Transcript Ecosystem Basics

Cycles in the Ecosystem
PA 4.6
I. Matter Cycles
A.
Unlike the continuous flow of energy from
the sun, the matter that is found on the Earth
is in a closed system.
1.
2.
That means that the amount we have now is the
same amount we had a million years ago.
Matter continuously cycles through out the parts
of an ecosystem, going from the environment to
living organisms and back to the environment.
B.
There are several major
cycles that are at work in
an ecosystem but we are
going to focus on three:
1. The water cycle
2. The carbon cycle
3. The nitrogen cycle
Let’s start with the water
cycle…
C.
Earth is considered the water
planet with over 70% of surface
covered with water.
1. More importantly, most
living things are dependent
on water and cannot exist
without it.
2. Do you know how much of
the human body is water?
a. 65%
3.
How long can we survive
without water?
a. 3-5 days depending on
conditions.
4.
So the water you are drinking today, is the same
water the dinosaurs bathed in 65 million years
ago.
Sounds gross…but isn’t because of the water
cycle.
D. The Water Cycle
1.
2.
3.
The water cycle (like all
the other cycles) is
driven by the energy of
the sun.
The purpose of the water
cycle is to collect, purify
and distribute the water
found on the Earth.
There are six major steps
to the water cycle.
I.
II.
Evaporation – the
energy of the sun
causes water to
evaporate (from
mainly the oceans),
changing from liquid
water to water vapor.
Condensation – as
the water vapor
cools, it condenses
into cloud droplets.
III.
IV.
Precipitation – as
the cloud droplets
grow, they form rain
(or snow or both)
which falls back to
the earth.
Runoff – if the
precipitation falls on
land, it washes
downhill by gravity
into lakes, rivers, or
ponds and
eventually the
ocean.
V.
VI.
Percolation/infiltration –
some of the water seeps
into the ground and
becomes groundwater.
Transpiration –
groundwater is absorbed
by plants and given off by
the leaves of plants due to
the energy of the sun and
respiration.
4.
5.
The water cycle can be
extremely fast or slow
depending on the
location and climate.
Humans are affecting
the water cycle through
pollution. Pollution
limits the amount of
water that is available
for use by humans and
other living organisms.
LET’S REVIEW….
Condensation
Runoff
E.
Carbon
1.
2.
3.
We are considered carbon-based life forms.
Carbon is the building block of life. It is
essential for DNA, proteins, fats, and
carbohydrates.
Carbon dioxide, CO2, is an essential greenhouse
gas that helps maintain heat in Earth’s
atmosphere.
Carbon can be found in the atmosphere, oceans,
and in rocks. Let’s review the carbon cycle…
The carbon cycle has
three natural steps.
I. Photosynthesis –
Producers (Plants) on
the land and in the
ocean take in CO2
and build organic
molecules with the
carbon.
4.
Decomposition
II. Respiration – the carbon
stored in organic
molecules (like sugars)
are used by the producers
and consumers for energy.
(These carbon molecules
travel through the food
web). Cellular respiration
releases CO2 back into the
atmosphere or water.
III. Decomposition –
when the waste
products or remains
of dead organisms are
broken down by
decomposers, CO2 is
released back into the
atmosphere and
oceans or
settle/combine with
sediments in the soil.
Decomposition
5.
6.
The carbon cycle has parts that exchange
carbon very quickly (photosynthesis and
respiration) and has parts that can take
millions of years. (formation of fossil fuels –
coal and oil)
Humans affect through deforestation and the
burning of fossil fuels. Fewer trees result in
less CO2 absorbed from the atmosphere.
Burning fossil fuels releases carbon that was
stored deep in the ground for millions of
years.
Let’s review the Carbon cycle…
F.
Nitrogen
1.
2.
3.
4.
Nitrogen is the most abundant gas found in the
Earth’s atmosphere.
Nitrogen is also an important component in
organic compounds such as proteins, DNA, and
chlorophyll.
However, the form of nitrogen that is most
abundant, N2, is not usable by producers or
consumers.
So how do we get the nitrogen that we
need…enter the nitrogen cycle.
5.
I.
II.
The nitrogen cycle is
driven by bacteria and has
five basic steps.
Nitrogen-fixation –
bacteria found in the roots
of plants (mainly legumes)
convert N2 gas into
ammonia (NH3)
Ammonification –
decomposers break down
organism remains and
releases ammonia.
III. Nitrification – another
type of bacteria convert
the ammonia (NH3)
into nitrates (NO3).
Nitrates are a form of
nitrogen that are usable
by producers.
(Lightening can also
change N2 into NO3)
IV. Assimilation – is the
uptake of nitrates by
producers. Consumers
get nitrogen by
consuming producers or
other consumers.
V. Denitrification –
another type of
bacteria breaks
down the nitrates
back into nitrogen
gas. (N2) Nitrogen
content is a limiting
factor for plant
growth.
6.
Humans are affecting the nitrogen cycle by adding
nitrogen-containing fertilizers to the environment
and through the burning of fossil fuels. (Nitrogen
oxides are emitted which can cause acid rain)
Let’s review the Nitrogen cycle…
Any Questions????
Ecological Succession
1.
2.
3.
Ecological Succession is a process in which
the communities of an ecosystem change over
time.
There are two types of succession: primary
and secondary. Both types of succession
follow a similar pattern.
Let’s focus on primary succession.
A. Primary succession occurs in places where an
ecosystem has never existed before. This could
be a newly formed volcanic island or land
exposed from a receding glacier.
B. As the exposed rock is weathered, the first species
appear. These species are called pioneer species.
They are small, grow quickly, and need minimal
resources to survive. Often are mosses and lichens.
C. The pioneer species breakdown the rock to form soil.
This allows other species to grow among the mosses
and lichens. Eventually the other species out
compete with the pioneer species and change the
community.
D. At each stage, competition among the species causes
a change in the dominant community. In the later
stages, larger, slower growing species displace the
smaller, faster growing species.
E.
As the ecosystem ages, the community
becomes more diverse. The process of
succession will continue until the ecosystem
reaches a climax community.


A climax community is the last stage of
succession. If left undisturbed, the ecosystem
will stay at the climax community.
The Oak-Hickory forests of PA is a climax
community.
F.
Disturbances in the
ecosystem, such as fire,
flood or human activity,
can slow the process of
succession down.
If the disturbance is
catastrophic, like a
tornado or volcanic
eruptions, the process
may have to start over
from the beginning.
Which leads us to….
G.
H.
Secondary
succession is the
process that begins in
an ecosystem that has
been disturbed or
destroyed.
 Typically occurs
on abandoned
farmlands, burned
or cut forests,
etc…
I. Secondary succession has similar stages compared
with primary succession. Remember that secondary
is regenerating an existing ecosystem. Primary is
forming a new ecosystem where none existed
before.