Transcript Part I and Chapter 1 - Pima Community College

Introduction
and
The Scientific Method
Chapter 1
Introduction
• Biology, the study of life, is rooted in the human
spirit.
• Biology is the scientific extension of the human
tendency to connect to and be curious about life.
• The adventure of biology takes us:
– Into a variety of environments to investigate
ecosystems
– To the laboratory to examine how organisms
work
– Into the microscopic world to explore cells and
the submicroscopic to explore molecules in cells
– Back in time to investigate the history of life.
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• This is the most exciting era for biology.
– The largest and best-equipped community of
scientists in history is beginning to solve
problems that once seemed insolvable.
– Genetics and cell biology are revolutionizing
medicine and agriculture.
– Molecular biology provides new tools to trace
the origins and dispersal of early humans.
– Ecology is helping evaluate environmental
issues, such as global warming.
– Neuroscience and evolutionary biology are
reshaping psychology and sociology.
• Unifying themes pervade all of biology.
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Figure 1.23x1 Biotechnology laboratory
Figure 1.23x2 Analyzing DNA
Lecture Outline
• Intro to Biology
– Hierarchical Organization of Life
– What is Life?
– What is a Cell?
– Emergent Properties
– Classification
– Evolution
• The Nature of Science
– Discovery and Hypothesis Driven Science
– Experimental Design
– The Culture of Science
The Hierarchical
Organization of
Life
What is Life?
Figure 1.3 Some properties of life
Properties of Life
•Cellular Organization
•order
•Genetic Blueprint
•Acquire and Use Energy
•Metabolism
•Responsiveness to the environment.
•Regulation (homeostasis)
•Growth and Development
•Reproduction
•Evolutionary Adaptation
Figure 1.3ax Order
Figure 1.3bx Reproduction
Figure 1.3cx Growth and development
Figure 1.3dx Energy utilization
Figure 1.7 An introduction to energy flow and energy transformation in an ecosystem
All Life is Made up of Cells
• Cells are the basic unit of
structure and function.
• All cells are enclosed by a
membrane that regulates
the passage of materials
between the cell and its
surroundings.
• All cells contain DNA, the
hereditary material.
There are two fundamental types of cells:
Prokaryotic cells are very small and simple. The
DNA is loose in the cytoplasm.
– Bacteria
Eukaryotic cells are
larger and more complex,
having a nucleus
and membrane bound
organelles.
• Found in plants,
animals, fungi and
protists.
Fig. 1.4
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Figure 1.5 The genetic material: DNA
The Emergent Properties of Systems
• Biological systems are much more than the
sum of their parts.
• New properties emerge due to the
arrangement and interactions of parts as
complexity increases.
• Example: A test tubes with chlorophyll,
carbon dioxide and all the other molecules
needed for photosynthesis cannot perform
photosynthesis.
The Power and Limitations of
Reductionism
• Scientists often reduce complex systems to
simpler components that are easier to study.
• Watson and Crick studied the molecular
structure of DNA. From this structure, they
inferred the chemical basis of inheritance.
• BUT disrupting a living system also interferes
with the meaningful understanding of all it’s
processes.
Diversity and unity are the dual
faces of life on Earth
• Diversity is a hallmark of life.
– At present, biologists have identified and named
about 1.5 million species.
• This includes over 280,000 plants, almost 50,000
vertebrates, and over 750,000 insects.
– Thousands of newly identified species are
added each year.
• Estimates of the total diversity of life range from
about 5 million to over 30 million species.
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• Biological diversity is something to relish and
preserve, but it can also be a bit overwhelming.
Fig. 1.9
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• In the face of this
complexity, humans
are inclined to
categorize diverse
items into a smaller
number of groups.
• Taxonomy is the
branch of biology
that names and
classifies species
into a hierarchical
order.
Fig. 1.10
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• Until the last decade, biologists divided the
diversity of life into five kingdoms.
• New methods, including comparisons of DNA
among organisms, have led to a reassessment of
the number and boundaries of the kingdoms.
– Various classification schemes now include
six, eight, or more kingdoms.
• Also coming from this debate has been the
recognition that there are three even higher
levels of classifications, the domains.
– The three domains are the Bacteria, Archaea,
and Eukarya.
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• Both Bacteria and Archaea have prokaryotes.
• Archaea may be more closely related to
eukaryotes than they are to bacteria.
• The Eukarya
includes at
least four
kingdoms:
Protista,
Plantae,
Fungi, and
Animalia.
Fig. 1.11
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• The Plantae, Fungi, and Animalia are primarily
multicellular.
• Protista is primarily unicellular but includes the
multicellular algae in many classification schemes.
• Most plants produce their own sugars and food by
photosynthesis.
• Most fungi are decomposers that break down dead
organisms and organic wastes.
• Animals obtain food by ingesting other organisms.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Underlying the diversity
of life is a striking unity,
especially at the lower
levels of organization.
• The universal genetic
language of DNA unites
prokaryotes, like
bacteria, with
eukaryotes, like
humans.
• Among eukaryotes,
unity is evident in many
details of cell structure.
Fig. 1.12
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• Above the cellular level, organisms are variously
adapted to their ways of life.
• This creates challenges in the ongoing task of
describing and classifying biological diversity.
• Evolution accounts for this combination of unity
and diversity of life.
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Evolution is the core theme of biology
• The history of life is a saga of a restless Earth
billions of years old, inhabited by a changing cast
of living forms.
– This cast is revealed
through fossils and
other evidence.
• Life evolves.
– Each species is one
twig on a branching
tree of life extending
back through
ancestral species.
Fig. 1.13
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• Species that are very similar share a common
ancestor that represents a relatively recent
branch point on the tree of life.
– Brown bears and polar bears share a recent
common ancestor.
• Both bears are also related through older
common ancestors to other organisms.
– The presence of hair and milk-producing
mammary glands indicates that bears are
related to other mammals.
• Similarities in cellular structure, like cilia, indicate
a common ancestor for all eukaryotes.
• All life is connected through evolution.
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• Charles Darwin brought biology into focus in
1859 when he presented two main concepts in
The Origin of Species.
• The first was that
contemporary species
arose from a succession
of ancestors through
“descent with
modification” (evolution).
• The second was that the
mechanism of evolution is
natural selection.
Fig. 1.14
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Darwin synthesized natural selection by
connecting two observations.
– Observation 1: Individuals in a population of
any species vary in many heritable traits.
– Observation 2: Any population can potentially
produce far more offspring than the
environment can support.
• This creates a struggle for existence among variant
members of a population.
• Darwin inferred that those individuals with traits
best suited to the local environment will generally
leave more surviving, fertile offspring.
– Differential reproductive success is natural
selection.
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Fig. 1.15
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Natural selection, by its cumulative effects over
vast spans of time, can produce new species
from ancestral species.
– For example, a population may be fragmented
into several isolated populations in different
environments.
– What began as one species could gradually
diversify into many species.
– Each isolated population would adapt over
many generations to different environmental
problems
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• The finches of the Galapagos Islands diversified
after an initial colonization from the mainland to
exploit different food sources on different islands.
Fig. 1.17b
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• Descent with modification accounts for both the
unity and diversity of life.
– In many cases, features shared by two
species are due to their descent from a
common ancestor.
– Differences are due to modifications by natural
selection modifying the ancestral equipment in
different environments.
• Evolution is the core theme of biology - a unifying
thread that ties biology together.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Nature of Science
• What is Science?
• Discovery Science
• Hypothesis Science
– The Scientific Method
• Deductive v. Inductive Reasoning
• Experimental Design
What is Science?
• An accumulation of knowledge about the
natural world.
• A method used to acquire more
knowledge about the natural world.
Characteristics of Science
• Science involves the critical evaluation of
ideas and information.
• It is the accumulation of verifiable information
on seeks natural causes for natural
phenomena.
– Science can teach you the value of rational
thought and a healthy skepticism.
– Science also provides us with a method of
critical thinking.
Science cannot:
• Address questions about morality, value or
faith.
• Prove or disprove the supernatural or the
existence of a supreme being.
Two Key Approaches to Science
• Discovery Science
• Hypothesis Driven Science
Discovery Science
• Observes and describes objects and
phenomenon.
• Carried out through careful observations and
precise measurements of the world around
us.
– Examples
• Descriptions of animal behavior
• Listing the species found in a area
• The sequence of the human genome
Hypothesis Driven Science
• A hypothesis is an educated guess based on
observations.
• Propose hypotheses, make deductions and
test predictions.
• The steps of this hypothesis driven inquiry
are known as the Scientific Method.
The Scientific Method
Hypotheses
• A hypothesis is an educated guess.
• The more hypotheses the better.
Predictions
• If a hypothesis is true, these are expected
observations or experimental results.
• Should be given as an “If … then…” statement.
– If (hypothesis), then (predicted results of
test)
• Also called deductions.
• For each hypothesis, it is good to have multiple
predictions.
The Test
•
Observations or an
experiment to test
your hypothesis.
• Should be designed
to measure specific
predictions.
• If the result of the
test does not agree
with your prediction,
go back to your
hypotheses
Literature Review
• Why would a review of the scientific literature
be useful?
– Saves time, money, suffering
• Can be a part of the ‘observation’ step of the
scientific method.
• The scientific literature
– Peer reviewed
– Primary literature consists of original
research articles.
– Secondary literature consists of review
articles, chapters in books etc. A synthesis
of many research articles.
Can the scientific method prove anything?
NO
(Statistics help give the probabilities)
Will discuss this in detail when you do
your own experiments in a future class
Scientific Facts
• Can disprove but not prove a hypothesis.
• How does something get accepted as fact?
– Multiple experiments
– Peer review
Theory
• Comprehensive
• Must be supported by extensive and varied
evidence
• Usually widely accepted
Scientific Models
Scientific Models
• Models are used to convey and to test ideas
and processes.
• They take many forms – diagrams, graphs, 3D objects, computer programs, mathematical
equations.
• May be a simple schematic, abstract, or very
‘life-like”
• The test of a model is how well it fits the
available data, and how accurately it predicts
the outcomes of new experiments.
The Culture of Science
• Competition and Cooperation
• Peer Review
– Scientific proposals must be evaluated by
scientist qualified in the area of research
before funds will be allocated.
– Before a scientific article is accepted into a
scientific journal, it must go though the
process of peer review.
Experimental Design
• Treatment
• Controls – limits test to just one variable
• Variables
– Independent – what you manipulate
(treatment)
– Dependent – what you measure
• Replication
The End.