01 intro to the science of life(1)
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© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko
PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, andCampbell Essential Biology with Physiology, Fourth Edition – Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Chapter 1Chapter 1Introduction: Biology Today
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• Biology is the scientific study of life
• The study of biology encompasses a wide scale of size and a huge variety of life, both past and present
THE SCOPE OF LIFE The Properties of Life
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• Biologists explore life at levels ranging from the biosphere to the molecules that make up cells
Life at Its Many Levels
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Figure 1.1a
(a) Order (b) Regulation
(d) Energy processing(c) Growth and development
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Figure 1.1b
(f) Reproduction
(g) Evolution(e) Response to the environment
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Figure 1.2-3
Organisms5
12
3
4
7
6
8
109
BiosphereEcosystems
Populations
Communities
Organ Systemsand Organs
Tissues
Cells
OrganellesMolecules and Atoms
NucleusAtom
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Ecosystems
• Each organism interacts continuously with its environment
– Organisms interact continuously with the living and nonliving factors in the environment
– All the living organisms in a specific area, along with all of the nonliving factors with which they interact, form an ecosystem
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Ecosystems
• The dynamics of any ecosystem depend on two main processes:
– Recycling of chemical nutrients
– Flow of energy
• Within ecosystems
– Nutrients are recycled but energy flows through
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Figure 1.3
ECOSYSTEMInflowof lightenergy
Outflowof heatenergy
Producers(plants and otherphotosyntheticorganisms)
Chemicalenergy(food)
Cyclingof
nutrients
Consumers(animals)
Decomposers(in soil)
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Cell Theory
• The cell is the level at which the properties of life emerge
• All organisms are composed of cells
• Cells are the lowest level of structure that can perform all activities required for life
– In other words, the smallest living organism is composed of at least one cell
• Cells are the subunits that make up multicellular organisms such as humans and trees
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• Cells share many characteristics
– All cells are enclosed by a membrane that regulates the passage of materials between the cell and its surroundings
– All cells have ribosomes where proteins are made
– Every cell uses DNA as its genetic information
Cells
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• We can distinguish two major types of cells:
1. The prokaryotic cell is
– Simpler and usually smaller because it lacks a nucleus and organelles
– Characteristic of bacteria and archaea
2. The eukaryotic cell is
– Subdivided by internal membranes into different functional compartments called organelles, the largest of which is the nucleus
– Found in protists, fungi, plants, and animals
Prokaryotes versus Eukaryotes
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Figure 1.4
Nucleoidregion Nucleus
Organelles
Prokaryotic cell (bacterium)
Smaller
Simpler structure
DNA concentrated innucleoid region, which isnot enclosed by membrane
Lacks most organelles
•••
•
••
•
•
Larger
More complexstructure
Nucleus enclosedby membrane
Contains many types of organelles
Eukaryotic cell
Co
lori
zed
TE
M
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• All cells use DNA as the chemical material of genes, the units of inheritance that transmit information from parents to offspring
• The chemical language of DNA
– Is common to all organisms
– Consists of just four molecular building blocks with names that are abbreviated as A, G, C, T
– A is for adenine, G for guanine, C for cytosine, and T for thymine
Cells and Their DNA
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Figure 1.5
A DNA molecule
The fourchemicalbuildingblocks of DNA
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• The entire “book” of genetic instructions that an organism inherits is called its genome
• The nucleus of each human cell packs two genomes, one from mom and one from dad, that are about 3 billion base pairs long
Cells and Their DNA
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Life in Its Diverse Forms
• Diversity is a hallmark of life
– The diversity of known life includes about 1.8 million species that biologists have identified and named
– Estimates of the total number of species range from 10 million to over 100 million
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Figure 1.7
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Grouping Species: The Basic Concept
• Biodiversity can be beautiful but overwhelming
• Categorizing life into groups helps us deal with this complexity
• Taxonomy is the branch of biology that names and classifies species
– It formalizes the hierarchical ordering of organisms into broader and broader groups
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The Three Domains of Life
• The three domains of life are
– Bacteria
– Archaea
– Eukarya
• Bacteria and Archaea have prokaryotic cells
• Eukarya have eukaryotic cells
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• Eukarya include
– Kingdom Plantae
– Kingdom Fungi
– Kingdom Animalia
– Protists (multiple kingdoms)
• Most plants, fungi, and animals are multicellular
• Protists are generally single-celled, but large multicellular seaweeds and kelps (aka algae) are also placed in this group
The Three Domains of Life
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• Bacteria and Archaea are all single-cell prokaryotic organisms
• The Eukarya are distinguished by how they obtain food
– Plants produce their own sugars and other foods by photosynthesis
– Fungi are mostly decomposers, digesting dead organisms
– Animals obtain food by ingesting (eating) and digesting other organisms
– The protists don’t fit neatly into this scheme because seaweeds and protozoans are very different
The Three Domains of Life
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Figure 1.8
Protists (multiple kingdoms)
Kingdom Animalia
Kingdom Fungi
Kingdom Plantae
DO
MA
IN E
UK
AR
YA
DO
MA
IN
AR
CH
AE
A D
OM
AIN
B
AC
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RIA
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EVOLUTION: BIOLOGY’S UNIFYING THEME
• The history of life is a saga of a constantly changing Earth billions of years old
– Fossils and other evidence document this history
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Figure 1.9
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• Life evolves
– Each species can be seen as one twig of a branching tree of life extending back in time through ancestral species more and more remote
– Species that are very similar, such as the brown bear and polar bear, share a more recent common ancestor
EVOLUTION: BIOLOGY’S UNIFYING THEME
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Figure 1.10
Millions of years ago
Giant panda
Common ancestor ofpolar bear and brown bear
2025 101530 5
Common ancestor of all modern bears
Ancestral bear
Spectacled bear
Sloth bear
Sun bear
American black bear
Asiatic black bear
Polar bear
Brown bear
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The Darwinian View of Life
• The evolutionary view of life came into focus in 1859 when Charles Darwin published On the Origin of Species by Means of Natural Selection
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• Darwin’s book developed two main points:
1. Species living today descended from a succession of ancestral species in what Darwin called “descent with modification,” capturing the duality of life’s
– unity (descent) and
– diversity (modification)
2. Natural selection is the mechanism for descent with modification (evolution)
The Darwinian View of Life
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Figure 1.11
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Observing Artificial Selection
• Artificial selection is the selective breeding of domesticated plants and animals by humans
• In artificial selection, humans do the selecting instead of the environment
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Figure 1.13a
(a) Vegetables descendedfrom wild mustard
Wild mustard
Cabbagefrom end buds
Cauliflowerfrom flowerclusters
Broccoli fromflowers and stems
Kale from leaves
Kohlrabifrom stems
Brusselssprouts from side buds
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Figure 1.13b
(b) Domesticated dogsdescended from wolves
Domesticated dogsGray wolves
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THE PROCESS OF SCIENCE
• There are two main scientific approaches:
– Discovery science is mostly about describing nature through verifiable observations and measurements
– What we see through discovery science causes us to ask questions and seek explanations
– This results in hypothesis-driven science where we try to explain why something is the way it is
– We make an educated guess called a hypothesis and then set out to test it through experimentation
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Figure 1.14a
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Figure 1.14b
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• Once a hypothesis is formed, an investigator can use logic to test it
– A hypothesis is tested by performing an experiment to see whether results are as predicted
– This deductive reasoning takes the form of “If…then” logic
Hypothesis-Driven Science
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Figure 1.15-3
Experimentdoes notsupport
hypothesis.
Experimentsupports
hypothesis;make morepredictions
and test.
ObservationThe remote
doesn’twork.
HypothesisThe
batteriesare dead.
QuestionWhat’swrong?
ExperimentReplace
batteries.
PredictionWith new
batteries, itwill work.
Revise.
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Theories in Science
• What is a scientific theory, and how is it different from a hypothesis?
– A scientific theory is much broader in scope than a hypothesis
– Theories only become widely accepted in science if they are supported by an accumulation of extensive and varied evidence
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The Culture of Science
• Scientists build on what has been learned from earlier research
– They pay close attention to contemporary scientists working on the same problem
• Cooperation and competition characterize the scientific culture
– Scientists check the conclusions of others by attempting to repeat experiments
– Scientists are generally skeptics
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• Science has three key features that distinguish it from other forms of inquiry
– Science depends on observations and measurements that others can verify
– It requires that ideas (hypotheses) are testable by experiments that others can repeat
– It also requires that hypotheses be falsifiable, i.e., there must be some circumstance that you could think of where the hypothesis could be proven false
The Culture of Science
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– Technology has improved our standard of living in many ways, but it is a double-edged sword
– Technology that keeps people healthier has enabled the human population to double to 7 billion in just the past 40 years
– The environmental consequences of this population growth may be devastating
Science, Technology, and Society
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