Cellular Organelles and Levels of Biotic Organization
Cellular Organelles
Cellular organelles comprise a supramolecular complex. Although they have their own characteristics, they cannot be considered living beings, as they do not meet the criteria for nutrition, relationships, and reproduction. Inside the cell, there are several cellular organelles such as mitochondria, peroxisomes, and the endoplasmic reticulum.
Viruses are macromolecular complexes consisting of two types of macromolecules: proteins and nucleic acids, and in some cases, lipids.
Levels of Biotic Organization
There are four levels of biotic organization unique to living things:
1. Cellular Level
This level includes cells, which are units of living matter formed by a membrane and cytoplasm. There are two types of cells:
Prokaryotic Cells
Prokaryotic cells lack a nuclear envelope; therefore, genetic information is scattered in the cytoplasm, although condensed in a region called the nucleoid.
Eukaryotic Cells
Eukaryotic cells have genetic information surrounded by a nuclear envelope, which isolates and protects it within the nucleus.
Cells are the smallest parts of living matter that can exist freely. Organisms composed of a single cell are called unicellular organisms and must perform all vital functions.
2. Multicellular Organism Level
This level comprises organisms composed of more than one cell, leading to differentiation and cell specialization. Here, we find different levels of complexity: tissues, organs, systems, and apparatuses.
Tissues
Tissues are collections of cells of similar origin that perform the same functions.
Organs
Organs are a number of different tissues that perform specific acts.
Systems
Systems are sets of similar bodies constituted by the same tissues but perform completely independent actions. For example, the nervous system, skeletal system, muscular system, or endocrine system.
Apparatuses
Apparatuses (e.g., the digestive system) consist of organs that can be very different (e.g., teeth, tongue, stomach) but perform coordinated actions to constitute a biological function (e.g., nutrition).
3. Population Level
Individuals of the same species (those capable of reproducing with each other and having fertile offspring) are grouped into populations (individuals of the same species that coincide in time and space).
4. Ecosystem Level
Populations are based in a particular area where they interact with other populations (community or biocenosis) and the non-organic environment (biotope). This partnership sets the called ecosystem, subject of study by biologists. Ecosystems can be as large or as small as we want, but the large terrestrial ecosystem is formed by the Biosphere (biocenosis) and the Land (biotope).