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 .
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• • • 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.
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Fig. 1.13
• • • • 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. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 1.14
• 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. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 1.15
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• 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, 3 D 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