According to Darwin, the fossils of glyptodont are considered as an ancient armadillo because they resemble the living armadillos in the present. These fossils serve as a strong evidence for evolution and ultimately helped Darwin to know how species had changed over the years.

c. species vary over time

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 what the Earth was like in the past.

a. fossils

The big idea about evolution is that it explains how different species have evolved from their ancestors. One example that shows an evolution in species is the peacock’s colorful feathers. A few thousand years ago, not all male peacocks have brightly colored feathers. However, since female peacocks always choose a male which has the fanciest or the brightest colored feathers, the genes responsible for the colorful feathers started to get passed on to the next generation. As a result, males peacocks have fancier feathers now than the ones that existed a thousand years ago.

The theory of evolution, which was proposed by Charles Darwin, explains how different species have evolved over time from their ancestors. Darwin discovered that the fossils of some animals that are already extinct have similarities to the living species.

Ostriches and emus are related as they are members of a diverse group of large flightless birds that are native to the Southern Hemisphere. Emus, which are endemic to Australia, are smaller and lighter when compared to ostriches, which are native to Africa. Moreover, ostriches have two toes, whereas emus have three toes. However, they are both fast runners.

The similarities between these two flightless birds reveal that a convergent evolution took place. They may look alike but they are not closely related. They are two different species that have common features or adaptations because they live in a similar habitat and they inhabit similar ecological niches.

Darwin discovered that the traits of some tortoises varied among the different islands of Galapágos. For an instance, the structure of the tortoise indicates their adaptation to different habitats. Since Hood Island has sparse vegetation, the tortoise inhabiting the island has a longer neck in order to reach the vegetation. On the other hand, the tortoise living in the Isabela island, which has lush vegetation, has a shorter neck.

The reason for this is because Darwin was able to notice the three important patterns of biodiversity, which tell us that species vary globally, locally, and over time. He observed how different animal species that were ecologically similar simply because they live in similar habitats. Moreover, related species often lived in different habitats within a local region or area. He also found out that some extinct animals share similarities with the living species today. This is an indication that species are evolving over time. These observations and patterns are all the evidence the gathered in order to prove the evolution of species through natural selection.

Thomas Malthus proposed the relationship between population and resources. He suggested that a high population growth may lead to overpopulation and it would negatively affect the supply of food and living space. As a result, the population would outgrow the resources. Since the human population cannot grow indefinitely, war, famine, and disease would take place to stop the growth.

c. disease, war, or famine

Choices A, B, and C are all incorrect. The process by which a farmer can breed cows that produce the most milk is called artificial selection, which is also known as selective breeding. This term is defined as the process of breeding certain animals and plants to produce an offspring with a desirable or useful trait. Therefore, the answer is D.

d. artificial selection

Some species of potato plants would carry useful genes like resistance to pests and diseases. In some farms, these useful traits are transferred to the offspring of the crop plants using selective breeding. In this way, farmers can increase the value of crop plants.

Other examples of selective breeding would include the following:
a. Selecting a fast and strong horse to breed for horse racing
b. Breeding hens that lay bigger eggs
c. Cultivating two different types of flowers and produce a hybrid flower

Lamarck made a hypothesis which says that animals change their bodies so they can better fit in their environment. He believed that the acquired characteristics of an organism are passed from one generation into the next. According to Lamarck, the curved beak of a flamingo could have been an acquired characteristic from its life experiences.

Lyell explained that the processes which shaped the Earth from the past are still continuing until the present time and observing these events may be the key to understanding our world even better. This idea helped Darwin to grasp the two big ideas behind geology: (1) Since Earth could change over time, it was possible that life could change too. (2) This also means that it would take a lot of years for life to change in the way he actually thought and suggested. In that case, the Earth is extremely old.

In biology, the term adaptation refers to the process in which individuals undergo a genetic or structural change to become better suited to its new environment. The akiapola’au’s curved beak is adapted to their habitat and flora. Since their natural habitat consists of moist and wet forests, these birds forage tree trunks and branches. Their curved beaks are used to probe insects and larvae and they occupy the woodpecker niche in their habitat.

a. an adaptation

In biology, the term fitness represents an individual’s ability to adapt and survive life. If an individual is able to live longer and reproduce more offspring in a given environment or condition, it has a high fitness.

c. evolutionary fitness

In biology, the term natural variation refers to the differences among cells, organisms, or groups of species. Due to the differences or variation among individuals, it allows the process of natural selection to take place. Variation among species can help individuals to adapt to certain conditions. As a result, those organisms which are not able to adapt will eventually die, whereas organisms which can survive will be able to reproduce. This event causes evolution to occur.

The living species that descended and underwent changes over time have experienced changes in their structures, habitat, and niches. This event is referred to as the principle of descent with modification. This principle explains how the species in the present have gone through multiple series of changes in their genetic and structural form. An example of this is when parents pass their genes to their offspring. However, the offspring do not get the exact same copy of the parents’ genes but instead, they are combined. When the combinations of genes are made, there might be changes or mutations which may occur along the way. As a result, genetic variation and evolution happened.

Not all adaptations are just purely based on physical features or structures. Some adaptations are also seen through the organism’s behavior. Behavior affects evolution when the differences among species in terms of their interbreeding methods such as courtship rituals and reproductive strategies are taken into account. For example, animals with a similar mating ritual tend to mate, whereas those animals with different mating rituals do not mate with each other simply because they are unable to respond. As a result, their behavioral patterns have made each group isolated from each other and the fitness of each group may come into the picture. Through natural selection, the group who survives will become more common over time and this allows the behavior of the species to undergo evolution too.

Intermediate fossil forms serve as the transitional stage between the ancestral form and its living descendants. These transitional fossils show how organisms have changed over time. For example, the Aetiocetus is the intermediate form between the modern gray whales and its ancestors, which are called Pakicetus. The main structure which can be observed in these species that has changed over time is the nostrils. The nostrils in the Pakicetus can be seen in front of the skull. In Aetiocetus, the nostrils are situated at the middle of the skull. In the gray whales, the nostrils are at the top of the skull.

Therefore, the answer is A.

a. how organisms changed over time

Choices B, C, and D are incorrect.

Homologous structures usually have the same embryonic tissues during its development stage due to the same evolutionary origin. However, when these tissues mature, their structures appear differently. On the other hand, analogous structures are organs that perform a similar function but they came from a different evolutionary origin.

The wings of a bat came from an ancestor that has forelimbs, whereas bees share a common ancestor with wasps and ants. In this case, the wings of the bat and the wings of the bees are analogous but not homologous. Therefore, the answer is A.

A. analogous structures

Dolphins have pelvic or hip bones when their ancestors walked on land millions of years ago. Over the years, their ancestors evolved and lost their hind limbs because these structures served no purpose anymore. The hip bones remained and they are called vestigial structures. These are inherited structures that do not serve a particular function. This is similar to the human’s tailbone.

Homologous structures usually have the same embryonic tissues during its development stage due to the same evolutionary origin. However, when these tissues mature, their structures appear differently. An example of two animal structures that are homologous include the limbs of the bats and the limbs of the birds. Bats have flaps of skin in their fingers and arms, whereas the birds contain feathers that extend in their arm. However, these two animals did not come from an ancestor that has wings. Birds and bats actually evolved from a common ancestor that has forelimbs.

The genetic code and homologous molecules are used to trace the evolution at a molecular level. Since living things are able to pass on genetic information to offspring, the genetic codes of living things exhibit a similar structure. Moreover, there are also homologous molecules that are found in living things. One specific example is the protein cytochrome c. It is a molecule that is responsible for cellular respiration.

The Grants’ worked on Darwin’s hypothesis by using a medium ground finch on one of the islands in Galápagos. They have conducted an observation on the finches’ offspring, beak structure, feeding, and mating behavior. They have discovered that the size of the bird’s beak is related to the way it feeds itself and the way they mate with other birds. According to the couple, evolution happened within just a span of a couple years. This opposed the notion of Darwin that evolution has occurred over thousands of years ago from a common ancestor.

Darwin integrated biogeography, anatomy, geology, chemistry, molecular biology, and genetics to support his theory of evolution. He had sufficient data to support his claim, wherein all his conclusions were derived from all the observations he made during his five-year voyage. When he saw different animal and plant species, he didn’t just identify them but he also studied them in action. He spent two decades to collect more information before he published his ideas and theories in a book.

Hemoglobin, which is a blood molecule that contains iron, is responsible for oxygen transport. In this case, vertebrates who have hemoglobin have a specialized respiratory function that involves blood and oxygen transport. This indicates how the lungs and gills of vertebrates have evolved over time.

The ability of microorganisms to withstand antibiotics shows an evolution via natural selection. The effect of the antibiotic is like an environmental pressure. Those bacteria that are not able to adapt will die, whereas those that contain genes that are able to resist the antibiotics are going to survive and reproduce. In this case, the genes, which are responsible for the resistance, are passed on to their offspring. As a result, the next generation becomes fully resistant to the antibiotics.

The brown mice are better adapted to this kind of habitat. Unlike the white mice, their brown color blends well with the environment. Since they are living in a wild habitat, their color is an effective defense against predation.

When natural selection takes place, it will favor those species that are able to survive and reproduce. The evolutionary success of organisms is increased when their fitness is high. In this case, the change in fitness can be caused by the environment.

For example, if we would place the mice in a different environment, their fitness level would certainly change. Brown mice are more fit than white mice when they are both placed in a grassy landscape. On the other hand, when they are both placed in a light-colored environment, white mice are able to avoid predators better than the brown mice.

Migration due to the changes in the environment and behavior can isolate the mice from each other. Due to the isolation of the smaller population from the original and larger population, natural selection and speciation would happen. If the smaller population could not adapt to their new environment, a natural selection will occur. Only those individuals with a greater fitness would survive and reproduce. As a result, the remaining ones will have a different gene pool from the other group. This event leads to speciation.

These events are all important when it comes to genetic variation since they can produce new types of species. Moreover, having different gene combinations can increase the survival rate of species. It can help to recover the loss of biodiversity in the ecosystem.

In evaluating the model of inheritance that is based on Lamarck’s ideas, these kinds of information can be used as pieces of evidence:

1. The ancestors of the wading bird have a range of leg lengths, which consists of short, average, and long leg length.

2. Inheritance is the process of transferring the natural characteristics and the genetic information of parents into their offspring. Oftentimes, individuals from the same family have similar characteristics.

3. Acquired traits cannot be passed down using the genes. Life experiences and skills are not transferred to the offspring.

4. Adaptation refers to the process in which living species undergo a genetic or structural change to become better suited to its new environment. An example of an adaptation is the akiapola’au’s curved beak. Since their natural habitat includes moist and wet forests, these birds forage tree trunks and branches and their curved beak is used to probe insects and larvae.

5. Organisms which are not able to adapt will eventually die, whereas organisms which can survive will be able to reproduce. This event causes evolution to occur.

6. The living species that descended and underwent changes over time have experienced changes in their structures, habitat, and niches. This event is referred to as the principle of descent with modification. This principle explains how the species in the present have gone through multiple series of changes in their genetic and structural form.

Darwin studied how the farmers bred plants and animals. He discovered that nature provides the variation and humans determine the useful traits of the organisms. To test this hypothesis, he bred plants and pigeon varieties. By choosing which pigeons to mate, he was able to produce offspring that has unusual traits.
Through this experiment, he found out the presence of inherited variation in most plant and animal species. He claimed that it is an essential factor that drives the evolution.

The new species would exhibit characteristics that suit the desert environment and similar traits with other vertebrates and desert animals. These characteristics may include:

a. thin body fur which allows heat loss
b. absence of sweat glands and concentration of urine to avoid dehydration
c. burrowing or staying under the rocks to avoid direct sunlight
d. nocturnal
e. Hox gene clusters would be the same with other vertebrates
f. share homologous traits or structures with other vertebrates
g. share analogous traits or structures with other desert animals

Species vary globally, wherein this pattern is exhibited when 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. Rheas, ostriches, and emus are related in such a way that they are members of a diverse group of large flightless birds that are native to the Southern Hemisphere. Emus, which are endemic to Australia, are smaller and lighter when compared to ostriches, which are native to Africa. Moreover, ostriches have two toes, whereas emus and rheas have three toes. However, they are all both fast runners.

The similarities and differences 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.

According to Darwin, the changes in the adaptations of species are caused by some changes in the environment. If old traits become not suited to the new environment, evolution via natural selection happens. One example is the way the color of the moths adapted to the changing environment during industrialization. Pollution has stained trees and caused the color of the moths to become darker. Because of this, it protected them against the birds that prey on them. Instead, the birds consumed light-colored moths, which resulted in a decline in the population of light-colored moths. This is the reason why there are more dark-colored moths in urban areas.

According to the graph, the perch diameter of brown anoles has declined over the years. In the year 1996, the diameter was 6 mm. However, when 1999 came, the perch diameter decreased to 3 mm.

Since most predators hunt and colonize the ground perches, the brown anoles stay several feet off the ground and abandon the ground perches to escape their predators. When the perch height increases, the perch diameter decreases. Therefore, the decrease in the diameter of the perch was likely due to the predation of the larger lizard predator.

The population of brown anoles would decline over time because they are hunted by the predators. In this case, natural selection would occur. Those species that have a higher fitness, which possesses small size, great reflexes, agility and speed to escape the predators, are likely to survive and reproduce. As a result, the next generation of anoles becomes lighter and faster to enable them to move far away from the predators and to inhabit branches that have a small diameter. Moreover, the feeding behavior of brown anoles can change over time. Since they inhabit the higher branches, they would consume insects in this part of the tree.

Dogs and penguins have the least numbers of cytochrome c that are different from the chimpanzees. The reason for this is because dogs, penguins, and chimpanzees are vertebrates. They all share some similar structures since they are related in terms of their evolutionary relationship. On the other hand, moths are classified as insects and yeast is classified as fungi. They have simpler features and structures when compared to vertebrates, which are more complex organisms. This is the reason why there were huge differences between them and chimpanzees at a molecular level.

Yeast is a single-celled fungus, whereas chimpanzees are multicellular organisms. In this case, a yeast would contain a different number of amino acids when compared to chimpanzees. Moreover, chimpanzees are more complex organisms, which is why their cells need a large amount of energy, which is produced during cellular respiration, to perform their functions and other life processes.

In evolution, genetics play a vital component since traits are transferred into the offspring through inheritance. This is the reason why genetic code and homologous molecules are used to trace the evolution at a molecular level. Since living things are able to pass on genetic information to offspring, the genetic codes of living things, such as plants, fungi, and animals, exhibit a similar sequence.

Moreover, there are also homologous molecules that are found in living things. One specific example is the protein cytochrome c. It is a molecule that is responsible for cellular respiration. Chimpanzees are considered the closest relatives of humans because they both share an equal number of cytochrome c and they share 99% of the human’s DNA.

Natural selection takes place in the following conditions:
1. There should be a struggle for existence, which means that there are more individuals that are born than can survive.
2. There should be a presence of heritable variation.
3. There should be a different fitness rate among individuals to initiate the “survival of the fittest.”

The theory of evolution explains how different species have evolved from ancient organisms. Evolution via natural selection can be observed using biogeography, which tells us the habitats of plant and animal species and their ancestors; the body structure and embryos, which tell us the homologous, analogous and vestigial structures; the fossil evidence, which tell us how modern species have evolved from their extinct ancestral origins; and the genetics and molecular biology of organisms.

From the observations and evidence that Darwin has gathered, he concluded that the three patterns of biodiversity are caused by some natural processes that happen in the environment, wherein these events and changes drive evolution to take place. These patterns also help us understand how modern organisms have evolved over time.

More importantly, evolution is a great reminder that life is always changing. It doesn’t only tell us what happened in the past, but it can also help us overcome the challenges we might face in the future, such as the deadly new viruses and drug-resistant microorganisms.