In Canada, winter defines us. At this time a white blanket of snow covers much of our country and a cold wind blows over the vast open spaces. But while nature appears to be asleep during the winter, the seeds that spread in autumn are busy getting ready to germinate in the Spring. A tiny seed grows and develops into a maple tree. One white egg develops into a Marsh Hawk. Another white egg develops into a chicken. Science cannot explain these miracles, but it can explain the development and growth of living things.

This involves the concept and knowledge of cell behaviour, such as cell division, mitosis (the process by which a nucleus forms two exact copies of itself) and the two most important things that cells do :   photosynthesis and respiration. Only some kinds of cells carry out photosynthesis, but all kinds of cells respire, i.e. they inhale and exhale air.

Photosynthesis makes food for life processes and respiration gives energy to them. Photosynthesis requires chlorophyll, light, carbon dioxide and water to make glucose and oxygen. Respiration does the reverse :   it uses up glucose and oxygen and produces carbon dioxide and water. Photosynthesis changes light energy into chemical energy and respiration changes chemical energy in glucose molecules into energy needed for life processes.

Thus, science explains the food chain, how habitats and ecosystems are formed, the ecology involved, and how air and water, plants and wildlife create the environment. But we need to understand how it works – grasp the fact that everything in nature is interrelated and that all living things interact and rely on each other. No living organism lives completely on its own. It depends on other organisms and they depend on it. That's what ecology is all about – it is the study of the relationship among organisms and between life forms and their environments.

Organisms interact on four levels :   individuals make up a population, populations make up a community, communities make up a biom, and bioms make up the biosphere. Any community of living things interacting with its environment is an ecosystem. And the important thing to remember is that since all parts of an ecosystem are interrelated, each part is affected by all the other parts. Therefore, if one part is changed in any way, all the other parts will be changed too, and equilibrium – the balance between opposing physical forces – is lost. That's why human interference, in a misguided attempt to "manage nature", has often such a negative impact on the environment.

To appreciate ecosystems we need to understand their two major components :   habitat and niches. The habitat of an organism is the place in which it lives. Think of it as the "address" of the organism. The niche of an organism is its total role in the natural community. Think of it as its "job" or "occupation."

Organisms in an ecosystem may be linked in feeding relationships, called food chains. Clover is food for the groundhog, the groundhog in turn is food for the fox, and a larger predator eats the fox. This is known as the food web :   who eats who defines an ecosystem. Some food chains are quite long, but many are just simple, let's say wheat > mouse > owl.

Then there are the feeding relationships in which organisms help provide food for other organisms without being eaten or killed themselves. These are parasitisms, mutualisms and commensalisms. Parasitism is a relationship between two organisms in which one benefits and the other is harmed (parasite and host). Mutualism is a relationship between two organisms in which both organisms benefit (lichen and fungus). Commensalism is a relationship in which one organism benefits and the other neither benefits nor suffers ("Old Man's Beard" lichen and spruce trees).

Nature is full of examples that can teach us about the mysteries of life. Take a chicken egg, for example. From shape to content, every feature of it is an example of perfection. The egg's shape is its strength. Its five principal parts provide the entire life support system for the developing bird. The egg shell is porous, allowing moisture to evaporate and oxygen to replace it. The shell membrane on the inside of the egg consists of two layers close to each other, except at the larger end of the egg where they separate to create an air pocket, which does not yet exist when the egg is laid. The egg white contains many crucial proteins, stores water and offers insulation from sudden changes in the outside temperature. The yolk is a mixture of suspended proteins, fats and carbohydrates. The germ – the most important part – is a pinhead-sized blob on top of the yolk that developes into a new chick. No single part of the egg is superfluous, everything exists to protect and nourish the developing life within.

Metamorphosis is another of nature's marvels. The change from a tadpole to a frog, or a caterpillar to a butterfly, not only requires that old limbs be discarded while new appendages sprout, but it also means that most of the creature's internal organs and nervous systems disappear, to be replaced by new equipment for moving, breathing and digesting food. Metamorphosis is a stunning feat of genetic engineering. Butterflies begin life as an egg that hatches into a caterpillar, which spins a silk cocoon (chrysalis) in which it begins its transformation to an winged insect.

And we can learn a lot from plants when it comes to seed propagation. Millions of years before humans invented the wheel, plants were already utilizing most of the methods we later devised for getting around. The catch is, of course, that plants themselves don't move from place to place – their seeds do. They accomplish this by rolling like wheels (tumbleweed), riding on wind (milkweed, dandelions) or water, (mangroves, coconuts), or being carried overland on the backs of animals (burdock) or the feet of birds. And so the cycle continues.

Think about some of these interactions, and our relationship and connectedness to the natural world around us, during your next hike in the Rouge Valley, where many of these wondrous things can be observed.

S.G.

Sources :   Planet Earth (Time), Canadian Wildlife Federation, Facts and Fallacies (Reader's Digest), Discovering Biological Science (W.A.Andrews et al.), and personal field notes.

You can find this issue of Nature Notes, as well as previous editions, on www.rougevalleynaturalists.com by clicking on "Nature Notes" and the icon More>

Mark your calendar for special nature days this year :

February 2 :   World Wetlands Day

March 31 :   Earth Hour

April 8 – 14 :   National Wildlife Week

May 12 :   International Migratory Bird Day

May 22 :   International Day of Biodiversity

June 8 – 14 :   Rivers and Oceans Week

November 21 :   World Fisheries Day