Ecology is derived from oikos (Greek) meaning ‘household’, and logos meaning ‘study’.
Ernst Haeckel (1866): oecologie—the economy of nature. What is ecology?
– Numerous definitions; difficult to define;
– The scientific study of how organisms interact with their environment;
– Environment. Ecology as a science
• Started as largely observational and descriptive;
• Natural history (study of how organisms are influenced by climate, soils, predators, competitors, and evolutionary history);
• Now, ecologists primarily conduct experiments, test hypotheses, and develop models.Ecology is a diverse science
– Plant ecology;
– Animal ecology;
– Physiological ecology;
– Population ecology;
– Community ecology;
– Ecosystem ecology;
– Landscape ecology;
– Applied ecology (problem solving);
– Conservation ecology;
– Restoration ecology.
Different types of ecology
Organizme. In this part of ecology we deals with individuals, the lowest unit of ecology. How do they cope with difficult environments. How do they go from birth to death? i.e. their life history. How do they reproduce and how do they interact with their mates and offspring?
Populations. Here we deal with groups of individuals of one species. In a certain population we might ask: ‘How many are old and how many are young? i.e. what is the structure of the population?’ Is the population growing, declining or in stasis?
Species. On this level we are dealing with how the species interact with other species. So this level of ecology deals with competition and predation.
Communities. Here we deal with all the species in a certain area. We might be interested in how many different types of species live in a certain place (diversity). Which species are the predators and which other species do they eat? i.e. food webs.
Ecosystems . The concept of an ecosystem is similar to that of a community, in that we look at all the components biotic (living) and abiotic (non living) in a certain area. But what makes this type of ecology different is that all the components are studied using the same ‘currency’, and this is usually energy. So in ecosystem ecology you would try to find out where and how much energy was going from one component to another. An individual ecosystem is then distinguished from another by the fact that there would be little energy flow between them.
The Earth’s beginnings…
The Earth is increadibely old. At first there were clouds of gas and dust called nebulae were scattered throughout the universe. Sun was forming as the dust cloud slowly condenses. Ssome sientists feel that meteorites once formed a small planet in our solar system that framented in space , while others view them simply as “leftover” material from theorginal nebula. Whatever the origin, they are materials from the beginnings of our solar system that have changed relatively little since their original formalion as rocks.
Geologists use radioactive age dating methods to netermine the age of rocks. Certain atoms in the rocks spontaneously change into different atoms over time through radioactive decay. B taking a rock (meteorite)apart atom by atom and finding out how many atoms have decayed, and knowing the rate of change (or half-life of the atom) scietists can work out how many years have passed since the rock formed. This is a tremendous simplifacation, but basically it is somewhat like counting rings in a tree to see how old it is. Many meteorites age-date at about 4.6 billion years.This is the currently accepted age of the Earth.
The early Earth was quite different from today with constant bombardment by meteorites, intense volcanism, and a poisonous atmosphere. However, fossils known as stromatolites in rock 3 to 3.5 billion years old show geologists that life evolved very early in the Earth’s history. During the time known as the Archean( 4 billion to 2.5 billion years ago) stomatolite fossils are very rare.Stomatolites are layered mounds, columns, and sheets found in the rock. They were originally formed by the growth of layer upon layer ofcyanobacteria, a single-celled photosynthesizing mikrobe growing on a sea floor. Cyanobacteria are prokariotic cells which lack a DNA-packaging nucleus. This simple organism would be the only life on Earth for the next 2 billion years.
Althought simple, cyanobacteria was ultimately responsible for one of the most importan “global chantes” that the Earth has undergone. Being photosynthetic, cyanobacteria produce oxygen as by-product. Photosynthesis is the only major source of free oxygen gas in the atmosphere. As stomatolites become more common 2.5 billion years ago, they gradually changed the Earth’satmosphere from a carbon dioxide-rich mixture to the present-day oxygen-rich atmosphere. This major change paved the way for the next evolutionary step, the appearance of life based on the eukaryotic cell.
Rising out of the Ocean…
They came from the oceans, where just a few billion years earlier the first animal life evolved followed by plants. So, you see, the occurrence of trees was quite full of twists and turns and came about quietly long after land plants had struggled to rise from the oceans. Yet, their existence is the essence of all life on the planet. There was
a time about 550 million years ago when life „exploded“ on the planet animal life. Nearly all of the animal groups in existence today – as well as many that no longer exist – first appeared on Earth during this time. It was the Cambrian Period, and this time of tumultuous and colossal animal diversity is called the Cambrian Explosion.Land plants evolved a little more quietly about 90 million years later, with trees evolving some 100 million years after the first land plants began to emerge from their oceanic origins. But neither animals nor plants could have evolved were it not for the protection and nurturing of the ocean.
According to the fossil record – about 3.5 billion years ago – the first preserved life are found in the form of bacteria. They appeared in the oceans after the surface (crust) began to cool and stabilize, the land masses began to take shape, and clouds formed to produce massive volumes of rainwater that created the seas. The atmosphere was much different than today and the surface was unprotected from the Sun. This period is known as the Pre-Cambrian, the time that immediately followed the formative, molten and gaseous stage of Earth as it and the rest of the solar system started to come together – or coalesce.
The first plants on Earth were a form of blue-green algae which appeared and lived in the oceans about 3.4 billion years ago according to the fossil record, protected from the harmful high energy radiation of the Sun. In the oceans, these plants were able to grow and photosynthesize as this high energy radiation was absorbed by the water. Now, to be perfectly clear about it, the first true algae (the kingdom protoctista) most likely made their first appearance about 2.4 billion years ago, but for sure by 1.8 billion years ago as the first acritarchs.
Some 470 million years ago, Earth would seem lifeless, inhospitable and very barren. For one thing, no trees – no plants at all -lived on the land!
Although animals were the first life forms on Earth, it was plants that paved the way for land animals to evolve. Plants did this by simultaneously increasing the percentage of oxygen in the Earth’s atmosphere and decreasing the percentage of carbon dioxide, a powerful greenhouse gas .
Still, if we were to travel back about some 470 million years ago, Earth would seem lifeless, inhospitable and very barren. For one thing, no trees – o plants at all – ived on the land !
The first land plants made their appearance way before trees started driving their roots into the hard crust of Earth’s surface, about 460 million years ago in the Ordovician period. Algae were the first land plants, moving from their aquatic origins to marshy and wet environments on land. It took consistent growth and diversification of land plants — including the eventual evolution of trees – to help break up the mostly iron-clad surface of the Earth.
To move from the water to land, plants had to adapt systems that would support their weight, provide transport of water and nutrients throughout their system, protect them from drying out, and insulate them from the sun and temperature changes. Obviously, if these adaptations were not difficult, plants would have moved on to land much earlier in the geological history of the Earth. Instead, they appear rather late in the history of life on this planet.
Trees first appeared and began to cover the land surface of the Earth some 370 million years ago. Today, we are so used to and dependent on trees that it’s hard to believe that animals could have existed without them or that they did not at least simultaneously evolve together in the beginning.
Trees, with their large and thick roots, helped break up the rocky crust of Earth’s surface to create the soil that would allow the development of new plant species, including other trees. And it was the greater evolution of plants and trees that enabled the evolution of larger and more diverse land animals, including mammals. (Keep in mind that the first land animals – bugs – were plant eaters, and they required more and diverse vegetation to evolve.)The First Tree…and Forests
The earliest known modern tree is the Archaeopteris, a tree that looked similar to a Christmas tree with buds, reinforced branch joints and wood similar to today’s timber. Its branches and leaves resembled a fern.When the archaeopteris tree first appeared 370 million years ago, it quickly covered most parts of the Earth with its first forests and was the dominant tree wherever the planet was habitable. During this time, most of Earth’s land masses were assembled south of the equator as part of the supercontinent Pangaea, which eventually split into the even continents that exist today. Can you imagine Antarctica being covered with forests!
Over the past 370 million years, countless new tree species have evolved and eventually became extinct – like the archaeopteris – as the Earth’s land masses moved about, climates changed, animal populations increased, and, of course, new species of plants evolved to take the place of the extinct ones.
Today there are approximately 100,000 known species of trees that exist throughout the world.Over 8,000 species are threatened with extinction and 976 of those are in a critical state.The importan of Trees
Trees are vitally important to world health on all levels. Globally, forests are essential to the health of ecosystems and their
functions, biodiversity and economics. Some of the many key functions of forests include climate regulation, the cycling and distribution of nutrients, and the provision of raw materials and resources. Trees cleanse the air and provide oxygen, help soil retain water, shield animals and other plants from the sun and other elements, and provide habitat for animals and plants. They help regulate the climate, cycle and distribute nutrients and provide raw materials and other resources. And don’t forget the awesome beauty they give us throughout each year!