Environmental SystemsTAKS Review SessionSpring 2007

Lecture 1

Energy Flow in Ecosystems

Movement of Energy

• Almost all of the life forms on earth get their energy from the sun and its light energy

Primary Productivity

• All photosynthetic (like plants) organisms take the light from the sun and convert it to chemical stored energy. This chemical energy is an organic compound (organic means having carbon).

Producers and Consumers

• All creatures and plants that create food with photosynthesis are called primary producers

• Creatures that eat the plants are called consumers

Trophic Levels

• Energy travels through the ecosystem and goes through levels.

• Each level is called a trophic level

Flow of Energy

• To understand the flow of energy lets say that when energy leaves the sun it is worth 100 dollars.

• Next when the plant makes food the energy is now worth 10 dollars

• When the rabbit eats the plant the energy is worth 1 dollar

• When the wolf eats the rabbit it is worth 0.1 dollars or 10 cents

Flow…

• So, as the energy moves through the ecosystem only 1/10th of it makes it to the next level!

The Trophic Levels

• The lowest level of the food chain is made up of the producers

• The second level of the chain is the herbivores (plant eaters)

• The third level is made up of the omnivores (eats plants and animals) and the carnivores (eats only meat)

Producer

Herbivore

Omnivore

Carnivore

The Special Case

• The Detritivores-worms, fungus, and bacteria-all survive by eating the dead things and returning the nutrients to the soil and air. If these creatures cause the decay they are called decomposers.

• They are on all trophic levels except the first

Energy

• As the energy moves from the producers to the herbivores, then to the carnivores, energy is lost in the form of heat.

• Because energy is lost, each level gets smaller (fewer # of organisms)

• For instance, there are more blades of grass than there are zebras and more zebras than there are lions.

Energy Pyramid

• Producers have the most members, then the herbivores have less, and the carnivores even less. This is because there is less energy available at each level. Think about it, there are many many plants (producers), many rabbits (herbivores), and few wolves (carnivores).

Pyramid of Energy

Biomass

• If we add up all the dry weight of tissue and other organic material in an ecosystem it is called Biomass

Pyramid of Biomass

Environmental SystemsTAKS Review SessionSpring 2006

Organism Interactions

Interactions among species

• 5 types of close interactions1.Predation

2.Parasitism

3.Competition

4.Mutualism

5.Commensalism

Predation – Co-evolution of Predator and Prey

• Tools: Predator – Improve efficiency at finding, capturing and consuming prey

Sharp Teeth Keen senses; sight, hearing, smell Strong, fast legs Camouflage

• Tools: Prey – Improve efficiency at hiding, evading and avoiding being eaten.

Sharp Teeth Keen senses; sight, hearing, smell Strong, fast legs Camouflage Spines Bad Taste / Warning Coloration / Mimicry

Predation – Co-evolution of Predator and Prey

Parasitism

• One individual benefits (parasite) while another is harmed (host).

Examples:

Ticks

Fleas

Tape Worms

Malaria

Parasitism – Co-evolution of Parasite and Host

• Tools: Parasite – Highly specialized physiologically and anatomically

Feeding apparatus Small size, hard to see Strong, attachment apparatus Natural pain killers at feeding site

Parasitism – Co-evolution of Parasite and Host

• Tools: Host – Defense Eyes, nose and mouth are

protected by tears, mucous and saliva

Grooming behaviors Natural body defenses

TAPE – WORM DIET!

Competition

• Use of a limited resource by two or more species

• Resources could be food (prey) or nesting sites, for example.

• Hyenas and Lions• Hawks and Eagles• Ducks and Geese

Commensalism

• When one species benefits and the other is not affected.

• Example: Bromeliads (Spanish Moss) grow on trees to obtain sunlight

• Barnacles on a whale• Birds that follow behind elephants and

eat the insects stirred up by the elephant