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Ecology 4 Notes
Interactions
between Species
Different ecosystems around the
world…


Although we haven’t discussed biomes in
detail yet, which ones do you think are
most “productive”?
Which ones are “least productive”?
Very productive ecosystems…




Tropical rainforests
Temperate evergreen and deciduous
forests
Savanna is pretty good…
THE MOST productive is actually the
estuaries, swamps, and marshlands!!!
Why would these be more
productive than tropical rainforests?

It has to do with the availability and
variety of niches…along with pretty
ideal conditions for organism growth and
prosperity…

More niches reduces
competition
What is a NICHE?

An organism’s role within the structure
and function of an ecosystem
How does it get nourishment?
 What is it’s habitat?
 Is it part of a predator/prey relationship?
Or some sort of symbiotic relationship?
 Who does this it compete with?
 How does it interact with abiotic
components of the environment?
(tolerance)

NICHE
 NOT
 Sum
just the habitat
total of an organism’s
use of its biotic and abiotic
resources.
Competition
 Interactions
within or between
populations for a limited resource.
The closer the niches, the more
intense the competition.
 Intraspecific more intense than
interspecific.
Gauses’ Competitive
Exclusion Principle

One species eliminates the other one
entirely when two species niches
overlap and the system is allowed to
go to saturation
 (intense
competition).
Paramecium caudatum
 Paramecium aurelia
(pg 78 text)

Paramecia – Kingdom Protista
(ciliate)
How similar can two species
niches be and still coexist?

If two species have overlapping
niches, it is to the advantage of
both to REDUCE COMPETITION.
 RESOURCE
PARTITIONING
Stable Coexistence
MacArthur’s
Warblers
5 North American Warblers appear to
have the same niche.
 How do they coexist?
 Resource partitioning

 Differences
in portions of trees where
they feed, nest, timing of feeding, etc.
Types of Community
Interaction
Commensalism (+ o)
 Mutualism (+ +)
 Predation / Parasitism (+ -)
 Competition (- -)

Parasitism, commensalism and mutualism =
all examples of symbiosis
Examples of Types of
Community Interaction
 Deer
and rabbits both feed on the
grass in a meadow.
Competition!
Examples of Types of
Community Interaction
 Remora
fish use suction cup like
structures to attach to sharks. They
get a free ride to lunch…
 But they don’t hurt the sharks…
 Sometimes they eat parasites… They
also eat small bits of food missed by
the shark or other host.
Remora attached to a tiger
shark
Commensalism / Mutualism
Examples of Types of
Community Interaction
 Protozoans
live in and digest cellulose
for termites.
 And they get a “free” place to live…
Trichonympha
Mutualistic
flagellated
protozoan
found in the
gut of
termites.
They digest
cellulose for
the termite.
Termites and Trichonympha
= Mutualism
Examples of Types of
Community Interaction
Fish-cleaning
shrimp set up
stations to remove parasites
from fish.
The shrimp get food….
Shrimp that cleans fish
Mutualism!!
Examples of Types of
Community Interaction
 Egrets
(birds) feed off of invertebrates
that cattle kick up when they walk
around the pasture.


Cattle Egrets
in England
Commensalism!
Examples of Types of
Community Interaction
Ants
feed off of sugary secretion
from Acacia tree and protect the
tree from herbivores.


Ant sipping
on sugar
from Acacia
Mutualism!
A tick on a horse…
As the tick is
sucking the
blood of the
horse, it is
benefiting while
the horse is
not…
Parasitism!



LICHENS
Algae provide
sugar and
possibly
nitrogen for
the fungus.
The fungus
helps to
maintain water
and minerals
for the algae.
This is a really good example of…
Mutualism!!!
Predation


Not really a symbiotic
relationship, but it is certainly
an important interaction
Permits energy flow from one
trophic (feeding) level to
another.
Predation
 Regulates
the population growth of
the next lower trophic level
Lynx
and Hare
Lynx
Hare in winter
Hare in summer
Would this be positive or
negative feedback?
NEGATIVE!!!!
Prey Techniques
Constant interaction between predator
and prey populations selects for increased
efficiency of both.
 Any characteristic that increases the
predator’s efficiency at detecting,
capturing or eating prey would be selected
for. Conversely, any prey characteristics
that would enhance its ability to avoid
detection, capture or being eaten would
also be selected for (an advantage)

It is an ARMS RACE!
(coevolution)
Escape utilizing behavior.
 Starling and peregrine falcon.
 Starlings tighten flying formation when
peregrines are nearby.
 Falcon has vision 5 times better than
humans.
 Stoops, closes wings and dives at
speeds greater than 200 miles per
hour
 Prey killed instantly by the talons.
Peregrine
Falcon
Starling
See Chapter 4 for more
details…
(pg 73-74 for defenses; also see
symbiotic relationship examples )