Download Primate Evolution

Gloria
G399 Earth Systems
Barbara J. Shaw
Understanding Evolution
Introduction to evolution
To biologists, evolution can refer to either a process or an organizing principle that is a
theory. Generally, the word evolution means change and the process of biological
evolution is derived from this definition. Biological evolution is a change in the
characteristics of a population of organisms that occurs over the course of generations.
Some of these changes in populations that are considered evolutionary are inherited via
genes. A good example of this process of biological evolution can be the species of
organism commonly known as head lice. The word Species means “kind” in Latin and
consists of a group of individuals that can regularly breed together, producing fertile
offspring, which are generally distinct from other species in appearance or behavior.
Back to the head lice species, as some parents of young children have discovered, some
populations of head lice in the United States have become resistant to the pesticide
permenthrin, found in over the counter delousing shampoos. Initially, lice infections were
readily controlled through treatment with these products; however, over time, populations
of lice changed to become less susceptible to the effects of these chemicals. However, do
not confuse yourself between these genetic change and environmental changes, because
there are other changes that may take place in populations as a result of environmental
change, which are not considered evolutionary. For instance, the average dress size for
women in the United States has increased from 8 to 14 over the past 50 years because of
an increase in our average calorie intake and average age, not because of a change in
genes. (Colleen Belk, Virginia Borden. Science for life. Page 226)
In order to understand Evolution better, we also have to understand some key terms
(Theories of evolution) that will be used in this lab. These include; homology and the
theory of classification. The concept of homology is the similarity in characteristics
among different organisms that has resulted from common ancestry. We will be looking
at a good example of this when we examine mammal’s forelimbs. So, even though we
may conclude that they have totally different function, we will come to realize that each
one of these limbs shares a common set of bones that are in the same relationship to each
other even though they may be different in size and relative proportion. Since in this case,
homology is in anatomy, that is physical structure, it can also be called comparative
anatomy (Page 238). There are two other kinds of homology that are worth mentioning
and very important to understanding evolution. These are; Homology in development and
homology in biochemistry. Homology in development was observed by Darwin and his
contemporaries. This was the resemblance of different chordates (Animal that have a
backbone or closely related structure) early in their development. He observed that all
chordates produce structures called pharyngeal slits, and most have tails as early
embryos. These similarities in early development support the hypothesis that humans,
bats, chickens, and snakes derived from an ancestor that developed along a similar
pathway and that these species thus share and evolutionary relationship with all other
chordates (Page 240). On the other hand, homology in biochemistry comes in the
understanding of the nature of biological inheritance. Scientists now understand that
differences among individuals arise largely from differences in their genes. These
differences are due to randomly occurring mutations that are passed on to descendants. It
stands to reason that differences among species must also derive from differences in their
genes. So, if the hypothesis of common descent is correct, then species that appear to be
closely related must have more similar genes than do species that are more distantly
related. The most direct way to measure the overall similarity of two species’ genes is to
evaluate similarities in their DNA (Page 240).
Lesson plan grade level:
Fifth grade
Total time for lesson:
30 minutes for set up and observation
Setting:
Science room or laboratory
Subjects covered:
Science (Human biology), Anthropology (Onsite data collection)
Topics:
Various theories of evolution including; common descent, comparative anatomy
Goals for the lesson:
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Students will examine Mammal forelimbs, and look at various characteristics
trying to find differences and similarities. They will either be given a handout
with various forelimbs pictures on them, or I will borrow some from PSU
museum to use.
They will try to relate the features they observed to their own body features
They will also observe that even though the world in populated by different
species; some of them have many similar characteristics.
Material need: (For 6 groups of five)
www.answers.com
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12 papers with homology of mammal forelimbs on them (2 per group; see
separate document for 12 tetrapod and 12 mammal handouts)
Example: the same skeletal elements are found in the forelimbs of all mammals
12 papers with the theory of classification (Shared characteristics between
humans and apes on them; 2 per group; see end of this document for handout)
Benchmark 2:
Life Science
Organisms
 Group or classify organisms based on a variety of characteristics
 Describe basic plant and animal structures and their functions
Diversity/Interdependence
 Describe the relationship between characteristics of specific habitats and
the organisms that live there
 Describe how adaptations help a species survive
Methods:
1. Each group gets a couple of papers for each theory
2. As a group, students start looking at various characteristics among various
mammals
3. At the same time, they note down the similarities and differences they notice
4. They will do this while comparing each animal’s forelimb to the one next to it.
5. Then I will give them background on each one of those animals they will be
looking at and their ancestors
6. They will then each try to compare some of the features they find on these
animals and what they have.
Assessment:
They will have one question to answer and will be the following; now that you have done
this experiment and have seen these features, what does evolution mean to you
personally? This question will be answered both by using their opinions and the
experiment they would have conducted. However, each individual’s opinion will come in
as a compliment to the experiment even though some people do not believe in evolution.
Transformation
Evolution happens to populations of living things that reproduce. However it isn't enough
to simply reproduce for there to be biological evolution, there must also be some system
of genetic inheritance. At least some of the generative information contained in the parent
must get passed onto the offspring.
Extension
This could be extended to many academic areas. One of them is archeology. Evolution is
very important in this field in the sense that it requires a study of features and looking
back in the past. Being able to go about searching for species of the past in various parts
of the globe in order to find a common ground among these species. It can also be
incorporated in cultural awareness classes. Especially with people now looking forward
to coexist in a planet where no boundaries exist anymore. Understanding the fact that we
may be different in one way or another, but we have similarities that may point in the
direction of a common ancestor is very crucial and significant for a peaceful existence.
Source: (www.voyagethroughtime.org)
http://upload.wikimedia.org/wikipedia/commons/9/91/Huxley_-_Mans_Place_in_Nature.jpg