Chapter 22: Descent with Modification: A Darwinian View of Life

What are the key features of natural selection?

(1.) Natural selection is a process in which individuals that have certain heritable traits survive and reproduce at a haigher rate than do other individuals because of those traits. (2.) Natural selection can increase frequency of adaptations that are favorable in a given environment. (3.) If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new condition, sometimes giving rise to new species.

What three key points do the S. Aureus and soapberry bug examples highlight about natural selection?

(1.) Natural selection is a process of editing, not a creative mechanism - A drug does not create resistant pathogens, it selects for resistant individuals that are already present in the population. (2.) In species that produce new generations in short periods of time, evolution by natural selection can occur rapidly - in just a few years (S. Aureus) or decades (soapberry bugs). (3.) Natural selection depends on time and place.

What are Charles Darwin's three key observations about life?

(1.) The striking ways in which organisms are suited for life in their environments (2.) the many shared characteristics (unity) of life (3.) the rich diversity of life

How have scientists directly observed evolution occurring in many instances?

(1.) the development of drug resistance in bacteria and other pathogens (2.) the fossil record has provided evidence for extinct species and for transitional forms of organisms, such as the ancestors of present-day horses (3.) homologies include similarities in structure, development, and DNA sequences in different organisms (4.) vestigial structures are homologous structures that have a reduced function or no function at all (Ex. The pelvic bones of whales) (5.) the geographic distribution of species, such as the high concentration of marsupial mammals in Australia, which provide evidence about common ancestors. In additions the endemic species found on many island chains yield information about evolution on those islands

During periods of rapid environmental change, what may happen to a species that was well-suited to the former environment?

(1.) the population may change so much in adapting to the new environment that is considered a new species (2.) the species may go extinct (3.) traits that were favorable in the original environment may be detrimental in the new environment (4.) individuals with particular traits that provide an advantage in the new environment will have higher reproductive success

During his voyage around the world, Darwin was inspired to think about evolution by _____________.

(1.) the unique organisms he saw in the Galápagos Islands (2.) the works of others such as Lamarck (3.) fossils he collected (4.) studying adaptations of organisms to their environment

How does evolution account for (a) the similar mammalian forelimbs with different functions and (b) the similar forms of the two distantly related mammals?

(A) Despite their different functions, the forelimbs of different mammals are structurally similar because they all represent modifications of a structure found in the common ancestor; thus, they are homologous structures. (B.) In this case, the similar features of these mammals represent analogous features that arose by convergent evolution. The similarities between the sugar glider and flying squirrel indicate that similar environments selected for similar adaptations despite different ancestry.

Stratum

(Plural, strata) A rock layer formed when new layers of sediment cover older ones and compress them.

Darwin's four postulates can be summarized as follows:

1. Individuals in a population vary in traits they posses. 2. Some trait differences are heritable. 3. Survival and reproduction success vare variable among individuals in a population. 4. Individuals with certain traits are more likely to survive and reproduce.

Evolutionary Tree

A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms

Vestigial structure

A feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors.

Fossil

A preserved remnant or impression of an organism that lived in the past.

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

What does it mean that organisms have a nearly universal genetic code?

A specific DNA sequence encodes the same information in one species as it would in nearly any other

Question 5: DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that:

A: Humans and chimpanzees share a relatively recent common ancestor.

Darwin's experiences during the voyage of the Beagle gave rise to his idea that new species originate from ancestral forms through the accumulation of ________. He reminded his theory for many years and finally published it in 1859 after learning that Wallace had come to the same idea.

Adaptations

All known organisms translate genetic information to produce protein molecules via the same genetic code. This finding strongly supports the hypothesis that ________.

All organisms are descended from a single common ancestor

Describe how overreproduction and heritable variation relate to evolution by natural selection.

All species have the potential to overreproduce - that is, to produce more offspring than can be supported by the environmnet. That ensures that there will be what Darwin called a "struggle for existence" in which many of the offspring are eaten, starved, diseased, or unable to reproduce for a variety of other reasons. Members of a population exhibit a range of heritable variations, some of which make it likely that their bearers will leave more offspring than other individuals (for example, the bearer may escape predators more effectively or be more tolerant of the physical conditions of the environment). Over time, natural selection resulting from factors such as predators, lack of food, or the physical conditions of the environment can increase the proportion of individuals with favorable traits in a population (evolutionary adaptation.

Explain how the following statement is inaccurate: "Antibiotics have created drug resistance in MRSA."

An environmental factor such as a drug DOES NOT create new traits, such as drug resistance, but rather selects for traits among those that are already present in the population.

______________ features share similar function, but not common ancestry, while __________ features share common ancestry, but not necessarily similar function.

Analogous; homologous

The Scala naturae, or scale of nature is based on the ideas of _________.

Aristotle believed that all living forms can be arranged on a ladder, or scale of increasing complexity.

The breeding of plants and animals for particular traits by humans is called ______.

Artificial selection - This is the mating of organisms with desirable characteristics. One example is the breeding of cows to produce offspring with higher milk yields.

Review the relationship between genotype and phenotype. Suppose that in a particular pea population, flowers with the white phenotype are favored by natural selection. Predict what would happen overtime to the frequency of the p allele in the population, and explain your reasoning.

As long as the white phenotype (encoded by the genotype pp) continues to be favored by natural selection, the frequency of the p allele will likely increase overtime in the population. If the proportion of white individuals increases relative to purple individuals, the frequency of the recessive p allele will also increase relative to that of the p allele, which only appears in purple individuals (some of which also carry a p allele).

Fossils show that dinosaurs originated 200-250 million years ago. Would you expect the geographic distribution of early dinosaur fossils to be broad (on many continents) or narrow (on one or few continents only)? Explain.

At the time that dinosaurs originated, Earth's land masses formed a single large continent, Pangaea. Because many dinosaurs were large and mobile, it is likely that early members of these groups lived on many different parts of Pangaea. When Pangaea broke apart, fossils of these organisms would have moved with rocks in which they were deposited. As a result, we would predict that fossils of early dinosaurs would have a broad geographic distribution (this prediction has been upheld).

Question 4: The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is most likely explanation for these data?

B: Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

Some drugs being developed specifically target and kill only S. Aureus; others slow the growth of MRSA but do not kill it. Because of how natural selection works and on the fact that bacterial species can exchange genes, explain why each of these strategies might be effective.

Both strategies should increase the time that it takes S. Aureus to become resistant to a new drug. If a drug that harms S. Aureus does not harm other bacteria, natural selection will not favor resistance to that drug in other species. This would decrease the chance that S. Aureus would acquire resistance genes from other bacteria -thus slowing the evolution of resistance. Similarly, selection for resistance to a drug that slows the growth but does not kill S. Aureus is much weaker than selection for resistance to a drug that kills S. Aureus - again slowing the evolution of resistance.

Scientific hypotheses must be testable. Applying this criterion, are Cuvier's explanation of the fossil record and Lamarck's hypothesis of evolution scientific? Explain your answer in each case.

By this criterion, Cuvier's explanation of the fossil record and Lamarck's hypothesis of evolution are both scientific. Cuvier thought that species did not evolve over time. He also suggested that sudden, catastrophic events caused extinctions in particular areas. These assertions can be tested against the fossil record. Lamarck's principle of use and discuses can be used to make testable predictions for fossil groups such as whale ancestors as they adapted to a new habitat. Lamarck's principle use and disuse and his associated principle of the inheritance of acquired characteristics can also be tested directly in living organisms.

3: Within six months of effectively using methicillin to treat S. Aureus infections in a community, all new S. Aureus infections were cause by MRSA. How can this best be explained?

C. Some drug-resistant bacteria were present at the start of the treatment, and natural selection increased their frequency

Evidence from molecular biology supports the theory of evolution by demonstrating that ___________.

Closely related organisms have more similar DNA and proteins than more distantly related organisms

The modern idea of extinction as a common occurrence in Earth's history was first proposed in the early 19th century writings of ______________.

Cuvier

_______________ advocated catastrophism, speculating that extinctions apparent the fossil record corresponded to a catastrophe, such as a flood or drought.

Cuvier

2: What observation helps Darwin shape his concept of descent with modification?

D: South American temperature plants are more similar to the tropical plants of South America than to the temperate plants of Europe.

Why was the age of the Earth important for Darwin's ideas about evolution?

Darwin thought that descent with modification occurred as a gradual, steplike process. The age of Earth was important to him because if Earth were only a few thousand years old (as conventional wisdom suggested), there wouldn't have been sufficient time for major evolutionary change.

Evolution

Descent with modification; the idea that living species are descendancts of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation

Seemingly dissimilar organisms such as hummingbirds, humans, and whales have similar skeletal structures. This most directly suggested to biologists that ___________.

Dissimilar organisms might have evolved from a distant, common ancestor

Charles Darwin hypothesize that the Galapagos had been colonized by organisms that had strayed from South America, and then __________, __________.

Diversified, giving rise to new species on the various

What is an example of convergent evolution?

Dolphins and sharks have similar streamlined body shape.

A challenge to tradition (pre-1860) ideas about species came from embryology, when it was discovered that __________.

Embryos of dissimilar organisms, such as sharks and humans, resemble each other

__________________________ can explain some biogeographic patterns.

Evolutionary Theory

_______ are hypotheses that summarize our current understanding of patterns of descent.

Evolutionary trees

Lamarck hypothesized that species _________, but the underlying mechanisms he proposed are not supported by evidence.

Evolve

Animals that possess homologous structures probably ______________.

Evolved from the same ancestor

The wing of a bat is homologous to the _________ of a whale.

Flipper

Cuvier studied _______ but denied that evolution occurs; he proposed that a sudden catastrophic events in the past caused species to disappear from an area.

Fossils

____________ show that past organisms differed from living organisms, that many species have become extinct, and that species have evolved over long periods of time; ________ also document the evolutionary origin of new groups of organisms.

Fossils; fossils

Hutton and Lyell thought that geologic change could result from _________________ that operated in the past in the same manner as they do today.

Gradual mechanisms

At the time Darwin voyaged on HMS Beagle, the popularly accepted theory in Western culture that explained the origins of Earth's plants and animals held that the various species ___________.

Had been created by divine intervention a few thousand years before

Analogous

Having characteristics that are similar because of convergent evolution, not homology

What is a true statement about Charle's Darwin?

He proposed natural selection as the mechanism of evolution.

What is an example of the process of evolution?

Herbivory - involved in the process of natural selection, since populations of herbivores must become adapted to particular plant species on which they feed

On an evolutionary tree __________.

Homologous characteristics form a nested pattern

The underlying skeletons of the arms, forelegs, flippers, and wings of different mammals are __________ that represent variations on a structural theme that was present in their common ancestor.

Homologous structures

Organisms share characteristics because of common descent (_____________) or because natural selection affects independently evolving species in similar environments in similar ways (__________).

Homology; convergent evolution

How did Hutton's and Lyell's ideas influence Darwin's thinking about evolution?

Hutton and Lyell proposed that geologic events in the past were caused by the same processes operating today, at the same gradual rate. This principle suggested that Earth must be much older than a few thousand years, the age that was widely accepted in the early 19th century. Hutton's and Lyell's ideas also stimulated Darwin to reason that the slow accumulation of small changes could ultimately produce the profound changes documented in the fossil record. In this context, the age of Earth was important to Darwin, because unless Earth was very old, he could not envision how there would have been enough time for evolution to occur.

Adaptations

Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment

A heritable trait is one that ______.

Is determined at least in part by genes passed from parents to offspring

To describe evolution as a "scientific theory" means that _______.

It is a broad model that is supported by many observations and much experimental evidence

______________ contended that human suffering is a product of humans reproducing faster than food and other resources can increase. This is actually a characteristic of many life-forms on Earth.

Malthus

What is a key observation that must be explained in a unifying theory about life?

Many basic characteristics are shared by living things.

When they were first sold, aerosol insecticides were highly effective in killing flies and mosquitoes. Now, several decades later, a much smaller proportion of these insects die when sprayed. The reason fewer insects die when they are sprayed is that _________________.

Many mosquitoes today are descendants of mosquitoes with insecticide-resistant characteristics

Darwin proposed that life's diversity arose from ancestral species through _______, a departure from prevailing views.

Natural selection

In the Origin of Species, Darwin proposed that over long periods of time, descent with modification produced the rich diversity of life through the mechanism of ________.

Natural selection

Researchers have directly observed ______________ leading to adaptive evolution in many studies, including research on soapberry bug populations and on MRSA.

Natural selection

In Darwin's descent with modification __________.

Natural selection can improve the match between an organism and its environment

Does the ability of a Mycobacterium tuberculosis cell to infect a new host depend on its drug-resistant phenotype?

No, drug-susceptible cells and drug-resistant cells are equally likely to infect a new host.

What insight did Darwin gain from reading Thomas Malthus' essay on human suffering?

Organisms have the capacity to produce more offspring than the environment can support.

Because he was well aware of the effect his theory of evolution would have on the public and on the Church of England, Darwin delayed publishing his work for several decades while he gathered additional evidence. After invoking selective breading of domesticated species as evidence that groups of organisms are capable fo change, he then proposed that natural populations can change as well. On which two lines of evidence did he base this proposal?

Organisms within a population vary, and all populations produce more offspring than can be supported by the environment, resulting in competition for survival within the population.

How does the concept of descent with modification explain both the unity and diversity of life?

Organiusms share characteristics (the unity of life) because they share common ancestors; the great diversity of life occurs because new species have repeatedly formed when descendant organisms gradually adapted to different environments, thereby becoming different from their ancestors.

We can view evolution in two related but different ways: as a ___ and as a ______. The ______ of evolutionary change is revealed by data from many scientific disciplines, including biology, geology, physics, and chemistry. These data are facts-they are observations about the natural world- these observations show that life has evolved over tine. The _______ of evolution consists of the mechanisms that cause the observed pattern of change. These mechanisms represent natural causes of the natural phenomena we observe.

Pattern; process; pattern; process

The smallest unit that can evolve is a(n) ________.

Population

According to the theory of evolution, anatomical and molecular homologies should __________.

Produce similar patterns of evolutionary relatedness

Charles Darwin __________.

Proposed natural selection as the mechanism of evolution

Endemic

Referring to a species that is confined to a specific geographic area.

Vestigial organs are _________.

Remnanats of structures that were useful to an organism's ancestors, but which are now non-functional or show reduced function

A biologist observed that a particular plant species is found in a forest but not in a nearby meadow. She hypothesizes that the plants could grow in the meadow but are not found there because their seeds have yet to land in the meadow. Which of the following would be the most appropriate way to scientifically evaluate this hypothesis?

Scattering seeds in several areas of the meadow and observing whether they start to grow

At the time Charles Darwin sailed on HMS Beagle, ________.

Several biologists had proposed that species might change over time, but none had suggested a convincing mechanism that might cause the change

Homology

Similarly in characteristics resulting form a shared ancestry

How did some strains of Staphylococcus aureus become resistant to antibiotic drugs?

Some members of the bacteria population must have had a genetic variation that made them resistant to antibiotics, and these bacteria had greater reproductive success than sensitive individuals.

Lyell's principle of uniformitarianism ____________.

Strongly influenced Darwin's view of how living organisms could change overtime

Homologous structures

Structures in different species that are similar becuase of common ancestry

Carolus Linnea's is considered to be the founder of __________, and he _____________.

The binomial classification system; thought that resemblances among different species reflected the pattern of their creation

In the United States today, about half of the corn crop is genetically engineered with a protein that is toxic to corn borers, an insect pest of corn. What condition would be necessary for evolution of resistance to the toxic protein to occur in the corn borer?

The corn borer must have or generate (by mutation) heritable variation in resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistance corn borers.

What statements describes the evolution by natural selection of Mycobacterium tuberculosis bacteria in their new environment?

The drug-resistance trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin.

An example of ongoing natural selection that dramatically affects humans is _____________.

The evolution of drug-resistant pathogens (disease-causing organism and viruses)

Convergent evolution

The evolution of similar features in independent evolutionary lineages

If you discovered a fossil of an extinct mammal that lived high in the Andes, would you predict that it would more closely resemble present-mammals from South American jungles or present-day mammals that live high in Asian mountains? Explain.

The fossil mammal species (or its ancestors) would most likely have colonized the Andes from within South America, whereas ancestors of mammals currently found in Asian mountains would most likely have colonized those mountains from other parts of Asia. As a result, the Andes fossil species would share a more recent common ancestor with South American mammals than with mammals in Asia. Thus for many of its traits, the fossil mammal species would probably more closely resemble mammals that live in South American jungles than mammals that live on Asian mountains. It is also possible, however, that the Andean fossil mammal could resemble a mammal from the mountains of Asia because similar environments had selected for similar adaptations (even though the fossil and Asian species were only distantly related to one another).

Summarize the different lines of evidence supporting the hypothesis that cetaceans descended from land mammals and are closely related to even-toad ungulates.

The hypothesis that cetaceans originated from a terrrestial mammal are closely related to even-toed ungulates is supported by several lines of evidence. For example, fossils document that early cetaceans have hind limbs, as expected for organisms that descended from a land mammal; these fossils also show that a cetacean hind limbs became reduced over time. Other fossils show that early cetaceans had a type of ankle bone that is otherwise found only in even-toad ungulates, providing strong evidence that even-toed ungulates are the land mammals to which cetaceans are most closely related. DNA sequence data also indicates that even-toad ungulates are the land mammals to which cetaceans are, most closely related.

Field study: Can a change in a population's food source result in evolution by natural selection?

The museum specimens and contemporary data suggest that a chance in the size of the soapberry's bug's food source can result in evolution by natural selection for a corresponding change in beak size.

A population of zooplankton is exposed to a smaller number of predatory fish that feed on the larger-sized (adult) zooplankton. Which of the following predictions would most likely occur based on the principles of natural selection?

The population will come to contain adult zooplankton that reach sexual maturity when they are relatively small.

Paleontology

The scientific study of fossils

Biogeography

The scientific study of the past and present geographic distribution of species.

Artificial selection

The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

Pangaea

The supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the land masses of Earth together.

What did Darwin observe about species on islands?

They are often closely related to species from the nearest mainland or neighboring islands.

True or Fale? It would be difficult to assess whether the drug-susceptible or drug-resistant phenotype in a population of Mycobacterium tuberculosis was more fit in an environment without antibiotics.

True

Darwin originally defined evolution as __________.

descent with modification

1: Poorly adapted individuals never produce offspring ________ (is/is NOT) an observation or inference on which natural selection is based.

is NOT