Chapter 15 Biology

Explain what is meant by "evolution", and give an example? (Short)

Evolution is the process by which modern organisms have descended from ancient organisms. As time progresses, organisms are subject to new environmental conditions. These new conditions cause organisms to adapt to their environment, so they can survive, and produce offspring. For example, the land tortoises Darwin observed during his trip to the Galapagos each evolved from a single species of tortoise that lived on the South American mainland. Over time, as the environment changed, the species evolved to the modern species we know now, from adaptations made to survive in new conditions.

Theory

A well-supported testable explanation of phenomena that have occurred in the natural world.

reasoning of Thomas Malthus regarding human population growth, and its influence on Darwin's thinking.

Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Conditions in England reinforced his pessimistic view of the human condition. When Darwin read Malthus's work, he realized that this reasoning applied even more strongly to plants and animals than it did to humans. This was because most organisms produce far more offspring than humans, and if all those offspring were to survive, the world would be overrun with them.

circumstances leading to Darwin's book On the Origin of Species being published.

Darwin didn't immediately publish his work because it was very controversial at the time. After Darwin received a short essay from Alfred Russel Wallace (a fellow naturalist who had been doing field work in Malaysia), which summarized the thoughts on evolutionary change that Darwin had been mulling over for almost 25 years, Darwin had an incentive to publish his own work. At a scientific meeting later that year, Wallace's essay was presented together with some of Darwin's work. Eighteen months later Darwin published his book.

relationship between inherited variation and artificial selection. Also know examples of each

During artificial selection, nature provides the inherited variation that passes from parent to offspring, and humans select those variations that they find useful. Examples: Humans choosing which plant provides the most food (artificial selection), a larger root that one plant passes on to its offspring (inherited variation)

The Struggle for Existence

The struggle for existence means that members of each species compete regularly to obtain food, living space, and other necessities of life. In this struggle, the predators that are faster or have a particular way of ensnaring other organisms can catch more prey. Those prey that are faster, better camouflaged, or better protected can avoid being caught. This struggle for existence was central to Darwin's theory of evolution.

Srengths and weaknesses of modern evolutionary theory.

Scientific advances in many fields of biology, along with geology and physics, have confirmed and expanded most of Darwin's hypotheses. Today, evolutionary theory offers vital insights to all biological and biomedical sciences—from infectious-disease research to ecology. Evolution is often called the "grand unifying theory of the life sciences." Evolutionary theory continues to change as new data are gathered and new ways of thinking arise. Researchers still debate such important questions as precisely how new species arise and why species become extinct. There is also uncertainty about how life began.

Fossil

The preserved remains of ancient organisms.

Common decent

The principle that states if we look far enough back, the logic concludes, we could find the common ancestors of all living things.

Decent with modification

The principle that states over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habits, and as a result, look different from their ancestors. Each living species has descended, with changes, from other species over time.

Evolution

The process by which modern organisms have descended from ancient organisms.

Artificial selection

The process in which nature provided variation in organisms, and humans selected those variations that they found useful.

Survival of the fittest

The process where individuals with characteristics that are not well suited to their environment either die or leave few offspring, while individuals that are better suited to their environment survive and reproduce most successfully.

Using Science Skills

There will be five items in this section of the test pertaining to Darwin's observations of tortoise species on the Galápagos islands. Please study Figure 15-3 on textbook page 371 to prepare for this portion of the test.

Geographical Distribution of Living Species

After Darwin discovered that those little brown birds he collected in the Galapagos were all finches, he began to wonder how they came to be similar, yet distinctly different from one another. Each species was slightly different from every other species. They were also slightly different from the most similar species on the mainland of South America. He finally decided that all these birds could have descended with modification from a common mainland ancestor. Darwin found entirely different species of animals on the continents of South America and Australia. Yet, when he looked at similar environments on those continents, he sometimes saw different animals that had similar anatomies and behaviors. Species now living on different continents, had each descended from different ancestors. However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of natural selection. Because of these similar selection pressures, different animals ended up evolving certain striking features in common.

Adaptation

Any inherited characteristic that increases an organism's chance of survival.

significance of his comparisons to living organisms to fossils he collected.

At this time, people knew that fossils were remnants of ancient life. When he collected these fossils, he compared them to living things in his time, and because of many similarities, Darwin thought that the ancient species could have evolved into the modern one.

various types of evidence that support Darwin's theory of evolution.

Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development, or embryology.

Darwin's activities and observations while on board the Beagle, as well as to what these activities and observations lead.

Darwin collected plant and animal specimens every time the ship was anchored. During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time, which is now supported by a huge body of evidence, and has become the theory of evolution.

Survival of the Fittest

Darwin observed that a key factor in the struggle for existence was how well suited an organism is to its environment. Darwin called the ability of an individual to survive and reproduce in its specific environment fitness. Darwin proposed that fitness is the result of adaptations. An adaptation is any inherited characteristic that increases an organism's chance of survival. Successful adaptations, Darwin concluded, enable organisms to become better suited to their environment and thus better able to survive and reproduce. The concept of fitness, Darwin argued, was central to the process of evolution by natural selection. Generation after generation, individuals compete to survive and produce offspring. Because each individual differs from other members of its species, each has unique advantages and disadvantages. Individuals with characteristics that are not well suited to their environment—that is, with low levels of fitness—either die or leave few offspring. Individuals that are better suited to their environment—that is, with adaptations that enable fitness—survive and reproduce most successfully. Darwin called this process survival of the fittest. Because of its similarities to artificial selection, Darwin referred to the survival of the fittest as natural selection. In both artificial selection and natural selection, only certain individuals of a population produce new individuals. Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species' fitness in its environment.

Descent with Modification

Darwin proposed that over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. As a result, species today look different from their ancestors. Each living species has descended, with changes, from other species over time. He referred to this principle as descent with modification. Descent with modification also implies that all living organisms are related to one another. If we look far enough back, the logic concludes, we could find the common ancestors of all living things. This is the principle known as common descent. According to this principle, all species—living and extinct—were derived from common ancestors. Therefore, a single "tree of life" links all living things.

Fossil Record

Darwin saw fossils as a record of the history of life on Earth. Darwin, like Lyell, proposed that Earth was many millions—rather than thousands—of years old. During this long time, Darwin proposed, countless species had come into being, lived for a time, and then vanished. By comparing fossils from older rock layers with fossils from younger layers, scientists could document the fact that life on Earth has changed over time. Darwin argued that the fossil record provided evidence that living things have been evolving for millions of years.

What is the relationship between fitness and adaptation? Give a specific example of each to demonstrate this relationship. (Short)

Fitness is an organisms ability to survive and reproduce in its environment, while adaptations are inherited characteristics that increase an organism's chance of survival. Adaptations can increase the fitness level of organisms, making them better suited to survive. An adaptation could be a new generation of tortoises with longer necks. With these longer necks, the fitness of the organism would increase because the adaptation makes it easier to get hard to reach food.

Vestigial organ

Homologous structures that don't serve an important function, and are reduced in size to the point where they are just traces of homologous organs in other species.

Hutton and Lyell

Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present. Because of them, Darwin thought, if the earth has being changing over millions of years, couldn't organisms be doing the same thing?

conclusions made by Hutton

Hutton, proposed that Earth was much more than a few thousand years old because, the resulting rocks, mountains, and valleys that are formed from layers of rocks being formed and moved, are then shaped by a variety of natural forces, including rain, wind, heat, and cold temperatures. Most of these geological processes operate extremely slowly, often over millions of years.

Lamarck's hypothesis recording evolution

Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species. Tendency Toward Perfection: Lamarck proposed that all organisms have an innate tendency toward complexity and perfection. As a result, they are continually changing and acquiring features that help them live more successfully in their environments. Use and Disuse: Because of this tendency toward perfection, Lamarck proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways. Inheritance of Acquired Traits: Lamarck thought that acquired characteristics could be inherited. If an organism somehow altered its body structure, this would be passed on to the next generation, which over time would lead to change. Hypothesis: Lamarck was one of the first scientists to hypothesize evolution, and to realize that organisms are adapted to their environments.

Conclusions made by Lyell

Lyell stressed that scientists must explain past events in terms of processes that they can actually observe, since processes that shaped the Earth millions of years earlier continue in the present. Volcanoes release hot lava and gases now, just as they did on an ancient Earth. Erosion continues to carve out canyons, just as it did in the past. Lyell's work explained how large geological features could be built up or torn down over long periods of time. Lyell helped Darwin appreciate the significance of geological phenomena that he had observe

Struggle for Existence

Members of a species compete regularly to obtain food, living space, and other necessities of life.

Various observations regarding patterns of diversity Darwin made in comparing plant and animal species on his voyage.

On his voyage, he discovered that diversity was everywhere. Even is places that had habitats similar to other places, there was diversity. He also found that organisms were always very well suited to their environment.

observations he made of plants and animals on the Galápagos Islands.

On the Galapagos Islands, Darwin noted that although the islands were close together, they all had very different climates. Hood island had sparse vegetation, the higher islands had greater rainfall and different assortment of plants and animals. Isabela Island had rich vegetation. Darwin made observations of the land tortoises and marine iguanas of each island. The giant tortoises varied in predictable ways from one island to another. The shape of the tortoise's shell could be used to identify which island a particular tortoise inhabited. Darwin also saw several types of birds, which he collected several of. He noticed that the different birds had different shaped beaks. He thought some of the birds were wrens, some were warblers, and some were blackbirds.

Homologous structure

Structures that have different forms but develop from the same embryonic tissues.

Homologous Body Structures

Structures that have different mature forms but develop from the same embryonic tissues are called homologous structures. Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from common ancestors. Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. If the presence of a vestigial organ may not affect an organism's ability to survive and reproduce, natural selection would not cause the elimination of that organ.

Natural selection

Survival of the fittest, that results in changes in the inherited characteristics of a population, which increase a species' fitness in its environment.

Fitness

The ability of an individual to survive and reproduce in its specific environment.

Explain four areas of evidence that support Darwin's theory of evolution. Provide specific examples of each.

The areas that Darwin used to support his theory of evolution were, the fossil records, the geographical distribution of living species, homologous body structures, and similarities in embryology. During Darwin's time, scientists knew that fossils were the remains of ancient life, and that different layers of rock had been formed at different times during Earth's history. Darwin noticed that the sizes, shapes, and varieties of related organisms preserved in the fossil record changed over time. By comparing cephalopod fossils found in older layers of rock, with the fossils found in younger layers, scientists concluded that the species had changed over time. The geographical distribution of living species supports the theory of evolution because, Darwin observed that in similar ecological environments, no matter where they were located, species developed similar behaviors and physical characteristics. This supports Darwin's theory of evolution because it demonstrates that species will adapt to their specific environments over time. For example, the muskrat of North America, and the Coypu of South America are geographically far away, but are exposed to similar environments. Because of this, these organisms show similar characteristics and behaviors despite how far away they are. Homologous body structures, or structures that have different mature forms but develop from the same embryonic tissues, also supports Darwin's theory of evolution because, researchers during Darwin's time had discovered that the limbs of reptiles, birds, and mammals, arms, wings, legs, and flippers, vary greatly in form and function from one another, but are all constructed from the same basic bones. Because of the striking similarities between these organisms that are very different, Darwin thought that they must have evolved with modification from an original ancestor. The similarities in embryology further support Darwin's theory of evolution because it shows that although the organisms are similar, they are still related because they develop in the same way. The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. These common cells and tissues, growing in similar ways, produce homologous structures. For example, in their early stages of development, chickens, turtles, and rats look similar, providing evidence that they shared a common ancestry.

Similarities In Embryology

The early stages, or embryos, of many animals with backbones are very similar. This does not mean that a human embryo is ever identical to a fish or a bird embryo. However, many embryos look especially similar during early stages of development. Groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates. These common cells and tissues, growing in similar ways, produce the homologous structures.

Influence of Hutton and Lyell on Darwin

This understanding of geology influenced Darwin in two ways. First, Darwin asked himself: If the Earth could change over time, might life change as well? Second, he realized that it would have taken many, many years for life to change in the way he suggested. This would have been possible only if the Earth were extremely old.

summarize the major points of Darwin's theory of evolution, You should be able to apply these points to sample populations.

• Individual organisms differ, and some of this variation is heritable. Most humans like different from one another, and parts of these looks are passed on to human children. • Organisms produce more offspring than can survive, and many that do survive do not reproduce. Maple trees produce tons of seeds, but only a few survive. Only a few of those survivors because mature enough to reproduce. • Because more organisms are produced than can survive, they compete for limited resources. Two wolves that are both hunting prey will have to compete with each other, for who gets the prey. • Each unique organism has different advantages and disadvantages in the struggle for existence. Individuals best suited to their environment survive and reproduce most successfully. These organisms pass their heritable traits to their offspring. Other individuals die or leave fewer offspring. This process of natural selection causes species to change over time. If a wolf is adapted with sharp teeth, that increases its fitness, it will have a better chance to survive and pass on its trait for those teeth. Those teeth would be an advantage over other organisms. • Species alive today are descended with modification from ancestral species that lived in the distant past. This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life. Horses and zebras have a common ancestor, if you go far enough back. From this ancestor, both of these species emerged with modifications from the original.