1.1. Levels of organization of the living beings

On studying the matter that constitutes human beings can distinguish them in various levels of structural complexity, which are called levels of organization. Currently allowed five levels of organization, of which the first three come to constitute an individual.


Is the abiotic level. There are four sub-levels:

1. Subatomic. It consists of subatomic particles, ie, protons, electrons and neutrons (and also its subparticles: eons, quarks, leptons,…)

2. Atomic. A basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. Aare the smallest part of a chemical element that can take part in a reaction.

3. Molecular. A molecule is an electrically neutral group of two or more atoms held together by covalent chemical bonds

4. Macromolecular. Polymers by the union of several molecules (ejs.: proteins, nucleic acids). The binding of various macromolecules are macromolecular associations (ejs: glycoproteins, chromatin). Finally, molecular associations may join to form organelles (ejs.: mitochondria and chloroplasts). Molecular associations constitute the boundary between the biotic and abiotic. For example, nucleic acids have the ability to self-replication.


There are five sub-levels too:

1. Cells. The basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life.

2. Tissues. A cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of similar cells and from the same origin, that together carry out a specific function.

3. Organ.  A collection of tissues joined in a structural unit to serve a common function.

4. Organ System. A group of organs that work together to perform a certain task. Common systems, such as those present inmammals and other animals, seen in human anatomy, are those such as the circulatory system, the respiratory system, the nervous system, etc.

5. Organism. Any contiguous living system (such as animal, fungus, micro-organism, or plant). In at least some form, all types of organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole.


The organisms are organizated in different increasing levels.

1. A population is all the organisms that both belong to the same group or species and live in the same geographical area.

2. Community. In biology, a community is a group of interacting living organisms sharing a populated environment.

3. Ecosystem.  An ecosystem is a community of living organisms (plants, animals and microbes) in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system. These components are regarded as linked together through nutrient cycles and energy flows. As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment, they can come in any size but usually encompass specific, limited spaces (although it is sometimes said that the entire planet is an ecosystem).


1. Why do we say that the levels of organization atomic and molecular are abiotic levels?

2.  What are the attributes that identify living things and make them different from inanimate matter?

3. What characterizes each level of organization in relation to lower it?

4. Make a diagram linking all levels of organization

REVIEW (bbc schools)

Levels of organization animation


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