Quick Ecology for Dummies
Ecology is the science of how everything is connected and intertwined
with each other. The stars, universe, energy, climate, trees and
flowers, bacteria, genetics, you and I. Ecology is the cytoplasm
of life containing all the different sciences, a holistic perspective
to our existence. It seems like an impossible task for anyone to
learn and understand all the intricacies of it, but everyone can
learn and understand the basic concepts.
The field of ecology can comprise everything existing,
and understanding my limitations this once, I have chosen to narrow
down this article to some of the important cycles and interactions
There are some central concepts, main functions we could say, that
keep the machinery of life working the way it does. The photosynthesis,
energy flow, nutrient and water cycles are the base of life, while
climate, geology and biological interactions shape the life into
different forms and behaviors. Below I will explain all of it in
more detail, and some parts I will exemplify by describing the exciting
life of lichen.
The green plants are the producers on earth, and
the rest of us are consumers. The plants use carbon dioxide, water
and sunlight to produce sugar, and this process is called photosynthesis.
A more scientific description would be:
6 CO2 + 12 H2O + ENERGY = C6H12O6 + 6 H2O + 6 O2
The sugar produced (C6H12O6) is stored energy from the sun, and
later when it is released, we can feel it as the heat around a camp
fire, or the received energy from a chocolate bar during a hike.
And from the formula above we can see that not only the produced
and stored sugar is important for other living organisms, but also
the rest product. This is where we get all our oxygen (O2) from.
Photosynthesis is the primary source of all biologically stored
energy, and our only natural source of oxygen. We need oxygen, which
the plants generously provide us with, and the carbon dioxide exhaled
by us, is in turn necessary for the plants. You could think of us
burning the stored energy with the help of oxygen as a reversed
Photosynthesis of Lichen
Some of lichen are made up of two organisms, a fungi and an green
algae or a blue-green cyanobacteria, and some lichen contain all
three of them. The algae/cyanobacteria component is the unit that
produce energy to the whole organism thru photosynthesis.
The sun constantly radiates humongous amounts of
energy all around it, and some of it also hit the earth. Green plants
transform the radiation into biologically stored energy, the first
level of consumers (herbivores) store the energy as proteins and
fat, and the consecutive levels of predators get their share of
the energy by consuming other animals and their energy reserves.
It is said that only 10 % of the energy from a previous level can
reach the next predator in line. Most of the energy disappear as
excrements and heat, and finally even the remaining energy in excrements
and carcasses become heat radiation due to the activity of mushrooms,
bacteria etc. Earth sends out as much heat radiation as it receives,
which is crucial in keeping it from overheating, but the emissions
of so called greenhouse gasses could disturb the balance by reflecting
back some of the radiation instead of letting it pass through. According
to the laws of physics, energy can't be created or destroyed, only
changed into forms of lower quality, and finally everything disappear
as heat radiation into the space, only to be transformed ones more
in the next Big Bang. Here we are talking about pretty large cycles
lasting for a long time.
In a more reasonable scope of time, energy can't really be recycled
like nutrients. A constant flow of new, high quality energy is needed
to keep the biological machine Earth from stalling. The energy is
needed for all kinds of biological activity, we wouldn't survive
for long if we didn't eat a few meals every day.
We understand the energy flow thru the system, and we know how to
calculate it, but we don't really know what energy is.
An astronomy professor once told me it's a philosophical question
impossible to answer.
Energy Distribution in Lichen
From a human perspective, the distribution of common energy resources
in lichen my not seem fair. The fungi surround it's algae and/or
blue-green cyanobacteria partners with special hyphae and extract
up to 80 % of the produced energy.
Nutrient and Mineral Cycles
In contrast to energy, all kinds of nutrients and
minerals are recyclable. Some of the stored, both organic and non-organic
substances, return to the soil when the plants die, while some of
the substances make a longer journey along the food chain before
returning. Bacteria, small animals in the soil and some mushrooms
take care of the final separation of all the remaining organic substances
from plants and animals. Two important recycling processes are the
carbon and nitrogen cycles. But we could of course take anything,
like manganese, copper, phosphorus or whatever, and describe it's
cycle in a similar manner. Bits and pieces of different elements
combine into a large variety of substances, ranging from bone tissue
to mushroom poisons and anything between an beyond. The mileage
may vary, but sooner or later all of it will be nothing but atoms
and ions again, ready to start the cycle ones more. The carbon and
nitrogen cycles, together with the cycle of water, are important
concepts when talking ecology, and I believe we need take a closer
look at them.
This cycle is closely connected to the photosynthesis,
so lets look at the formula again. 6 CO2 + 12 H2O + ENERGY = C6H12O6
+ 6 H2O + 6 O2. The chemical symbol for carbon is C, carbon dioxide
CO2, and sugar (glucose) C6H12O6. From the formula above we can
see that, to be able to make and store energy in different sugar
compounds, the plants need a supply of carbon dioxide. And where
does it come from? We have already learned that all animals exhale
carbon dioxide as the result of reverse photosynthesis. We burn
the stored energy in sugar compounds with the help of oxygen, and
the rest product is carbon dioxide. But that is not all. Carbon
in living organisms is stored as biological energy, and it is released
as carbon dioxide into the atmosphere thru decomposition when the
organisms die. Some of the carbon is stored as calcium carbonate,
CaCO3, in living organisms as shells, antlers and bones. Some of
the calcium carbonate is stored in sea bottoms when the organisms
die, and is due time and pressure metamorphosed into limestone,
and later when the geological activity push the sea bottom above
sea level, the carbon is again available to the atmosphere. Some
of the carbon is also stored as peat, mineral coal, petroleum and
natural gas. By burning all this stored energy, we release large
amounts of carbon dioxide, a greenhouse gas, into the atmosphere,
and global warming is knocking on the door.
Nitrogen is needed to build proteins and other
necessary things like amino acids, important when we are for example
talking about genetics. There is also energy stored in nitrogen
compounds in dead organic substance, energy needed by the decomposers.
The dead organic substance is separated into amino acids and other
organic leftovers. Amino acids and urea-nitrogen is used by some
groups of bacteria as an energy source, and they in turn leave ammonium
as a rest product, ammonium which is the starting-point when transforming
organic nitrogen into non-organic. The main source of nutrients
for the plants are non-organic ammonium and nitrate. Now, let's
have a look at the chemical formula to see how it is done. The process
is a two-stage rocket, and first the ammonium (NH3) is transferred
into nitrite (HNO2), and then the nitrite into nitrate (HNO3).
2 NH3 + 3 O2 = 2 HNO2 + 2 H2O + Energy
2 HNO2 + O2 = 2 HNO3 + Energy
Both transformations are done by bacteria, and both stages require
oxygen to be present. These products remain in the soil. But nitrogen
is also released into atmosphere from anaerobe (lacking oxygen)
environments like swamps as nitrogen gas (N2) or laughing-gas (N2O).
Also this is taken care by bacteria. Plants need the non-organic
nitrogen compounds. Some plants can take it directly from the atmosphere
while most of them get it from the soil. The rest of the living
organisms need to feed on the organic nitrogen, amino acids and
proteins stored in plants, and predators of course get their nitrogen
by eating their prey. If you look at the two formulas above, you
can see that energy is released both times. You can feel it as the
heat inside a compost, a heat which can become high enough for the
substance to start burning.
Lichen and Nitrogen
The blue-green cyanobacteria which are found in about 10 - 15 %
in all lichen, can utilize the atmospheric nitrogen directly. Lichen
lacking a cyanobacteria component need to wait for the rain to bring
the nitrogen to them.
Water is necessary for the transportation of all
the stuff, like nutrients and minerals, from the soil into the plants,
and between cells and organs in everything living. Large quantities
of water is transferred into the atmosphere due to the evaporation
from oceans, and half of the water used by trees and plants are
released into the atmosphere during photosynthesis. The total perspiration
done by animals doesn't really count for a lot in the final equation.
The urine and excrements on the other hand contain a lot of nutrients
for the plants; water is needed for the transportation and disposal
of rest products.
When warm air, containing all the risen moisture, hit cooler areas,
the moisture condensate and fall back on earth as rain or snow.
And now it is available for the plants and animals again.
Lichen and Water
Lichen can stay dry for a long time, and when they finally receive
water, the dry organism may absorb up to 35 times its weight in
water. Lichen can also absorb moisture from dew or directly from
the air if the humidity is high enough and the temperature is low.
When the lichen get hold of water, it have the ability to retain
it for a long time.
Climate and Geology
These are the external non-biological factors all
life forms in an area need to adapt to in one way or another. The
geological makeup of the ground determine the amount and mixture
of nutrients and minerals available for the plants, and the climate
dictate what kind of adaptions are necessary in order to survive
and to be able to utilize the substances. The adapted plants then
determine the mixture of herbivores, and they in turn the predators.
All the animals also naturally need to adapt to the climate.
Due to the lichens ability to absorb and retain water, it has been
possible for them to colonize exposed surfaces, deserts and polar
regions. Specially the crustose lichens that can be embedded within
the stones they are growing on and very hard to remove, are particularly
well suited for a life in harsh environments. The photosynthesis,
energy production, can only begin and continue when the humidity
is right and the lichen is transparent enough for the sunlight to
pass through, and this is also the only time when the lichens grow.
Lichen disintegrate the stones they are growing on, both physically
and chemically, and the minerals thus made available make it easier
for other organisms to move in.
All life forms are constantly struggling for survival
and to spread their genes, and they will do anything to attain their
goals. The competition rage between individuals within the species,
as well as between different species. Nature is a battlefield where
no prisoners are taken and no true altruism exists. And it is all
about energy resources. No big difference between groups of chimpanzees
fighting over a fruit tree or a carcass, and Bush invading Iraq.
Except that we humans need to moralize and justify our actions.
These interactions have led to a variety of strategies for survival.
Some have chosen ingenious camouflages, others have bright colors
signaling "poisonous", some can run or fly fast, others
dig themselves deep into the soil. There are species active during
the night while others prefer the day-time hours, some have specialized
to live in hot deserts and others in freezing polar regions. But
no matter how well something is adapted, there will always be a
predator specialized in capturing that particular species. There
is a constant competition between the evolutionary forces of predators
and their prey.
There are interactions on an individual level, as well as within
and between populations and organism societies. I believe all of
us understand the meaning of an "individual". There are
of course extreme cases and to define an "individual"
might not be as straightforward as we think, but if you think of
a raven or an elephant as being an individual, that is enough for
now. Population is a group of individuals within some defined boundaries,
for example a lake, your backyard or a country. The organism society
finally, is all the biological life; plants, fish, birds, insects
etc within defined boundaries.
The individuals within a population contend for the same food and
living quarters among themselves, but they also need to put up a
fight against other species in the organism society they belong
to. There is also exchange of genetic material (individuals emigrating
and immigrating) between different populations.
Survival Strategies of Lichen
Lichen is not a single organism but a partnership, a symbiosis,
between two or three organisms living together. You can sometimes
see lichen described as an ecosystem, i.e. an ecological community
together with its environment, functioning as a unit. The fungi
component in lichen protect it's algae and/or cyanobacteria parts
from drying up, protect from too strong sunshine, and take care
of water-absorbtion. The green algae components in turn provide
the lichen with energy thru photosynthesis, and the blue-green cyanobacteria
component, if present, with both photosynthesis and with nitrogen
directly from the air. The fungi part keep it's partners from reproducing
sexually, but may itself give it a try. Lichen produce over 600
chemicals, and at least some of them are assumed to be for defense
purposes. Some of them are used as defense against diseases and
parasites, while others are used to make the lichen taste unpleasant
to animals. But even so, in tough environments like deserts and
polar regions, lichen are used as food by some animals like mountain
goats, sheep and caribou, and it is the only food source for rock
ptarmigans during the winter months in barren mountain areas in
Everything in nature is in a constant flux. Mountain
ranges and oceans appear and disappear, lakes turn into bogs and
plants invade previously barren areas. Some of the large scale changes
are not so easy to see due to the slowness of the process, like
continents drifting away or getting closer, while the plant succession
in an area is faster and more easily noticed. Deciduous trees arrive
behind grasses and herbaceous plants and finally the forest is invaded
by firs, or pine if the ground is dry. And all the changes on the
plant level is of course reflected in the mixture of animals. Earth
have been hit by many catastrophes, and species have appeared and
disappeared even without the help of us humans, but it is a bit
sad to have to think of ourselves as a disease killing and poisoning
everything. But as hard as it may be to believe it, we once actually
managed to do some good too. The cultivation of land opened up large
areas with pasture-land, groves and meadows which gave the landscape
a greater variation and a multitude of habitats and species. But
then the industrialization hit us, and in the name of economy and
effectiveness, all the diversity was ditched, drained and squared.
Now we have large mono-cultures with a few dominant species. Nature
is constantly changing and the species with it.
Ekologi - för miljöns skull, 2002 (Ingemar Hjort)
Printed study material about lichen, 2007 (Elisabeth Wiklund)
+ pieces of information that I have gathered during my life, and
still remember, but impossible to tell anymore what the actual sources
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