Question

How does the history of the Earth show evolutionary relationships? Include how climate, geologic time scale, fossil record and radiometric dating impact the Earth through continental drift, extinction events, and environmental changes. How do these events lead to adaptations that demonstrate evolutionary relationships between organisms?

Answer 1

Looking into the rock record, the past time on Earth is divided into four immense periods of times known as eons. These four eons are

A) Hadean – It existed some 4.6 billion to 4 billion years ago

B) Archean - It existed some 4 billion to 2.5 billion years ago

C) Proterozoic - It existed some 2.5 billion to 541 million years ago

D) Phanerozoic - It existed some 541 million years ago to the present

Currently no only record from Hadean Eon (record comes from meteorites and lunar rocks) exists in present time.

The four eons (mentioned above) are further divided into eras, periods, and epochs based on the geologic time scale. The oldest available fossil Fig Tree Chert is somewhere around 3 billion year old and have been identified as bacteria (mainly prokaryotes). Earth is around 4.6 billion years old hence it is believed that origin of life must have occurred after few hundred million years from the birth of Earth. This because the atmosphere in the initial time period was ionized and not suitable for origin of life. Chemical analyses on organic matter showed that straight-chain geometry of hydrocarbons had been preferred since ages and this is based on the discovery of Porphyrins , isoprenoid derivatives pristane and phytane and products of cell lipids. Nonbiological processes formed equal amounts of long-chain carbon compounds as the biological processes. Carbon isotope C12 was the first element to have formed out of any non-biological processes. Cyano bacterias (chlorophyll containing bacteria’s) in the early Archean Eon became evident for that as they carried out photosynthesis or methanogenesis where C12 was concentrated to C13.

In Proterozoic Eon, various kinds of bacteria and protist fossils originated such as acritarchs (spherical, robust unidentified fossils) and Ediacaran fauna. Nearly 100 species were found in sandstone formations. Ediacarans developed microbial symbionts for nourishment

Along with Ediacarans and acritarchs, several microfossils and organism in the pre-Phanerozoic, or Precambrian showed indirect evidence for oxygen-producing mechanism.

Most of the earliest fossils evolved from their aquatic forms. By the end of Phanerozoic Eon, life has evolved on both land and water and include majorly mollusks and arthropods (541 million years ago) at the base of the Cambrian Period of the Phanerozoic Eon. Plants and fungi appeared some 360 million years ago in the Devonian Period

Many lineages became extinct, some persisted and changed with the changing climatic and weather condition (such as change in height and depth of biosphere). Environment on Earth is heterogeneous which means it has diverse geological and climatic features such as mountains, oceans, and deserts have extremes temperature, humidity, and water availability. This variability in the form of diverse microenvironments, oxygen-depleted oceanic oozes, mineral outcrops, organic-rich springs, variety of ecological niches etc lead to diversification and convergence of species.