as they take in nutrients they need to survive.


Trophic Efficiency

Biomass is the mass of living cells and tissues that has been assembled by organisms using solar energy.


Leaves, stems, wood, roots, and flower nectar all packed with chemical energy that has been converted from solar energy.


Animals indirectly rely on solar energy too, by eating plants or other animals that eat plants.

Trophic efficiency is a measure of how much of the energy in organisms at one trophic level is transferred to the next higher trophic level.


This percentage is always less than 100% because organisms use much of the energy from the biomass they consume for their life functions, and they produce wastes.


Trophic efficiencies usually quite inefficient – only about 10%.


In a sample food chain, if primary consumer biomass contains 1000 units of energy, only 10% of energy is transferred to next trophic level (only 100 units of energy). Of those 100 units, 10 units reach next trophic level, and of those 10 units, only 1 will reach next trophic level.


Several reasons why biomass decreases from one trophic level to the next: herbivores may not eat all parts of the plant (ex. May only eat tops of plant and leave roots), not everything eaten is digested (ex. Fur), energy is lost as heat from the bodies of organisms in every trophic level.


Because of inefficiency of energy transfer among trophic levels, usually fewer carnivores than herbivores, and fewer herbivores than plants.


Biomass – the total mass of living organisms in a defined group or area


Trophic efficiency – a measure of the amount of energy or biomass transferred from one trophic level to the next higher trophic level


Water Pollution and Bioaccumulation

As caterpillar, monarch butterfly, feeds on plant called milkweed and ingests toxins, or poisonous substances from the milkweed, which are stored in the butterfly, in tissues where they do not harm it.
Ingestion of toxins at a rate faster than they are eliminated is called bioaccumulation

In this example, bioaccumulation works to advantage of species.


If fewer individuals of species are eaten because they are poisonous, more individuals will survive to reproduce.


In contrast, bioaccumulation of toxins from human-made pollution can be devastating to a species, since they can cause health problems or death.

Biomagnification is a process that is related to bioaccumulation, and is the increase in the concentration of a toxin as it moves from one trophic level to the next.


Bioaccumulation – a process in which materials, especially toxins, are ingested by an organism at a rate greater than they are eliminated


Section Summary

Biosphere relies on a constant source of solar energy

Chlorophyll in primary consumers converts solar energy through photosynthesis


Most of the stored energy in one trophic level does not move to the next trophic level


Bioaccumulation and biomagnification can result in unhealthy levels of pollutants in organisms