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I. Ecosystem Components
A. Ecology – from the Greek oikos (“house”
or “place to live”)
B. Ecology is the study of how organisms
interact with one another and their
environment.
C. An organism is a form of life. Organisms can be
classified into species. Scientists have no
concrete idea how many species exist on earth.
Kinkajous (Honey Bear)
Rainforest Mammal
related to the raccoon
D. Estimates range between 4 million to 100
million species exist (most microscopic
organisms and insects)
E. The best estimates are that there are 1014 million species
F. So far scientist have named and
classified only about 1.8 million species.
G. A population is a group of individuals of the
same species occupying a given area at the
same time
Ex. Blue morpho butterflies
H. In most populations individuals of the
same species vary in their genetic make
up – they don’t all look or act alike.
I. This is called genetic diversity
J. Genetic diversity is crucial if a population
is to survive.
K. Populations of all the different species
occupying a particular habitat make up a
biological community.
L. An ecosystem is a community of different species
interacting with one another and their non-living
environment. Ecosystems include abiotic and
biotic factors.
Diverse Ecosystems:
Rainforest – Greatest species diversity of
any ecosystem due to warm temperatures
and abundant rainfall.
Cloud Forest – Rainforests in high elevation.
Name comes from the constant clouds
that envelop them – moist air all the time
to feed
Dry Pacific Forest – Dry season, on which
side of the mountains?
Mangrove swamps – Estuarine ecosystem
on Pacific coast, provide the perfect
habitat for juvenile species.
Coral Reefs
II. Species Interactions
A. Organisms interact with multiple other
organisms of the same and different
species.
1. Intraspecific Interactions – Interactions
among members of the same species
2. Interspecific Interactions – Interactions
between two or more members of
different species
II. Species Interactions
B. These interactions influence individual
fitness, population density, species
distribution, and even extinction levels or
rates.
C. When looking at interspecific species
interactions, its helpful to ask if the
interaction is beneficial or detrimental to
each species involved.
II. Species Interactions
D. The following chart shows the
relationship between two species in each
type of interspecific interaction.
+ = positive effect
- = negative effect
0 = neutral
II. Species Interactions
** From Hillis, Sadava, Heller, and Price
Interaction
Effect on Species I
Effect on Species II
Interspecific
competition
-
-
ConsumerResource:
Predator, herbivory,
parasite
+
-
Mutualism
+
+
Commensalism
+
0
Amensalism
-
0
III. Interspecific Competition (-/-)
A. Interspecific competition is competition
between members of two or more
species. Usually multiple species are
using the same resource and species are
competing to get access to resource.
B. Remember that anytime an organism has
to compete for something it expends
energy and personal resources, even if it
does “win” the competition.
III. Interspecific Competition (-/-)
C. Again, intraspecific competition is
competition between members of the
same species (food, mates, etc). Think
about how many ways human’s lives are
dominated by intraspecific competition.
D. Niche – The set of physical and biological
conditions a species requires to survive,
grow, and reproduce.
III. Interspecific Competition (-/-)
E. Both inter (between species) and intra
(within species) competition often occurs
over limiting resource – plants growing to
get sunlight, competition among predators
that depend on the same prey species,
etc.
III. Interspecific Competition (-/-)
F. Limiting Resource/Factor: Too much or
too little of any factor in the environment
can limit the growth of a population, even if
all other factors are present.
G. Limiting resources/factors in land
ecosystems include: temperature, water,
light, nutrients.
III. Interspecific Competition (-/-)
H. Limiting resources/factors in aquatic
ecosystems include: salinity, dissolved oxygen
content, nutrients, light, and temperature.
I. Carrying capacity is the number of
organisms an area can support based on
the limiting factors present
J. Competitive exclusion principle = two
species competing for the same limiting
resource in the same way can’t coexist.
Either one species will go extinct or one
species will adapt via resource
partitioning.
III. Interspecific Competition (-/-)
K. Resource partitioning will often occur
between species in the same environment.
Resource partitioning occurs when two
species divide a resource based on
differences in species behavior or
morphology.
III. Interspecific Competition (-/-)
L. If two species reduce competition by
using the same resource at different times,
it is called temporal resource partitioning.
M. Many plants do this by flowering at
different times of year, or day – some
plants flower at night to attract different
pollinators.
N. Wolves and coyotes are also an example
of temporal resource partitioning. They
are both top predators, but can live in the
same region because wolves are more
active in early to mid evening, coyotes are
most active from midnight to dawn.
O. Spatial resource partitioning – species
reducing competition by using different
habitats. Top predators often do this by
having different hunting territories.
P. Desert plants often do this as well by
having different root systems – some
have a wide area of very shallow roots,
while others have very small area of deep
tap roots.
Q. Morphological resource partitioning – the
evolution of differences in body size or
shape to exploit different resources in the
same area.
R. Darwin’s Galapagos finch classic
example – 14 different finch species with
differences in beak morphology allowed
them to eat different types of seeds.
IV. Consumer/Resource
Interactions (+/-)
A. Consumer/resource interactions are the
interactions between species that are
commonly thought of as predator/prey
type interactions.
IV. Consumer/Resource
Interactions (+/-)
B. Predation – organism kills another nonplant organisms
C. Herbivory – organism consumes plants
D. Parasitism – organism consumes
nutrition/tissue (blood) from another
organism, usually not killing.
III. Interactions Between
Species
E. Keystone Species – Organism that is
more important for ecosystem
maintenance than would be evident by the
raw numbers of organisms or biomass in
the ecosystem.
F. Removal of keystone species often
substantially alters the food chain of an
area.
G. The classic examples of a keystone
species is otter in a kelp-forest marine
food web. The sea otter eats sea urchins,
which in turn eats the kelp. When sea
otters are removed the sea urchin
population explodes and overgrazes the
kelp, causing complete loss of the kelp.
Kelp forms a forest which provides food
and shelter for a wide range of organisms.
H. Usually keystone species in ecosystems
are top predators.
IV. Consumer/Resource
Interactions (+/-)
I. Consumer/Resource interactions drive an
“evolutionary arms race” between
consumer and resource.
J. “Prey continually evolve better defenses
and predators continually evolve better
offenses and neither gain any lasting
advantage over each other.”
Evolutionary Arms Race
Weapons
K. Predator: Speed, size, weapons,
strength, sharp senses, armor
piercing/crushing tools, means of
detoxifying poisons.
L. Prey: camouflage, speed, size, weapons,
mimicry, thick armor, poisonous
V. Mutualism (+/+)
A. Symbiosis “living together”
B. Mutualism is a type of symbiosis
1. Mutualism - both species benefit
• Ex. Ants and the Acacia Tree
– Ants protect the tree
– Tree provides nectar and home
for ants
C. Examples:
1. flowers and pollinators (bees, bats, flies,
hummingbirds)
2. Humans and bacteria living in digestive
system
V. Mutualism (+/+)
D. Mutualistic relationships are an exchange
between two or more organisms that
positively benefit the fitness of both
species involved
E. Fitness = An individual’s ability to survive
and reproduce
V. Mutualism (+/+)
F. Species aren’t altruistic – they don’t
purposely do nice things for others. They
are acting in their own self interest and
usually accidentally benefit other species.
1. Bees visit flowers to get nectar, when they
are at the flower the pollen rubs off on
bee, then pollen is taken to another flower
as bee tries to get more nectar.
V. Mutualism (+/+)
G. Lots of cheating is involved in mutualism
– some flowers don’t actually provide
nectar, some bees bite the bottom of the
flower to get nectar and the pollen doesn’t
rub off on them.
VI. Commensalism ( +/ 0)
A. Commensalism – one organism benefits while
the other is neither helped nor harmed (no
effect on the fitness of second species).
B. Usually commensalism happens when a
species’ feeding behavior makes food more
available to another species.
VI. Commensalism ( +/ 0)
C. Example 1: Brown- headed cowbirds
follow herds of cattle, eating insects
flushed out by cows eating and tromping
around in grass (don’t eat the insects OFF
of cows).
D. Dung beetles – Use animal poo to eat
and lay eggs in. Animals not affected in
any way by dung beetle behavior.
E. The classic example…
Clownfish and Sea Anemones
-the clownfish is protected
by the nematocysts of the
sea anemone
- the sea anemone is
neither helped or harmed
However… sea anemone may
Benefit from N compounds in
Fish waste, or the fish may eat
Some of the anemone’s food….
VII. Amensalism (-/0)
A. Amensalism = one species harmed, one
species unaffected
B. Mostly accidental relationships – big
animals step on insects, humans kill
worms when plowing fields, etc.