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UNITY AND DIVERSITY OF LIFE
BIOLOGY is the study of living organisms and their interactions with the environment.
Therefore, this semester’s topics will include animals, plants, microbes, and fungi, as
well as ecology (how they interact with the environment). Biology is the study of living
things. But what is life? What distinguishes living from non-living things?
7 Properties Associated with life:
1) Order
2) Reproduction
3) Growth and development
4) Energy processing
5) Response to the environment
6) Regulation
7) Evolutionary adaptation
Order
• This close-up of a sunflower illustrates the highly ordered structure that typifies
life. Living cells are the basis of this complex organization.
Reproduction
• Organisms reproduce their own kind. Here, an emperor penguin protects its baby.
Growth and Development
• Inherited information in the form of DNA controls the pattern of growth and
development of all organisms, including this hatching crocodile.
Energy processing
• When this bear eats its catch, it will use the chemical energy stored in the fish to
power its own activities and chemical reactions.
Response to the environment
• All organisms respond to environmental stimuli. This Venus flytrap closed its trap
rapidly in response to the stimulus of a damselfly landing on it.
Regulation
• Many types of mechanisms regulate an organism’s internal environment, keeping
it within limits that sustain life. Here is a typical lemur behavior with a regulatory
function (sunbathing), which helps raise the animal’s body temperature on cold
mornings.
Evolutionary adaptation
• The leaf-like appearance of this katydid camouflages it in its environment. Such
adaptations evolve over many generations as individuals with traits best suited to
their environment have greater reproductive success and pass their traits to
offspring.
Scope of Biology
• Biology is an enormous scope, and can be studied in two ways:
• The vertical dimension is studying biology based on size from largest (the
biosphere) to smallest (non-living molecules).
• The horizontal dimension is studying biology across the great diversity of species,
learning about classification of organisms.
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THE VERTICAL DIMENSION OF BIOLOGY
THE BIOSPHERE
The biosphere consists of all the environments on Earth that are inhabited by life. It
includes land and water such as oceans, lakes, and rivers; it also includes the atmosphere
to an altitude of several kilometers.
ECOSYSTEMS
An ecosystem consists of all living things in a particular area, along with all the nonliving
components of the environment with which life interacts, such as soil, water, atmospheric
gases, and light. Examples of an ecosystem are forests or coral reefs.
COMMUNITIES
A community is all of the living organisms within a particular ecosystem. The
community of a forest includes all species of trees, plants, animals, fungi, and bacteria
that live there. The tree in your backyard is home to two cardinals, a colony of ants, a
wasp's nest, four squirrels, and trillions of bacteria. Together, all of these organisms
represent a community.
POPULATIONS
A population consists of all the individuals of a species living within the bounds of a
specified area. For example, a forest may include a population of sugar maple trees, and
a population of American black bears. We can now refine our definition of a community
as the set of populations that inhabit a particular area.
ORGANISMS
An organism is an individual living thing. Each of the maple trees and other plants in a
forest is an organism, and so is each forest animal such as a frog, squirrel, bear, and
insect. The soil is also full of micro organisms such as bacteria.
ORGANS AND ORGAN SYSTEMS
An organ is a body part consisting of two or more tissues. Examples of human organs are
the brain, heart, and kidney. Examples of a tree’s organs are its leaves, stems, and roots.
An organ system is a group of organs which cooperate in a specific function. For
example, the human digestive system includes such organs as the tongue, stomach, and
intestines.
TISSUES
A tissue is a group of similar cells which perform the same function. Examples of human
tissues include the epidermis (skin), muscle, and bones. Leaves have one type of tissue
on their surface which contains pores to allow carbon dioxide to reach the interior of the
leaf. They have another type of tissue within the leaf, which is the area where of
photosynthesis occurs.
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CELLS
The cell is the fundamental unit of structure and function of each organism. Some
organisms, such as amoebas and most bacteria are single cells. Other organisms,
including plants and animals, are multicellular. Instead of a single cell performing all the
functions of life, the multicellular organism has a division of labor among specialized
cells. In humans, examples of a specialized cell include a nerve cell (neuron), a muscle
cell (myofibril), and a bone cell (osteocyte).
ORGANELLES
An organelle is like a miniature organ within a single cell. It has a specific function for
that cell. An example of an organelle in a human cell is a nucleus. An example of an
organelle in a plant cell is a chloroplast.
MOLECULES
A molecule is a chemical structure consisting of two or more atoms. If one of the atoms is
carbon, it is an organic molecule. If there is no carbon, it is an inorganic molecule. An
example of a plant molecule is chlorophyll. Examples of organic molecules used by
animals are carbohydrates, proteins, and fats. Examples of inorganic molecules used by
animals are salt and water.
Life is organized in a hierarchical fashion. The following sequence illustrates that
hierarchy increases in complexity: Molecule, organelle, cell, tissue, organ, organ system,
organism, population, community, ecosystem, and biosphere.
COURSE OVERVIEW
Within the vertical dimension of biology, one of the topics that we will spend
considerable time on this semester is ecology, including ecosystem dynamics and
energy conservation.
ECOSYSTEM DYNAMICS
On the cover of your biology textbook is a pelican. They belong to a group of animals
called Aves, also known as birds, which are believed to have evolved from ancient
feathered dinosaurs. Pelicans have fishing skills that are well suited to the ocean habitat.
They can dive into the ocean and catch a fish six the below the surface. There are
hunting helps regulate the size of fish populations. Because it is comfortable floating on
the waves, it is also an ideal scavenger. Small fishing boats can therefore toss away
unwanted fish parts without polluting the water. But some fishermen see the birds as
competition rather than trash collectors, and a slaughter thousands of the birds.
Additionally, when humans use pesticides, the rain washes the pesticides into the soil,
which gets carried into the water table, which leads to the oceans, where it accumulates in
fish and birds that ate them. The pesticides will cause a bird to lay a very thin egg shell
so that it breaks before it hatches. Because of this, a pelican population was almost
wiped out. The birds first disappeared entirely from Louisiana and been banished from
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other coastal areas as well. In 1970 the brown pelican was declared an endangered
species. Biologists argued that only a ban on pesticides such as DDT would save the
birds, and in 1972 that ban was enacted. Because of these efforts, they are once again
thriving in many coastal areas. However, as their numbers grow, they are continuing to
face problems when they encounter humans. The young pelican on the cover of this book
is at a bird sanctuary in Florida which cares for birds injured by boat propellers or fishing
lines. All organisms are connected to the environment and other organisms.
Each organism interacts continuously with its environment, which includes other
organisms as well as nonliving factors. For example, the roots of a tree absorb water and
minerals from the soil. The leaves take in carbon dioxide from the air. Solar energy
absorbed by chlorophyll drives photosynthesis, which converts water and carbon dioxide
to sugar and oxygen. The tree releases oxygen to the air, and its roots help form soil by
breaking up rocks. Both the organism and the environment are affected by the
interactions between them. The tree also interacts with other of life, including soil
microorganisms and animals that eat its leaves and fruit.
The dynamics of any ecosystem include two major processes. One process is the cycling
of nutrients. For example, minerals acquired by plants will eventually be returned to the
soil by microorganisms that decompose dead leaves, roots, and fruit. The second major
process and an ecosystem is the flow of energy from sunlight  producers  consumers.
Producers are plants and other photosynthetic organisms that convert light energy to
chemical energy. Consumers are organisms, such as animals, that feed on producers and
other consumers.
ENERGY CONSERVATION
Moving, growing, reproducing, and other activities of life require organisms to perform
work. Work depends on a source of energy. The exchange of energy between an
organism and its surroundings often involves the transformation of one form of energy to
another. For example, when a leaf produces sugar, it converts solar energy to chemical
energy in the form of sugar molecules. When an animal’s muscle cells use sugar as fuel
to power movements, they convert chemical energy in the form of sugar to kinetic energy
(the energy of motion). During the course of these conversions of one energy form to
another, thermal energy is dissipated to the environment in the form of heat. In contrast
to chemical nutrients, which recycle within an ecosystem, energy flows through an
ecosystem, usually entering the system as light and exiting the system as heat. The
ultimate source of energy flowing into nearly all ecosystems is sunlight. The ultimate
source of energy flowing out of nearly all ecosystems is heat.
CELLS’ HEREDITARY INFORMATION
Another topic we will cover this semester is the structure and function of cells,
including their role in nutrition, the function of enzymes and proteins, the use of
energy, and how a cell reproduces.
A cell is the lowest level of organization that can perform all activities required for life.
For example, the ability of a cell to divide and form new cells is the basis for all
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reproduction and for the growth and repair of multicellular organisms. Your every
movement is based on the activities of your muscle cells. Your every thought is based on
the activities of your nerve cells. Even the process of breathing is the cumulative product
of cellular activities.
Within the nucleus of a cell there are structures called chromosomes, which are made out
of DNA. On the chromosomes are genes, which are the units of inheritance that transmit
information from parents to offspring. Your hair color, for example, is the result of genes
that you inherited on your parents.
Each chromosome is a very long DNA molecule with hundreds or thousands of genes
arranged along its length. The DNA of chromosomes replicates as a cell prepares to
divide; therefore, each of the two offspring cells inherit a complete set of genes. Each of
us began life as a single cell stocked with DNA inherited from our parents. Within the
genes are molecules that encode the information for building the entire body. In this
way, DNA directs development and maintenance of the entire organism.
Each DNA molecule is like a chain with many links. Each link of the chain is one of four
kinds of chemical building blocks called nucleotides. The way DNA encodes a cell’s
information is similar to the way we arrange letters of the alphabet into precise sequences
with specific meanings. The word rat, for example, conjures up an image of a rodent.
The words tar and art, which contained the same letters, mean very different things.
Libraries are filled with books containing information encoded in varying sequences of
only 26 letters. Our genetic information is likewise made out of only four nucleotides
(letters of the alphabet); however each gene (word) may be thousands of letters in length.
Most genes program the cell’s production of large molecules called proteins. Each gene
codes for a different protein which has a unique shape and function in the cell. One
protein might be part of a muscle, while another protein might be an antibody. The DNA
provides the hereditary blueprint for these proteins, but the proteins themselves are the
tools that actually build and maintain the cell.
THE HORIZONTAL DIMENSION OF BIOLOGY
TAXONOMY
Taxonomy is that part of biology dedicated to naming, describing, and classifying
species. The categories are ordered into a series of groups of increasing breadths.
Until the last decade, taxonomy was divided into five kingdoms, including the plant and
animal kingdoms. But with new understanding of DNA sequences, biologists are reevaluating the system of classification. The debate over the number of kingdoms is still
continuing, but there is a consensus that the kingdoms of life can now be grouped into
three even higher levels of classification called domains. The three domains are named
Bacteria, Archaea, and Eukarya.
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Bacteria and Archaea are both prokaryotes (unicellular and microscopic). Eukaryotes are
multicellular organisms, and include the kingdoms of plants, animals, and fungi.
Who are we? For humans, here is our classification:
Domain: Eukarya
Kingdom: Animal
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: sapiens
(Memory Aid: Dashing King Phillip Came Over From Greece, Singing)
Animals
What’s the difference between an animal and a plant? An animal can move from one
place to another, they don’t get food from sunlight, and their body structure is fixed.
Mammals
Mammals are born with a placenta and produce milk for the offspring.
Primates
Primates have an opposable thumb (can touch each of the other fingers).
Good depth perception because the eyes are in front of the head.
Gestation (length of pregnancy) is lengthy.
One birth at a time is the norm.
Juvenile period of dependency is long.
There is an emphasis on learned behavior and complex social interactions.
Humans and apes are both primates. There are four types of modern apes: gibbons,
orangutans, gorillas, and chimpanzees. Humans can be distinguished from modern apes
by walking upright, dental features, shape of face, and brain size.
Hominids
• Make use of symbolic language (writing)
• Walk on two legs
Evolutionists say that our ancestors are Australopithecus, which evolved in eastern Africa
4 MYA (million years ago). The most famous Australopithecus fossil is called Lucy
(The name derives from the Beatles’ song “Lucy in the Sky with Diamonds.”). Although
her brain was quite small, Lucy walked upright.
Homo sapiens
There is only one genus and species of hominids and that is Homo sapiens. In Latin,
Homo sapiens means “wise or rational man”.
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We Are One Species
Bacteria, Archaea, plants, animals, and fungi are very diverse organisms. Even within our
own species there are variation is race. Races are actually just slight differences in
ethnicity that developed as an adaptation to the climate of a region. But inside plants,
animals, fungi, and people, our molecules are all the same. Thus, there is unity within the
diversity of life.
Match the following to their descriptions
Animals-B
A. walk on two legs, make use of symbolic language (writing)
Mammals -C
B. can move from one place to another, body structure is fixed.
Primates -E
C. born with a placenta and produce milk for the offspring.
Hominids-A
D. wise or rational man.
Homo Sapiens -D
E. Opposable thumb, long gestation, learned behavior
Match the following taxonomy terms for a human being
Kingdom: C
A. Homo
Order: B
B. Primate
Family: E
C. Animal
Genus: A
D. sapiens
Species: D
E. Hominid
EVOLUTION AND NATURAL SELECTION
Also during the course of this semester, we will discuss the topic of evolution and
natural selection.
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The history of life is documented by fossils and other evidence that the Earth and
its life forms is changing and evolving.
This evolutionary view of life came into sharp focus in 1859, when Charles
Darwin published one of the most controversial books ever written: The Origin of
Species by Natural Selection.
This book articulated two main points. First, Darwin presented evidence to
support his view that modern species arose from a succession of ancestors.
Darwin called this “descent with modification”.
This phrase captures both the unity of life (descent from common ancestors) and
the diversity of life (modifications that evolved as species branched from their
common ancestors).
Descent with Modification (Evolution)
• Descent with modification implies that modern species arise from a common
ancestor.
• As evidence for this theory, the arms of a bat, human, horse’s forelegs, and whale
flippers all contain the same skeletal architecture, including the same bones,
joints, nerves, and blood vessels.
• In the Darwinian view, the unity of mammalian limb anatomy indicates the
inheritance of that structure from a common ancestor, the diversity of the
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forelimbs having been modified by natural selection operating over millions of
generations in different environmental conditions.
NATURAL SELECTION
• Darwin's second main point was to propose a mechanism for evolution, which he
called “natural selection”.
• He started with two observations.
1) Individuals in a population vary in their traits, many of which are
passed on from parents to offspring.
2) A population can produce far more offspring than the environment can
support.
• From these two observations, Darwin inferred that those individuals with
heritable traits best suited to the environment are more likely to survive and
reproduce than others.
• As a result of this unequal reproductive success over many generations, a higher
and higher proportion of individuals will have the best traits for survival.
• The result of natural selection is evolutionary adaptation, the accumulation of
favorable traits in a population over time.
Natural selection is when the natural environment selects for the propagation of certain
traits. For instance, consider an area where the soil has been blackened by a recent brush
fire. A population of insects there contains beetles that are either white or gray; a predator
bird can easily pick out the white colored insects and the beetles with the white coloration
are eliminated from the population. The survivors reproduce, carrying on their genetic
coloration, enhancing the survival and reproductive success of the dark-colored bugs.
This is natural selection.
SCIENTIFIC METHOD
We will also spend some time on the scientific method so you understand what
process a researcher goes through to document new discoveries.
The word “science” is derived from a Latin verb meaning “to know”. At the heart of
science is inquiry, a search for information and explanation, often focusing on specific
questions. Biology blends two main processes of scientific inquiry: discovery science
and hypothesis-based science. Discovery science is mostly about describing nature.
Hypothesis-based science is mostly about explaining nature. Most scientific inquiries
combine these two research approaches.
Discovery science describes natural structures and process through careful observation
and analysis of data. For example, discovery science gradually built our understanding of
cell structure, and it is currently expanding our understanding of genetics. Observation is
the use of senses to gather information, sometimes with the help of tools such as
microscopes that extend our stances. Recorded observations are called data. Some data
is qualitative, taking the form of recorded descriptions rather than measurements in
numbers. For example, Jane Goodall spent decades recording her observations of
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chimpanzee behavior in the jungle. She also documented her observations with
photographs and movies. In addition, she recorded behavior with quantitative data,
recorded as specific measurements.
Hypothesis-based science starts with an observation that leads to a question about the
cause or explanation for the observation. A hypothesis is a tentative answer to some
question. It is usually an educated guess based on past experience and current
knowledge. You notice that over the past month, many students have started wearing a
new style of school sweatshirt. You think to yourself, maybe the bookstore recently
started selling this new sweatshirt style. This prediction is an example of a hypothesis.
A scientific hypothesis makes a prediction that can be tested by designing an experiment.
We all use hypotheses in solving everyday problems. For instance, suppose your
flashlight stops working. That's an observation. The question is: Why doesn't the
flashlight work? Two reasonable hypotheses are:
1. The batteries are dead
2. The bulb is burned-out
Each of these alternative hypotheses makes predictions you can test with experiments. For
example, the dead battery hypothesis predicts that replacing the batteries will fix the
problem. The experiment is to replace the batteries with new ones. If the flashlight then
works, the hypothesis was validated. In the flashlight does not work, the experiment falsifies
the hypothesis. The second hypothesis can then be tested by replacing the light bulb.
This example illustrates two important qualities of scientific hypotheses. First, a
hypothesis must be testable; there must be some way to check out the validity of the
idea. Second, a hypothesis must be falsifiable; there must be some experiment that could
reveal it such an idea is actually not true. To be scientifically valid, a hypothesis must be
testable and falsifiable.
Ideally, an experiment should contain a “control” component. This means that two
experiments are conducted, one differing from the other by only a single variable.
The role of a control in an experiment is to provide a basis of comparison to the
experimental group. For example, a company that sells cereal wants to prove that it
lowers cholesterol. They find 1000 volunteers to eat this cereal for three months and
have their cholesterol measured before and after the experiment. A proper experimental
design should include another 1000 volunteers who are as similar as possible to the
experimental group (in age, ethnicity, health status, etc.) who do not eat that cereal.
Another component of an ideal experiment is that all possible variables are eliminated
between the control group and the experimental group. For example, if the volunteers who
eat this cereal are all in their mid-- 20s and exercise daily, and the volunteers in the control
group are middle aged and do not exercise, there are two variables in this experiment that
were not eliminated. Thus, the results of the experiment are not valid.
An Actual Case Study of Hypothesis-Based Science
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New discoveries in science start with the observation: Many poisonous animals are
brightly colored so that predators will recognize them as poisonous and stay away. But there
are also mimics. These imposters look like poisonous species but are actually harmless.
After an observation comes a question: What is the function of such mimicry?
And then a hypothesis is formed: Such deception is an evolutionary adaptation that reduces
the harmless animal’s risk of being eaten.
In 2001, biologists David and Karin Pfenning, along with William Harcombe, one of their
students, designed an experiment to test the hypothesis that “mimics benefit because
predators confuse them with the harmful species”. A poisonous snake called the eastern
coral snake has colored rings of red, yellow, and black. Predators rarely attack these snakes.
The predators do not learn this avoidance behavior by trial and error; a first encounter with a
coral snake would usually be deadly. Therefore, natural selection has apparently increased
the frequency of predators that inherit an instinctive ability to recognize the coloration of the
coral snake. A non-poisonous snake called the scarlet king snake mimics the ring coloration
of the coral snake. (Humans can remember the difference by this phrase: red and yellow kill
a fellow, red and black venom lack).
Both types of snakes live in North and South Carolina, but the king snake’s geographical
range also extends into regions where no coral snakes are found. This makes it possible
for researchers to test a key prediction of the mimicry hypothesis: Mimicry should help
protect king snakes from predators, but only in regions where coral snakes also live.
Avoiding snakes with warning coloration is an adaptation of predator populations that
have evolved in areas where the poisonous coral snakes are present. The mimicry
hypothesis predicts that predators adapted to the warning coloration of coral snakes will
attack king snakes less frequently then will predators in areas where coral snakes are
absent.
The researchers placed equal numbers of artificial brown snakes and artificial coral
snakes in field sites throughout North and South Carolina, including the region where
coral snakes are absent. After four weeks, they retrieved the fake snakes and recorded
how many had been attacked by looking for a bite or claw marks. The most common
predators were foxes, coyotes, and raccoons, but Black Bears also attacked some of the
artificial snakes.
The data fit the key prediction of the mimicry hypothesis. Compared to the brown
artificial snakes, the ringed snakes were attacked by predators less frequently only in field
sites within the geographic range of the poisonous coral snakes.
This case study provides an example of a controlled experiment, one that is designed to
compare an experimental group (the artificial king snakes) with a control group (the
artificial brown snakes). Ideally, the experimental and control groups differ only in the
one factor the experiment is designed to test-- in our example, the effect of the snake’s
coloration on the behavior of predators. Without the control group, the researchers would
not have been able to rule out the number of predators in a different test areas as the
cause of the different numbers of attacks on the artificial king snakes. The clever
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experimental design left coloration as the only factor that could account for the low
predation rate on the artificial king snakes placed within the range of coral snakes.
SCIENCE, TECHNOLOGY, AND SOCIETY
This semester, we will also discuss genetic research in our society, and how
biotechnology benefits humanity. We will also talk about population and pollution
concerns on our planet, including global warming.
Endangered species, genetically modified crops, global warming, air and water pollution,
the cloning of embryos, nutrition controversies, emerging diseases, medical advances-- is
there ever a day that we don't see several of these issues featured in the news? Biology,
the science of life, has an enormous impact on our everyday life.
The goal of science is to understand natural phenomena. In contrast, technology
generally applies scientific knowledge for some specific purpose. Science and
technology can benefit society. The discovery of the structure of DNA 50 years ago has
led to the many technologies of DNA engineering that are being used today in the field of
medicine, agriculture, and genetics. The direction that technology takes depends on the
wants and needs of people and on the social environment of the times.
With advances in technology come difficult choices. For example, under what
circumstances is it acceptable to use DNA technology to check if people have genes for
hereditary diseases? Should such tests always be voluntary, or are there any
circumstances when genetic testing should be mandatory? Should insurance companies
or employers have access to the information?
Technology has improved our standard of living in many ways, but not without
consequences. Technology that keeps people healthier has enabled the earth's population
to double to over 6 billion in just the past 40 years. The environmental effects of this
growth can be devastating. Global warming, toxic wastes, acid rain, deforestation,
nuclear accidents, and extinction of species are just some of the repercussions. Science
can help us identify such problems and provide insight into what course of action may
prevent further damage. But solutions to these problems have as much to do with
politics, economics, and cultural values as with science and technology. Therefore, every
citizen has a responsibility to develop a reasonable amount of scientific literacy.
Whether you are a scientist or not, issues come up at the poll booth for a vote and all
citizens should be educated about how science works and about the potential benefits and
risks of specific technology.
From the molecules to the biosphere, biology is directly connected to our everyday lives.
This course will give you an education about the science of life and help you apply that
understanding to evaluate issues ranging from your own personal health to the well-being
of the whole world.
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