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– 1st Law – conservation of energy, all energy

must be accounted for– 2nd 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 The

SunSun

Light Energy Fates

• Reflectance

• Absorption by non-photosynthetic systems

• Radiated back to space

• Absorption by photosynthesis

Let’s follow the sun’s energy

Light energyLight energy

Carbondioxide

WaterPhoto-

synthesis Glucose Oxygengas

• 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)

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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 typeInteraction type Effect on Effect on Actor Actor

Effect on Effect on TargetTarget

1. Herbivory1. Herbivory BeneficialBeneficial HarmfulHarmful

2. Predation2. Predation BeneficialBeneficial HarmfulHarmful

3. Competition3. Competition HarmfulHarmful HarmfulHarmful

4. Symbiosis4. Symbiosis

ParasitismParasitism BeneficialBeneficial HarmfulHarmful

CommensalismCommensalism BeneficialBeneficial NeutralNeutral

MutualismMutualism BeneficialBeneficial BeneficialBeneficial

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

Hightide

Chthamalus

Balanus

Low tide

• The effect on the actor is harmful and the effect on the target is harmful

Chthamalus Chthamalus can live lower on the shore but doesn’t because it is can live lower on the shore but doesn’t because it is competitively displaced by competitively displaced by BalanusBalanus. Higher mortality of juvenilles as well.. 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 (The Cattle Egret (Bubulcus ibisBubulcus ibis) forages in pastures and ) forages in pastures and fields among livestock such as cattle and horses, feeding on fields among livestock such as cattle and horses, feeding on the insects stirred up by the movement of the grazing the insects stirred up by the movement of the grazing animals. The egrets benefit from the arrangement, but the animals. The egrets benefit from the arrangement, but the livestock, generally, do not.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 removalBird benefits by getting food while buffalo benefits from removalof potential parasites.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.