Transcript Ecology Part 3

Ecology Part 3
Food chain is the sequence of organisms including
producers (autotrophs), primary consumers
(herbivores), secondary consumer, (herbivore
eating carnivores), tertiary consumers (carnivore
eating carnivores), and decomposers, through
which energy and materials may move in a
community. In most communities the food chain
are called trophic levels.
These are 2 food chains
for two different
environments, terrestrial
and marine.
The mouse in the food chain to the
left is operating as a:
A) primary consumer
B) secondary consumer
C) tertiary consumer
D) quaternary consumer
E) producer
ANS: B
The mouse is consuming a
grasshopper, which is primary
consumer. Secondary
consumers “eat” primary
consumers.
The primary consumer in this food
chain is
A) the hawk
B) the daisy
C) the grasshopper
D) the mouse
E) Snake
ANS: C
The grasshopper is eating
plants, which makes the
grasshopper a primary
consumer.
The phytoplankton in this food chain is
operating as a
A) primary consumer
B) secondary consumer
C) tertiary consumer.
D) quarternary consumer
E) producer
ANS: E
Phytoplankton (such as algae)
are producers that can make
their own “food” through
photosynthesis
In most communities
the food chains are
completely
intertwined to form a
food web. The
direction of the arrow
indicates the
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 hard-and-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.
This pyramid reflects a(n)
_____________ in moving from the
bottom to the top.
A) a gain in biomass
B) increase in numbers of individuals
C) loss of energy
D) decrease in the size of the
organism
E) in light energy
ANS:
C
There is a loss energy from one
trophic level to the next due to %
of energy converted to unusable
energy, when consumed, not all
the energy (matter) is used, and
if it is a stable ecosystem some
of the food will not be eaten.
Less than 10 % of
the energy can
make it from level
to the next. There
are reasons why
only 10% of the
energy can move
from one level to
the next.
1. Lack of complete consumer harvest of available biomass.
2. The inability to assimilate all that is consumed.
3. Loss of energy due to dissipation of heat energy.
4. Energy used for growth and reproduction.
Which of the following is NOT a reason why
some of the usable energy is not transferred
from one trophic level to another?
A) There is a loss in usable energy due to
conversion to heat energy.
B) There is less food eaten at each successive
level
C) The supporting trophic level is not
completely consumed by the successive trophic
level.
D) Food consumed is not completely digested.
E) A great amount of energy is used for
growth and reproduction
ANS: B
There is a loss energy from
one trophic level to the next
due to % of energy converted
to unusable energy, when
consumed, not all the energy
(matter) is used, and if it is a
stable ecosystem some of the
food will not be eaten.
This is represented by the
pyramid of productivity with the
producers at the base and the last
consumer at the top. Usually
producers are engaged in
photosynthesis but the term also
includes chemosynthesis. In
general only 10% of the energy
from one level can move to a
successive level. The right is
showing the flow of energy.
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.
However the size, growth rate, and longevity of the
species at various trophic levels are important
determining factors.
Which of the following is not
supported by the pyramid of
productivity?
A) Pyramid of numbers
B) Pyramid of net productivity
C) Pyramid of energy
D) Pyramid of biomass
ANS: B
Net productivity is the excess
amount of carbon that is fixed into
organic compounds after the
consumers have utilized the organic
compounds in the ecosystem. Net
productivity can either positive
meaning that more carbon is being
fixed than consumed or it can be
negative meaning that more carbon
compounds are being consumed than
fixed.
Because of energy loss, in general moving from the producers to the
tertiary consumers, there is a decrease in biomass. However in certain
aquatic ecosystems this is not the case because the reproduction of the
algae occurs at a fast rate, and they are consumed at a fast rate. At any
one moment, there may be a greater mass of primary consumers than
producers (this is an exception!)
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 rate at which producers to “fix” or
convert carbon dioxide into organic material. Consumers reduce
gross primary productivity by consuming the producers. Producers
also reduce gross primary productivity because they also engage in
cellular respiration. Net primary productivity is the rate at which
organic material is produced beyond what is needed by the
producers in an ecosystem.
A dominant species in an ecosystem is a species 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.
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.
Which of the following
is considered to the
keystone species in this
drawing?
A) whales
D) kelp
B) otters
E) cannot be determined
C) sea urchins
ANS:B
A keystone species is one that would have devasting
effects if is were removed from the ecosystem.
Otters are the keystone species. For example,
otters feed on sea urchins and sea urchins feed on
kelp. Where otters are present, sea urchins are rate
and kelp beds are abundant. When otters are absent,
urchins a plentiful and the kelp beds are reduced.
Recently the orca whales have been preying on sea
otters. This increases the sea urchins and decreases
the kelp beds.
Foundation species are species that exert their effect by changing
their environment profoundly. Ex. Beavers can profoundly
change the environment by damming a creek or river.
Species diversity refers to the different number of species in a
given area. One should also looks at relative numbers of each
species as well. This factor is called species richness. 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. This
first community is described
as having species richness.
Which of the following is more
susceptible to damage from some sort
of ecological disturbance?
A) a desert
B) a temperate deciduous forest
C) a coniferous forest
D) a corn field
E) a savannah
ANS: D
A cornfield typically has only
one species of plant. This
makes the biome very
vulnerable to disease
compared to the other biomes
Which of the following is true
concerning the drawing?
A) Community 2 has more
species diversity than
community 2.
B) Community 2 has more
species diversity than
community 1.
C) Community 2 has more
species richness than
community 1.
D) Community 1 has more
species richness than
community 2.
ANS: D
Both forest have four different
species of trees present but the
first forest has almost equal
numbers of the four different trees
whereas the second drawing has
mostly species A. The first drawing
is considered to have more species
richness than the second drawing.
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 establish.
Primary succession: begins with bare rock or sand and involves
the first 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: often the first organisms to colonize a
“new” area will be lichens followed by mosses. These plants may
produce acids as a waste produce that breaks down rocks
leading to the formation of soil.
Once soil formation is begun, ferns
may come in and colonized the area.
Its rhizoids helping to form more soil,
and as they die and decompose, the soil
may become more rich suitable for
different types of organisms. It is easy
to see that organisms can change the
environment they interact with.
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. The
disturbance can be the result of fire,
tornados, floods and other like events, with
secondary succession being the recovery of
the community after that disturbance.
Examples: abandoned crop lands, unused
rail roads etc.
Which of the following is an
example of an event that would
require primary succession to
reestablish the biome?
A) a retreating glacier
D) a flood
B) a forest fire
E) a hurricane
C) a field being plowed
ANS: A
Primary succession involves
the building of soil. Of the
conditions listed above, a
retreating glacier, would leave
an area behind that would
require the building of soil.
Ecological succession may lead to a stable
community of plants and animals called the
climax community. Catastrophic events
(hurricanes, volcanoes, fires, etc.) may
disturb a climax community, causing the
process of succession to occur again. 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 (terrestrial) biomes are named
for their climax community or dominant
type of plant life.
The major types of biomes are the tundra,
taiga, temperate deciduous forest,
grassland, tropical rain forest, and
desert.
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 (sometimes called “coniferous forest”)
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.
Play coniferous
forest movie
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
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.
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 and 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. It causes global warming.
Nitrogen is used for proteins and nucleic acids. The air is over
75% N2, but this nitrogen can not be used by plants or animals
because of its triple bond. N2 is broken down by bacteria into NH4
(ammonia), then NO2 (nitrite) and finally NO3 (nitrate). Plant
roots absorb this NH4, NO2 or NO3 and then make amino acids
and then proteins. Animals get their nitrogen from eating plants
or other animals. Nitrogen also gets into the soil when man uses
fertilizers made from factories.
Nitrification is the process of putting N2 into the ecosystem.
Another way to get nitrogen into the ecosystem is through
decaying organisms and wastes.
Plants absorb water through their roots. Land animals absorb
water from their food or drink it. Aquatic animals are bathed
in it. Water gets into the atmosphere from cellular respiration,
transpiration and evaporation from the oceans. Water vapor
condensing will result in percipitation (rain or snow). The
excess nitrogen and sulfur in the air (pollution) combines with
the water. This results in acid rain. This leech minerals from
the soil killing plants.
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.
There are times when unwanted chemicals accumulate in
organisms through the food chain. In the 1960's, cities sprayed
with DDT, a chemical to get rid of mosquitoes. This chemical
accumulated in the lakes. It found its way into the aquatic plants.
Fish ate the plants and DDT accumulated in the fish. Eagles ate
the fish. DDT accumulated in the eagles. It affected their eggs as
the shells were not hard. The chicks would not hatch. As a result,
eagles became endangered.
This process that results in greater and greater concentrations of a
toxin as one moves up the food chain is called biological
magnification.