Energy Flow and Symbiosis Notes

Energy Flow Through an Ecosystem

• Objective: To follow the flow of energy through trophic levels (food chain, food web, ecological pyramid) and understand the differences between producers, consumers, herbivores, carnivores, omnivores, and detritivores.

Ecological Organization

• Organization Levels (Smallest to Largest):
  • Organism: Individual, single life form.
  • Population: Group of organisms of the same species.
  • Community: Two or more populations of different species.
  • Ecosystem: Community of living organisms and abiotic (non-living) factors.
  • Biome: Types of ecosystems defined by their climate.
  • Biosphere: All living and abiotic things on Earth.
• Interdependence: Organisms are interdependent within an ecosystem.
• Niche: Organisms occupy a niche within an ecosystem, which they are adapted for, and competition for resources (habitat, water, mates, food) occurs when different organisms occupy the same niche.

Autotrophs (Producers)

• An autotroph, or producer, is an organism that gets its energy by producing the energy itself.
  • Photoautotrophs: produce energy through photosynthesis (e.g., plants, algae).
  • Chemoautotrophs: produce energy through inorganic compounds (e.g., archaebacteria).

Heterotrophs (Consumers)

• A heterotroph, or consumer, is an organism that gets its energy by consuming other organisms.
  • Herbivore: Eats only plants.
  • Carnivore: Eats animals.
  • Omnivore: Eats both plants and animals.
  • Detritivore: Eats fragments of dead matter.
    • Decomposer: Breaks down dead matter, recycling the nutrients back to the soil.

Food Chains, Food Webs, and Ecological Pyramids

• Illustrate feeding relationships and show how energy and matter flow in an ecosystem.

Food Chain

• A food chain is one representation of the flow of energy through the trophic levels of an ecosystem.
• The arrows show the one way flow of energy from the sun to the producers and then to the consumers.

Food Webs

• Food Webs describe the complex feeding relationships within an ecosystem. Food webs link all the food chains in an ecosystem together.

Trophic Levels

• Each step in a food chain or food web is called a trophic level.
• A trophic level describes the position an organism occupies in a food chain, food web, or ecological pyramid.
• A producer (an autotroph) is an organism that converts energy from the sun into usable energy for consumers (heterotrophs).

Energy Flow

• The ultimate source of energy on Earth comes from the Sun.
• The flow of matter in an ecosystem is cyclic (it is recycled).

Energy Transfer

• The first trophic level (producers) contains 100% of energy available in the ecosystem.
• Only 10% of the energy moves up each trophic level. The other 90% is lost as heat.
• Energy is lost due to the cost of living, including growth, metabolism, waste (feces), and cellular respiration; energy is lost to daily living as heat.

Ecological Pyramids

• An ecological pyramid is a diagram that shows the relative amounts of energy, biomass, or numbers of organisms at each trophic level.
• Biomass is the total mass of living matter at each trophic level.

Types of Ecological Pyramids

• Pyramid of Energy: Available energy decreases at each higher trophic level; energy is lost as heat. Only about 10% of energy is transferred from one level to the next.
• Pyramid of Biomass: Available biomass decreases at each higher trophic level.
• Pyramid of Numbers: Population size decreases at each higher trophic level.

10% Rule

• Ecological pyramids demonstrate that about 90% of energy is lost in the form of heat from one level to the next. Only 10% of your food is actually incorporated into making you!
• $100\% \text{ Energy} \rightarrow 10\% \text{ Energy} \rightarrow 1\% \text{ Energy} \rightarrow 0.1\% \text{ Energy}$

Atypical Pyramids

• Aquatic ecosystems often have less biomass at the producer level because phytoplankton (producers) are quickly consumed by zooplankton.
• Numbers pyramids can vary based on the size of the organism (e.g., one large oak tree supports many insects).

Symbiosis

• Definition: A relationship in which two species live closely together.
• These relationships can benefit, harm, or have no effect on one or both species involved.
• Purpose: To fulfill basic needs (food, shelter, protection/safety).

Types of Symbiotic Relationships

Mutualism (+ | +)

• Occurs when both organisms benefit.
• Examples:
  • Birds get nectar and pollinate the flower in return.
  • Ants sting predators of the plant Acacia; ants get food & a place to live in return.

Commensalism (+ | 0)

• Occurs when one organism benefits and the other organism neither benefits nor is harmed.
• Example:
  • Epiphyte - orchid makes its own nutrients, grows on tree to reach sunlight. Neither plant is harmed.

Parasitism (+ | -)

• Occurs when one organism (the parasite) benefits and the other (the host) is harmed.
• Example:
  • Mistletoe takes nutrients away from trees.

Predation (+ | -)

• Occurs when one organism (the predator) hunts another organism (the prey) for food.
• Example:
  • Cougar hunts, kills, and eats deer.

Competition

• An interaction between organisms in which both organisms are harmed.
• Occurs when species occupy the same niche.
• The species that is best adapted to complete the job will usually fill the niche.
• Niche: All the physical, chemical, and biological factors that a species needs to survive, stay healthy, and reproduce in an ecosystem.
• Example:
  • Asian carp, an invasive species accidentally introduced into the Illinois and Mississippi Rivers, are outcompeting native fish for food and habitat. They are voracious filter feeders and can grow to over 100 lbs.