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By the Jurassic period, the sophisticated aerial webs of the orb-weaver spiders had already developed to take advantage of the rapidly diversifying groups of insects. A spider web preserved in amber, thought to be 110 million years old, shows evidence of a perfect "orb" web, the most famous, circular kind one thinks of when imagining spider webs.
The fibers are pulled out by the calamistrum, a comblike set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated ...
The principle of homology: The biological relationships (shown by colours) of the bones in the forelimbs of vertebrates were used by Charles Darwin as an argument in favor of evolution. In biology , homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry , regardless of current ...
Homology is the term used to characterize the similarity of features that can be parsimoniously explained by common ancestry. Homoplasy is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution.
The principle of phylogenetic reconciliation was introduced in 1979 [14] to account for differences between genes and species-level phylogenies. In a parsimonious setting, two evolutionary events, gene duplication and gene loss were invoked to explain the discrepancies between a gene tree and a species tree.
In addition, Cytochrome b is commonly used as a region of mitochondrial DNA to determine phylogenetic relationships between organisms due to its sequence variability. It is considered most useful in determining relationships within families and genera. Comparative studies involving cytochrome b have resulted in new classification schemes and ...
Phylogenies showing the terminology used to describe different patterns of ancestral and derived trait states. [1] Imaginary cladogram. [2] The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. [2]
Spider behavior refers to the range of behaviors and activities performed by spiders. Spiders are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom . They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms [ 1 ] which is reflected in their ...