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.

Main 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 in nature.
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.

Photosynthesis

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.

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.

Energy Flow

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.

Carbon Cycle

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 Cycle

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 Cycle

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.

Tough Colonizers
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.

Biological Interactions

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 Sweden.

Ecological Succession

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.

 

References

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 were.