26.2 History of Life on Earth

• The fossil remains of larger organisms are more likely to be found than those of smaller organisms.

• It is more likely that a species existed over a larger area.
• The first three eons were preserved within the fossil record because they were preceded by the Cambrian era, which saw a rapid increase in the diversity of life.

• Inland species are less likely to become fossils than those that lived in these time periods.
• We will look at these time periods later in the chapter.

• Over the past 4 years, there have been changes in living organisms that are likely to be formed in or near water.

• Genetic changes in organisms can exist for a long time and are more likely to be found as fossils than species that have recently changed.
• Changes in the abili can be long ago or short.

• Due to the chemistry of fossilization, certain environments on Earth have undergone dramatic changes that have organisms more likely to be preserved than other organisms.

• New types of organisms have been allowed to flourish by certain types of fossils.
• It is interesting to paleontologists.
• The locations where paleontologists search for a species or group of species have lost a significant bias.
• They tend to search next.

• The surface of the Earth cooled during the first 2.5 billion years of its existence.
• Ice Ages alternate with warmer periods during the last 2 bil lion years, as the Earth has undergone major fluctuations in temperature.

• Although the fossil record is incomplete, it has provided a wealth of information regarding the history of the types of life that existed on Earth, such as tropical rain Earth.

• Over the past 4 billion years, the composition of the gases surrounding the Earth has changed.

• The types of environmental changes that have affected the gence of organisms that are capable of photosynthesis are listed.

• Increased levels of oxygen are thought to have led to the emergence of key organisms during the Archaean eon.

• Major events and changes in species diversity occurred during the Paleozoic, Cenozoic, and Mesozoic eras.

• Higher O 2 came into existence as a result of increases in animal body sizes.
• The first fossils of organ levels.

• The events discussed later in this chapter have an important effect on Unit V.

• The organisms are surrounded by bodies of water.
• Two different environments were created around an eruption, sometimes causing extinctions.
• The major landmasses, known as the continents, shifted islands as a result of volcanic eruptions in the oceans.
• Massive eruptions can cause so much debris into their positions that they can be separated from each other.

• The organisms in the flooded regions have been affected by the Earth.
• Glaciers have been hit by meteorites.
• Large meteorites have moved across continents and altered the composition of species on affected Earth's environment.

• The snowball Earth hypothesis was proposed in 1992 by Americangeo Biologist Joseph Kirschvink, which suggests that the Earth was covered by ice during parts of the time period and that large numbers of species went extinct at the same time.
• The hypothesis was developed over time.
• There are several types of geological evidence that can be found at tropical latitudes, including deposits of glaciers.
• Time periods are often based on the occurrence of mass extinctions, the boundaries between geological existence of a completely frozen Earth remains controversial.

• The extinction of some species and the emergence of new ones is a recurring pattern in the history of life.

• All life-forms were prokaryotic during the 1 billion years of the Archaean eon.

• Over time, an important factor that greatly influenced the emergence of new continents has changed.

• There is a layer on top.
• Many layers of cells and sedi are used to obtain energy.

• Heterotrophs are two critical consequences of the emergence and proliferation of ancient cyanobacteria.
• The autotrophic nature of these bactes consume other organisms.

• Plants absorb light energy and use it to grow.

• Aerobic (with oxygen) respiration is the answer.
• Not resolved.
• The emergence of those living near deep-sea vents may have been aided by aerobic respiration, according to some biologists.
• Chemicals that were made near the vents would have been used in the explosion of the organ and life-forms.
• Next, these life-forms are described.

• Many scien tists believe that the first living cells were Heterotrophs.

• Their manner of growth is a possible reason.

• The aquatic environment where these cyanobacteria live is rich in minerals such as calcium.
• The mats that stood were large.
• Genetic material is found in the form layers.
• They deplete the carbon dioxide in the three distinct organelles as they grow.

• This causes calcium carbonate in the water to grad the nucleus and mitochondria, and plant and algal cells also have ually precipitated over the bacterial cells.
• To address the issue of the origin of the lower layers.
• Stromatolites are typically 1 m in diameter.
• There are mats ofbacteria on top of each other.
• Evidence of early autotrophic organisms can be found in the existence of fossil stromatolites.
• Stromatolites have formed in western Australia.

• The ancient were found in the three organelles.

• The nuclear genome of the cells was contributed by bothbacteria and archaea.

• The ability to invaginate is derived from ancientbacteria.

• Several hypotheses have been proposed to explain the origin of the nuclear genome.
• The association between ancientbacteria and archaea is the most widely accepted.

• The host is where the invagination process lives.

• According to researchers, an archaeal species evolved a nuclear envelope.

• It could lead to an enclosure of the genetic material in a nuclear envelope.

• The invagination process taking up materials from the environment is described in Chapter 5.
• The closest modern establish asymbiosis along these lines.

• Some genes from the bacterium were transferred to the archaeal host cell and the resulting genetic material became the nuclear genome.

• The genes were transferred to the nucleus.

• The analyses of genes from mitochondria, chlo in mitochondria, or Mito chondria may have arisen from this event.

• A chondria found in cells is likely a result of an event involving a group ofbacteria that resembled modern a-proteobacteria.

• There is a chance that the first eukaryotic cell was a remnant of an event in which an ancestor of thisbacterial species was involved.

• The relationship between two dif ferent proteobacteria was reported in 2001.

• The small clumps of organ called a bacteriome are unicellular.
• Recent analysis has shown that dif cells of the same cell type, or larger groups of cells with two distinct species ofbacteria inside the host cells share their own cell types.

• Biflagellate is a type of observa where each cell has two flags.

• A simple multicellular organisms is formed from a single cell.
• The cells in this species are biflagellate.

• The first multicellular eukaryotes are thought to have arisen around 26.8d.
• The more complex organisms have two 1.5 bya in the middle of the Proterozoic eon.
• The reproductive cells are not the same as the bifla cells of multicellular eukaryotes.

• Simple multicellular organisms are believed to have originated Overall, an analysis of these four species of algae illustrates three different ways.
• One possibility is that some of the principles found in complex multicellular species can be found in cells aggregated to form a colony.

• Modern organisms in produce daughter cells that adhere to one another are examples of multicellular organisms that arise from a single cell.

• A smal multicel ular organisms can be produced by the daughter cells.
• Multicellular organisms have different cell types according to the fossil record.

• 3 is another way that multicellularity can occur.
• When a single cell divides, a larger percentage of the cells stick together.
• In simple multicellular organisms, the survival of the multicellular organisms, as well as the reproductive and fungi, as well as in species with more complex body plans, such cells are specialized for the sole purpose of producing offspring.

• The first multicellular animals may or may not have arisen from an aggregation process.
• The first animals were not divisions.
• Most animals occur by cell division and attachment.

• An example shows the level of com and left side mirror images.

• Chapter 26 states that it facilitates movement.

• In southern China in 2004, Jun-Yuan Chen, a Chinese paleontologist, and his colleagues presented a fossil that they said was the earliest known ancestor of animals with bilateral symmetry.
• The fossil is 600 million years old.

• The abundance of fossils of plants and animals that have been identified as Guizhouena can be found in this fossil of an early animal.

• Three other species have bilateral symmetry.

• They are recent and we have many fossils from these eras.

• Charles Walcott covered periods in 1909.
• Rocks and fossils of that age were first discovered at this region.

• The period was warm and wet, with no evidence of ice at the excellent preservation of the softer tissues, which makes this deposit poles.

• Charles Walcott discovered the original site in the Canadian Rockies.
• The site has been turned into a quarry for fossils.
• The Marrella fossil was found at this site.

• All of the major types of invertebrates that exist today were present by the middle of the Cambrian period.
• The fossil record shows that over 100 major animal groups have different body plans.
• Echinoderms, arthropods, mollusks, clams and snails, and verte brates are some of the groups that still exist.
• Many new species of animals have arisen since this time, but they have not shown a major reorganization of body plan, but rather variations on themes that were established during or prior to the Cambrian explosion.

• There are three possible causes of the explosion.

• Some scientists theorize that the changes observed in animal species may have allowed them to exploit new environments.

• The increase in diversity may be related to atmospheric oxygen levels.
• More complex body plans became possible only after the atmospheric oxygen reached a certain threshold.

• 3 cm is an "evolutionary arms race" between interacting species.

• About 250 mya were extinct in the Cambrian period.
• There are many species of brachiopods.

• For this to happen, certain species evolved adapta communities consisting of organisms that prevented them from drying out.

• Ancestors of spiders and centipedes were present.
• Early land plants and arthropods may have first invaded the earliest fossils of vascular plants, which have tissues that are special to the land.

• The glaciers caused the water levels to drop.
• A mass extinction in which as much as 60% of the existing marine ally dry conditions occurred across much of the northern landmasses occurred in the Devonian period.

• The southern landmasses were mostly covered by the oceans.

• The climate species saw a major increase in the number of mate changes observed.
• During the Silurian period, the vegetation was mostly small plants.
• The melted plants caused the ocean levels to rise.
• Gymnosperms did not emerge as a new major type.
• The first trees and forests were formed after the end of the Devonian.
• There was an expansion of terres changes among existing species.

• Many new types of fishes appeared in the fossil record.
• In addition, and other animals became plentiful.
• The first four coral reefs made their first appearance during this period.

• Gymnosperms replaced the forest of fernlike plants.
• They needed water to lay their eggs.

• Amphibians were prevalent in the oceans, but reptiles became the dominant verte ing species.
• Sometimes this period is called brate species.

• The largest mass extinction in the history of life on Earth took place at the end of the Permian period.

• The cause of mass extinction is not well understood.

• The term Carboniferous of terrestrial species and lowered ocean levels refers to the deposits of coal in a rock.
• Another hypoth of carbon was formed.
• The ideal conditions for the formation of coal were created by the large volcanic eruptions in Siberia.

• The land was covered by forest swamps during the cooler period.

• Plants and trees became more common.
• Middle animals are called mesybic.
• The first insects appeared.
• Changes in animal and plant species were seen by giant dragonflies.
• Sometimes this era has a wingspan of over 2 ft.
• The Age of Dinosaurs was called because the animals flourished and became more diverse.
• Amphibians were very active.
• The climate was very hot during the Mesozoic era.
• Terrestrial environments were relatively dry and one innovation seemed to be beneficial.
• The amniotic egg may have had ice in it.
• The amniotic egg was found at either pole in reptiles.
• The leathery or hard shell prevented the desiccation of the Triassic embryo, and the other two periods.

• This innovation was important for the emergence of reptiles.

• New reptile groups such as crocodiles and turtles were abundant in this period.
• The first dinosaurs emerged during the middle of the Triassic.
• The small rior regions of Pangaea were dry, with great seasonal fluctuations.

• During the skeletons, this group became extinct.
• The Megazostrodon was long.

• The illustration is based on fossils.