Energy

• Open and Closed Systems

  1. The biosphere (earth) is a closed system
  2. 2. A closed system means that energy can enter and matter cannot enter.
  3. 3. Ecosystems are considered as open systems.
  4. 4. An open system means that energy can enter and matter can enter.
• All organisms require energy for:

  • growth
  • tissue maintenance
  • reproduction
  • locomotion/movement

  1. The main concept for all ecosystems is how energy is transferred from one part of the ecosystem to the others.
  2. Many factors affect this. Some are related to the living things themselves (biotic) while others are not alive (abiotic).
  3. Food is biotic. For example, an apple is biotic
• Important Vocabulary

  
  

  Trophic Level - the feeding level of an organism in a food chain or food web

  
  

  Producer - organisms that produce their own food from inorganic things and can also be referred to as an autotrophs, and are plants.

  
  

  Consumer - organisms that eat other organisms for food and can also be referred to as a heterotrophs, and are animals.

  
  

  Herbivore - Primary (first-order) consumers; animals that eat plants

  
  

  Carnivore - Secondary (second-order) or tertiary (third-order) consumers; animals that eat other animals
• Energy Flow in Photosynthetic Ecosystems

  1. Sunlight is the initial energy source for almost all communities.
  2. NOT all light that reaches Earth can be used.
  3. Producers use light energy to synthesize organic molecules during photosynthesis.
  4. Then, consumers break down these organic molecules to produce ATP during cellular respiration.
  5. Therefore, an ecosystem's entire energy supply is determined by the photosynthetic activity of the producers.
• Pattern of Energy Distribution

  99% of the Earth's energy comes from solar radiation. It is a combination of many forms of energy (light, heat, UV)Of this:

  
  

  34% is REFLECTED back into space by atmospheric gases, clouds, dust and surface. The amount varies in location and season. Higher Albedo = more reflection.

  
  

  42% is ABSORBED by the atmosphere, soil, and water. Different substances absorb heating differently and this uneven heating and rotation of the Earth produces wind, air currents, and storms.
• Pattern of Energy Distribution

  23% is used to drive the WATER cycle. Evaporated water accumulates in the atmosphere, cools, forms clouds, and then precipitates in rain or snow.

  
  

  1% drives the wind and water currents.

  
  

  0.023% is used for photosynthesis.

  
  

  Photosynthesis produces O2 and consumes CO2.

  
  

  Cellular Respiration produces CO2 and consumes O2.

  
  

  Photosynthesis and Cellular Respiration replenish each other and create a balance.
• Energy Flow in Chemosynthetic Environments

  While most ecosystems on Earth rely on the sun as their main source of energy, there are many places on Earth where sunlight cannot reach.

  1. This includes underground and at the bottom of oceans where it is too deep for light to penetrate.
  2. Microbes in such places use inorganic minerals in their environment
• Energy Flow in Chemosynthetic Environments

  1. Organisms that make their own food from chemicals are called chemoautotrophics and are considered autotrophs (make their own food).
  2. Chemosynthesis - the process in which some types of microorganisms use energy from chemical reactions to produce organic (carbon-containing) compounds as food for themselves
• Chemoautotrophs

  1. Hydrothermal vents in the deep ocean a unique ecosystem have evolved in the absence of light. The animals that live around these vents make their living from the chemicals that come out of the seafloor in the vent fluids.
  2. Because they are a local food source, hydrothermal vents usually have high biomass (life) compared to very few animals outside of the vent areas, as those animals are dependent on food dropping down from above, making them scavengers.
• Chemoautotrophs

  1. Chemosynthetic microbes live on or below the sea floor, and even within the bodies of other vent animals as symbionts. Where microbial mat covers the seafloor around vents, grazers such as snails eat the mat, and predators come to eat the grazers.
• Energy Flow

  1. Energy (sunlight) that enters an ecosystem is used to make food by producers.
  2. This energy is then transferred throughout the ecosystem as consumers eat the producers, and consumers eat other consumers.
  3. Not all energy is transferred from one trophic level to the next.
  4. Most energy is used by the organism to perform its functions (moving, growing, etc).
  5. In most cases, the energy is lost as heat.
• Decomposers

  1. Decomposers help to recycle biomatter.
  2. When an organism dies or makes waste material (feces, urine, etc) decomposers feed upon those remains.
  3. In doing so, they return organic biomatter to the ecosystem giving nutrients to the producers.
• Food Chains

  A food chain is a simplified (but not realistic) way of explaining energy flow. The food chain describes who may eat whom in a community.

  Producers always occupies the first trophic level in a food chain.

  Herbivores always occupies the second trophic level in a food chain.

  Carnivores always occupies the third trophic level in a food chain.

  
  

  The arrow points which way the energy is going.

  Only one type of organism can occupy a trophic level.

  One organism cannot occupy more than one trophic level.

  Decomposers are assumed to be feeding off of all trophic levels.
• A specialist is only able to eat specific foods and have a specialized environment.

  eg. Panda only eats bamboo

  
  

  A generalist is able to eat many foods and can survive in many environments.

  eg. Grizzly bear eats meat, berries, fruits
• Food Webs

  A food web is a more accurate representation of the feeding relationships between organisms in an ecosystem and has several connected food chains. Food webs are more accurate as it includes more than one food source for organisms.

  Apex predator - the predator at the top of the food chain. Nothing eats them.
• The First Law of Thermodynamics (the law of conservation of energy)

  States that energy can change forms but cannot be created or destroyed. Therefore, the energy entering is the same amount of energy leaving.
• The Second Law of Thermodynamics

  States that energy can be changed from one form to another. During any change, it is not 100% efficient and some energy is lost as waste energy or heat.
• The Laws of Thermodynamics

  When these laws are applied to an ecosystem, as energy flows through the community, there is energy loss at each trophic level.

  Much of this loss is in the form of heat which is lost when food molecules are broken down in the cells.
• Energy In Trophic Levels

  There would be less energy loss in the community if only herbivores fed on the producers. The loss for each trophic level is around 90%.

  As the energy flows through more carnivores, two things happen:

  1. there is continued energy loss.
  2. a limit is reached on the food chain (size).

  The longer the food chain, the less energy is left for the organisms at the end (or apex predator) of the food chain.
• Ecological Pyramids

  the transference of energy throughout the ecosystem can be represented by using a pyramid.

  Pyramid of numbers

  • least accurate
  • shows the number of organisms that exist at the trophic level in the ecosystem. Very few apex predators exist.
  • However, it may not always have a pyramid shape. (eg. a single tree can provide food for several insects, or a school of piranhas.)
• Ecological Pyramids

  2. Pyramid of biomass

  • shows the amount of dry mass of organisms at each trophic level.
  • Biomass is a measure of stored energy.
  • Dry mass = water has been removed.

  Occasionally, a pyramid of biomass does not show the regular pyramid shape, but such instances are extremely rare.

  • this happens when the population has a high reproductive rate. (eg. bacteria around hydrothermal vents - the chemosynthetic microbe quickly split and regrow)
• Ecological Pyramids

  3. Pyramid of energy

  • always accurate
  • shows the amount of available energy at each trophic level
  • it will always have a pyramid shape.

  Ecological Pyramids Overview:

  1. The base contains the highest number or organisms, biomass, and energy of the ecosystem. It is where the producers are found.
  2. The top contains the lowest number of organisms, biomass, and energy in the ecosystem. It is where the apex predator is found.
• Calculating Energy of Efficiency

  1. The energy of efficiency is the percentage of available energy that is transferred from each trophic level.
  2. Typical energies of efficiency are between 10-20%. This means that 80-90% is lost as heat.

  Formula:

  Energy of efficiency = amount of energy transferred to the trophic level / amount of energy at previous level x 100%

  Do you have to include sig digs? YES

  Do you have to show your work? YES
• Food Chains and Population Interdependency

  In ecosystems, populations have a profound effect on each other. A change in one population of organisms will cause changes to other populations

  
  

  Flower nectar → Honey bee → Frog → Heron

  
  

  1. If there was a large rainfall that caused more flowers to grow, it would be expected that the honey bee population increases. This would result in the frog population increasing. Then the heron population would increase.

  2. If there was a drought, then the honey bee, frog, and heron population would all decrease.
• Biomagnification

  1. Also known as bioamplification, biomagnification is the accumulation of chemicals in the tissues of organisms. These chemicals are acquired from the animal's food and water, and are often toxic.
  2. Because these chemicals are not used by the organism's:

  -metabolic processes

  -difficult to excrete

  it tends to accumulate or build up.

  3. As a result, these chemicals are found in higher concentrations in higher trophic levels.
• Biomagnification Part 2

  1. Chemicals such as mercury, selenium, nickel, chlorinated hydrocarbons are some of the more serious examples of biomagnification.
  2. Sources for these chemicals are often pesticides that get into the water.

  3. Concentrations of these chemicals are often in (ppm) or (ppb).
• DDT

  DDT controlled and acted as a poison to insects; mainly mosquitoes with malaria.

  The negative side effects were:

  • Humans: cancer, infertility, miscarriage, diabetes
  • Birds: thin eggshells

  In some countries, DDT would accumulate and kill top predators, leading the population of other organisms to grow uncontrollably.