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Topic Review
Segmentation
Segmentation in biology is the division of some animal and plant body plans into a series of repetitive segments. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda, Chordata, and Annelida. These three groups form segments by using a "growth zone" to direct and define the segments. While all three have a generally segmented body plan and use a growth zone, they use different mechanisms for generating this patterning. Even within these groups, different organisms have different mechanisms for segmenting the body. Segmentation of the body plan is important for allowing free movement and development of certain body parts. It also allows for regeneration in specific individuals.
  • 6.6K
  • 29 Sep 2022
Topic Review
Saltation
In biology, saltation (from la saltus 'leap, jump') is a sudden and large mutational change from one generation to the next, potentially causing single-step speciation. This was historically offered as an alternative to Darwinism. Some forms of mutationism were effectively saltationist, implying large discontinuous jumps. Speciation, such as by polyploidy in plants, can sometimes be achieved in a single and in evolutionary terms sudden step. Evidence exists for various forms of saltation in a variety of organisms.
  • 3.9K
  • 29 Sep 2022
Topic Review
Clays and the Origin of Life
Clays are able to replicate and drive the evolution of metabolism; they have the catalytic ability to synthesize monomers (amino acids, nucleotides and so on) and polymerize them, resulting in RNA–peptide worlds in which RNA replicates (genes) and, in cooperation with coded peptides, drives the evolution of the cell. 
  • 3.1K
  • 25 Feb 2022
Topic Review
Mosaic Evolution
Mosaic evolution (or modular evolution) is the concept, mainly from palaeontology, that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts. Another definition is the "evolution of characters at various rates both within and between species".408 Its place in evolutionary theory comes under long-term trends or macroevolution.
  • 2.6K
  • 28 Sep 2022
Topic Review
Human–Environment Relationships: Culture and Pedagogy
Human culture can be regarded as the general context where the human–environment relationships take place and develop. Interestingly, studies on human culture and cultural evolution have been enriched with some novel perspectives that appear to dovetail with recent developments in evolutionary biology. All this allows a fresh and promising understanding of the fundamentals of human-environment interaction, according to which the environment can be shown to exert a pedagogical role for humanity, and humanity can be understood as a species modifying the environment to the aim of modifying itself.
  • 2.3K
  • 23 Feb 2022
Topic Review
Origin and Terrestrialization of Arthropods
Arthropods, the most diverse form of macroscopic life in the history of the Earth, originated in the sea. Since the early Cambrian, at least ~518 million years ago, these animals have dominated the oceans of the world. By the Silurian–Devonian, the fossil record attests to arthropods becoming the first animals to colonize land, However, a growing body of molecular dating and palaeontological evidence suggests that the three major terrestrial arthropod groups (myriapods, hexapods, and arachnids), as well as vascular plants, may have invaded land as early as the Cambrian–Ordovician. These dates precede the oldest fossil evidence of those groups and suggest an unrecorded continental “Cambrian explosion” a hundred million years prior to the formation of early complex terrestrial ecosystems in the Silurian–Devonian.
  • 2.1K
  • 04 Nov 2022
Topic Review
Animal Diet Analysis
Diet analysis is a critical content of animal ecology and the diet analysis methods have been constantly improving and updating. Traditional diet analysis methods include direct observation of foraging behavior, the cafeteria diet, microscopic identification of prey remains in fecal and stomach contents. The molecular-based analysis of animal diets has recently become popular, as they confer high resolution and accuracy, which is mainly achieved through the cloning sequencing or the next generation sequencing (NGS) on the amplification of prey DNA in dietary samples.
  • 1.9K
  • 01 Dec 2021
Topic Review
Ecology and Evolution of Saccharomyces cerevisiae
The yeast distributes ubiquitously in nature with clearly structured populations. The baker’s yeast Saccharomyces cerevisiae has become a powerful model in ecology and evolutionary biology. The global genetic diversity of S. cerevisiae is mainly contributed by strains from Far East Asia, and the ancient basal lineages of the species have been found only in China, supporting an ‘out-of-China’ origin hypothesis. The wild and domesticated populations are clearly separated in phylogeny and exhibit hallmark differences in sexuality, heterozygosity, gene copy number variation (CNV), horizontal gene transfer (HGT) and introgression events, and maltose utilization ability. The domesticated strains from different niches generally form distinct lineages and harbor lineage-specific CNVs, HGTs and introgressions, which contribute to their adaptations to specific fermentation environments. 
  • 1.6K
  • 01 Mar 2022
Topic Review
Inclusive Fitness
In evolutionary biology, inclusive fitness is one of two metrics of evolutionary success as defined by W. D. Hamilton in 1964. An individual's own child, who carries one half of the individual's genes, is defined as one offspring equivalent. A sibling's child, who will carry one-quarter of the individual's genes, is 1/2 offspring equivalent. Similarly, a cousin's child, who has 1/16 of the individual's genes, is 1/8 offspring equivalent. From the gene's point of view, evolutionary success ultimately depends on leaving behind the maximum number of copies of itself in the population. Prior to Hamilton's work, it was generally assumed that genes only achieved this through the number of viable offspring produced by the individual organism they occupied. However, this overlooked a wider consideration of a gene's success, most clearly in the case of the social insects where the vast majority of individuals do not produce (their own) offspring.
  • 1.5K
  • 28 Nov 2022
Topic Review
Vitamin D Scarcity in Arctic and  Tropical Peoples
Vitamin D metabolism differs among human populations because the species has adapted to different natural and cultural environments. Two environments are particularly difficult for the production of vitamin D by the skin: the Arctic, where the skin receives little solar UVB over the year; and the Tropics, where the skin is highly melanized and blocks UVB. In both cases, natural selection has favored the survival of those individuals who use vitamin D more efficiently or have some kind of workaround that ensures sufficient uptake of calcium and other essential minerals from food passing through the intestines. Vitamin D scarcity has either cultural or genetic solutions. Cultural solutions include consumption of meat in a raw or boiled state and extended breastfeeding of children. Genetic solutions include higher uptake of calcium from the intestines, higher rate of conversion of vitamin D to its most active form, stronger binding of vitamin D to carrier proteins in the bloodstream, and greater use of alternative metabolic pathways for calcium uptake. Because their bodies use vitamin D more sparingly, indigenous Arctic and Tropical peoples can be misdiagnosed with vitamin D deficiency and wrongly prescribed dietary supplements that may push their vitamin D level over the threshold of toxicity.
  • 1.4K
  • 20 Oct 2022
Topic Review
Dinosaurs
According to Britannica, dinosaurs are described as “Triceratops, contemporary birds, their most recent common ancestor and all of their descendants.” However, for biologists, it could be simpler to picture dinosaurs as reptiles with hind limbs held erect beneath the trunk, similar to how mammals’ hind limbs are held.
  • 1.4K
  • 06 Jan 2023
Topic Review
Y Chromosome Evolution and Functional Specialization
The Y chromosome is one of the sex chromosomes found in males of animals of different taxa, including insects and mammals. Among all chromosomes, the Y chromosome is characterized by a unique chromatin landscape undergoing dynamic evolutionary change. Being entirely heterochromatic, the Y chromosome as a rule preserves few functional genes, but is enriched in tandem repeats and transposons. Due to difficulties in the assembly of the highly repetitive Y chromosome sequence, deep analyses of Y chromosome evolution, structure, and functions are limited to a few species, one of them being Drosophila melanogaster. Here researchers survey comparative evolutionary history of the fly and human Y chromosomes, and functions of Y-linked piRNA clusters ensuring sex-specific piRNA silencing. 
  • 1.4K
  • 09 May 2022
Topic Review
Cognition-Based Evolution
Cognition-Based Evolution (CBE) asserts a comprehensive alternative approach to phenotypic variation and the generation of biological novelty. In CBE, evolutionary variation is the product of natural cellular engineering that permits purposive genetic adjustments as cellular problem-solving. CBE upholds that the cornerstone of biology is the intelligent measuring cell. Since all biological information that is available to cells is ambiguous, multicellularity arises from the cellular requirement to maximize the validity of available environmental information. This is best accomplished through collective measurement purposed towards maintaining and optimizing individual cellular states of homeorhesis as dynamic flux that sustains cellular equipoise. The collective action of the multicellular measurement and assessment of information and its collaborative communication is natural cellular engineering. Its yield is linked cellular ecologies and mutualized niche constructions that comprise biofilms and holobionts. In this context, biological variation is the product of collective differential assessment of ambiguous environmental cues by networking intelligent cells. Such concerted action is enabled by non-random natural genomic editing in response to epigenetic impacts and environmental stresses. Random genetic activity can be either constrained or deployed as a ‘harnessing of stochasticity’. Therefore, genes are cellular tools. Selection filters cellular solutions to environmental stresses to assure continuous cellular-organismal-environmental complementarity. Since all multicellular eukaryotes are holobionts as vast assemblages of participants of each of the three cellular domains (Prokaryota, Archaea, Eukaryota) and the virome, multicellular variation is necessarily a product of co-engineering among them. 
  • 1.2K
  • 20 May 2021
Topic Review
The Syngameon Enigma
When a group of three or more species are connected by hybridization, they form a syngameon.
  • 1.2K
  • 20 Apr 2022
Topic Review
The Chromosome Organization in the Cell Nuclei
The spatial organization of the genome into the cell nucleus plays a central role in controlling several genome functions, such as gene expression and DNA replication timing during the S-phase of the cell cycle. Here we show how chromosomes are organized in the cell nucleus according to the gene density and to the GC-level of the various chromosomal bands, allowing a corrected and coordinated gene expression during cell life. The human genome, such as the genome of the other mammals, is composed by two very different parts: one very gene-dense, replicated at the onset of the S-phase, very GC-rich and the other endowed with opposite features. These two genomic compartments are localized far apart within a chromosome, with regions having intermediate properties located between them. This determines a zig-zag organization of the larger chromosomes, to position the gene-poorest genome compartment at the nuclear periphery and the gene-richest one at the nuclear interior.
  • 1.1K
  • 05 Jan 2022
Topic Review
Seeking Sense in the Hox Gene Cluster
The Hox gene cluster, responsible for patterning of the head–tail axis, is an ancestral feature of all bilaterally symmetrical animals (the Bilateria) that remains intact in a wide range of species.
  • 1.1K
  • 20 Dec 2022
Topic Review
Exploring Behavioural Plasticity of Cats
Understanding behavioural plasticity and other recently evolved traits of domestic cats may lead to management strategies that maximise health and welfare of cats, wildlife, and humans—otherwise domestic cat behaviour may be ‘misunderstood’. Importantly, interdisciplinary research using expertise from biological and social sciences, and engaging human communities, should evaluate these management strategies to ensure they maintain optimal welfare of free-ranging domestic cats while preserving biodiversity and protecting wildcats.
  • 1.1K
  • 26 Jul 2022
Topic Review
The Role of Commensal and other Non-Pathogenic Bacteria
Not only pathogenic bacteria are reservoirs of antibiotic resistance and virulence genes. Opportunistic pathogenic bacteria, commensal bacteria, and mutualistic bacteria (here named non-pathogenic for simplification) may also carry resistance and virulence genes. However, contrary to pathogenic strains, which are the target of the immune system, non-pathogenic bacteria can colonize hosts for prolonged periods because hosts do not need to be rid of them. Thus, the basic reproductive number of a non-pathogenic bacterial strain, a measure of the strain’s fitness and denoted as R0, is likely to be much higher than one. That is, the expected number of colonized hosts by a single colonized host in a population not yet colonized by that strain is higher than one, which implies that this strain can spread exponentially among hosts. This spread has peculiar consequences for the spread of virulence and resistance genes. For example, computer models that simulate the spread of these genes have shown that their diversities should correlate positively throughout microbiomes. Bioinformatics analysis with real data corroborates this expectation.
  • 1.1K
  • 07 Feb 2023
Topic Review
Minor Intron Splicing
Pre-mRNA splicing is an essential step in gene expression and is catalyzed by two machineries in eukaryotes: the major (U2 type) and minor (U12 type) spliceosomes. While the majority of introns in humans are U2 type, less than 0.4% are U12 type, also known as minor introns (mi-INTs), and require a specialized spliceosome composed of U11, U12, U4atac, U5, and U6atac snRNPs. The high evolutionary conservation and apparent splicing inefficiency of U12 introns have set them apart from their major counterparts and led to speculations on the purpose for their existence.
  • 1.1K
  • 21 Jun 2021
Topic Review
Microchromosome Organization in Birds
Interchromosomal rearrangements involving microchromosomes are rare events in birds. To date, they have been found mostly in Neognathae and Neoaves (e.g., Psittaciformes, Falconiformes, and Cuculiformes), although only a few orders have been analyzed. Hence, cytogenomic studies focusing on microchromosomes in species belonging to different bird orders are essential to shed more light on the avian chromosome and karyotype evolution. Relevant hypothetical Neognathae, Neoaves and other ancestral karyotypes can be reconstructed to trace these rearrangements. In a more recent study, a comparative chromosome mapping for chicken microchromosomes 10 to 28 was performed using interspecies BAC-based FISH hybridization in five species, representing four Neoaves orders (Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes). These results suggest that the ancestral microchromosomal syntenies are conserved in Pteroglossus inscriptus (Piciformes), Ramphastos tucanus tucanus (Piciformes), and Trogon surrucura surrucura (Trogoniformes). On the other hand, chromosome reorganization in Phalacrocorax brasilianus (Suliformes) and Hydropsalis torquata (Caprimulgiformes) included fusions involving both macro- and microchromosomes. Fissions in macrochromosomes were observed in P. brasilianus and H. torquata. No interchromosomal rearrangement involving microchromosomes were found to be shared between avian orders where rearrangements were detected. These findings suggest that convergent evolution involving microchromosomal change is a rare event in birds and may be appropriate in cytotaxonomic inferences in orders where these rearrangements occurred.
  • 1.0K
  • 21 Oct 2022
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