Fossils are formed when the remains of living things were buried under the sediments. These sediments eventually harden into rock and as a result, the shapes of the organisms are preserved. Therefore, fossils are found in sedimentary rock layers.

b. sedimentary rock

A trilobite fossil is a good index fossil. Index fossils are remains of an organism that existed for only a short period of time. This type of fossil is useful when determining the relative age of rocks because it matches rock layers.

a. index fossils

Fossils are from the remains of ancient living things that are formed and buried under the sediments. These are the traces that serve as clues to the Earth’s history, particularly the environment and ecosystem of the ancient groups of organisms that existed in the past. They also show evidence on how living organisms have evolved or changed over time.

Half-life is the term that refers to the time in which one-half of an unstable atom undergoes radioactive decay. This unit is used to measure the absolute age of rock in radiometric dating.

The plate tectonics theory explains that the plates are moving slowly along the Earth’s surface due to the convection currents in the mantle. It tells us how formation, movement, and subduction happen on the Earth’s plates. Over time, the movement of plates results in the changes in the distribution of organisms, and the formation of volcanoes and mountain ranges, as well as earthquakes.

The geologic time scale is developed by the scientists to show the development of ancient life-forms and the geologic events which took place in the Earth’s history. Unlike the time scale that we use during the present time, the geological time scale uses relative and absolute dating to determine the eras or the timeline of the Earth’s history.

In order for the geologists to determine the age of rocks, geologists use the relative age and absolute age of rocks. Relative age is the rock’s age compared to the other rocks. It can be similar when comparing your age to another person’s age. In measuring sedimentary rocks, geologists use the law of superposition. According to the law of superposition, youngest rock layers are positioned at the top and older ones are at the bottom. Aside from the law of superposition, geologists also use clues from igneous rocks, such as extrusion and intrusion, and index fossils, which is useful when it matches rock layers.

On the other hand, an absolute age refers to the numeric age of the rocks. To get the absolute age of rock layers, geologists use radioactive dating. The rate of decay in a radioactive element, which is the element’s half-life, can tell the time when a rock was formed due to the elements in its composition.

In a convergent evolution, organisms that are not closely related forms similar structures that are favored by natural selection. Eventually, different organisms become more alike due to this pattern of evolution.

b. not closely related

Since the polar bear evolved from a common bear ancestor, this pattern of evolution is called an adaptive radiation. In adaptive radiation, single species evolve into different groups in order to fill new or different ecological niches.

a. adaptive radiation

A clade is a term that is defined as the group of species that evolved from a single common ancestor and all of its descendants. A clade is usually illustrated in a cladogram, wherein evolutionary relationships or connections among species are shown. Moreover, the species are grouped into their clades using their shared derived characteristics.

b. relationships based on shared derived characteristics

When a geologic change occurs in a slow and steady rate rather an abrupt one, the evolution happens over a long period of time. This pattern of evolution is said to be under the gradualism theory.

c. gradualism

A punctuated equilibrium occurs when a period of stability is ceased by brief periods of rapid changes. Therefore, the rate of change varies from a stable period into a rapid change.

c. varying rates of change

Darwin found large flightless birds called rheas that are native in South America. He noticed that the rheas resemble the ostrich from Africa and the emu from Australia. The similarities between these flightless birds reveal that a convergent evolution took place. They may look alike but they are not closely related. These different bird species have common features or adaptations because they live in a similar habitat and they inhabit similar ecological niches.

In coevolution, the relationship between two organisms becomes specific or closely connected that neither one can survive without the other. Due to this reason, the evolution of one organism is often followed by the evolution of the other organism.

For example, the flowering plant and an insect share a close relationship since insects feed on the flower and assist in their pollination. Once the flowering plant undergoes evolution, the insect would eventually evolve and develop specialized parts that would enable it to feed on the flowering plant.

The Earth’s early atmosphere contains carbon dioxide, nitrogen, and water vapor. Moreover, there is only a little amount of oxygen. According to scientists, this composition made the sky orange and the oceans brown.

a. carbon dioxide, water vapor, nitrogen, and oxygen

The experiment by Miller and Urey has demonstrated the formation of organic molecules using a simulation that imitated the conditions of the Earth’s early atmosphere. In this experiment, they were able to form amino acids from inorganic materials. This served as a proof that the organic compounds, which are responsible for sustaining life on Earth, were formed from the simpler compounds that are present in the Earth’s early atmosphere.

a. amino acids

According to the endosymbiotic theory, the prokaryotes and eukaryotes had a symbiotic relationship in the past, wherein the prokaryotes lived inside the eukaryotes. Eventually, the prokaryotes evolved into mitochondria and chloroplasts and they became a part of the modern eukaryotic cell.

d. the endosymbiotic theory

A protocell, which is also known as a protobiont, is similar to a modern cell in terms of its composition, structure, and function. Just like a cell, it is composed of proteins and a cell membrane. In addition, it also undergoes growth and division or mitosis.

The color of the sky depends on the atmosphere’s composition and its thickness. The Earth’s early atmosphere contains carbon dioxide, nitrogen, and water vapor, as well as a tiny amount of other substances, such as carbon monoxide, hydrogen sulfide, and hydrogen cyanide. Moreover, there is only a little amount of oxygen. According to scientists, this composition made the sky orange.

According to the experiments conducted by Stanley Miller and Harold Urey, the organic compounds, which are responsible for sustaining life on Earth, were formed from the simpler compounds that are present in the Earth’s early atmosphere.

Fossil records give us the history of life on Earth and the past environments it had. It shows the ancient groups of organisms that existed on this planet. However, it is often incomplete because some remains of ancient organisms were destroyed by geological forces, weathering, and erosion. Moreover, only the hard exoskeleton or endoskeleton of organisms was preserved since the soft parts were either eaten or destroyed.

Fossils give us a glimpse of the Earth’s history and the past environments it had. It shows the ancient groups of organisms that existed on this planet. When the environment changed, the organisms adapted and evolved. By studying the rock layers and index fossils, the scientists were able to create a timeline to show how life-forms developed over time. They have arranged the data they have gathered according to the order of the relative age of the rocks and fossils. Eventually, scientists were able to tie all the pieces of evidence together and concluded how the environment changed over time.

After a mass extinction, the population would grow rapidly. The reason for this event was due to the fact that the carrying capacity of a particular ecosystem would increase since there were only a few species competing for resources and there were more ecological roles or niches available for new species. Eventually, the groups that have survived would evolve quickly and this event would lead to the restoration of biodiversity and balance in a particular ecosystem.

One great example is the mass extinction during the end of the Cretaceous period, which happened about 65 million years ago. This event wiped out all the dinosaurs. The absence of dinosaurs has helped the mammals to evolve and multiply quickly. Since there is no competition for food with dinosaurs, mammals were able to dominate many different habitats, including land, water, and air. When vegetation started to regrow and evolve, it provided a great food source for mammals. these conditions have allowed most life-forms to flourish.

The experiment conducted by Miller and Urey used a model that represented the conditions of the early Earth. First, the water was boiled to form water vapor. Then, methane, ammonia, and hydrogen are added into the water vapor and the gas mixture was bombarded with electricity to simulate a lightning. Later on, a cold water cooled the chamber and formed droplets. After seven days, the liquid that was collected was further examined. They were able to identify the presence of amino acids and other organic compounds in the liquid.

On the other hand, the experiment cannot fully explain how proteins were assembled to create life. There is also no substantial proof that tells us the exact composition of the Earth’s early atmosphere. Therefore, the results of this experiment were unreliable.

The Earth’s atmosphere would be different if photosynthetic bacteria did not evolve. Since oxygen is one of the end products of photosynthesis, the oxygen content in the atmosphere has increased and all the living beings were able to sustain their life processes. Without photosynthesis, life would not be possible on Earth.

According to the Law of Superposition, layer C is the oldest sedimentary rock layer and layer A is the youngest layer of sedimentary rock. The law of superposition states that rock layers are deposited in such a way that the oldest rocks are at the bottom, whereas the younger rocks are on top. As the sediment forms and gets deposited, it hardens into a sedimentary rock. This goes on as a new layer of sediments goes on top of the other.

Index fossils are remains of an organism that existed for only a short period of time. This information is used by the geologists to identify the relative age of rock layers. Since the same index fossils are found between rock layers B and F, these ancient organisms belong to the same age or time period.

This pattern of evolution is seen in sharks, which are cartilaginous fishes, dolphins, which are marine mammals, and penguins, which are aquatic flightless birds. Since these animals thrive in an aquatic environment, they developed fins and flippers, which are modified limbs for swimming, due to convergent evolution and not from a common ancestor.

The coevolution that occurs between a monarch and a milkweed is similar to “defense” and “counter defense” mechanism. The reason for this is because these two organisms show a predator-prey relationship. For every defense that the milkweed plant does, there is a counter defense from the monarch caterpillar.

When the caterpillar hatches, the monarch’s bed of dense hairs act as the barrier to the caterpillar’s consumption of the leaf. Eventually, the behavior of caterpillar evolved. Instead of consuming the leaf directly, they would shave the bed of hairs so that they can have access to the leaves. However, the milkweed plant provides a good counter defense by developing a specialized structure that secretes poisonous liquid when the caterpillar sinks its mandibles into the leaf. In turn, the caterpillar would evolve in order not to get poisoned but to use this poisonous liquid to protect itself against other predators.

Fossils are usually deposited in layers; hence, they are found in sedimentary rocks. Fossils are organic sedimentary rocks that are formed when the remains of living organisms and other sediments settle at the bottom of a body of water, such as rivers and oceans. Eventually, after deposition, compaction and cementation will take place. These events will turn the sediments into rock.

In this case, fossils are usually seen in the rocks along the walls of the river and they are less likely seen in the tropical rainforest, let alone in the mouth of an active volcano. This environment is not capable of preserving the remains of ancient organisms since they are quickly destroyed by the hot temperature.

Since ferns usually grow abundantly in moist and shady areas, a rainforest is an ideal environment for these plants. There is a possibility that the dry, dusty state of Wyoming was actually a lush tropical rainforest back in the old days.

When the environment changes, the living organisms try to adapt to the new conditions. Those that are able to survive will reproduce and continue to evolve over time. These species, which evolved over time, have gone through multiple series of changes in their genetic and structural form, as well as their ecological roles. The way plants and animals behave and look makes them suited to their habitats.

On the other hand, living things or biological forces also shape the environment. They help form landscape as living organisms build soil from sand, rocks and other sediments. They also help recycle the nutrients in our planet and provide other ecosystem services.

The term background extinction is also referred to as the “everyday” or normal extinction because it occurs in a slow and steady rate, which represents stability and change. Ecosystems have a particular carrying capacity and nature has its own ways in controlling the population growth. This only shows that some species become extinct because all life cannot be sustained indefinitely on Earth.

If the Cenozoic era started from 11:39 PM and ended at midnight, it would have lasted for 21 minutes. Therefore, 21 minutes is equivalent to 1.46% of the 24-hour period.

Mass extinction occurs when the majority of the species go extinct in just a short period of time or a single event. On the other hand, background extinction is characterized by a slow and steady rate of extinction with an estimated of about 1 to 5 species per year. In this case, the newspaper article reported a background extinction since it said there were 12 species that have gon extinct for the past few years.

Furthermore, the cause of extinction can help evaluate the information. Mass extinction usually occurs when there are volcanic eruptions, collision of asteroids, and sea level rise. On the other hand, background extinction occurs due to ecological factors, such as diseases, climate change, deforestation, and competition.

After 14 billion years, 50% of the Thorium-232 sample would decay. As a result, half of the sample, which has a mass of 12.0 micrograms, would decay and form lead-208 once it reaches its stable state.

According to the graph, uranium-238 has a half-life of 4.5 billion years. This means that half of the uranium-238 would decay after 4.5 billion years. Since Earth is 4.5 billion years old, 1/2 of the radioactive element has already decayed. In this case, in order for the Earth to have 1/4 or 25% of the uranium-238, it must exist for 2 half-lives. The two half-lives of this element would be equivalent to 9 billion years.

In a pattern of punctuated equilibrium, the stability occurs in long periods of time, whereas the genetic changes occur in short episodes. The relationship between time and genetic changes indicates that species are often stable in terms of their morphology or structure. However, small variations may happen over a short period of time and this is often associated with speciation events, such as isolation.

The evidence in the example suggests that punctuated equilibrium is likely to continue as time goes on. As seen in the example, the pattern shows periods of stability and rapid changes.
In this case, we can expect that the stable periods are followed by the rapid burst of changes in species, which are triggered by the sudden or unexpected changes in the environment.

Fossils are usually deposited in layers; hence, they are found in sedimentary rocks. Fossils are organic sedimentary rocks that are formed when the remains of living organisms and other sediments settle at the bottom of a body of water, such as rivers and oceans. Eventually, after deposition, compaction and cementation will take place. These events will turn the sediments into rock.

The experiment by Miller and Urey has demonstrated the formation of organic molecules using a simulation that imitated the conditions of the Earth’s early atmosphere. First, the water was boiled to form water vapor. Then, methane, ammonia, and hydrogen are added into the water vapor and the gas mixture was bombarded with electricity to simulate a lightning. Later on, a cold water cooled the chamber and formed droplets. After seven days, the liquid that was collected was further examined. They were able to identify the presence of amino acids and other organic compounds in the liquid.

Therefore, the answer is yes. This experiment served as a proof that the organic compounds, which are responsible for sustaining life on Earth, were formed from the simpler compounds that are present in the Earth’s early atmosphere.

In a pattern of punctuated equilibrium, the stability occurs in long periods of time, whereas the genetic changes occur in short episodes. In this case, when there is little or no changes in the morphology or physical structure of species, this state is called stasis.

When Gould and Eldredge claimed that stasis is data, it indicates the absence of change does not mean that there is no evolutionary change. If stasis occurs due to a stabilizing selection, then It actually indicates that the phenotypes of organisms are changing between one generation to the next. When the genetic diversity is maintained, this would allow the species to adapt to different environmental conditions; hence, species can evolve at a later time.