Transcript Ecology Part 3

Ecology Part 3
A FOOD CHAIN is the sequence of organisms
through which energy and materials may move
in a community.
In Communities, each level of the food chain is
called a Trophic Level
The usual order of this transfer is from Producers
to Consumers to Decomposers……..
These are 2 food chains
for two different
environments, terrestrial
and marine.
In most communities
the food chains are
completely
intertwined to form a
FOOD WEB.
The direction of the
arrow indicates the
upward movement of
energy and material.
The successive levels of food
and energy in the food
chains are called trophic
levels. The producers
constitute the first trophic
level, and the primary
consumers, the second and
so on.
Since many species eat a varied diet, trophic levels are not hardand-fast categories. At each trophic level there is a loss of energy
from the system. Only a small percentage of the energy at one
trophic level is available for the next. (usually about 10%)
Lost energy and materials is usually caused by one or more of the
following:
1. The inability to consume and process all that is eaten
2. Loss of energy due to dissipation of heat energy.
3. Energy is used for growth and reproduction.
The PYRAMID of PRODUCTIVITY is the basis
that a pyramid of biomass exists. In general the
decrease of energy at each successive trophic level
means that less biomass can be supported at each
level. Hence the total mass of carnivores in a given
community is almost always less than the total mass
of herbivores.
The pyramid of productivity and the pyramid of biomass support
the pyramid of numbers. This is because in general, carnivores
are larger than the herbivorous prey . Since total biomass tends to
decline at successive trophic levels, it follows the number of
individuals must decline at each level (except decomposer which
outnumber all other groups combined).
GROSS PRIMARY PRODUCTIVITY is the ability of
producers to “fix” or convert carbon dioxide into organic
material.
NET PRIMARY PRODUCTIVITY is the amount of organic
material that is produced beyond what is needed by the living
organisms in an ecosystem.
A DOMINANT SPECIES in an ecosystem are species which are
present in the greatest numbers or greatest biomass.
A KEYSTONE SPECIES is an important species that can exert
an effect on regulating others in a community. For ex.
Phytoplankton is a Keystone species in the marine environment
Sea otters are considered
to be a keystone predator
species. Sea otters prey
on sea urchins. Sea
urchins eat kelp. Where
sea otters are plentiful,
sea urchins are rare and
kelp beds are plentiful.
Where sea otters are
population is low, sea
urchins are plentiful and
kelp beds are almost
absent.
Whales in the last 20 years have been preying on sea otters, this
has increased the sea urchin population and decreased the kelp
beds off the coast of western Alaska.
SPECIES DIVERSITY refers to the different number of species
in a given area.. In general, the greater the species diversity of an
ecosystem, the more stable the ecosystem.
•An ecosystem with fewer species may be more susceptible to
damage from some sort of disturbance, however it may recover
quickly.
•An ecosystem with more species may be more stable and less
resistant to change from a disturbance, however it may be more
difficult for the ecosystem to recover when a serious disturbance
does occur.
While both of these
ecosystems have the same
number of species of trees,
the first community is more
stable because of the relative
number of individual trees is
almost equal unlike the
second community where
one species dominates.
SUCCESSION: is the process of change in
which one community of organisms replaces
another. This happens after some sort of
change- volcano, fire, tornado, etc has
disturbed the environment. As each
community is established, the environment is
modified and change making it possible for
another community to become established.
Primary succession: begins with bare rock or sand and involves
first the building of soil. Once organisms colonize an area, they
change it so that other organisms may follow. Examples include
what happens after a volcano erupts or glacier retreats.
Primary succession: begins with bare rock or sand and involves
first the building of soil. Once organisms colonize an area, they
change it so that other organisms may follow. e.g. The first
organisms to colonize the area may be mosses and lichens.
These plants may produce acids as a waste produce to break
down rocks in the formation of soil. Simple plant species will
begin the next step
Succession over time from simple to complex organisms
Another example of succession is that found in a pond. First
the pond is barren but then the aquatic plants die and
sediments begin to fill in and begins to be ringed by vegetation.
The beginnings of pond succession. It
is barren with little vegetation.
50 yrs. the pond is bordered
by mature cottonwood trees.
2 yrs. the pond is ringed by vegetation
including cotton wood saplings.
150-200 yrs. the pond has become a
meadow, the pond is ringed by
vegetation.
Secondary succession- Soil is present and
occurs at a much more rapid rate. Can be the
result of fire, tornados, floods and other like
events. Examples also include abandoned crop
lands, unused rail roads etc.
The Pioneer Species are the first types of
life to grow in a newly created area.
Ecological succession may lead to a stable
community of plants and animals called the
Climax Community.
A Biome is an environment that has a
characteristic climax community.
The earth has two main types of biomes,
land biomes and aquatic biomes.
Most land biomes are named for their
climax community or dominant type of
plant life.
The major types of biomes are the arctic,
tundra, taiga, temperate deciduous
forest, grassland, tropical rain forest,
and desert.
Arctic Biome
Where found- Extreme North and South Poles,
Extreme elevation as in tops of Mountains Ranges
Plant Life- None
Animal Life- Marine organisms including
penguins, seals, Killer Whales, Phytoplankton,
Zooplankton, Krill
Extreme cold, Long winters, little direct sunlight
TUNDRA
Where Found: northern North America, Europe, Asia
Plants: mosses, lichens, grasses, a few stunted trees
Animals: caribou, reindeer, wolves
Other Characteristics: permafrost – creates freezing and
thawing cycle
TAIGA
Where Found: most of Canada and Asia
Plants: pine trees
Animals: bears, wolves, moose, elk, voles, wolverines,
Characteristics: long and cold winter, summers
completely thaws the soil.
TEMPERATE DECIDUOUS FOREST
Where Found: southern Canada, eastern U.S., Europe,
and Japan
Plants: trees that lose their leaves (oak, maple, birch)
Animals: huge variety, including fox, deer, moose, etc.
Characteristics: lands cleared by hunting and farming
GRASSLANDS
Where Found: interior of many continents
Plants: grasses and small leafy plants
Animals: grazers and browsers
Characteristics: Large variation in temperature and seasonal
changes. Grazing and prairie fires halts succession.
TROPICAL RAIN FORESTS
Where Found: South America, S.E. Asia, Central
Africa, Central America
Plants: rich vegetation in canopy and undergrowth
Animals: colorful insects, lizards, amphibians, reptiles,
small mammals
o
Characteristics: 200 – 400 cm rain, constant (25 C)
DESERTS
Where Found: northern Africa, southern Asia, central
Australia
Plants: cactus and other non-leafy plants
Animals: lizards, small rodents
Other Characteristics: very little rainfall, although some
deserts have seasonal rain
Aquatic Biomes---- May be either, Fresh
Water, Salt Water or Estuary.
Fresh Water Biomes have three levels, each depends
on the amount of Sunlight it receives and the depth of
the Water.
1. Littoral Zone- Shallow water near the shore. Edges
of lakes and big ponds, edges of Rivers and Streams
and Swamps. Plenty of Aquatic plants, amphibians
and small fish
2. Limnetic Zone- Area close to the surface but away
from shore. Limited floating plants, algae, surface fish
3. Profundal Zone- Area is deep water below the
limits of sunlight. Life limited to bottom feeders,
bacteria, worms. Not all freshwater biomes have a
Profundal zone.
Salt Water (Marine) Biomes- There are also
three levels of Zones in Marine Biomes.
1. Shoreline (Coastal) Zone- Beach areas –
abundant grasses and palm trees in tropical
areas. Crabs, Sea Birds, Oysters etc.
2. Surface Zone- Open Ocean where sunlight
penetrates to about 300 meters. Fish, dolphin
and floating seaweeds. Plankton is abundant!
3. Abyssal Zone- Zone below 300 Meters. Total
absence of Light. Water Pressure is greater
with depth. Few organisms can live here as
there is little food available. Large
invertebrates such as tube worms, squid and
other exotic species can be found here.
Estuary----Bay like areas where Salt water
and Fresh water mix- The three largest
Estuaries in the US are the Chesapeake Bay,
San Francisco Bay and Long Island Sound
Estuaries are in tidal zones and may also
include Marshlands near the coast. Highly
diverse in life, many bay plants,
invertebrates, fish, mollusks, birds and
mammals. Maybe the most complex of all
food webs!
Biogeochemical Cycles
In Nature
Nutrients are recycled into the
ecosystem unlike energy. The
major nutrient cycles are water,
carbon, nitrogen and
phosphorus.
In the Carbon Cycle, carbon is recycled mainly through the process
of photosynthesis, cellular respiration and burning of fossil fuels.
Carbon dioxide (CO2) and carbon monoxide emissions have been
increasing in the atmosphere. It allows light energy in, but traps the
reflected heat energy in atmosphere so that it does not go back into
space. Potential Global Warming could have disastrous effects!
•Nitrogen used for proteins and nucleic acids. The air is over 75%
N2, but this nitrogen can not be used because of its triple bond.
•Nitrogen Fixation occurs in Legume Plants and Lightning
•Animals can only get their nitrogen from eating plants or other
animals.
•Nitrogen also gets into the soil when man uses fertilizers made
from factories.
•Bacterial Nitrification is the process of putting N2 back into the
ecosystem. Another way to get nitrogen into the ecosystem is
through decaying organisms and wastes.
Water Cycle- Water passes from the
atmosphere to the ground as precipitationRain, Snow, Sleet, Hail, and Dew occur
when the atmosphere cannot hold the
moisture.
•Rainfall may soak into the soil, be taken
up by plants or animals or may run-off into
creeks, streams or other bodies of water. A
very high % of water is in groundwater.
•Water returns to the atmosphere by
Evaporation, Transpiration and
Respiration.
The phosphate cycle is the one nutrient that does not have an
atmospheric component. It cycles through the soil and water. The
main source of phosphorous is the weathering of rocks.