As anticipated, there are some basics that need to be able to consciously address sapute before our trip attrraverso the wonders of life on earth and its evolution. Just as, before leaving for the beach or the mountains we are busy in preparing the suitcases and everything you need, so you need to acquire a wealth of notional basis to start with confidence and without doubt our adventures.
For this reason, the next post will be a sort of list of preparations, the basics are absolutely necessary. Of course, since this is a blog for everyone, try to be more concise and clear as possible and hopefully a little boring. If anyone has any questions, or if you find my mistake, or want clarification, feel free to leave comments.
Important Notice: not here explain nothing about evolutionary theory, its history and its basic concepts. This is because of time (it would be a speech too long and wide) and because I believe that at least some things on the evolution are known even to the less educated (for example, I sincerely hope that all readers will accept the Darwinian theory of evolution and who have half a clue what the phrase means "descent with modification").
The first of this series of posts talking about what are the general characteristics of animals, the main protagonists of this blog and in particular its basic structure.
We humans possess a large number of features in common with other animals, for example, as they burn energy in making our actions, we have reproduced and are all trained by the same basic unit: the cell. This is because
(notion of the theory of evolution) all descend from a single common ancestor, from which we have inherited these characteristics shared by us and other living things.
Starting from this first organism, however (the common ancestor of all other living beings), each taxon (taxon = set of organisms whose morphological characteristics and / or genetic can group them into a group distinguishable from all other organisms) then evolved differently, developing different characteristics depending on the selective pressure of its habitat.
Regarding the organization of the body of living beings, there are two major distinctions regarding the number of cells in an organism.
The first condition is that having a single cell, composed of all the organelles and structures useful for survival, such that, even alone, can ensure prosperity and progeny. This condition, called unicellular organization, is present in many organisms such as protozoa.
Many other living beings, including plants, fungi and metazoans (true animals), are formed by more than one cell, that the different cells cooperate with each other, helping in the functions necessary for survival whole organism. This organization is called multicellular or multicellular .
The origin of these two different morphology will be the subject of future posts.
In multicellular living things, cells are in close contact with each other, exchanging information and carrying out different functions depending on their structure. A step in the complex organization of living cells that is observed when they perform different functions are to come together to form a fabric , just a collection of cells specialized for a specific task. More tissue can join together to form organs even more specialized. Bodies are for example the heart, lungs, brain. Last level of complexity is the formation of systems, in which various organs work together to perform a specific function, often associated with requirements necessary for life, such as nutrition, reproduction, respiration, etc..
The organization of the cells, as well as enable a lifestyle more or less complex, leads the body to have a structurally well defined differently according to differences in habitat and evolutionary history of each body. Ovvimanete this is related to the development of the body and its degree of complexity. (Even the origin of the body will be a future post).
omit some concepts of biology and embrionologia relatively strong (as the various models of segmentation); what interests me now is to reach two important concepts of zoology and animal anatomy: the body symmetry and coelom.
The symmetry of a body refers to the number and type of axes (lines) that can pass from the center of the body so as to divide it into two halves exactly the same morphology (symmetrical). Within metazoans, there are two different types of symmetry, a radial (typical of organisms such as jellyfish or sea urchins), in which two or more axes can cut the body into two mirror-image, and a symmetry bilateral, in which the body can be divided into two mirror image halves (left and right) from a single axis of symmetry. This condition is seen for example in humans, in dogs, crocodile, in the ant, in the snail and in a large number of animals (most of them). The acquisition of such a body structure (bilateral) will be, as we shall see, one of the biggest events of the evolutionary history of life on Earth.
coelom without cavities ( acelomati ) or a similar structure to the body cavities of embryonic origin but different ( pseudocoelom ).
As we shall see, the acquisition of the cavities will be another of the great achievements of the evolution of animals.
I hope not to have bored too, but I was anxious that these concepts were very clear, since, especially in the early PaleoStorie will be used quite often.
In the next post we will see other basics, in particular, will be presented in the next few fundamental concepts of systematics.
soon!
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