Chapter 22

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Campbell Biology
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What are the 3 key observations about life?

Organisms are suited for their environments, there are shared characteristics of life (unity), and there are differing characteristics of life (diversity)



"Descent with modification", the idea that current species are descendants of ancestral species that are different than themselves. This is the explanation of the 3 keys of life.


Compare the PATTERN of evolutionary change and the PROCESS of evolutionary change

Pattern - revealed by data/facts (observations of the natural world).

Process - consists of the mechanisms that produce the observed pattern of change. (these mechanisms represent natural causes of the natural phenomena we observe).


What did the Greek philosophers, before Darwin, suggest?

That life changed over time


How did Aristotle view species?

he viewed species as unchanging and believed that each form of life had a permanent place on a "ladder" of lifeforms based on complexity.


What was Aristotle's view consistent with?

The Old Testament (species designed by God, suited for environments because God made them perfect)


What did Carolus Linnaeus develop?

in order to classify life's diversity he developed a binomial format for naming species. He adopted a "nested" classification system in which similar species were grouped into increasingly general categories. (similar species in same genus, similar genera in same family, etc) (1700s)


What did Darwin base classification on?

Evolutionary relationships



remains of organisms from the past



super-imposed layers of rock covered by new layers of sediment (fossils in stratum show the organisms that existed at the time that that layer was formed)



the study of fossils


What changes from one layer of stratum to the next?

Older stratum has fossils that are dissimilar to current life forms, and from one layer to the next new organisms' fossils appeared and old disappeared.


Who was Georges Cuvier? What did he infer?

He developed paleontology, he inferred extinctions but not evolution. (Thought each boundary between stratum represented a catastrophic event that destroyed many species in an area and that it was later repopulated by different species migrating from different areas)


Who were James Hutton and Charles Lyell? How did their work relate to one another?

Hutton was a geologist who proposed the geological features formed due to gradual mechanisms over time. Lyell proposed that the same geologic processes that happened in the past are also happening today, at the same rate. (early 1800s)


How did Hutton and Lyell's work relate to Darwin's?

Darwin proposed that if geologic change came from slow continuous actions (rather than from sudden events), that a slow and subtle process also produced biological change. He also proposed that if geologic change was a slow process that the Earth must be much older than a few thousand years like society had previously believed.


Who was Jean-Baptiste de Lamarck?

He proposed how life changes over time. He recognized that the match of organisms to their environments could be explained by gradual evolutionary change, but his mechanism was incorrect. He explained the change with "use and disuse" (parts of the body that are used get stronger and unused parts deteriorate), and "inheritance of acquired characteristics" (organism could pass these modifications to its offspring). He also believed that evolution happens because organisms have a drive to become more complex, which Darwin rejected. Darwin agreed that variation was introduced partially through the inheritance of characteristics.


What did Darwin's dad want him to do? What did he do instead?

Dad sent him to medical school, he quit to be a clergyman.


What did Darwin do shortly after school?

Was a conservation partner to captain Fitzroy on "The Beagle" in 1831, he charted the South American coastline and observed plants and animals on the shore.


What did Darwin learn from Lyell's "Principles of Geology" book?

He learned that earth couldn't be just a few thousand years old


What was Darwin's hypothesis about the Galapagos islands?

He believed that the Galapagos islands were colonized by organisms that strayed from South America and diversified to create new species.



inherited characteristic of organisms that enhance survival and reproduction in specific environments.



the idea that individuals with certain inherited traits survive and reproduce at higher rates because of those traits


Who submitted a similar idea to Darwin's in 1858?

Alfred Russel Wallace had the same idea of natural selection and submitted for publication before Darwin. Though Wllace wanted Darwin to be known as the main architect of the idea and Darwin's book, "The Origin of Species", won over most scientists due to its logic and evidence.


Instead of saying "evolution" in his book "The Origin of Species", what did Darwin call it?

"Descent with modification"


What is the unity of life due to?

One ancestral organism


What do the different parts of a tree represent of the history of life?

The tips of the twigs represent groups of organisms living in the present day, unlabeled branches are extinct groups, and each fork of the tree is the most recent common ancestor of the lines of evolution coming from that branch.


What is the diversity of life due to?

descent with modification (evolution) over a long period of time



the process of modifying species by breeding those with desired traits. This proves Darwin's theory because the original organism is different than the ancestors of it.


Darwin argued that a similar process to artificial selection occurs in nature. What observations did he base this off of and what inferences did these observations lead to?

Observation 1: members of a population vary in traits

Observation 2: species produce more offspring than will survive

Inference 1: those with traits that allow higher surveil will produce more offspring

Inference 2: unequal ability to survive and reproduce will lead to favorable traits over a number of generations.


Explain the connection between natural selection and over-reproducing. What does this connection lead to?

Of the many born (over-reproducing), only a small amount will survive and leave their own offspring (natural selection). There will eventually be an increase in the proportion of favorable traits in the population because throughout the generations those with the favorable traits will survive longer and reproduce more. Throughout the generations the organisms will also be an even greater match for their environment.


Do individuals evolve?

No, populations evolve over time


Will natural selection change a trait that all organisms in a population have?

No, natural selection amplifies and diminishes traits that vary in the population but cannot change a trait that all organisms have.


Darwin acknowledged that evidence for some things in his research was lacking. When were these gaps filled in?

In the last 150 years discoveries have been made that filled in many of the gaps


What happens when an organism switches to a new food source?

They adapt to be able to eat the food that they eat, this sometimes changes based on what environment they live in and what food is available.


Explain the evolution of drug-resistant bacteria

In the bacterium, Staphylococcus aureus, certain genetic varieties (STRAINS) known as methicillin-resiistant S. aureus (MRSA) are very powerful. In the past decade MRSA has become much more dangerous. In 1943 penicillin became the first widely used antibiotic, but by 1945 more than 20% of S aureus strains were resistant to it. The bacteria developed an enzyme, penicillinase, that could destroy penicillin. New antibiotics were used that were not destroyed by penicillinase but eventually the bacteria resisted it as well. In 1959 the antibiotic methicillin was used and within 2 years MRSA emerged. Some S aureus populations were able to synthesize their cell walls with a protein not affected by methicillin. These resistant individuals reproduced at higher rates and they became more common, leading to the spread of MRSA.


Explain why natural selection depends on time and place.

adaptions that are an advantage in the current environment are favored. What is beneficial in one situation may be useless or even harmful in another.


What is the main evidence of evolution?

analyzing similarities among organisms (all forms of life use essentially the same genetic code, suggesting that all species descended from common ancestors with this code)



similarity resulting from common ancestry



Homologous structures- represent variations on a structural theme that was present in a common ancestor. Some homologous structures can only be revealed in the early stages of development and are not visible in adult organisms. One big homology in all of life is that all forms of life use essentially the same genetic code. Some homologous genes have acquired new functions, some have retained their original functions, and some have lost their function.

Vestigial structures - remnants of features that served a function in ancestors but now have little importance. These are a kind of homologies.


What type of pattern do homologous characteristics make up?

a nested pattern - all life shares the deepest layer, and each successive smaller group adds on their own homologies.


If an evolutionary tree shows that an organisms is a common ancestor of another organism, what does this mean?

More recent common ancestors are more closely related to each other. The organisms are closely related.



The evolutionary tree explains the morphological gaps that sometimes exist between related groups of organisms. The evolutionary tree reflects evolutionary relationships among groups of organisms and is a hypothesis that summarizes our understanding on patterns of descent.



independent evolution of similar features in different lineages. This happens when different lineages adapt to similar environment in similar ways but are not closely related.



Analogous - share features because of convergent evolution. Similar function but NOT common ancestry.

Homologous - due to common ancestry but do not necessarily have similar functions.


What are fossils evidence of?

Evolution. they show the pattern of evolution, that there are differences between the past and the present, and that some organisms that existed once are now extinct. They tell us about the origins of new groups of organisms. We can also see from fossils that over tie, descent with modification produced increasingly large differences among related groups of organisms, ultimately resulting in the diversity of life we see today.


What do fossils tell us about cetaceans?

the earliest cetaceans lived 50-60 million years ago and before that most mammals were terrestrial. Fossils allow us to understand the transition from land life to sea life and let us see how cetacean limb structure changed over time, leading to the loss of hind limbs and the development of flippers and tail flukes. This fills in some other gaps between ancestral and living cetaceans. We can also see from fossils that cetaceans are closely related to even-toed ungulates (deer, pigs, camels, cows, etc).



the scientific study of the geographic distributions of species.


What are geographic distributions of organisms influenced by?

multiple factors, including CONTINENTAL DRIFT (slow movement of Earth's continents over time).



About 250 million years ago all of Earth's landmasses were in a single large continent called Pangaea. Roughly 200 million years ago, Pangaea started breaking apart. By 20 million years ago the continents we know today were within a few hundred kilometers of their present locations.


What can we predict using our knowledge of evolution and continental drift?

We can predict where fossils of different groups of organisms might be found, and we can use evolution to explain biographic data. (ex: islands generally have species that are endemic, but the islands are colonized by species from the nearest mainland and eventually new species were adapted to their new environments)



found nowhere else in the world


What is Darwin's view on the pattern and process of evolution?

Pattern - life has evolved over time

Process - natural selection is the cause of the pattern of evolution.



A theory is more comprehensive than a hypothesis. It accounts for many observations and explains a variety of phenomena. (has lots of evidence and explains a lot of things)


Is natural selection the only mechanism responsible for evolution?

No, scientists make new discoveries using a wide range of experimental approaches and genetic analysis all the time.


*What was the prevailing belief prior to the time of Lyell and Darwin?

Earth is a few thousand years old, and populations are unchanging


*Evolutionary trees are properly understood by scientists to be _____



*What are the four postulates of natural selection?

Variation in population, heritable variation, selection, differential survival or reproduction


*What is an accurate combination of postulates 1 and 2 (variation in population and heritable variation) of natural selection?

Heritable variation exists for traits among individuals in a population.


*What is an accurate combination of postulates 3 and 4 (selection and differential survival and reproduction) of natural selection?

Individuals experience differential success in their ability to survive or reproduce.


*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.


*Describe 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.


*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. Which of the following conditions 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 nonresistant corn borers.


*True or false? 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.



*The theory of evolution through natural selection is considered a scientific theory because _____

it is broad enough in scope to explain many observations, it is supported by a massive body of evidence from many disciplines, and it is general enough to provide many testable hypotheses


*How would you best describes a theory in terms of observations relating to it?

They are supported by, and make sense of, many observations.


*DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

None of the individual insects should have possessed genomes that made them resistant to DDT


*What in a whale is homologous to the bones in the wing of a bird?

bones in the flipper of a whale


*What piece of evidence most strongly supports the common origin of all life on Earth?

All organisms use essentially the same genetic code.


*Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. What information would best help distinguish between an explanation based on homology versus one based on convergent evolution?

The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.


*Ichthyosaurs were extinct aquatic reptiles distantly related to living lizards. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are _____

adaptations to a common environment and examples of convergent evolution.


*the vegetarian finch is genetically no more similar to the tree finches than it is to the ground finches, despite the fact that it is placed in the same genus as the tree finches. Based on this finding, it is reasonable to conclude that the vegetarian finch ____

is no more closely related to the tree finches than it is to the ground finches, despite its classification


*When Darwin wrote On the Origin of Species, he knew very little about the subject of _____, an essential component of evolutionary theory today.



*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 ______

humans and chimpanzees share a relatively recent common ancestor.