The Cambrian

I. The term “Cambrian” refers to a significant period in the history of life on earth, the Cambrian, occurring from 540/505 million years ago, is the first period of the Palaeozoic Era on the geological time scale. The Cambrian Period is characterized by desert land areas, warm seas, and rapid early diversification of marine life resulting in the rise of almost all modern animal phyla.

II. The terms “Cambrian Explosion”/”Cambrian Boom” are adopted by fossils records because of a rapid evolutionary increase of a variation of new animal phyla and animal diversity in earth’s history, during the Cambrian Period. The cause is still unknown but there are some theories attempt to explain it. Ecological relationships among species, comprising from predator-prey relationships, food web changes and competition for food and space, may have been the cause. Another assumed cause is the increasing levels of oxygen in the atmosphere and a rise of oceanic calcium concentrations through environmental changes.

III. A) Trilobite
B) Kainops invius/ Phacops
C)

D) The trilobites are part of the Arthropoda phylum. The trilobite class is allocated into ten orders; over 20,000 species are believed to have existed. Sizes of trilobites vary from 1mm to nearly 70 cm. All trilobites were marine, due to the Cambrian ozone, that made it impossible for life to survive on land (except for one-celled algae), but the oceans they inhabitated were different from today. With such a diversity of species and sizes, assumptions on the ecology of trilobites includes planktonic, swimming, and crawling forms, and we can believe they complete a diverse set of trophic niches, although perhaps mostly as detritivores, predators (on smaller inverterbrates), or scavengers. They’ve only been found to have occupied many different ocean environments, from shallow flats and reefs, to deeper ocean bottoms, and even the water column. Trilobites have a hard exterior presumed to be used for protection, strong thick shells with distinguishing features known as prospon. Some species could even roll into a tiny ball for protection. Their heads are called cephalons, and might contain eyes and defined cheeks; their tails are called pygidiums. Under the thorax, under each segment, was a pair of legs, and some species sported a number of spikes on top. They were amongst the first species to develop sophisticated eyes. Their vision was highly sensitive to motion and had a worthy depth of field with slight distortion. Trilobites have a central axial lobe with pleural lobes on either side; this too is common to all trilobites. The central axial lobe tracks through the length of the body containing the glabella, or middle ration of the cephalon.
E) Trilobites were an incredibly successful species for nearly 300 million years, due to the species rapid evolution trends and development of adaptions to the different environments in the Palaeozoic oceans that they inhabited. Comparing two species from the early and later stages of the Cambrian, the differences are plentiful .The first trilobites were far more primitive, not having the advanced features such as eyes and a spine. Over time primitive trilobites are slowly by more refined and diverting species. These species had shed segments, developed eyes and spikes, features personalized by the habitats the trilobites have survived in. Changes gradually occurred in regions when no major events had arisen to trilobite species. Trilobites were so successful due to being the most dominate species and their ability to adapt to changes in the environment, and their predators.
F) 250 million years ago the trilobites were becoming sporadic as new groups of predators evolved but went extinct during the Permian/Triassic mass extinction. 90% of species were lost, being the largest mass extinction of earth’s history. Although the cause is not certain massive volcanism, the eruption of toxic gases from the earth’s crust and asteroid