Biological Organization Levels and Fundamental Characteristics of Life

Level 2: Multicellular Organisms

Multicellular organisms consist of creatures composed of more than one cell. This level involves the surge of differentiation and cell specialization. Here we find different levels of complexity: tissues, organs, systems, and apparatuses.

While tissues are collections of cells of similar origin that perform the same functions, organs are composed of a number of different tissues that perform specific actions.

Systems are sets of similar organs, constituted by the same tissues, but which perform completely independent actions. Apparatuses (e.g., the digestive apparatus), consisting of organs that can be very different (e.g., teeth, tongue, stomach, etc.), perform coordinated actions to constitute what is called a biological function (e.g., nutrition).

Components of Multicellular Organization

• Tissues: Clusters of specialized cells that are very similar, perform the same function, and share a common origin.
• Organs: Structural and functional units of higher living beings. They consist of several different tissues and perform a specific action.
• Systems: Clusters of similar organs that perform independent actions. For example, the nervous, skeletal, muscular, or endocrine systems.
• Apparatuses: Clusters of organs that can be very different, but whose actions are coordinated to form a specific biological function.

Level 3: Population

Individuals of the same species (those capable of reproducing with each other and having fertile offspring) are grouped into populations. A population is defined as individuals of the same species that coincide in time and space.

Level 4: Ecosystem

Populations exist within a particular area where they interact with other populations (known as the Community or Biocenosis) and the non-organic environment (the Biotope). This partnership defines the Ecosystem, a primary subject of study for biologists.

Ecosystems can be as large or as small as desired, but the largest terrestrial ecosystem is formed by the Biosphere (the global Biocenosis) and the planet Earth (the global Biotope).

Fundamental Characteristics of Living Organisms

Nutrition

The ability of a living being to acquire external material and use it to grow in size and develop, or simply to maintain its structures and perform other vital functions.

Relationship (Sensitivity)

The ability to detect external stimuli and provide adequate responses to them. Without this function, living beings could not perform other vital functions such as nourishment and reproduction.

Reproduction

The ability to originate new individuals that are the same as, or very similar to, the parents.

The Field of Ecology

Ecology is interrelated with the following 5 levels of organization of matter:

1. Organisms (Agencies)
2. Populations
3. Communities
4. Ecosystems
5. Ecosphere or Biosphere

Organisms (Agencies)

The organism is the unity of life, represented in each species, from the tiniest (microorganisms) to large ones, that interact to keep.