Ecology: Animal Interactions Trophic Pyramids and Trophic Webs

Review of Energy Principles Photosynthesis – converts light energy into chemical energy (glucose). Respiration – converts chemical energy (glucose) to chemical energy (ATP). Laws of Thermodynamics –1 st Law – conservation of energy, all energy must be accounted for –2 nd Law – order to disorder  heat

What is Ecology? study of the interaction between abiotic and biotic components of……

How do non-photosynthetic organisms capture energy? They eat! What happens to some of the energy that they acquire? What is it turned into? What do they eat? Where does the energy in what they eat come from? The Sun

Light Energy Fates Reflectance Absorption by non- photosynthetic systems Radiated back to space Absorption by photosynthesis

Let’s follow the sun’s energy Light energy Carbon dioxide Water Photo- synthesis Glucose Oxygen gas Let’s just follow it through Photosynthesis –Step 1: light energy absorbed by photosynthesis –Step 2: photosynthetic process (light dependent reactions) –Step 3: energy is now in form of glucose and can be stored in other carbohydrate forms (starch, cellulose, etc.) If glucose is eaten by an animal it can remain as glucose or stored as either glycogen or chitin

Terrestrial Food Chain (Step 4)

Aquatic Food Chain (Step 4)

Direction of Energy Flow

Energy Pyramid Since the heat is no longer useful, at each step, the amount of useful energy from our original burst of sunlight is reduced.

Energy Energy passes through biological systems –Energy enters the system via photosynthesis –Energy passes through the biological system through trophic levels via metabolism (cellular respiration) –Energy leaves the biological system in the form of heat.

Energy does not flow linearly - Food Webs

Interactions Between Organisms Interspecific interactions are interactions between species. Intraspecific interactions are interactions within the same species. Interaction type Effect on Actor Effect on Target 1. Herbivory BeneficialHarmful 2. Predation BeneficialHarmful 3. Competition HarmfulHarmful 4. Symbiosis ParasitismBeneficialHarmful CommensalismBeneficialNeutral MutualismBeneficialBeneficial

1. Herbivory Herbivory - the interaction is beneficial to the actor but harmful on the target Herbivore Omnivore

2. Predation Carnivore Omnivore Predation- the interaction is beneficial to the actor but harmful on the target

Without Pisaster With Pisaster (control) Predation effect on species diversity within a community ecosystem

Competition Ocean High tide Chthamalus Balanus Low tide The effect on the actor is harmful and the effect on the target is harmful Chthamalus can live lower on the shore but doesn’t because it is competitively displaced by Balanus. Higher mortality of juvenilles as well.

Symbiotic Interactions Parasitism- effect on the actor is beneficial and harmful on the target.

Commensalism The effect on the actor is beneficial and the effect on the target is neutral. The Cattle Egret (Bubulcus ibis) forages in pastures and fields among livestock such as cattle and horses, feeding on the insects stirred up by the movement of the grazing animals. The egrets benefit from the arrangement, but the livestock, generally, do not.

Mutualism The effect on the actor is beneficial and the effect on the target is beneficial Bird benefits by getting food while buffalo benefits from removal of potential parasites.

You should be able to: Follow energy from the sun through a food chain or food web, and identify the conversions that happen. Use a food web or food chain to identify the trophic relationships of represented organisms. Identify the immediate source of energy for an organism and the original source of energy for all organisms. Explain the role of detritivores in a food chain or food web. Explain why the energy pyramid is shaped the way it is. Explain/identify how different types of interactions affect both of the organisms involved.