A Community is composed of groups of species
living together in a given area.
In order to survive, organisms must
successfully compete for available
Community Interactions include:
• The following are forms of Interspecific
Competition (competition between
Competition: Gause’s Principle
Gause mixed two species of
together forcing them to compete
for a limited food supply. He proved
that when two species compete for
the same resources, they occupy
the same niche, one species will
outcompete the other and one
species will be eliminated. This is
Competition Exclusion Principle.
• Some species coexist with apparent competition for
the same resources. However, more careful studies
show that they actually occupy slightly different
niches. By securing different resources in slightly
different ways, individuals improve their chances of
This dividing up of resources is called
Example: Three species of fish coexist on a small pond by feeding in different
regions of the pond, one fish is a bottom dweller, one is a surface feeder and the
other obtains its food by using different feeding behaviors.
A predator is any animal that totally, or partly, consumes a plant
• Predators can be categorized as follows:
A True Predator kills and eats another animal
spends most (or all) of its life living in, or on,
another organism obtaining nourishment form
the host by feeding on its tissues or fluids.
Although the host may be weakened, the host
does not usually die until the parasite has
completed at least one life cycle.
is an insect that lays its eggs on a host.
After the eggs hatch, into larvae, they
feed on the host’s tissues and fluids.
Larvae feeding on a caterpillar
A Symbiotic Relationship is the
relationship between two species
living together. Three types of
Symbiotic relationships exist:
(both organisms benefit)
The algae supply sugars
for the fungi, and the
minerals, water, a
place to attach, and
herbivores and UV
(one organism benefits, the other is neither helped nor harmed)
Many birds build their nests in trees. The tree is
unharmed by the presence of the nest.
(one organism benefits, the other is harmed)
Tapeworms living in the
digestive tracts of
nutrients from their
• Ecological Succession is the change in the composition of
species over time. Succession describes how one community
with certain species is gradually replaced by another
community consisting of different species. The original
community is called the Pioneer Community (made up of
Pioneer species). The Pioneer species is usually r-selected.
The final community is called the Climax Community. The
Climax Community is usually k-selected. The Climax
Community usually remains unchanged until it is destroyed by
some natural catastrophe, such as a fire.
Causes of Ecological Succession
• The following changes trigger Ecological Succession. These
changes occur because species that make up communities alter
the habitat by their presence.
• 1. Substrate Texture may change from solid rock, to sand, to
fertile, as rock erodes.
• 2. Soil Ph may decrease due to the decomposition of certain
• 3. Soil Water Potential – to ability of the soil to retain water.
• 4. Light Availability may change overtime from partly shady to full
sun, or from full sun to partial shade, etc…
• 5. Crowding may cause over competition for resources triggering
Primary Succession occurs on
substrates that have never previously
supported living organisms
The Primary Succession of a Rock begins with the establishment of Lichens. First
fungal spores land on the rocks and begin to grow. Next, fungal hyphae (root-like
structures used to anchor the fungus to the rock) attach to the rocks. The Fungus acts as
a net and captures water and photosynthetic bacteria and algae for the air. The algae in
return feeds its sugars to the fungus. The fungus gives the algae a place to live…. The
algae feeds the fungus…. Both organisms benefit. There are other types of Primary
Succession, such as the Primary Succession of a Sand Dune.
Secondary Succession begins in habitats where
communities were entirely or partially destroyed
by some kind of damaging event. For Example,
fire, floods, erosion, overgrazing, etc….
The Secondary Succession of a Pond
The pond starts to fill in with soil from rains and snow melt
Eventually the pond becomes a Marsh
The Marsh continues to dry out and soon becomes a Meadow
filled with grasses and flowers
The Meadow continues to evolve
The Meadow becomes an Aspen Grove
The Aspens eventually give way to
the Fir and Pine Trees
Succession Continues until a Climax Community is
The Biosphere is divided into regions called
Each Biome (region) is occupied by characteristic communities or
ecosystems of plants and animals and a specific climate. Climates are
defined by the region’s average amount of rainfall and average
The predominant vegetation is strongly influenced by climatic conditions such as temperature
• A diagram of mean annual temperature versus mean annual precipitation can show how biomes
and climates differ.
• There are not sharp boundaries between biomes - one biome gradually changes into another.
• Directions: Use the climatogram and the mean annual temperature and precipitation listed below
to name the biome.
• 2° temp. and 60 cm precipitation = coniferous forest
• 25° temp. and 300 cm precipitation =
• 15° temp. and 200 cm precipitation =
• 20° temp. and 80 cm precipitation =
• 20° temp. and 25 cm precipitation =
• -10° temp. and 25 cm precipitation =
• 15° temp. and 25 cm precipitation =
• 15° temp. and 75 cm precipitation =
• 15° temp. and 200 cm precipitation =
Biomes are divided into the:
Eight Terrestrial Biomes Two Aquatic Biomes
1. Tundra 1. Ocean Zones
2. 2. Tropical Forests 2. Freshwater Zones
3. Temperate Forests
5. Temperate Grasslands
are subject to winters so
cold that the ground
freezes. During the
summer, the upper
topsoil thaws, but the
deeper soil, the
During the summer, the
melted topsoil supports a
community consisting of
mosses, grasses, lichens
and other vegetation
with small root systems
and tolerant of soggy
soils. Animal life consists
of caribou, musk oxen,
arctic foxes, snowshoe
hares, and others.
are characterized by high
temperature and heavy rainfall.
The vegetation consists
predominately of tall trees that
branch only at their tops,
forming a spreading canopy that
allows little light to reach the
forest floor. Epiphytes (plants
that live commensally on other
plants) and vines commonly
grow on the trees, but due to
lack of light, little grows on the
Plant life includes trees, mosses,
orchids and bromeliads.
Monkeys, snakes, lizards, insects
and birds are common.
Temperate Deciduous Forests
• Temperate forest: biome
in which even amount of
precipitation falls in all
four seasons, averaging
from 70 to 150 cm
forest type is determined
by the dominant treee
species, which typically
includes oak, beech,
maple, birch, and hickory;
animal life includes
squirrels, rabbits, and
are characterized by
(pines, firs, spruces and
other trees with
needles for leaves).
Winters are cold, and
precipitation is in the
form of snow.
Typical mammals include:
moose, bears, wolves,
lynxes and hares.
receive less water and are
subject to lower
temperatures than the
savannas. It’s too dry
for trees. The North
American prairie is an
animals include the
North American bison.
are grasslands with
scattered trees. Because
savannas are tropical,
they are subject to high
they receive considerably
less water than rain
include: zebras, giraffes,
wildebeests and gazelles.
Carnivores include: lions,
leopards and cheetahs.
Characterized by - less than 10
inches of rain between and
between 10 and 18 degrees
Celsius. Plant life consists of
evergreen shrubs and small
trees. A few examples of
animals are : coyotes, jack
rabbits, mule deer, alligator
lizards, horned toads,
praying mantis, honey bee
are hot and dry. Plants are
almost all ground-hugging
shrubs and short woody
trees. All of the leaves are
packed with nutrients.
Some examples of these
kinds of plant are
Turpentine Bush, Prickly
Pears, and Brittle Bush and
Yucca trees. Animals
include small nocturnal
(only active at night)
carnivores. There are also
insects, arachnids, reptiles,
and birds. Cold Deserts
have animals like Antelope,
Ground Squirrels, Jack
Rabbits, and Kangaroo Rats.
• Covers 70% of the planet’s
• 3% salt (mostly NaCl)
• The Photic zone recieves
enough sunlight for
photosynthetic oranisms to
• The Aphotic zone does not
recieve enough sunlight for
photosynthetic oranisms to
• The Benthic zone is the
(where oceans meet land)
The major adaptation that intertidal creatures must
have is adaptation to life out of water for extensive
periods of time. In the water these creatures behave
the same as most other marine animals. However,
when water is scarce there are a few factors these
creatures have to take into consideration,
especially loss of water, predators, and support.
The loss of water can be fatal to some sessile
intertidal creatures. Crabs, such as the Common
Spider Crab and the Arrow Crab can scurry into
pools of water to release stress. Other animals have
to conserve the water. For instance, we found many
bivalves , mussels and clams, can seal in water
during low tide. The exoskeletons that these
animals have also serves as a barrier to predators.
Some predators that were seen included various
crabs, star fish, and snails (gastropods). Crabs can
also be seen.
In the warm shallow waters
which line the continents and
surrounding islands lie
barriers called coral reefs.
Coral is a living organism
consisting of animal and
algae tissues. Corals feed like
plants through the process of
photosynthesis, and like
animals, they also use their
tentacles to catch micro-
The Neritic Zone is rich with plankton, organisms. The coral reef is
communities of small organisms that drift also host to other species
with the ocean currents.
such as starfish, octopi, and
The Open Ocean
(The Pelagic Zone)
Out in the open
ocean is what is
called the pelagic
zone, which is host
to many species of
fish and marine
,and some floating
The area where freshwater
meets saltwater, is called an
estuary; this area usually
characteristics, trees and
algae, seaweed, wetland flora,
and various species of
invertebrates, birds, reptiles
and crustaceans congregate
into a complex ecosystem,
serving as a "trade center" to
the world's aquatic biomes.
include ponds, lakes, rivers and streams.
Freshwater biomes are defined
as having low salt
freshwater biomes have
less than 1% salt.
Freshwater biomes include
ponds and lakes, which
have still water, wetlands
and streams and rivers
which have running water.
Lakes and Ponds
Are filled with organic matter Oligotrophic Lakes
and vegetation. The water is Contain little organic matter
usually murky. As the and are relatively clear.
amounts of algae and plants Contain fish and support
increase, the number of large populations of
bacteria increases. These otters, birds, reptiles and
conditions reduce the amphibians.
amount of dissolved oxygen.
Rivers and Streams
Rivers and streams mostly get started from mountainous ice
and snow melting and springs. Ultimately, rivers and
streams end up at the ocean or another waterway. Since
this water is in constant motion, it is quite different in fauna
and flora to that of lakes and ponds. Some fish, such as
river trout, and scavengers such as crayfish can be found in
various areas of the river. The colder areas are host to
salmon and other more vigorous fish, while the warmer
areas, rich in sediment and decaying matter are inhabited
by catfish, carp, and other bottom feeders. River plants
include floating weeds and algae, mostly found forming
around rocks and submerged tree roots.
Other areas of still waters, or wetlands,
such as glades, swamps, and
marshes support a large variety of
aquatic flora and fauna. Aside from
plants such as sedges and pond lilies,
the wetlands also support a few
types of trees, such as cypress,
which are highly adapted to the high
humidity of these regions. The
wetlands are rich in life forms, from
reptiles, to mammals, to amphibians
and birds, to hundreds of
insects. Some wetlands, such as the
ones found in the San-Francisco Bay
area, are host to shellfish, shrimp,
and other marine creatures due to
their high salt content.