Download Cycles of Life: EXPLORING BIOLOGY Module 1: Biological

Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 1: The Unity and Diversity of Life
Objectives:
1. List and describe major characteristics of living things that distinguish them from non-living matter.
2. Describe the general pattern of energy flow through the earth’s life forms, and explain how their
interactions help cycle the earth’s resources.
3. Explain what is meant by the term unity, and identify possible causes of similarities between earth’s
organisms.
4. Explain what is meant by the term diversity, and identify possible causes for the great diversity of life
forms on earth.
Video Synopsis:
Beginning with the features that distinguish living matter from non-living matter, this segment provides
an overview of the living world, expanding on the theme “What is life?” What is meant by unity? By
diversity? Dr. Paul Saltman describes the role of energy from the sun and its importance to living
organisms. Dr. Christopher Wills discusses sexual reproduction as a means of genetic diversification.
Questions:
1. What are the major characteristics of life exhibited by all organisms?
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Organization
Metabolism
Sense and respond
Cell division
Reproduction
Require energy
2. What does the second law of thermodynamics require that energy be used for?
• To maintain order.
• Order is a major characteristic of all living things.
• Without order, the organism dies.
3. Why is sexual reproduction so important to the continued existence of life on earth?
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To diversify characteristics.
To adapt to the changing environment.
4. Explain the organization of multicellular organisms from cell level through the entire organism.
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Cell
Tissue
Organ
Organ system
Organism
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5. It has been said that life exhibits both unity and diversity. How can this be true?
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All living things exhibit most of the same characteristics.
Almost all living things look and act differently.
Follow-up Activities:
1. Visit a particular habitat (a pond, a grassy area, a garden) and list the different organisms you find.
Next, make a list of the non-living things you find.
2. Select three different organisms as examples and identify the different characteristics of life that each
of those organisms exhibit.
3. Select one animal and one plant. List as many ways as you can that these organisms are similar to
each other. Then list as many ways as you can that these organisms differ from each other. Design a
chart or diagram to show how all the organisms you found in the first activity contribute to the
energy flow and cycling of materials in this area.
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Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 2: Scientific Method
Objectives:
1. Generally describe how biologists proceed through a scientific investigation.
2. Distinguish between a scientific hypothesis and a theory.
Video Synopsis:
Biologists Bonnie Roohk and John Moore outline the steps in the scientific method against the backdrop
of a specific example: researchers apply the techniques in an investigation of pesticide resistance in
mosquitoes. Students see examples of observation, hypothesis, experimentation, collating results and
forming conclusions.
Questions:
1.
Outline the steps in the scientific method.
• Observations
• Hypothesis
• Experimentation
• Results
• Conclusions
2.
What roles do tools or instruments have to play as scientists pursue the scientific method?
• Extend the senses allowing for keener observations.
• Allow experimental results to be quantified.
3.
What are at least two characteristics of a scientific fact? Why is permanence, or unchangeability, not
one of these characteristics?
• Verifiable.
• Repeatable.
• It is possible that improved or altered methods of observation will cause a “fact” to be modified.
4. Support or refute the statement that a scientific theory is a speculation, i.e., an individual idea or guess
as to the cause of a natural phenomenon.
• The above statement is more descriptive of a hypothesis than a theory.
• A theory is an explanation of a natural phenomenon based on different lines of evidence gained
from repeated experimentation.
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Follow-up Activities:
1. After every hard rain you find dead earthworms lying on the street. Formulate a hypothesis regarding
these observations and suggest an experiment to test your hypothesis.
2. Select a research article from the library or perhaps the Internet and identify the hypothesis,
variables, and controls used in the chosen study.
3. Obtain a copy of the March 1997 issue of Natural History. Read the article by Stephen Jay Gould
concerning the lack of conflict between science and religion, and then discuss what Gould means by
the NOMA principle.
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Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 3: Microevolution: The Theory of Natural Selection
Objective:
Outline the major elements of the theory of evolution by natural selection, and identify the ideas and
observations that influenced Darwin as he developed the theory.
Video Synopsis:
Charles Darwin’s theory of evolution by natural selection is presented by John Moore, a noted Darwin
scholar, who discusses its major concepts. Additional historical insight is provided by Ernst Mayr, who
was a pioneer in defining the concept of “species” in the 1940s. Students will track Darwin’s cruise to the
Galapagos Island and see how he connected the animals found there to species known in South America
and Europe. The story of how his theories became accepted by the scientific community concludes this
segment.
Questions:
1. As summarized by Drs. Moore and Mayr, what are the major elements of Darwin’s theory of
evolution by means of natural selection?
• Populations overproduce.
• Adult populations, however, remain fairly constant in number.
• Therefore, organisms must struggle for survival.
• Variations exist in the population.
• Nature selects those organisms with variations best suited to the environment for survival.
• Selected organisms reproduce successfully, thereby passing on these traits to their offspring.
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What concept of Malthus did Darwin draw on to help frame his theory of natural selection?
• In his essay on populations, Malthus postulated that populations produced more individuals than
are capable of surviving on the limited resources available, therefore there must exist a struggle for
survival.
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3. Which poorly understood area of biology in the 1800s caused Darwin to have a problem explaining
the theory of natural selection?
• Genetics, the mechanisms of heredity, was poorly understood. Darwin was formulating his ideas
before Mendel had even published his particulate theory of inheritance.
• The variations so necessary to the theory of natural selection were difficult to explain, in light of
the blending theory of inheritance in vogue during Darwin’s time.
4. How did Darwin interpret his observations of the living armadillos and the armadillo-like fossils that
he encountered in South America?
• Darwin reasoned that there might well be a relationship between the living armadillos and the
fossil remains found in the sediment immediately below the living ones.
• He hypothesized that the living animals he encountered were the modified descendants of the
animals represented by the fossils.
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Follow-up Activities:
1. Examine a population of snails or “pill” bugs from your neighborhood or purchase a population of
bean seeds at the market. Identify several ways the members of your chosen population vary from
one another.
2. The Galapagos Islands are sometimes referred to as a “natural laboratory for evolution.” Research
such aspects as the origin and location of the islands, as well as the ocean currents that effect them
and some of the plants and animals that inhabit them, to see why the above quote might be so
appropriate.
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Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 4: Evolution In Action
Objectives:
1. Describe a population in terms of its gene pool and its allelic, or gene, frequencies.
2. Discuss the disturbing forces which can result in evolution, i.e., changes in the gene frequencies of a
population.
3. Use the example of pesticides to discuss how humans can act as agents of directional selection.
Video Synopsis:
A more complete coverage of the pesticide resistance of mosquitoes is shown in this segment. The way in
which these insects evolve through mutation and natural selection is the main question. How are
mosquito populations affected by genetic and environmental conditions? In evaluating the insects’
response to the pressure of insecticides, the segment discusses selection pressures. We hear again from
Richard Meyer and James Webb, vector control scientists, and George Georghiou and Ernst Mayr, experts
in genetics and the selection process.
Questions:
1. What does a gene, or allelic, frequency represent?
• The gene pool is the total genetic makeup of a population. Operationally, the gene pool includes
all of the genes in a population for the particular trait being studied.
• The fraction of the total number of a particular allele in the population, divided by the sum of
all of the alleles for that trait in the population, represents the allelicfrequency of that gene, or
allele.
2. Describe a non-evolving population in terms of the frequencies of its alleles.
• In a non-evolving population, the frequencies of its alleles remain constant from generation to
generation.
3. Discuss several disturbing forces which can cause changes in the gene frequencies of a population,
thereby bringing about evolution.
• Mutations: Changes in the genetic material which are the only way new alleles arise.
• Genetic drift: Chance fluctuations in the gene frequencies of small populations.
• Gene flow: The introduction or removal of genes from a population due to immigration or
emigration.
• Selection pressure: Environmental conditions favor a particular expression (phenotype), or
militate against it, so that a directional change occurs. Certain environmental conditions can also
result in disruptive or stabilizing pressures.
4.
What do pesticides and antibiotics have in common?
• Both are chemical agents used to kill pests or pathogens.
• Both act as agents of directional selection by favoring resistant organisms and selecting against
sensitive ones. Such agents can bring about evolutionary change over very few generations.
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Follow-up Activities:
1. Contact your local vector control district and make arrangements to visit the district operations
center or invite the Education Coordinator to visit your class. When you’ve made contact, determine
other ways, in addition to the application of pesticides, that potentially harmful mosquitoes are
controlled. Also find out what other disease carrying vectors are in your area.
2. A non-evolving population is represented by the Hardy-Weinberg rule. Using your text book or
another reference book, study the Hardy-Weinberg rule and discuss how it might be used to describe a
population.
3. Directional selection pressure is only one of at least three types of pressures that the environment
can exert. Research this topic in order to identify two other types of pressure. Record an example or
two of each type of pressure identified.
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Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 5: Macro-evolution
Objectives:
1. List what biologists generally accept as evidence to support the theory of evolution, and explain how
comparative anatomy and morphology, bio-geography, palentology and other techniques are used to
reconstruct the past.
2. Generally describe the breakup of the supercontinent Pangea and the movement of tectonic plates in
the Mesozoic and Cenozoic eras. Relate this movement to evidence in the fossile record.
3. Identify some of the principle organisms associated with the Cenozoic era.
Video Synopsis:
As a theory, evolution is consistently being tested and evaluated. Scientists explain that each piece of
new evidence contributes to completing a picture of life as it developed from the beginning – a dynamic
and continuing process over a vast span of time. Evidence of this evolutionary connection is found in the
fossil record. Paleontologists Eric Scott and Kathleen Springer explain how discovering fossils gives one a
“snapshot in time” of the animals and ecosystems of an era. Fossils give clues to phylogeny, how one
animal species is related to another.
Questions:
1. What kinds of organisms are typically preserved as fossils? Why is it important to date those fossils?
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Typically, organisms with hard body parts like shells, teeth, or bones are found in the fossil
record.
Single-celled and soft-bodied organisms can still be preserved under special circumstances (amber)
although not nearly as often.
Dating of specimens is especially important if one is to establish evolutionary rates and trends.
If one is making a case for feature ‘A’ to be more primitive than feature ‘B’, then the dates such
features appeared in the fossil record should support that trend.
2. How do fossils help piece together the "family tree" of a given plant or animal?
• Scientists study as many different related specimens as they can find and they study differences in
the morphologies.
• The relatedness of the jaw structures of giant ground sloth are based on shape and pattern
of the teeth.
• By arranging specimens of a region over time, patterns of change and branches from common
ancestors emerge.
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What is the value of the construction site fossils compared to those from the tar pits?
• The abundance of fossils in the valley allowed scientists to better study numbers of organisms and
ecological relationships between them over time.
• Other locations like those in the tar pits, don't have the large numbers of different fossils,
although each specimen is more complete.
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4. How do fossils provide evidence for the theory of continental drift?
• Seemingly related fossils found on opposite sides of the world, have been found in what can be
interpreted as a single “range”, only if the continents are “fit” together.
5. What other methods do scientists use to reconstruct the past besides studying fossils?
• Modern analogs of extinct species including habits and physiology (i.e. bite pressure), as well as
comparative anatomy and morphology of living species.
• Current distribution of living species as well as of fossils (bio-geography) is also important.
• Although not presented here, DNA and protein studies of living and extinct specimens,
embryological development patterns, or evidence of vestigial structures.
• The key to this portion of the discussion is to note that fossil evidence does not stand alone.
Follow-up Activities:
1. Prepare a timeline describing the geological and biological history of the world making sure you
accurately reflect relative time on earth.
2. Using charts and other illustrations, trace the evolution of one species or group of animals or plants
over time.
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Cycles of Life:
EXPLORING BIOLOGY
Module 1: Biological Concepts
Segment 6: The Evolutionary Timeline
Objectives:
1. Discuss the concept of punctuated equilibrium and the role of factors that encourage increased rates of
speciation and the formation of larger taxonomic groups.
2. Identify some of the factors that have brought about mass extinction and replacement of species in
the past.
3. Identify some of the principle organisms associated with the Mesozoic era.
Video Synopsis:
Macro-evolution is the larger picture of species’ change over time, their patterns and trends. In this
segment, the concepts of homologous structures and shared characteristics are described by Dr. Blaire Van
Vaulkenburgh. By studying the teeth and bones of ancient wolves and saber tooth cats, she is able to
reconstruct these animals that disappeared long ago. Dr. David Bottjer discusses extinctions in general –
why they occur and why the history of earth is dotted with mass extinctions.
Questions:
1. Does evolution occur slowly and gradually or in fits and starts?
• There appear to have been several different times of rapid change.
• In between those times, however, evolution appears to have been more slow and gradual.
2. Why do species become extinct?
• Changes in the environment
• New competition
• Habitat destruction
• Excessive hunting
3.
What does extinction of one species mean to the surviving species in the same environment?
• With the exit of one or more species, a role in the ecosystem becomes open.
• With no competition from an already adapted species, other less adapted organisms have a chance
to move into the empty "ecospace".
• Diversification may result.
4. What caused 90% of the marine organisms to die out, ending the Paleozoic era?
• A massive lava flow created flood basaltes and belched poisonous gases which killed most of
organisms that lived at the time.
• Today the remnants of this flow are called the Siberian traps. This flow was so large, if it covered
the earth it would be 15 feet deep.
5.
What stimulated the evolution of mammals at the end of the Mesozoic era?
• A catastrophic event, most likely an extraterrestrial object striking the earth, caused massive
changes in the environment which killed many of the dinosaurs and opened the ecospace.
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Follow-up Activities:
1. Research recent evidence regarding the mass extinction of the dinosaurs. What evidence can you find
that a catastrophic event may have occurred?
2. Research evidence about the rate of extinctions today. What areas are experiencing the greatest rate
of extinction and why?
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