Molecular clock calculations estimate the origin of stem group Malpighiales at around 100 Mya ( million years ago ) and the origin of crown group Malpighiales at about 90 Mya.

Molecular phylogenetics has also been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend.

Molecular clock and fossil dating suggest echidnas split from platypuses 19 – 48 million years ago.

* Molecular clock

Molecular clock users have developed workaround solutions using a number of statistical approaches including maximum likelihood techniques and later Bayesian modeling.

simple: Molecular clock

# REDIRECT Molecular clock

Molecular clock analyses suggest that P. falciparum is as old as the human line ; the two species diverged at the same time as humans and chimpanzees.

* Molecular clock hypothesis

Molecular clock analyses suggest that the ancestor of the nesomyines colonized Madagascar about 20-25 million years ago.

Molecular explanation for intelligence …, Brunel University Thesis, HDL. handle. net

Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line.

She is the head of a research group, which is located in the Weatherall Institute of Molecular Medicine and working on a wide range of biological disciplines encompassing molecular biology, biochemistry, cellular immunology and intracellular neurophysiology.

* Molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material.

** Molecular dynamics, the study of motion on the molecular level

Molecular chemistry deals with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics deals with the laws governing their structure and properties.

Molecular orbitals are usually constructed by combining atomic orbitals or hybrid orbitals from each atom of the molecule, or other molecular orbitals from groups of atoms.

Molecular surgical tools, guided by molecular computers and injected into the blood stream could find and destroy cancer cells or invading bacteria, unclog arteries, or provide oxygen when the circulation is impaired.

Drexler argues that we may need to wait until our conventional nanotechnology improves before solving these issues: " Molecular manufacturing will result from a series of advances in molecular machine systems, much as the first Moon landing resulted from a series of advances in liquid-fuel rocket systems.

* The primary technical reference work on this topic is Nanosystems: Molecular Machinery, Manufacturing, and Computation, an in-depth, physics-based analysis of a particular class of potential nanomachines and molecular manufacturing systems, with extensive analyses of their feasibility and performance.

Molecular mass is sometimes called molecular weight.

Molecular clouds, and especially " giant " molecular clouds ( GMCs ), are often the home of astronomical masers.

Molecular nanotechnology is a speculative subfield of nanotechnology regarding the possibility of engineering molecular assemblers, machines which could re-order matter at a molecular or atomic scale.

Molecular genetic testing by linkage analysis or direct mutation screening is available clinically ; however, genetic heterogeneity is a significant complication to molecular genetic testing.

Molecular spectra can be obtained due to electron spin states ( electron paramagnetic resonance ), molecular rotations, molecular vibration and electronic states.

* Chemistry: Molecular theory — Kinetic theory of gases — Molecular orbital theory — Valence bond theory — Transition state theory — RRKM theory — Chemical graph theory — Flory-Huggins solution theory — Marcus theory — Lewis theory ( successor to Brønsted – Lowry acid – base theory ) — HSAB theory — Debye – Hückel theory — Thermodynamic theory of polymer elasticity — Reptation theory — Polymer field theory — Møller – Plesset perturbation theory — Density Functional Theory — Frontier molecular orbital theory — Polyhedral skeletal electron pair theory — Baeyer strain theory — Quantum theory of atoms in molecules — Collision theory — Ligand field theory ( successor to Crystal field theory ) — Variational Transition State Theory — Benson group increment theory — Specific ion interaction theory

; Molecular modelling: Methods for modelling molecular structures without necessarily referring to quantum mechanics.

* Molecular physics: The discipline of the electrons surrounding the molecular nuclei and of movement of the nuclei.

* Molecular replacement – if a related structure is known, it can be used as a search model in molecular replacement to determine the orientation and position of the molecules within the unit cell.

Molecular electronics, sometimes called moletronics, involves the study and application of molecular building blocks for the fabrication of electronic components.

Molecular electronics comprises two related but separate subdisciplines: molecular materials for electronics utilizes the properties of the molecules to affect the bulk properties of a material, while molecular scale electronics focuses on single-molecule applications.

An animated picture with explanations, and a spreadsheet that ' constructs ' the clock for each moment in the year and at each place in the world is to see in a Didactic explanation

Though the paper did not provide any explanation for why amino acid differences in a protein should accumulate at a uniform rate ( the essential assumption of the molecular clock ), it did show that the results were fairly consistent with those of paleontologists.

This makes it easier to reconcile molecular clock data that suggests that the angiosperms diverged from the gymnosperms around.

** Systematics: taxon — taxonomy — scientific classification — phylogeny — evolutionary tree — cladistics — synapomorphy — homology — molecular clock

By constructing a calibration curve of the ID of species ' pairs with known divergence times in the fossil record, the data could be used as a molecular clock to estimate the times of divergence of pairs with poorer or unknown fossil records.

Application of the molecular clock principle revolutionized the study of molecular evolution.

By using the technique called the molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated.

For example geochemical signatures from rocks may help to discover when life first arose on Earth, and analyses of carbon isotope ratios may help to identify climate changes and even to explain major transitions such as the Permian – Triassic extinction event .< ref name =" Twitchett "> A relatively recent discipline, molecular phylogenetics, often helps by using comparisons of different modern organisms ' DNA and RNA to re-construct evolutionary " family trees "; it has also been used to estimate the dates of important evolutionary developments, although this approach is controversial because of doubts about the reliability of the " molecular clock ".

Y-chromosomal Adam probably lived between 60, 000 and 200, 000 years ago, judging from molecular clock and genetic marker studies.

However, calculations of Y pestiss evolutionary age, found using the number of synonymous single nucleotide polymorphisms ( SNPs ) in conjunction with molecular clock rates, date the emergence of the biovars prior to any of the historical epidemics due to the length of time needed to accumulate such mutations.

The oldest fossil " proto-frog " appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago.

The earliest known fossil diatoms date from the early Jurassic (~ 185 Ma ), although molecular clock and sedimentary evidence suggests an earlier origin.

A defect in the human homologue of the Drosophila " period " gene was identified as a cause of the sleep disorder FASPS ( Familial advanced sleep phase syndrome ), underscoring the conserved nature of the molecular circadian clock through evolution.

It is now known that the molecular circadian clock can function within a single cell ; i. e., it is cell-autonomous.

However, current molecular clock estimates indicate that Ficus is a relatively ancient genus being at least 60 million years old, and possibly as old as 80 million years.

The time she lived is calculated scientifically, based on the molecular clock technique of correlating elapsed time with observed genetic drift, see Mitochondrial Eve.

This approximation, which reflects the " molecular clock " hypothesis that a roughly constant rate of evolutionary change can be used to extrapolate the elapsed time since two genes first diverged ( that is, the coalescence time ), assumes that the effects of mutation and selection are constant across sequence lineages.

( In the case of nucleotide sequences, the molecular clock hypothesis in its most basic form also discounts the difference in acceptance rates between silent mutations that do not alter the meaning of a given codon and other mutations that result in a different amino acid being incorporated into the protein.

While unrooted trees can always be generated from rooted ones by simply omitting the root, a root cannot be inferred from an unrooted tree without some means of identifying ancestry ; this is normally done by including an outgroup in the input data or introducing additional assumptions about the relative rates of evolution on each branch, such as an application of the molecular clock hypothesis.

Conserved sequences, such as mitochondrial DNA, are expected to accumulate mutations over time, and assuming a constant rate of mutation provides a molecular clock for dating divergence.

Some of the key topics that spurred development of the field have been the evolution of enzyme function, the use of nucleic acid divergence as a " molecular clock " to study species divergence, and the origin of noncoding DNA.

The advent of protein sequencing allowed molecular biologists to create phylogenies based on sequence comparison, and to use the differences between homologous sequences as a molecular clock to estimate the time since the last common ancestor.

In the late 1960s, the neutral theory of molecular evolution provided a theoretical basis for the molecular clock, though both the clock and the neutral theory were controversial, since most evolutionary biologists held strongly to panselectionism, with natural selection as the only important cause of evolutionary change.