Though life existed before the Cambrian explosion, it was likely not present wit

Question

Though life existed before the Cambrian explosion, it was likely not present with the same diversity.

Life in the oceans was incredibly active before the first species began to move onto the continents.

After the Cambrian explosion, the number of species in oceans greatly increased.

Greater competition among species led to more rapid and advanced adaptations to escape predators. Adaptations also led to the origin of amphibians and plants, leading the habitation of land.

Amphibians were able to move into swampy regions and tidal pools, escaping predators and exploring new habitats.

Similarly, plants faced new challenges moving onto land, including coping with wind and gravity without the support provided by ocean water, but ultimately thriving and evolving into large trees.

A drier period, the Paleozoic Era, resulted in vast changes of land plants and animals.

Green algae require freestanding water to survive and are ancestors of modern plants. Early in this era, the first plants appeared on land that did not require freestanding water.

A group of plants, called the gymnosperms, proliferated later in the era because their seeds were well adapted for the drier environment of the time.

The drier climate was problematic for amphibians because they must return to water to lay their eggs. This was an opportunity to gain a competitive advantage for a new group: the reptiles.

The eggs of reptiles have a shell, allowing them to be laid on land, which was a primary factor in the spread of these animals.

Then, the Great Permian Extinction occurred.

This extinction was likely the result of global warming associated with volcanism. Estimates of extinction are 90 percent of marine species and 70 percent of terrestrial species.

The warming would have allowed anaerobic bacteria to thrive, putting large amounts of hydrogen sulfide into the atmosphere.

This extinction paved the way for the dinosaurs, who thrived during the Triassic, Jurassic, and Cretaceous periods, until the KT boundary (Cretaceous–Tertiary boundary).

The timing of the KT boundary coincides with the carbonaceous meteorite impact that lead to the extinction the dinosaurs.

Increased predation meant adaptations: bigger brains, Appearance of this group allowed travel from swamp to land Green algae were ancestors of Plants adapted to drier climates his organism. It had restricted Seeds were fertlized without freestanding water This group's shell-covered eggs allowed offspring to be born outside of the water t of acute senses, mobility and size and faster mobili The Great Permian Extinction occurs, causing loss of many marine and terrestrial vertebrate Dinosaurs and many other species become extinct 3,800 Ma 4,600 Ma 2,000 Ma Archean Eon Eon Fishes ourish 488 M Period Silurian M Ma Period Devonian M Period 359 Ma oic Era Palcoz First First plants invade Mississippian the land Period 31a Ma Pennsylvanian flourish Periodo Permian Period 251 Ma First reptiles Triassic Period Jurassic Period Era Cretaceous Period 65.6 Ma

Explanation / Answer

The events from oldest age to youngest age are as follows:

1. Green alagae were ancestors of these organisms. It had restricted mobility and size.

2. Plants adapted to drier climates. Seeds were fertilized without free standing water.

3. Appearance of this group allowed travel from swamp to land.

4. This group's shell-covered eggs allowed offsprings to be born outside water.

5. The great Permian extinction occurs.

6. Increased predation meant adaptions : bigger brains, developement of acute senses, faster mobility.

7. Dinosaurs and many others became extinct.

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