Download Lecture 12

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
Sun
Light Energy
Fates
• Reflectance
• Absorption by
nonphotosynthetic
systems
• Radiated back
to space
• Absorption by
photosynthesis
Let’s follow the sun’s energy
• 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
Light energy
Carbon
dioxide
Water
Photosynthesis
Glucose
Oxygen
gas
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
Interaction type
• Interspecific
interactions are
1. Herbivory
interactions
between species.
Effect on
Target
Beneficial
Harmful
Beneficial
Harmful
Harmful
Harmful
Parasitism
Beneficial
Harmful
Commensalism
Beneficial
Neutral
Mutualism
Beneficial
Beneficial
2. Predation
• Intraspecific
interactions are
interactions
within the same
species.
Effect on
Actor
3. Competition
4. Symbiosis
1. Herbivory
• Herbivory - the interaction is beneficial to the
actor but harmful on the target
• Herbivore
• Omnivore
2. Predation
• Predation- the interaction is beneficial to the
actor but harmful on the target
• Carnivore
• Omnivore
Predation effect on species diversity within a community
ecosystem
With Pisaster
(control)
Without
Pisaster
Competition
• The effect on the actor is harmful and
the effect on the target is harmful
High
tide
Chthamalus
Balanus
Ocean
Low
tide
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.