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 We
recommend that all students take a few minutes to review the last segment of
Biology 115 concerning the principles of evolution and classification before
diving into the lessons below. Follow the link above to go to Biology 115:
Principles of Evolution and Divergence and Diversity (Lessons 1 and 2).
 In this course, we will just be looking at all the organisms
on Earth and all of the places where they live. If that seems
like too much to keep track of, this first lesson presents ten
key points to help bring some order to this undertaking.
Although we will be considering the incredible diversity of life
on Earth and the myriad different ways that organisms interact,
try to look at this information in light of the ten unifying
concepts presented here.
Learning Objectives
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How do we learn about ancient life?
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What were the first living organisms on Earth?
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How are organisms named?
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How did eukaryotic organisms arise?
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What is the impact of multicellularity on complexity?
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How did improvements in reproductive success shape
evolution?
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How is structure related to function?
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How do organisms interact with each other and with
their environments?
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What does it take to maintain a balanced ecosystem?
 Earth is a small planet orbiting a fairly nondescript star, and
the biosphere is only a thin skin on this little planet. But
this little planet has been teeming with life for almost 4
billion years! We are going to find out a little bit about all
that life. Where did all the organisms come from? How did they
get to be the way they are? How do they interact? How does their
environment affect them? How do they affect their environment?
How do we keep track of all this stuff?
Learning Objectives
- Sit for a while in amazement and wonder at the nature of
our biosphere, solar system, galaxy and universe.
- Be inspired.
 Evolution is often defined as
a change in the heritable characteristics of organisms over time. It involves a
complex interplay between the DNA of organisms in a population and the
environment in which that population lives. Tracing evolution often involves
constructing phylogenetic trees that help us visualize how organisms are related
to one another and how they have changed over time. Finally, it is important to
realize that evolution can occur at very different rates, depending, once again,
on the interplay between the characteristics of a particular population of
organisms and the environment in which those organisms survive and reproduce.
Learning Objectives
- How is evolution defined?
- Why is each of the following terms crucial to the definition of
evolution: change, heritable characteristics, population, time?
- Understand how a phylogenetic tree is used to show
evolutionary relationships among different types of
organisms.
- Why might rates of evolution differ significantly for
different organisms?
 Fossils are preserved evidence of the existence of organisms.
They may be mineralized shells and skeletons, mosquitoes
preserved in amber, human footprints, or casts of tree trunks.
Fossils give us a glimpse of ancient ecosystems and the
organisms that inhabited them, but the fossil record is
incomplete and biased toward preserving certain types or parts
of organisms. With a little logic, a little luck, and a good
dose of radiometric dating, it is possible to deduce many things
about the way organisms once lived and how they have changed
through time. In this lesson we will investigate how scientists
think about fossils and how they are used to understand ancient
ecosystems, evolutionary relationships among different
organisms, and the effects of major extinctions.
Learning Objectives
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How do we use the Principle of Superposition to
understand the relationships between different
fossils?
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What is the difference between relative and
absolute time scales? How is each determined?
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Understand the limitations of the fossil record.
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Understand how the geologic time scale has been
assembled.
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What is a common event following mass extinctions? Why
might this be?
 Humans have a great desire to classify things, and
the organisms
with which we share our planet seem to be particularly fascinating
to us. While many different
schemes have been used to classify organisms, the Linnaean
system is still the basis of the hierarchical classification
system used by most scientists today. Instead of thinking only
about morphological attributes, however, classification today
aims at elucidating the evolutionary relationships among
organisms. Because these relationships can be quite complex,
statistical methods are increasingly being used to build the
phylogenetic trees that describe how organisms are most likely related to
one another. Learning Objectives
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Understand the types of data used to classify
organisms.
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Understand the naming conventions of the Linnaean
classification system.
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Understand the structure/basis of different types of
phylogenetic trees. What is a node? What is a clade
and why is it an important concept in understanding
phylogenies?
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