Transcript Chapter 1 The Science of Biology

Chapter 1
The Science of Biology
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1–1 What Is Science?
• Science is a process of inquiry,
asking questions, the answers to
which produce a body of knowledge,
which is subject to change and
revision.
• The goal of science is to investigate
and understand the natural world, to
explain events in the natural world
and to use those explanations to
make useful predictions.
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• Science only deals with the natural
world. Biology is a field in science
that focuses on the study of life.
• An understanding of science and the
scientific approach is essential to
making intelligent decisions.
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• Scientists collect and organize
information in a careful, orderly way,
looking for patterns and connections
between events.
• Scientists propose explanations that
can be tested by examining evidence.
Scientists try to explain events
logically and analytically.
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• Scientific thinking begins with
observation, the process of gathering
information about events or
processes in a careful, orderly way.
• Observation generally involves using
the senses, particularly sight and
hearing.
• Data consists of observations that do
not differ whether collected by one
person or another.
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• Two types of data:
– Quantitative data: expressed in numbers,
obtained by counting or measuring.
– Qualitative data: descriptive and involves
characteristics that can’t usually be counted.
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• Scientists use data to make inferences, a
logical interpretation based on prior
knowledge or experience.
• A hypothesis is a proposed scientific
explanation for a set of observations.
• Scientific hypotheses must be proposed in
a way that enables them to be tested.
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Nazca lines (Peru)
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• Science is an ongoing process, knowledge is
constantly being reevaluated, revised and
updated because of new tools, techniques and
discoveries.
• Good scientists are skeptics, questioning
existing ideas and new hypotheses.
• Common steps for scientists to gather
information and answer questions are known as
scientific methods. Not every scientific
investigation uses every method nor do all
investigations lead to scientific theory.
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Crop
circles
Mars Man
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1-2 How Scientists Work
•
While there are no fixed steps, generally
the scientific method involves:
1) MAKE OBSERVATIONS: observations
utilize the senses to gather information.
Scientific discovery often takes place
when a scientist observes something no
one has noticed before.
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2) ASK A QUESTION: observations
may lead to unanswered questions.
(Research may provide information
about previous investigations of the
question or suggest appropriate
approaches to the problem.)
3) FORM A HYPOTHESIS: an
explanation for a question or a
problem that can be formally tested.
A good hypothesis predicts a
relationship between cause and
effect.
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4) SET UP A CONTROLLED
EXPERIMENT: While we use the term
experiment informally, a scientific
experiment is an investigation that tests
a hypothesis by the process of collecting
information under controlled conditions.
A controlled experiment involves two
groups:
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a) Experimental group: test group that receives
experimental treatment. A variable is the
factor of an experiment that can change. In a
controlled experiment, only one variable is
tested at a time. There are three types of
variables:
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Constants (controlled variables): same for both
the control and variable group.
Independent (Manipulated) variable: variable that
is deliberately changed.
Dependent (Responding ) variable: changes in
response to the manipulated variable (what
happened).
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b) Control group: group that receives no
experimental treatment, the standard
against which results are compared.
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5) RECORD AND ANALYZE
RESULTS: keeping a written record
of observations and data. Data from
an investigation can be considered
confirmed only if repeating the
investigation several times yields
similar results.
6) DRAWING A CONCLUSION: Use
evidence to determine whether the
hypothesis was supported or refuted.
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7) REPORTING RESULTS: Results
are only useful if they are made
available to other scientists for
peer review. Other scientists can
try to verify the results by repeating
the procedure.
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• It is not always possible to do an
experiment to test a hypothesis.
– Alternative investigations may utilize fieldwork or
surveys or large groups of subjects, controlling as
many variables as possible.
• As evidence accumulates from scientific
investigations, a particular hypothesis may
become so well supported that scientists
consider it a theory. A theory is a well-tested
explanation that unifies a broad range of
observations.
– No theory is considered absolute truth. As new
evidence is uncovered, a theory may be revised
or replaced.
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1 – 3 Studying Life
• The word biology means the study of
life. A biologist is someone who uses
scientific methods to study living
things.
• Describing what makes something
alive is not easy.
• No single characteristic is enough to
describe a living thing.
• Some non-living things share one or
more traits with living things.
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Living things share
the following
characteristics:
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1. Living things are made
up of units called cells.
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• All living things show an orderly structure, known as
organization.
• Although living things are very diverse, they are all
unified in having cellular organization.
• A cell is a collection of living matter enclosed by a
barrier (cell membrane) that separates the cell from
its surroundings.
• The cell is the lowest level of structure capable of
performing all of the activities of life.
• Cells are complex and highly organized despite their
small size.
• Unicellular organisms are living things that consist of
only a single cell.
• Multicellular organisms contain hundreds, thousands
or even trillions of cells with a variety of shapes and
sizes. Each type of cell is specialized to perform a
different function.
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2. Living things reproduce.
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• All organisms produce new organisms
(offspring) through a process called
reproduction.
• Reproduction is essential for the continuation
of an organism’s species (group of
organisms that can interbreed and produce
fertile offspring in nature.)
• There are two types of reproduction:
– Sexual reproduction: two cells from different
parents unite to produce the first cell of the new
organism. Offspring differ from their parents in
some ways.
– Asexual reproduction: new organism has a single
parent. Offspring and parents have the same
traits.
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3. Living things are based on
a universal genetic code.
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• The directions for inheritance are
carried by a molecule called
deoxyribonucleic acid (DNA).
• Every organism, with a few minor
variations, interprets the genetic code of
DNA in the same way.
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4. Living things grow and
develop.
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• Growth is an increase in the amount of living
material and the formation of new structures.
• Growth can occur by increasing the size of a
single cell or increasing the number of cells.
• Development is all of the changes that take
place during the life of an organism.
• The development of specialized cells from a
single fertilized egg cell is called
differentiation, because the cells produced
look different and perform different functions.
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5. Living things obtain and
use materials and energy.
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• Organisms take in energy and materials and transform it
to do many kinds of work such as grow, develop,
reproduce, and stay alive.
• The combination of chemical reactions through which an
organism builds up or breaks down materials as it
carries out life processes is called metabolism.
• All organisms get the material they need from their
surroundings, or environment. The way organisms
obtain energy varies.
• Plants, some bacteria and most algae obtain their
energy directly from sunlight through photosynthesis.
They convert materials using light energy into a form of
stored energy (glucose molecules).
• Other organisms rely on photosynthetic organisms for
their energy by eating plants or indirectly by eating
organisms that ate plants. Decomposers obtain energy
from organisms that have died by breaking down the
organisms.
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6. Living things respond to
their environment.
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• Organisms live in a constant interface with their
surroundings, or environment, which includes
other living organisms (biotic factors) as well as
non-living factors (abiotic factors) like air, water,
temperature and weather.
• Anything in an organism’s external or internal
environment that causes to react is a stimulus.
A reaction to a stimulus is a response.
• External stimuli, which come from the
environment outside an organism, include light
and temperature.
• Internal stimuli come from within an organism.
For example, trees that drop their leaves in the
fall conserve water and avoid freezing during
the winter.
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7. Living things maintain a
stable internal environment.
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• Even though conditions in the external
environment may vary widely, the internal
conditions of most organisms stay fairly
constant.
• The process by which they do this is called
homeostasis.
• A breakdown in homeostasis can result in
disease or even death.
• Homeostasis often involves internal feedback
mechanisms, which respond to internal
stimuli. A thermostat in your home maintains
a constant temperature in your home.
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Negative feedback mechanism:
A thermostat
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• A similar “thermostat” regulates human body
temperature.
• Human body temperature is a constant 37oC
(98.6oF), regardless of the external
temperature of the environment.
• If the external temperature gets too hot and
causes the human body temperature to rise,
the body responds by sweating, which helps
remove excess heat from the skin.
• If the external temperature gets too cold and
causes the human body temperature to drop,
the body responds by shivering.
• The muscle contraction when shivering
produces heat, warming the body.
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• Another example of homeostasis: human blood sugar
levels.
• The blood contains a constant amount of sugar in the
blood. Yet the amount of sugar available to the body
changes.
• After you eat a meal high in sugar, blood sugar levels
rise.
– This stimulates the pancreas to produce a hormone (chemical
signal) called insulin.
– Insulin targets the liver and muscle cells of the body and tells
them to take up the excess sugar and store it, bringing blood
sugar levels back to normal.
• After several hours of not eating, the sugar in the blood
is used by the cells for energy, causing the blood sugar
levels to drop.
– This stimulates the production of a second hormone from the
pancreas called glucagon.
– Glucagon stimulates the liver and muscles to release sugar into
the blood and help raise the blood sugar levels back to normal.
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• Animals are not the only organisms to use
homeostasis.
• Plants must regulate carbon dioxide intake and
water loss.
– Plants use structures call stomata (singular: stoma)
to do so.
– Stomata are microscopic holes in a plant leaf
(usually on the underside) that allow gases to enter
and leave and water vapor to leave as well.
– Each stoma consists of two guard cells, which
control the opening and closing of stomata by
responding to changes in water pressure.
– When guard cells are swollen with water, the stoma
is open.
– When the guard cell loses water, the opening closes,
limiting further water loss from the leaf.
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Plant Leaf
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8. Taken as a group, living
things change over time.
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• Although individual organisms
experience many changes during
their lives, the basic traits they
inherited from their parents usually
do not change.
• A group of organisms, however, can
change over time through the
process of evolution.
• Any inherited structure, behavior or
internal process that enables an
organism to respond to
environmental factors and live to
produce offspring is called an
adaptation.
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• There are always some differences in the
adaptations of individuals within any
population of organisms.
• As the environment changes, some
individuals have adaptations that make
them better suited to the new conditions
and more likely to survive and reproduce.
As a result, individuals with these
adaptations become more numerous in the
population.
• Over time, the characteristics of a species
will change so that all individuals have the
adaptation.
• This process of change over time is called
evolution. Life evolves as a result of the
interaction between organisms and their
environments.
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