Classification of Organisms
Today, there are some features that we pay attention to when classifying living things. We can list them as follows;
- Cellular organization (Protozoa - Metazoa)
- The existence of embryo layers (Ectoderm-Endoderm-Mesoderm)
- The existence of similar parts in the body
- The existence of the skeleton
- Similarity of Nitrogenous Discharges
- Structures of systems like nerves, digestion, circulation
- Sequence in DNA
- The body symmetry
- The existence of structures such as fins, wings, arms
- Body cavity types
Sometimes it is not possible to put any organism in a clear classification system. For example, bacteria have a cell, but they do not have real nuclei. The organisms that do not have such nuclei are called monera. In cells with nuclei such as paramesium, oglena, amoeba, they are collected in two separate kingdoms as protista. It is made of millions of cells in many other organisms. They are multicellular, so they are called metazoa. Except for prokaryotes, living things have nuclei in their cells. Creatures with real nuclei are called eukaryotic creatures.
The creatures, which are divided into two main groups as prokaryotes and eukaryotes, are collected in five main kingdoms; monera, protista, fungi, plants and animals. Let's learn them in more detail.
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1. Monera Kingdom:
It consists of simple, one-celled autotrophic and hetotrophic organisms. They have no nuclei and membrane-surrounded organelles. They differ from the protists with these aspects.
1) Bacteria 2) Archaea
1) Bacteria:
- They are single celled organisms with prokaryotic cell structure.
- Because they are prokaryotic cells, they do not have organelles other than the ribosome. The ribosomes of bacteria differ in eukaryotes in both size and protein comparison.
- In all bacteria, the cell is surrounded by a dead wall. The structure of the wall contains peptidoglycan instead of cellulose, unlike the wall of plant cells.
- Some bacteria have capsules outside the cell wall. It increases the ability of the capsule bacteria to make disease (being a pathogen).
- The genetic substance (DNA) is dispersed into the cytoplasm.
- In oxygen-breathing bacteria, the cell membrane forms folds towards the cytoplasm. These folds are similar to the inner membrane of the mitochondria, this structure is called mesosome.
- One-way gene exchange between two living bacteria is called conjugation. The bacteria that come together form a cytoplasmic bridge between them. One of the bacteria copies the plasmid it has and sends it to the other bacteria via the cytoplasmic bridge. This event increases genetic diversity.
2) Archaea:
- Arcs are prokaryotic one-celled organisms. There are histone proteins surrounding their DNA and cell walls are made of false peptidoglycan. Some, like bacteria, have plasmids.
- Most known arcs are chemosynthetic.
- Arcs can live in very high temperatures and in high acidic environments.
- There are species that are fed as chemoototrof and hetetrof.
- Psycrophilic arcs can live in very cold environments.
- Thermophilic arcs are those that can live in very hot places such as geothermal resources or volcano mouths.
- Halophilic arcs can live in very salty environments.
The Original Author: Mrs. Şerife (Erden) SARICA
