Difference Between Genus and Species

Main Difference – Genus vs Species

Genus and species are two taxonomic ranks, which are used in the biological classification of the organisms on earth. The main difference between genus and species is that genus is a lower classification level that lies below family and above species, whereas species is the fundamental category of closely related organisms that lies below the genus. Organisms in each taxonomic rank consist of similar characteristics. An organism of a particular taxonomic ranking, genus or species cannot interbreed with another taxonomic ranking to produce a fertile offspring. In the binomial nomenclature of organisms, the genus is the first part of the binomial name whereas the species is the second part.

Key Areas Covered

1. What is a Genus
      – Definition, Criteria, Characteristics
2. What is a Species
      – Definition, Criteria, Characteristics
3. What are the Similarities Between Genus and Species
      – Outline of Common Features
4. What is the Difference Between Genus and Species
      – Comparison of Key Differences

Key Terms: Biological Classification, Binomial Nomenclature, Family, Genus, Offspring, Species, Taxonomic ranking

What is a Genus

A genus refers to a principle taxonomic classification, which ranks below family and above species. It consists of a collection of different species with similar characteristics. In binomial nomenclature, the name of the genus comes first, and it is followed by the name of the species. For example, the scientific name of the modern human is Homo sapiens sapiens. Homo is the genus of humans whereas sapiens sapiens is the species name.

Figure 1: Biological Classification

Criteria for Classification

Three criteria are used to define a genus.

Monophyly – All descendants of a particular ancestral taxon are ranked together.
Reasonable compactness – The characteristics of the descendants should not be expanded too much.
Distinctness – Similar DNA sequences, biogeographical features, ecological features and morphological features of the organisms can be used to rank them in a particular genus.

Difference Between Genus and Species_Figure 2

Figure 2: Aster

Aster is a genus of flowering plants. The members of the genus Aster is shown in figure 2.

What is a Species

A species refers to a closely related group of organisms, which comprise similar characteristics and interbreed to produce a fertile offspring. It is considered as the fundamental unit of the classification of organisms. Some hybrid species are also fertile. In order to define a particular species, the similarities in the DNA sequences, morphological, and ecological features can be considered. Sometimes, a particular species may consist of different breeds with great variations.

Figure 3: Panthera tigris amoyensis

Most of the times, similar species live in similar habitats since they originate from a common ancestor. The defining of a species may become difficult due to variation within the species. A south Chinese tiger (Panthera tigris amoyensis), which is a species of tiger is shown in figure 3.

Similarities Between Genus and Species

Both genus and species are taxonomic rankings, which contain organisms with similar characteristics.
Typically, organisms in different genera and species cannot interbreed with each other.
Both genus and species names are used in the binomial nomenclature of organisms.

Definition

Genus: A genus is a principle taxonomic classification, which ranks below family and above species.

Species: A species is a closely related group of organisms, which comprise similar characteristics and interbreed to produce a fertile offspring.

Level of Ranking

Genus: Genus is a higher classification than species.

Species: Species is the most fundamental level of the classification of organisms.

Composition

Genus: A genus is composed of different species.

Species: Species is composed of different subspecies.

Number of Organisms

Genus: A genus consists of a large number of organisms.

Species: Species consists of a fewer number of organisms.

In Binomial Nomenclature

Genus: Genus is the first part of the binomial name of a particular organism.

Species: Species is the second part of the binomial name.

Conclusion

Genus and species are two taxonomic rankings of the biological classification of organisms. Species is the fundamental taxonomic rank of organisms, which contains a group of closely-related organisms, interbreeding to produce a fertile offspring. A genus is a closely-related group of several species. The main difference between genus and species is the level of the each taxonomic ranking in the biological classification.

Reference:

1. “Genus.” Wikipedia, Wikimedia Foundation, 24 Sept. 2017, Available here. Accessed 27 Sept. 2017.
2. “GCSE Bitesize: What is a species?” BBC, Available here. Accessed 27 Sept. 2017.

Image Courtesy:

1. “Biological classification L Pengo tweaked” (Public Domain) via Commons Wikimedia
2. “972278” (Public Domain) via Pixabay
3. “2012 Suedchinesischer Tiger” By J. Patrick Fischer – Own work (CC BY-SA 3.0) via Commons Wikimedia