Download Homework/class-work Unit#10 evolution and natural

Name: ____________________________ Homework/class-work Unit#10 evolution and natural selection (25 points)
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assignment will lose 5 points, 2 will lose 10 points, 3 will be considered incomplete and given a zero.
1. Darwin reading:
Date: __________________
Most educated people in Europe and the Americas during the 19th century had their first full
exposure to the concept of evolution through the writings of Charles Darwin. Clearly, he
did not invent the idea. That happened long before he was born. However, he carried out the
necessary research to conclusively document that evolution has occurred and then made
the idea acceptable for scientists and the general public. This was not easy since the idea of
evolution had been strongly associated with radical scientific and political views coming out
of post-revolutionary France. These ideas were widely considered to be a threat to the
established order in Britain.
Charles Darwin was born into a moderately wealthy family in Shrewsbury, England. His
father, Robert, had the largest medical practice outside of London at the time and his mother,
Susannah Wedgwood, was from a family of wealthy pottery manufacturers. Charles grew up
in comparative luxury in a large house with servants. However, this was a socially very
conservative time in England that set narrow limits on a young man's behavior and future
possibilities. The constraints on women in Darwin's social class were even greater. Most
were given only enough education to efficiently manage the homes of their future husbands
and raise their children. Young men were expected to go to university in order to prepare
themselves to become medical doctors, military officers, or religious leaders in the Church of
England. Most other occupations were considered somewhat unsavory.
Darwin started university at 16 in Edinburgh as a medical student. He showed little academic interest and dropped out after two years
(1825-7). He then went to Cambridge University to study theology. It was there that his life's direction took a radical change. He
became very interested in the scientific ideas of the geologist Adam Sedgwick and especially the naturalist John Henslow with whom
he spent considerable time collecting specimens from the countryside around the university. Darwin also was influenced by the
writings of the late 18th century evolutionists, including his grandfather, Erasmus.
Following graduation from Cambridge with a degree
in theology, Darwin was clearly more interested in
biology than he was in a clerical career. Fortunately,
John Henslow was able to help him secure a birth on a
British Navy mapping expedition that was going
around the world on a five year long voyage. Darwin
sailed in 1831 on the ship H.M.S. Beagle as an unpaid
naturalist and companion for the captain, Robert
Fitzroy. Darwin was only 22 years old at the time.
The Beagle was a compact 90 feet long ship with a
crew of 74. There was little space, even for the
captain. It was during the beginning of this voyage
that Darwin read the early books of Charles Lyell and
became convinced by his proof that
uniformitarianism provided the correct
understanding of the Earth's geological history. This intellectual preparation along with his research on the voyage were critical in
leading Darwin to understand evolution. Especially important to the development of this understanding was his visit to the Galápagos
Islands in the Eastern Pacific Ocean. It was there that he began to comprehend what causes plants and animals to evolve.
The Galápagos Islands have species found in no other part of the world, though similar ones exist in South America. Darwin was
struck by the fact that the birds were slightly different from one island to another. He realized that the key to why this difference
existed was connected with the fact that the various species live in different kinds of environments.
Darwin identified 13 species of finches in the Galápagos Islands. This was puzzling since he knew of only one species of this bird on
the mainland of South
America, 600 miles to the
east, where they had all
presumably originated. He
observed that the Galápagos
species differed from each
other in beak shape. He also
noted that the beak varieties
were associated with diets
based on different foods. He concluded that when the original South American finches reached the islands, they dispersed to different
environments where they had to adapt to different conditions. Over many generations, they changed anatomically in ways that allowed
them to get enough food and survive to reproduce.
Today we use the term adaptive radiation to refer to this sort of branching evolution in which different populations of a species
become reproductively isolated from each other by adapting to and eventually become separate species.
Darwin came to understand that any population consists of individuals that are all slightly different from one another. Those
individuals having a variation that gives them an advantage in staying alive long enough to successfully reproduce are the ones that
pass on their traits more frequently to the next generation. Subsequently, their traits become more common and the population
evolves. Darwin called this "descent with modification."
The Galápagos finches provide an excellent example of this process. For instance, among the birds that ended up in arid environments,
the ones with beaks that were better suited for eating cactus got more food. As a result, they were in better condition to mate. In a very
real sense, nature selected the best adapted varieties to survive and to reproduce. This process has come to be known as natural
selection.
Darwin did not believe that the environment was producing the variation within the finch populations. He correctly thought that the
variation already existed and that nature just selected for the most suitable beak shape and against less useful ones. Some of Darwin's
supporters ultimately described this process as the "survival of the fittest." This is very different from Lamarck's incorrect idea that
the environment altered the shape of individuals and that these acquired changes were then inherited.
Nineteenth century critics of Darwin thought that he had misinterpreted the Galápagos finch data. They said that God had created the
13 different species as they are and that no evolution in beak shape has ever occurred. It was difficult to conclusively refute such
counter arguments at that time. However, 20th century field research has proven Darwin to be correct.
In 1798, Thomas Malthus, an English clergyman and pioneer economist, published an extensive article entitled Essay on the
Principles of Population. In it he observed that human populations will double every 25 years unless they are kept in check by limits
in food supply. By the late 1830's, Darwin came to realize that all plant and animal populations have this same potential to rapidly
increase their numbers unless they are constantly checked by limitations in food, water, and other resources that are essential for
survival. This fact was key to his understanding of the process of natural selection. He realized that the most fit individuals in a
population are the ones that are least likely to die of starvation and, therefore, are most likely to pass on their traits to the next
generation.
A good example of natural selection was discovered among "peppered"
moths living near English industrial cities. These insects have varieties
that vary in wing and body coloration from light to dark. During the 19th
century, sooty smoke from coal burning furnaces killed the lichen on trees
and darkened the bark. When moths landed on these trees, the dark colored
ones were harder to spot by birds that ate them and, subsequently, they
more often lived long enough to reproduce. Over generations, the
environment continued to favor darker moths. As a result, they
progressively became more common. By 1895, 98% of the moths in the
vicinity of English cities like Manchester were mostly black. Since the
1950's, air pollution controls have significantly reduced the amount of
heavy particulate air pollutants reaching the trees. As a result, lichen has
grown back, making trees lighter in color. Now, natural selection favors
lighter moth varieties so they have become the most common. This trend
has been well documented by field studies undertaken between 1959 and
1995 by Sir Cyril Clarke from the University of Liverpool. The same
pattern of moth wing color evolutionary change in response to increased and later decreased atmospheric pollution has been carefully
documented by other researchers for the countryside around Detroit, Michigan.
Darwin did not rush his ideas about natural selection into print. There was a Christian evangelical fervor in England at the time. He
could have been charged with sedition and blasphemy for publishing his unpopular theory. After returning from the voyage around the
world on H.M.S. Beagle, he settled down in England, married Emma Wedgwood (his first cousin), raised a large family, and quietly
continued his research. In 1842 and 1844, he wrote relatively short summaries of his theory, but they were not widely read outside of
British scientific circles. It was not until he was 50 years old, in 1859, that he finally published his theory of evolution in full for his
fellow scientists and for the public at large. He did so in a book entitled On the Origin of Species. It was very popular and
controversial from the outset. The first edition came out on November 24, 1859 and sold out on that day. It went through six editions
by 1872.
What finally convinced Darwin that he should publish his theory was the draft of an essay that he received in the summer of 1858
from a younger British naturalist named Alfred Wallace, who was then hard at work collecting biological specimens in Southeast
Asia for sale to museums and private collectors. Darwin was surprised to read that Wallace had come upon essentially the same
explanation for evolution. Being a fair man, Darwin later insisted that Wallace also get credit for the theory during debates over its
validity carried out by the British Royal Society. We now know that Darwin deserves most of the credit. In 1837, one year after he
returned from the voyage on the Beagle, he made detailed notes on the idea of evolution by means of natural selection. At that time
Wallace was only 14. In addition, it was Darwin's book, rather than Wallace's essay, that had the most impact on the Victorian public.
Darwin not only described the process of natural selection in more detail, but he also gave numerous examples of it. It was his On the
Origin of Species that convinced most educated people in the late 19th century that life forms do change through time. This prepared
the public for the acceptance of earlier human species and of a world much older than 6000 years.
Both Darwin and Wallace failed to understand an important aspect of natural selection. They realized that plant and animal
populations are composed of individuals that vary from each other in physical form. They also understood that nature selects from the
existing varieties those traits that are most suited to their environment. If natural selection were the only process occurring, each
generation should have less variation until all members of a population are essentially identical, or clones of each other. That does not
happen. Each new generation has new variations. Darwin was aware of this fact, but he did not understand what caused the variation.
The first person to begin to grasp why this happens was an obscure Central European monk named Gregor Mendel. Through plant
breeding experiments carried out between 1856 and 1863, he discovered that there is a recombination of parental traits in offspring.
Sadly, Darwin and most other 19th century biologists never knew of Mendel and his research. It was not until the beginning of the
20th century that Mendel's pioneer research into genetic inheritance was rediscovered. This was long after his death. He never
received the public acclaim that was eventually showered on Darwin.
Charles Darwin's convincing evidence that evolution occurs was very threatening to many Christians who believed that people were
created specially by God and that they have not changed biologically since that creation. The idea that there could have been
prehistoric humans who were anatomically different from us was rejected for similar reasons. However, Charles Lyell's geological
evidence that the Earth must be much older than 6,000 years and the rapidly accumulating fossil record of past evolution convinced
educated lay people in the 1860's to think what had been unthinkable earlier.
Archaeological confirmation of the existence of prehistoric Europeans had been accumulating since the 1830's. However, until the late
1850's, it had been widely rejected or misinterpreted. Much of this evidence had been collected by Jacques Boucher Crèvecoeur de
Perthes, a customs officer in northern France in the early 1800's. His hobby was collecting ancient stone tools from deep down in the
Somme River gravel deposits. Since he found these artifacts in association with the bones of extinct animals, he concluded that they
must have been made at the time that those animals lived.
Boucher de Perthes tried to publish his findings in 1838. They were rejected by all important scientists and journals. The prehistoric
stone tools usually were dismissed as being only "lightning stones" (i.e., the remnants of lightning bolts). However, by 1858, his
claims were beginning to be accepted by some enlightened Western European scientists. Darwin's publication of On the Origin of
Species the following year convinced even more educated people that Boucher de Perthes had been right.
Darwin's popularizing the idea of evolution also made it possible for scientists to begin to accept that some of the makers of Boucher
de Perthes' prehistoric tools had already been discovered and that their bones were in museums. These bones had been found in several
Western European countries during the first half of the 19th century. However, they had all been dismissed as being from odd looking
modern people. During the 1860's, some were correctly determined to be from an earlier species or variety of people who had lived
during the last ice age--i.e., long before recorded history. We now know that these ancient people were mostly Neandertals, who lived
about 130,000-29,000 years ago.
Questions: Answer the following questions based on your reading:
1. Where was Charles Darwin born?
2. When Charles Darwin dropped out of medical school, what did he study next?
3. Darwin was influenced by the scientific methods of two men that started him on his study of Biology. Who where they?
4. When did Darwin set sail on the H.M.S. Beagle?
5. What is unique about the Galápagos Islands?
6. How and why did Darwin’s finches vary?
7. What was unusual when comparing the mainland finches and the Galápagos finches?
8. What is adaptive radiation?
9. What is descent with modification?
10. What is it called when nature selects the best adapted variants to survive and reproduce?
11. Natural selection can also be called:
12. Who thought that the environment altered the shape of individuals and that these acquired changes were then inherited?
13. Thomas Malthus thought that the human population would double every ___________ years.
14. Explain how pollution changed the “normal” natural selection pattern among the peppered moths?
15. When did the first edition of the Origin of Species come out?
16. What scientific discipline was Darwin lacking knowledge of that would have helped him understand his research better?
17. Why were many people threatened by Darwin’s theories?
2. Evolution and natural selection reading:
Date: ________________
Evolution implies a change in one or more characteristics in a population of organisms over a period of time.
Evidence for evolution:
In his book Darwin offered several pieces of evidence that favored evolution. In a subdued manner, he attempted to convince the
scientific community of the validity of his theory.
Paleontology:
One piece of evidence offered by Darwin is
found in the science of paleontology.
Paleontology deals with locating, cataloging and
interpreting the life forms that existed in past
millennia. It is the study of fossils-the bones,
shells, teeth, and other remains of organisms, or
evidence of ancient organisms, that have survived
over eons of time.
Paleontology supports the theory of evolution
because it shows a descent of modern organisms
form common ancestors. Paleontology indicates
that fewer kinds of organisms existed in past eras,
and the organisms were probably less complex.
As paleontologists descend deeper and deeper
into layers of rock, the variety and complexity of the fossils decreases. The fossils from the uppermost rock layers are most current
forms. Fossils from the deeper layers are the ancestors of modern forms.
Comparative anatomy:
More evidence for evolution is offered by comparative anatomy. As
Darwin pointed out, the forelimbs of such animals as humans,
whales, bats and other creatures are strikingly similar, even though
the forelimbs are used for different purposes (that is, lifting,
swimming, and flying). Darwin proposed that similar forelimbs have
similar origins, and he used this evidence to point to a common
ancestor for modern forms. He suggested that various modifications
are nothing more than adaptations to the special needs of modern
organisms.
Darwin also observed that animals have structures they do not use.
Often these structures degenerate and become undersized compared
with similar organs in other organisms. The useless organs are called
vestigial organs. In humans, they include the appendix, the fused tail
vertebrae, the wisdom teeth, and the muscles that move the ears and
nose. Darwin maintained that vestigial organs may represent structures that have not quite disappeared. Perhaps an environmental
change made the organ unnecessary for survival, and the organ gradually became nonfunctional and reduced in size. For example, the
appendix in human ancestors may have been an
organ for digesting certain foods, and the
coccyx at the tip of the vertebral column may be
the remnants of a tail possessed by ancient
ancestor.
Embryology:
Darwin noted the striking similarity among
embryos of complex animals such as humans,
chickens, frogs, reptiles, and fish. He wrote that
the uniformity is evidence for evolution. He
pointed out that human embryos pass through a
number of embryonic stages inherited from
their ancestors because they have inherited the
developmental mechanisms from a common
ancestor. These mechanisms are modified in a
way that is unique to an
organism’s way of life.
The similarities in
comparative embryology
are also evident in the early stages of development. For example, fish, bird, rabbit, and human embryos are
similar in appearance in the early stages. They all have gill slits, a two chambered heart, and a tail with muscles
to move it. Later on, as the embryos grow and develop, they become less similar.
Comparative biochemistry:
Although the biochemistry of organisms was not well known in Darwin’s time, modern biochemistry indicates
there is a biochemical similarities in all living things. For example, the same mechanisms for trapping and
transforming energy and for building proteins from amino acids are nearly identical in almost all living systems.
DNA and RNA are the mechanisms for inheritance and gene activity in all living organisms. The structure of the genetic code is
almost identical in all living things. This uniformity in biochemical organization underlies the diversity of living things and points to
evolutionary relationships.
Mechanisms of Evolution:
Evolution does not occur in individuals but in populations. A population is an interbreeding group of individuals of one species in a
given geographic area. A population evolves because the population contains the collection of genes called a gene pool. As changes
in the gene pool occur, a population evolves.
Mutation:
Mutation, a driving force of evolution, is a random change in a population’s gene pool. It
is a change in the nature of the DNA in one or more chromosomes. Mutations give rise to
new alleles: therefore, they are the source of variation in a population.
Mutations may be harmful, but they may also be beneficial. For example, a mutation may
permit organisms in a population to produce enzymes that will allow them to use certain
food material. Over time, these types of individuals survive, while those not having the
mutations perish. Therefore, natural selection tends to remove the less fit individuals,
allowing more fit individuals to survive and form a population of fit individuals.
Gene flow:
Another mechanism of evolution may occur during the migration of individuals
from one group to another. When the migrating individuals interbreed with the
new population, they contribute their genes to the gene pool of the local
population. This establishes gene flow in the population. Gene flow occurs, for
example, when wind carries seeds far beyond the bounds of the parent plant
population. As another example, animals may be driven off from a herd. This
forces them to migrate to t new population, thereby bringing new genes to a gene
pool. Gene flow tends to increase the similarity between populations of the same
species because it makes gene pools more similar to one another.
Genetic drift:
Another mechanism for evolution is genetic drift. Genetic drift occurs
when a small group of individuals leaves a population and establishes a
new one in a geographically isolated region. For example, when a small
population of fish is placed in a like, the fish population will evolve into
one that is different from the original. Fitness of a population is not
considered in genetic drift, nor does genetic drift occur in a very large
population.
Natural selection:
Clearly, the most important influence on evolution is natural selection,
which occurs when an organism is subject to its environment. The
fittest survive and contribute their genes to their offspring, producing a
population that is better adapted to the environment. The genes of less fit individuals are eventually lost. The important selective
force in natural selection is the environment.
Environmental fitness:
Environmental fitness may be expressed in several ways. For example, it may involve an individual’s ability to avoid predators, it
may imply a greater resistance to disease, it may enhance ability to obtain food, or it may mean resistance to drought. Fitness may
also be measured as enhanced reproductive ability to attract a mate. Better adapted individuals produce relatively more offspring and
pass on their genes more efficiently than less adapted individuals.
Questions: Answer the following questions based on your reading:
1. What is a gene pool?
2. What is gene flow? How can it cause evolution?
3. How does embryology give scientists supporting evidence for evolution?
4. What is natural selection? What does it cause?
5. How does the depth of a fossil relate to age?
6. How does biochemistry give scientists supporting evidence for evolution?
7. How does environmental fitness and adaptation relate?
8. Why do small population evolve faster than large populations?
9. How can a mutation cause evolution?
10. Why do scientist believe that many organisms have similar structures?
3. Evolution questions:
Date: _________________________
1. What is the evolution of beak size in Galapagos finches a response to?
2. According to Darwin, why does evolution occur?
3. What evidence exists that allows scientists to infer that evolution occurs gradually over time?
4. Why do the traits of individuals best adapted to survive become more common in each new generation?
5. What does natural selection cause?
6. What must exist in a population for natural selection to occur?
7. What are the structures to the right called?
8. What does the similarity of these structures
suggest?
9. Explain how modern species have come to exist?
10. What are structures that are reduced in size and
no longer have a function in modern species
called?
11. From the principle of superposition, what can
generally be determined about fossils in a
sequence of sedimentary rock?
12. What is the similarity in the body shape of a
whale and a fish is an example of? Why did this
similarity arise?
13. Although they do not have recent ancestors, birds
and bats have similar body shapes necessary for powered flight. What pattern of evolution does this relationship
represent?
14. What type of evolution normally occurs when you move part of a species population to a new habitat?
15. What must a trait increase within an individual in order to be considered an evolutionarily favorable trait?
16. How is the breeding of show dogs (pure breeds) similar or dissimilar to natural selection?
4. Review:
Date: ____________________
1. What is the name of the ship that Darwin traveled on when discovering the theory of evolution?
2. Who is the father of evolutionary thought?
3. Which islands gave Darwin the information he needed to complete his theory of evolution?
4. What organism did Darwin observe that led him to the theory of evolution?
5. What was the difference in the organisms in question 5 and why did that difference exist?
6. What was the name of Darwin’s book?
7. True or false: Darwin was the first person to speak about evolution.
8. True or false: Darwin was the first person to back the theory of evolution with scientific evidence.
9. Was the theory of evolution completely accepted when Darwin first published his book? If not, who opposed it?
10. What are three pieces of evidence for the theory of evolution?
11. What do you call two structures that are similar is structure between two species but are used for different purposes?
12. What do you call a structure that still exists in an organism that may have had a purpose in an ancestor but no longer is
needed by the modern species?
13. What is the accumulation of adaptations over time?
14. Name a pair of homologous structures.
15. Name two vestigial structures.
16. Why are some individuals born with a tail (from an evolutionary standpoint)?
17. What phenomenon is most likely responsible for a species to have two different colors (example the peppered moth)?
18. What are two pieces of embryological evidence in favor of evolution?
19. How does evolution work?
20. Does natural selection work directly on a species phenotype of genotype?
21. Any change in an organism’s phenotype that allows it a better chance for survival is called:
22. In order for natural selection to occur, the organism’s phenotype must allow it greater
_______________________________ and __________________________ success.
23. Name three things that could cause an organism within a species to be selected for.
24. Because some organisms are selected for, their _____________ will be passed down with a greater frequency and slowly
change the ___________________ of the population and gradually cause _______________________.
25. Name the three ways that natural selection can act on a population.
26. Which type of natural selection will most likely cause one species to become two?
27. Which type of natural selection will slow evolution down?
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Which type of natural selection favors the extreme forms of the population?
What evolves?
Which type of natural selection pushes a species in a direction?
Which type natural selection favors the average forms of the population?
Which type of natural selection favors one of the extreme forms of the population?
Why is the peppered moth situation a good example of natural selection? Even though this is a widely used example of
natural selection, why do you think the “natural” in natural selection does not completely fit?
What is a group of closely related individuals that can interbreed and have fertile offspring?
Why is appearance not always the bet way to tell if two individuals are in the same species?
How do you know that there is genetic variation within a population?
What do you call all members of the same species living in the same location?
What is the entire genetic make up of a population called?
True or false: Individuals not populations evolve.
Hardy and Weinberg came up with a theory that will determine when a population will __________________ or not.
What are the five conditions of Hardy-Weinberg equilibrium?
Any population that is not in Hardy-Weinberg equilibrium will:
How do populations break the rules of Hardy-Weinberg equilibrium?
What are the two ways that gene flow can occur?
What causes mall populations to evolve?
What is genetic drift? Name two types of genetic drift.
When an event drastically changes the number of individuals in a population and the survivors are left to repopulate the
area the reaming genes in the gene pool may be very different than the original population. This is known as the:
Evolution is caused by a small group of individuals starting a new colony. This is an example of the:
What is the biggest cause of the disturbance of Hardy-Weinberg equilibrium?
What is the biggest cause of evolution?