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Organism. An organism is defined in a medical dictionary as any living thing that functions as an individual. [1] Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what an organism is.
[5] [6] [7] This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside Earth. [8] [9] Philosophical definitions of life have also been put forward, with similar difficulties on how to distinguish living things from the non-living. [10]
Biochemistry is the study of chemical processes within and relating to living organisms. Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions.
v. t. e. In biology, taxonomy (from Ancient Greek τάξις (taxis) 'arrangement' and -νομία (-nomia) ' method ') is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given a ...
A domain contains one or more kingdoms. Intermediate minor rankings are not shown. In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla (singular phylum). Traditionally, some textbooks from the United States and Canada used a system of six kingdoms (Animalia ...
The authors note that these estimates are strongest for eukaryotic organisms and likely represent the lower bound of prokaryote diversity. [18] Other estimates include: 220,000 vascular plants, estimated using the species-area relation method [19] 0.7-1 million marine species [20] 10–30 million insects; [21] (of some 0.9 million we know today ...
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
In genetics, the phenotype (from Ancient Greek φαίνω (phaínō) 'to appear, show' and τύπος (túpos) 'mark, type') is the set of observable characteristics or traits of an organism. [1][2] The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological properties ...