"Species" - what is it, definition of the term
A species represents the fundamental taxonomic rank comprising a set of organisms that interbreed under natural conditions, yielding fertile progeny, and that exhibit a shared genetic composition, morphological traits, and ecological niche; this classification distinguishes one such group from others, as illustrated by the rat and mouse, which each constitute separate biological entities despite belonging to the same family.
Detailed information
Rats and mice belong to the lowest rank of biological classification, grouping organisms that share a common gene pool and can produce fertile offspring. This rank is defined by genetic continuity, morphological similarity, and ecological niche occupation.
Rattus, the genus that includes true rats, comprises several well‑documented taxa. The most widespread are:
- Rattus norvegicus – large body size, robust skull, omnivorous diet; native to Eurasia, now global.
- Rattus rattus – slender build, long tail, prefers arboreal habitats; originally from Africa and Asia, now cosmopolitan.
- Reproductive cycle: gestation 21–23 days, litter size 5–12, sexual maturity reached at 5–6 weeks.
- Habitat flexibility: urban sewers, agricultural fields, forest edges; high adaptability to human environments.
- Disease vectors: capable of transmitting leptospirosis, hantavirus, and plague bacteria.
Mus, the genus representing true mice, includes the following prominent taxa:
- Mus musculus – small body, high reproductive rate; native to South Asia, now worldwide.
- Mus spretus – larger ears, restricted to Mediterranean regions; used in comparative genetics.
- Reproductive cycle: gestation 19–21 days, litter size 4–8, sexual maturity at 6–8 weeks.
- Habitat range: indoor structures, grain stores, grasslands; exhibits rapid population turnover.
- Research importance: model organism for genetics, immunology, and pharmacology due to short life span and well‑mapped genome.
Both groups display rapid breeding, omnivorous feeding habits, and high tolerance for varied climates, which explains their success as commensal species. Their physiological and genetic traits make them central to laboratory studies, while their propensity to inhabit human settlements creates challenges for public health and infrastructure.