Molecular biology is the study of biology at a molecular level. This field overlaps with other areas of biology, particularly with genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interrelationship of DNA, RNA and protein synthesis and learning how these interactions are regulated.
Cell biology studies the structural and physiological properties of cells, including their behaviors, interactions and environment. This is done on both the microscopic and molecular levels, for single-celled organisms such as bacteria as well as the specialized cells in multicellular organisms such as humans. Understanding the structure and function of cells is fundamental to all of the biological sciences. The similarities and differences between cell types are particularly relevant to molecular biology.
Anatomy considers the forms of macroscopic structures such as organs and organ systems.
Genetics is the science of genes, heredity and the variation of organisms. Genes encode the information necessary for synthesizing proteins, which in turn play a large role in influencing (though, in many instances, not completely determining) the final phenotype of the organism. In modern research, genetics provides important tools in the investigation of the functions. Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.
Developmental biology studies the process by which organisms grow and develop. Originating in embryology, modern developmental biology studies the genetic control of cell growth, differentiation and “morphogenesis,” which is the process that progressively gives rise to tissues, organs and anatomy. Modern organisms for developmental biology include the round worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, the zebrafish Danio rerio, the mouse Mus musculus and the weed Arabidopsis thaliana. (A Model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in that organism provide insight into the working of other organisms).
Physiological
Physiology studies the mechanical, physical and biochemical processes of living organisms by attempting to understand how all of the structures functions as a whole. The theme of “structure to function” is central to biology Physiological studies have traditionally been divided into plant physiology and animal physiology, but some principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about the physiology of yeast cells can also apply to human cells. The field of animal physiology extends the tools and methods of human physiology to non-human species. Plant physiology borrows techniques from both research fields.
Physiology studies how for example nervous, immune, endocrine, respiratory and circulatory systems, function and interact. The study of these systems is shared with medically oriented disciplines such as neurology and immunology.
Evolutionary
Evolutionary research is concerned with the origin and descent of species, as well as their change over time and includes scientists from many taxonomically oriented disciplines. For examples, it generally involves scientists who have special training in particular organisms such as mammalogy, ornithology, but use those organisms as systems to answer general questions about evolution.
Evolutionary biology is partly based on paleontology, which uses the fossil record to answer questions about the mode and tempo of evolution, and partly on the developments in areas such as population genetics and evolutionary theory.
In the 1980’s developmental biology re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of evolutionary developmental biology. Related fields often considered part of evolutionary biology are phylogenetics, systematics and taxonomy.
Systematics
A phylogenetic tree of all living things based on rRNA gene data, showing the separation of the three domains bacteria, archaea and eukaryotes as described initially by Carl Woese.
Trees constructed with other genes are generally similar although they may place some early branching groups very differently, presumably owing to rapid rRNA evolution. The exact relationships of the three domains are still being debated.
Multiple speciation events create a tree structured system of relationships between species.
The role of systematics to study these relationships and thus the differences and similarities between species and groups of species. However, systematics was an active field of research long before evolutionary thinking was common.
The classification, taxonomy and nomenclature of biological organisms is administered by the International Code of Zoological Nomenclature, International code of Botanical Nomenclature and International code of Nomenclature of Bacteria for animals, plants and bacteria respectively.
The classification of viruses, viroids, prions and all other sub-viral agents that demonstrate biological characteristics is conducted by the International Code of Virus classification and nomenclature. However, several other viral classification systems do exist.
Traditionally living things have been divided into five kingdoms; Monera, Protista, Fungi, Plantae, Animalia.
However, many scientists now consider this five-kingdom system outdated. Modern alternative classification systems generally begin with the three-domain system: Archaea (originally Archaebactera), Bacteria (originally Eubacteria), Eukaryota (including protists, fungi, plants and animals).
These domains reflect whether the cells have nuclei or not as well as differences in the chemical composition of the cell exteriors.
Further, each kingdom is broken down recursively until each species is separately classified. The order is: Domain kingdom; Phylum; Class; Order; Family; Genus; Species.
There is also a series of intracellular parasites that are “on the edge of life” in terms of metabolic activity, meaning that many scientists do not actually classify these structures as alive, due to their lack of at least one or more of the fundamental functions that define life. They are classified as viruses, viroids, prions or satellites.
The scientific name of an organism is generated from its genus and species. For example, humans are listed as Homo sapiens. Homo is the genus and sapiens the species. When writing the scientific name of an organism, it is proper to capitalize the first letter in the genus and put all of the species in lowercase. Additionally, the entire term may be italicized or underlined.
The dominant classification system is called the Linnaean taxonomy. It includes ranks and binomial nomenclature. How organisms are named is governed by international agreements such as the international code of Botanical Nomenclature (ICBN), the International Code of Zoological Nomenclature (ICZN) and the International Code of Nomenclature of Bacteria (ICNB).
A merging draft, Bio code was published in 1997 in an attempt to standardize nomenclature in these three areas, but has yet to be formally adopted.
The Bio code draft has received little attention since 1997; its originally planned implementation date of January 1, 2000 has passed unnoticed. However, a 2004 paper concerning the cyanobacteria does advocate a future adoption of a Bio code and interim steps consisting of reducing the differences between the codes.
The International Code of Virus Classification and Nomenclature (ICVCN) remains outside the Bio code.
Ecology
Mutual symbiosis between clown fish of the genus Amphirion that dwell among the tentacles of tropical sea anemones. The territorial fish protects the anemone from anemone eating fish and in turn the stinging tentacles of the anemone protects the clown fish from its predators.
Ecology studies the distribution and abundance of living organisms and the interactions between organisms and their environment. The habitat of an organism can be described as the local abiotic factors such as climate and ecology, in addition to the other organisms and biotic factors that share its environment.
One reason that biological systems can be difficult to study is that so many different interactions with other organisms and the environment are possible, even on the smallest of scales. A microscopic bacterium responding to a local sugar gradient is responding to its environment as much as a lion is responding to its environment when it searches for food in the African savanna.
For any given species, behaviors can be co-operative, aggressive, parasitic or symbiotic. Matters become more complex when two or more different species interact in an ecosystem. Studies of this type are within the province of ecology.
Ecological systems are studied at several different levels, from individuals and populations to ecosystems and the biosphere. The term population biology is often used interchangeably with population ecology, although population biology is more frequently used when studying diseases, viruses and microbes, while population ecology is more commonly when studying plants and animals. As can be surmised, ecology is a science that draws on several disciplines.
Ethology studies animal behavior (particularly that of social animals such as primates and canids) and is sometimes considered a branch of Zoology. Ethologists have been particularly concerned with the evolution of behavior and the understanding of behavior in terms of the theory of natural selection. In one sense, the first modern ethologist was Charles Darwin, whose book, the Expression of the Emotions in Man and Animals, influenced many ethologists to come.
Bio geography studies the spatial distribution of organisms on the Earth, focusing on topics like plate tectonics, climate change, dispersal and migration and cladistics.
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