Test: Unit 4 - Evolution

Charles Darwin found fossils that looked like ancient versions of living species. This suggests that these species existed long before the present day. If Earth was only 6000 or 2000 years old, as the other options suggest, it would not allow enough time for these ancient versions of species to exist. Therefore, the most reasonable explanation is that Earth is much more than 6000 years old.

Modern humans are members of the species Homo sapiens. This is the correct answer because Homo sapiens is the scientific name for modern humans. Homo neanderthalensis, Homo habilis, and Homo erectus are all different species of early humans that lived before modern humans evolved.

Geographic isolation refers to a type of reproductive isolation where physical barriers like oceans, mountains, or deserts prevent populations from interbreeding. These barriers create separate habitats for different populations, limiting their gene flow and leading to the development of distinct species over time. This isolation is crucial in promoting speciation and the formation of new species.

Scientists often take dirt samples from the area around the fossil find to help determine the relative age of the fossil. By analyzing the layers of sediment and the types of rocks present in the dirt samples, scientists can establish the geological context of the fossil. This information allows them to estimate the age of the fossil based on the age of the surrounding rock layers, providing valuable insights into the timeline of Earth's history and the evolutionary timeline of species.

Two organisms that are closely related would have very similar DNA sequences because they share a common ancestor. Over time, genetic mutations occur and accumulate, leading to slight differences in DNA sequences. However, organisms that are closely related will have fewer genetic differences compared to those that are distantly related. Therefore, their DNA sequences will be more similar, reflecting their shared evolutionary history.

Adaptation is the correct answer because it refers to a feature or trait that allows an organism to better survive in its environment. Through the process of natural selection, organisms with advantageous adaptations are more likely to survive and reproduce, passing on these beneficial traits to future generations. This enables the species to better adapt and thrive in their specific environment over time.

A species is a term for a group of similar organisms that can reproduce and produce fertile offspring. This means that individuals within a species are able to mate and produce offspring that are also capable of reproducing. This is a fundamental concept in biology and is used to classify and categorize different organisms based on their ability to interbreed and produce viable offspring.

Evolution is the correct answer because it refers to the process of biological change over time, where descendants gradually differ from their ancestors. This process occurs through mechanisms such as natural selection, genetic mutation, and genetic drift. Evolution is a fundamental concept in biology and explains the diversity of life on Earth. It is supported by extensive scientific evidence from various fields, including genetics, paleontology, and comparative anatomy.

The most common reason for finding only the skull of an ancient hominid is that scavengers can carry off the smaller bones much more easily. Scavengers such as hyenas, lions, and other animals are attracted to the remains of dead animals and often carry away smaller bones to their dens or feeding grounds. The skull, being larger and more solid, is less likely to be carried off and therefore more likely to be preserved and found by archaeologists. This is why it is common to find only the skull of an ancient hominid.

If an organism has a vestigial structure, it means that the structure is present in the organism but no longer serves a purpose. This suggests that the structure was functional in an earlier ancestor but has become obsolete in the current organism. Therefore, the correct answer is "earlier ancestor."

The correct answer is "a trace of an organism that existed in the past." Fossils are the preserved remains, impressions, or traces of organisms that lived in the past. These traces can include bones, shells, footprints, or even imprints of leaves or feathers. Fossils provide valuable evidence of past life forms and help scientists understand the history and evolution of different species.

The graph shows a shift in the population towards one extreme phenotype over time. This indicates that individuals with this extreme phenotype have a higher fitness and are more likely to survive and reproduce. This is characteristic of directional selection, where the average phenotype of the population changes in a specific direction.

Natural selection is the process by which individuals that are better adapted to their environment have a higher chance of survival and reproductive success. This leads to the passing on of advantageous traits to future generations, while individuals with less favorable traits are less likely to survive and reproduce. This process ultimately drives the evolution of species over time, as favorable traits become more common in a population. Sexual selection, genetic drift, and gene flow are other mechanisms that can influence the genetic composition of a population, but they are not specifically related to individuals being better suited to their environment.

The graph depicts disruptive selection. Disruptive selection occurs when individuals with extreme traits have higher fitness than individuals with intermediate traits. In the graph, the individuals with the highest and lowest trait values have the highest fitness, while those with intermediate trait values have lower fitness. This leads to the splitting of the population into two distinct groups with different trait values.

Members of the same species can exhibit variations, which refer to the differences in their physical traits or characteristics. These variations can be caused by genetic factors, environmental factors, or a combination of both. Variations are important for the survival and evolution of a species as they provide the raw material for natural selection to act upon. Through variations, individuals within a species can have different advantages or disadvantages in their ability to survive and reproduce, leading to the gradual change and adaptation of the species over time. Adaptations, mutations, and genetic isolation are related concepts but do not encompass the overall differences between members of the same species.

The two groups that most hominid species are classified into are Australopithecus and Homo. Australopithecus is a genus of early hominids that existed in Africa around 4 million to 2 million years ago, while Homo is a genus that includes modern humans and their closest extinct relatives. These two groups represent different stages of human evolution and are important in understanding the development of our species.

Hybridization refers to the process of crossing two different species that have common genes. This can result in the creation of hybrids, which possess a mixture of genetic traits from both parent species. Hybridization is often used in breeding programs to introduce desirable traits from one species into another, and it plays a significant role in the diversification of species.

Homo habilis is the correct answer because it is commonly referred to as "Handy Man." This species lived approximately 2.4 to 1.4 million years ago and is considered one of the earliest members of the genus Homo. Homo habilis is known for its stone tool-making abilities, which earned it the nickname "Handy Man." This species played a significant role in human evolution by demonstrating early tool use and technological advancements.

Oncology is the study of cancer, which does not directly provide evidence for evolution. Biogeography studies the distribution of species, which can provide evidence for evolution through patterns of migration and adaptation. Embryology studies the development of embryos, which can provide evidence for evolution through similarities in early stages of development across different species. Paleontology studies fossils, which can provide evidence for evolution through the discovery of transitional forms. Therefore, all the given branches of science except oncology provide evidence for evolution.

The evidence of modern whales having vestigial pelvic bones and lungs instead of gills suggests that their ancestors lived on land. This is because pelvic bones are typically found in land-dwelling animals for the attachment of hind limbs, and lungs are adapted for breathing air rather than extracting oxygen from water like gills. Therefore, it can be inferred that whales evolved from terrestrial ancestors and gradually adapted to an aquatic lifestyle over time.

Catastrophism is the theory that suggests that floods and earthquakes have occurred frequently in Earth's history. This theory proposes that these natural disasters are caused by sudden and violent events, rather than gradual processes. It suggests that the Earth's landscape has been shaped by catastrophic events, such as floods and earthquakes, rather than slow and continuous changes. This theory contrasts with uniformitarianism, which argues that geological processes occur gradually over long periods of time. Gradualism and natural selection are unrelated to the occurrence of floods and earthquakes.

Stabilizing selection is depicted in the graph because it shows that the individuals with average or intermediate traits have the highest fitness and are favored by natural selection. This leads to a reduction in the variation of the trait over time, as extreme traits are selected against.

Prosimians are considered the oldest living primate group because they are believed to have evolved earlier than other primate groups. They are small, nocturnal primates with characteristics such as a wet nose, large eyes, and a keen sense of smell. Prosimians include lemurs, tarsiers, and lorises. They are found primarily in Madagascar, Southeast Asia, and Africa. This group is considered to be more primitive compared to old world monkeys and hominids, which have evolved more recently. Gorillas, on the other hand, are a species within the hominid group and are not considered the oldest living primate group.

Hominids are a group of primates that includes humans and their closest relatives. One of the characteristics of hominids is walking upright, which distinguishes them from other primates who primarily walk on all fours. Another characteristic is the presence of opposable thumbs, which allow for fine motor skills and tool use. Hominids are also known for having large brains, which are associated with higher cognitive abilities. However, prehensile tails, which are tails that can grasp or hold objects, are not a characteristic of hominids.

A population refers to a group of individuals of the same species that exist in the same geographic area. This term is commonly used in ecology and biology to describe the number of organisms of a particular species in a specific location. It helps scientists understand the dynamics, distribution, and interactions within a species.

Genetic variation can occur when there is a random alteration in the DNA sequence of a gene, which is referred to as a mutation. This change can lead to differences in the genetic code, resulting in variations in traits and characteristics within a population. Mutations can be caused by various factors such as errors during DNA replication, exposure to mutagens, or spontaneous changes in the DNA sequence. These mutations can then be passed on to future generations, contributing to the overall genetic diversity within a species.

Allele frequency refers to the proportion or percentage of a particular allele in a population's gene pool. It is a measure of how common or rare a specific allele is within a population. This frequency can be influenced by factors such as natural selection, genetic drift, gene flow, and mutation rates. By studying allele frequencies, scientists can gain insights into patterns of inheritance, genetic diversity, and population dynamics.

Erasmus Darwin was Charles Darwin's poetic grandfather. Erasmus was a physician, natural philosopher, and poet who had a significant influence on Charles Darwin's thinking and scientific pursuits. He was known for his evolutionary ideas and poetic writings, which laid the groundwork for Charles Darwin's own theories on evolution. Therefore, Erasmus Darwin is the correct answer in this context.

The term "variation" refers to the differences in physical traits among individuals within a group. It signifies that individuals within a population may have different characteristics, such as height, eye color, or hair type. "Change" refers to a general alteration or modification, which may not necessarily involve physical traits. "Adaptation" refers to the process by which organisms adjust to their environment over time. "Species" refers to a group of organisms that can interbreed and produce fertile offspring. Therefore, "variation" is the most appropriate term to describe the differences in physical traits among individuals in a group.

The combined alleles of all the individuals in a population is called the gene pool. The gene pool represents the total genetic diversity within a population and includes all the different alleles for every gene present in the population. It is an important concept in population genetics and evolution as it influences the potential for genetic variation and adaptation within a population.

The development of a new color in a rose through artificial selection refers to the intentional breeding and selection of roses with desired traits by scientists. They selectively cross-pollinate roses with specific color traits, allowing only those with the desired color to reproduce. Over time, this process leads to the development of roses with the new color. This is different from natural selection, which is a process driven by environmental factors and survival advantages. Descent with modification refers to the gradual changes in species over generations, while overproduction refers to the production of more offspring than can survive.

Scientists have identified bipedal locomotion as the first step in human evolution. This means that the ability to walk upright on two legs was a crucial characteristic that distinguished early humans from their primate ancestors. Bipedalism allowed our ancestors to free up their hands for tool use and eventually led to the development of other human traits such as increased brain size, language, and art. Therefore, bipedal locomotion is considered the initial key adaptation that set humans on the path to becoming the species we are today.

Random mating is not a mechanism for evolution because it does not cause any changes in the gene pool of a population. In random mating, individuals mate without any preference for certain traits or characteristics, and there is no selection pressure acting on the population. As a result, the frequency of alleles in the gene pool remains unchanged over generations, and no new genetic variations are introduced. In contrast, natural selection, sexual selection, and genetic drift can all lead to changes in the genetic makeup of a population over time, driving evolution.

The fact that large, flightless birds are found on different continents supports the theory of evolution because it suggests that these birds evolved separately on each continent after their ancestors were separated by geographic barriers. This is known as convergent evolution, where similar traits evolve independently in different species due to similar environmental pressures. The presence of flightless birds in different locations indicates that these birds adapted to similar ecological niches on different continents, which is consistent with the concept of evolution.

In natural selection, the selective agent refers to the factor or condition in the environment that determines which individuals are more likely to survive and reproduce. It is the environment itself that acts as the selective agent, as it determines the traits and characteristics that are advantageous for survival and successful reproduction. The environment plays a crucial role in shaping the process of natural selection by favoring individuals with traits that are better suited to their specific ecological niche.

Paleoanthropologists study human evolution by analyzing various sources of evidence. They rely on fossilized bones to understand physical characteristics, endocasts of the brains to examine brain structures, and molecular clocks to estimate the timing of evolutionary events. However, they do not use written historical records as these records generally do not extend far enough back in time to provide information on human evolution. Therefore, written historical records are not a useful tool for paleoanthropologists in unraveling the mysteries of human evolution.

Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characteristics, which suggests that if an organism used a structure extensively, causing it to grow, that trait of the larger structure could be passed on to its offspring. This theory, known as Lamarckism, was one of the earliest attempts to explain how traits are inherited and was later proven to be incorrect by the discovery of genetics.

The correct answer is natural selection. Natural selection is the process by which individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to future generations. In this scenario, animals with a change in body color that allowed them to better hide from predators would have a higher chance of survival compared to those without the advantageous trait. Over time, the population would be dominated by individuals with the advantageous body color, illustrating natural selection.

The condition of "no overproduction" is not a requirement for Hardy-Weinberg equilibrium. Hardy-Weinberg equilibrium assumes that there is no natural selection, no sexual selection, no mutation, no genetic drift, and no gene flow. Overproduction refers to the idea that populations produce more offspring than can survive, leading to competition for resources and natural selection. However, this condition is not necessary for the maintenance of genetic equilibrium according to the Hardy-Weinberg principle.

Temporal isolation is a form of reproductive isolation in which two populations reproduce during different times of the year. This means that even if the populations are in the same geographic area and could potentially mate, they are unable to do so because they have different breeding seasons or times of reproductive activity. This can lead to the development of genetic differences and ultimately result in the formation of separate species.

A dead tree is not a type of fossil because it is a non-living organism that has undergone decomposition, whereas fossils are the preserved remains or traces of once-living organisms. Casts of a brain, molds of a foot, and fossilized "droppings" are all examples of fossils because they are the preserved remains or traces of organisms that have been mineralized over time.

Lucy, the ancient bipedal hominid, is a member of the species Australopithecus aferensis. This is determined based on fossil evidence and analysis, which has identified Lucy's skeletal features and characteristics as belonging to this species. Australopithecus aferensis is an extinct species of early hominids that lived in East Africa around 3.9-2.9 million years ago. Lucy's discovery has provided valuable insights into human evolution and our understanding of early hominid species.

Homo neanderthalensis is the correct answer because it is the only hominid species that co-existed with Homo sapiens in Europe. Homo erectus, Homo habilis, and Homo robustus did not overlap in time or geographical location with Homo sapiens in Europe.

The wing of an ostrich would be classified as a vestigial structure. This is because ostriches have wings, but they are unable to fly. The wings have become reduced in size and are no longer functional for flight, making them vestigial.

The Taung Child, an ancient bipedal hominid, is a member of the species Australopithecus africanus. This species is known for being one of the earliest known ancestors of modern humans. The Taung Child, discovered in South Africa in 1924, played a crucial role in providing evidence for the theory of human evolution. Its fossilized skull provided valuable insights into the physical characteristics and development of early hominids.

Radiometric dating is the correct answer because it refers to the process of determining the age of rocks or fossils by measuring the decay of radioactive isotopes. This method relies on the fact that certain isotopes decay at a known rate, allowing scientists to calculate the time since the rock or fossil formed. Relative dating is a different method that compares the age of one object to another, while speed dating is a social activity unrelated to dating fossils. Geologic time scaling is a term used to describe the division of Earth's history into different time periods.

Homo sapiens is not a monkey because it belongs to the species of great apes, specifically humans. Monkeys are a separate group within the primate order, characterized by their smaller size, long tails, and different anatomical features. While baboons, lemurs, and tarsiers are all examples of monkeys, Homo sapiens is not.

When an individual emigrates from its population, it leaves the population and takes its genetic material with it. This results in a decrease in the genetic diversity of the population because the gene pool becomes smaller. The genetic diversity of a population is important for its overall health and ability to adapt to changes in the environment. Therefore, when individuals emigrate, it reduces the genetic diversity and can have negative effects on the population's long-term survival and adaptability.

When a few individuals start a new colony, it most likely results in genetic drift through the founder effect. This is because when a small group of individuals establishes a new population, the genetic makeup of the founding individuals becomes the basis for the entire population. As a result, any genetic variations present in the founding individuals will become more prevalent in the new population, leading to genetic drift. This process can result in reduced genetic diversity and the potential for unique genetic traits to become more common in the population.

Homo erectus is believed to be the direct ancestor of modern humans. Fossil evidence suggests that Homo erectus lived approximately 1.9 million to 70,000 years ago and had characteristics similar to modern humans, such as a larger brain size and the ability to walk upright. This species is considered a crucial link in the evolutionary chain leading to Homo sapiens, making it the most likely option for humans' descendants.