Marine-dwelling forms fall to the bottom of the ocean at death and are more likely to be buried in sediments than terrestrial forms, making them less likely to decompose rapidly.
Burrowing species are "pre-buried;" at death they stay buried, where they are less likely to decompose rapidly.
Recent fossils are still likely to be present on Earth; the fossils of more ancient organisms are more likely to be in rocks that have eroded away or been changed by heat or pressure.
Pollen grains have a tough case so they resist decomposition.
Desert-dwelling forms are rarely buried in wet sediments, where decomposition is slow and conditions for fossilization are optimal.
Flying animals tend to have very light skeletons, so have few hard parts that fossilize well.
Sharks and rays have cartilaginous skeletons, which are not as hard as bone and thus fossilize much less readily.
Flowers are so soft that they decompose readily and rarely fossilize.
The Proterozoic is the time period prior to the Cambrian and the appearance of large numbers of large, morphologically complex animals; the Phanerozoic is the time period from the Cambrian to the present.
The initial radiation of land plants.
The initial radiation of bilaterally symmetric animals.
The greatest mass extinction of all time.
The diversification of dinosaurs.
The Cambrian is "explosive" because most of the animal phyla living today appear in a relatively short time-including groups that became particularly species-rich such as arthropods, mollusks, and vertebrates. The "explosion" occurred over 38 million years, however.
Almost all Ediacaran fossils lack hard parts and limbs and most have radial symmetry. Most species present are sponges, cnidarians (jellyfish and relatives), or ctenophores (comb jellies). Cambrian fossils include many bilaterally symmetric species with hard parts and limbs, and include arthropods, mollusks, and vertebrates.
An adaptive radiation is the evolution of a large number of morphologically and ecologically diverse descendant species from one or a small number of founding species. They result from new ecological opportunities or morphological innovations that allow individuals to exploit resources in new ways.
Mass extinctions eliminate 60% of the species alive in less than one million years; any rate slower than this is considered background extinction. In addition to involving many more species in a short amount of time, mass extinctions are global in extent and involve a wide diversity of lineages.
The date of first appearance in the fossil record only records the first known instance where an individual of a species fossilized and was found; the species had to have existed before that.
Some fossils of bilaterally symmetric animals have been found prior to the Cambrian, and molecular clock data suggest that the lineages listed evolved long before the Cambrian.
It would mean that the Cambrian explosion was triggered at least in part by ecological opportunity-specifically, lack of competition from species that existed prior to the extinction event.
Large animals that move extensively have higher oxygen demands than smaller animals that rarely move under their own power.
Many possible examples; see text for details on Hawaiian Drosophila and Galapagos finches.
The evidence for the impact includes the Chicxulub crater and an array of features found in sediments dated to the K-T boundary: the iridium anomaly, microtektites, shocked quartz, and tsunami deposits.
Global cooling would result from the dust and soot from the impact and the wildfires it triggered, along with massive amounts of sunlight-scattering sulfur dioxide.
This is an opinion question, but it is important that you support your opinion with data.
Most terrestrial rocks that form during a particular interval become eroded away, leaving only patches.
No-marine birds that dive are just much more likely to sink to the bottom of the ocean at death and become buried in sediments, where they can fossilize.
Nautiloid eggs may have been able to lie dormant during the initial impact, while ammonite larvae were wiped out by rapid changes in ocean currents and seawater chemistry.
The presence of shocked quartz suggests that a large impact may have been associated with the mass extinction at the end of the Permian; the lack of iridium suggests that no such impact occurred.
Extinction has occurred constantly throughout the history of life, but the current rate of extinction is higher than at almost any time in the planet's history.
