1 an introduction to life on earth. overview: inquiring about the world of life evolution is the...
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1An Introduction to Life on Earth
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Overview: Inquiring About the World of Life
• Evolution is the process of change that has transformed life on Earth
• Biology is the scientific study of life
• Biologists ask questions such as:
– How a single cell develops into an organism
– Living things are all descended from a single-celled ancestor (a single common ancestor).
– The characteristics shared by all organisms logically lead to the conclusion that all life has a common ancestry
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Order
Evolutionary adaptation
Responseto theenvironment
Reproduction
Growth anddevelopment
Energyprocessing
Regulation
Fig. 1-3
Characteristics shared by all living organisms
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Fig. 1-3a
Order
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Fig. 1-3b
Evolutionaryadaptation
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Fig. 1-3c
Responseto theenvironment
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Fig. 1-3d
Reproduction
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Fig. 1-3e
Growth and development
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Fig. 1-3f
Energy processing
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Fig. 1-3g
Regulation
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Theme: New properties emerge at each level in the biological hierarchy
• Life can be studied at different levels from molecules to the entire living planet
• The study of life can be divided into different levels of biological organization
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Fig. 1-4
The biosphere
Communities
Populations
Organisms
Ecosystems
Organs and organ systems
Cells
Cell
Organelles
Atoms
MoleculesTissues
10 µm
1 µm
50 µm
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The biosphere
Communities
Populations
Organisms
Ecosystems
Fig. 1-4a
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Fig. 1-4b
Organs and organ systems
Cells
Cell
Organelles
Atoms
MoleculesTissues
10 µm
1 µm
50 µm
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Fig. 1-4c
The biosphere
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Fig. 1-4d
Ecosystems
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Fig. 1-4e
Communities
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Fig. 1-4f
Populations
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Fig. 1-4g
Organisms
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Fig. 1-4h
Organs andorgan systems
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Fig. 1-4i
Tissues50 µm
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Fig. 1-4j
Cells
Cell
10 µm
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Fig. 1-4k
1 µm
Organelles
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Fig. 1-4l
Atoms
Molecules
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Life Consists of Organized Systems at a Hierarchy of Scales (1)
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Life Consists of Organized Systems at a Hierarchy of Scales (2)
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Theme: Organisms interact with their environments, exchanging matter and energy
• Every organism interacts with its environment, including nonliving factors and other organisms
• Both organisms and their environments are affected by the interactions between them
– For example, a tree takes up water and minerals from the soil and carbon dioxide from the air; the tree releases oxygen to the air and roots help form soil
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Ecosystem Dynamics
• The dynamics of an ecosystem include two major processes:
– Cycling of nutrients, in which materials acquired by plants eventually return to the soil
– The flow of energy from sunlight to producers to consumers
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Fig. 1-5
Sunlight
Ecosystem
Heat
Heat
Cyclingof
chemicalnutrients
Producers(plants and other photosynthetic
organisms)
Chemical energy
Consumers(such as animals)
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Theme: Cells are an organism’s basic units of structure and function
• The cell is the lowest level of organization that can perform all activities required for life
• All cells:
– Are enclosed by a membrane
– Use DNA as their genetic information
• The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms
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Figure 1-1 The cell is the smallest unit of life
organelles
nucleus
cell wall
plasmamembrane
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25 µm
Fig. 1-7
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• A eukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus
• By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles
• Bacteria and Archaea are prokaryotic; plants, animals, fungi, and all other forms of life are eukaryotic
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1 µmOrganelles
Nucleus (contains DNA)
Cytoplasm
Membrane
DNA(no nucleus)
Membrane
Eukaryotic cellProkaryotic cellFig. 1-8
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Theme: The continuity of life is based on heritable information in the form of DNA
• Chromosomes contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid)
• DNA is the substance of genes
• Genes are the units of inheritance that transmit information from parents to offspring
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DNA Structure and Function
• Each chromosome has one long DNA molecule with hundreds or thousands of genes
• DNA is inherited by offspring from their parents
• DNA controls the development and maintenance of organisms
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NucleicontainingDNA
Sperm cell
Egg cell
Fertilized eggwith DNA fromboth parents
Embryo’s cells withcopies of inherited DNA
Offspring with traitsinherited fromboth parents
Fig. 1-9
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• Each DNA molecule is made up of two long chains arranged in a double helix
• Each link of a chain is one of four kinds of chemical building blocks called nucleotides
• http://www.youtube.com/watch?v=gbSIBhFwQ4s
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Fig. 1-10
Nucleus DNA
Cell
Nucleotide
(a) DNA double helix (b) Single strand of DNA
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Figure 1.9 DNA Is Life’s Blueprint
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• Genes control protein production indirectly
• DNA is transcribed into RNA then translated into a protein
• http://www.youtube.com/watch?v=C8OL1MTbGpU
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Grouping Species: The Basic Idea
• Taxonomy is the branch of biology that names and classifies species into groups of increasing breadth
• Domains, followed by kingdoms, are the broadest units of classification
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Fig. 1-14Species Genus Family Order Class Phylum Kingdom Domain
Ursus americanus(American black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Each species has a distinct scientific name,
a binomial:•
Genus name•
Species name
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The Three Domains of Life
• The three-domain system is currently used, and replaces the old five-kingdom system
• Domain Bacteria and domain Archaea comprise the prokaryotes
• Domain Eukarya includes all eukaryotic organisms
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Fig. 1-15(a) DOMAIN BACTERIA
(b) DOMAIN ARCHAEA
(c) DOMAIN EUKARYA
Protists
Kingdom Fungi
KingdomPlantae
Kingdom Animalia
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Fig. 1-15a
(a) DOMAIN BACTERIA
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Fig. 1-15b
(b) DOMAIN ARCHAEA
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• The domain Eukarya includes three multicellular kingdoms:
– Plantae
– Fungi
– Animalia
• Other eukaryotic organisms were formerly grouped into a kingdom called Protista, though these are now often grouped into many separate kingdoms
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Fig. 1-15c
(c) DOMAIN EUKARYA
Protists
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia
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1.3 How Do Scientists Study Life?
• Multicellularity occurs only among the Eukarya
– Unicellular (single-celled) organisms are found in
• Bacteria
• Archaea
– Multicellular (many-celled) organisms are found in Eukarya, within the kingdoms
• Fungi
• Plantae
• Animalia
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Unity in the Diversity of Life
• A striking unity underlies the diversity of life; for example:
– DNA is the universal genetic language common to all organisms
– Unity is evident in many features of cell structure
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Fig. 1-16
Cilia ofParamecium
Cross section of a cilium, as viewedwith an electron microscope
Cilia ofwindpipecells
15 µm 5 µm
0.1 µm
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Charles Darwin and the Theory of Natural Selection
• Fossils and other evidence document the evolution of life on Earth over billions of years
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Fig. 1-17
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1.1 What Is Life?
• Organisms, collectively, have the capacity to evolve
– Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life
– Changes in DNA within populations occur over the course of generations, which results in evolution
• Populations are groups of the same type of organism living in the same area
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1.2 What Is Evolution?
• Evolution explains the diversity of life on Earth
• Evolution provides an explanation for the similarities found among different types of organisms
– Chimpanzees and people have various physical features in common
– DNA of humans differs from that of chimpanzees by less than 5%
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Scientists use two main forms of inquiry in their study of nature
• The word Science is derived from Latin and means “to know”
• Inquiry is the search for information and explanation
• There are two main types of scientific inquiry: discovery science and hypothesis-based science
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Discovery Science
• Discovery science describes natural structures and processes
• This approach is based on observation and the analysis of data
• Data are recorded observations or items of information
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Types of Data
• Data fall into two categories:
– Qualitative, or descriptions rather than measurements
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Types of Data
• Data fall into two categories:
– Quantitative, or recorded measurements, which are sometimes organized into tables and graphs
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Hypothesis-Based Science
• Observations can lead us to ask questions and propose hypothetical explanations called hypotheses
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The Role of Hypotheses in Inquiry
• A hypothesis is a tentative answer to a well-framed question
• A scientific hypothesis leads to predictions that can be tested by observation or experimentation
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1.4 What Is Science?
• The scientific method is an important tool of scientific inquiry
– The scientific method consists of six interrelated elements
• Observation
• Question
• Hypothesis
• Prediction
• Experiment
• Conclusion
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Fig. 1-24
Observations
Question
Hypothesis #1:Dead batteries
Hypothesis #2:Burnt-out bulb
Prediction:Replacing batterieswill fix problem
Prediction:Replacing bulbwill fix problem
Test prediction Test prediction
Test falsifies hypothesis Test does not falsify hypothesis
• For example,
– Observation: Your flashlight doesn’t work
– Question: Why doesn’t your flashlight work?
– Hypothesis 1: The batteries are dead
– Hypothesis 2: The bulb is burnt out
• Both these hypotheses are testable
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Observations
Question
Hypothesis #1:Dead batteries
Hypothesis #2:Burnt-out bulb
A Closer Look at Hypotheses in Scientific Inquiry
• A hypothesis must be testable and falsifiable
• Hypothesis-based science often makes use of two or more alternative hypotheses
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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A Closer Look at Hypotheses in Scientific Inquiry
• Failure to falsify a hypothesis does not prove that hypothesis
– For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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Determining the Variables
• Dependent Variable
– Measure, counted or observed in response to experimental conditions
• Independent Variable
– Variable or experimental condition manipulated
• Controlled Variable
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The Procedure
• Procedure
– Sequence of steps to be performed for experiment
• Replication
– Repeat procedure
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• Control
– Independent variable held at established value or omitted
• Prediction
– Tests hypothesis, If……then statements
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Scientific Theory
•Broad in scope
•Generates new hypotheses
•Supported by large body of evidence