Chapter one Exploring Life
Dec 31, 2015
Inquiring About LifeAn organism’s adaptations to its environment are the result of evolution
For example, the ghost plant is adapted to conserving water; this helps it to survive in the crevices of rock walls
Evolution is the process of change that has transformed life on Earth
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Biology is the scientific study of life
Life is recognized by what living things do
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Living things share 8 characteristics:
1. Living things are made up of units called cells.a. Every organism is composed of at least one cell.
1.) single-celled or unicellular
2.) many-celled or multicellular
b. There are two broad categories of cells:1) prokaryotic—no organized nucleus nor
membrane bound organelles; found in bacteria and cyanobacteria
2) eukaryotic—do have an organized nucleus and membrane-bound organelles such as Golgi apparatus and mitochondria. All other organisms such as plants and animals have this kind of cell.
2. Living things reproduce. There are two basic kinds of reproduction:
a) Asexual—only one parent and all offspring are identical; for example, binary fission of bacteria or amoebas.
b) Sexual—two cells from different parents unite to produce the first cell of a new organism.
3. Living things are based on a universal genetic code (DNA).
a) The directions for inheritance are found in deoxyribonucleic acid or DNA.
b) The genetic code is basically the same for all organisms on Earth.
4. Living things grow and develop.a) For single-celled organisms, growth is mostly an
increase in size.b) Multicellular organisms go through a process called
development, where cells divide and differentiate into different kinds of cells.
Life Requires Energy Transfer and Transformation
A fundamental characteristic of living organisms is their use of energy to carry out life’s activities
Work, including moving, growing, and reproducing, requires a source of energy
Living organisms transform energy from one form to another For example, light energy is converted to
chemical energy, then kinetic energyEnergy flows through an ecosystem, usually
entering as light and exiting as heat© 2011 Pearson Education, Inc.
5. Living things obtain and use materials and energy.
a) The combination of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes is called metabolism.
b) Autotrophs (also called producers)—plants, most algae, and some bacteria obtain their energy directly from the sun through photosynthesis.
Animals eatleaves and fruitfrom the tree.
Leaves take incarbon dioxidefrom the airand releaseoxygen.
Sunlight
CO2
O2
Cyclingof
chemicalnutrients
Leaves fall tothe ground andare decomposedby organismsthat returnminerals to thesoil.
Water andminerals inthe soil aretaken up bythe treethroughits roots.
Leaves absorblight energy fromthe sun.
Figure 1.5
c) Heterotrophs (also called consumers)—most other organisms, rely on the energy stored during photosynthesis.1. Herbivores—eat plants and other photosynthesizing
organisms2. Carnivores—eat the herbivores or other carnivores3. Omnivores—eat both plants and animals4. Decomposers—such as bacteria and fungi; obtain
energy from the remains of organisms that have died
Figure 1.6b
Heat
(b) Using energy to do work
When energy is usedto do work, someenergy is converted tothermal energy, whichis lost as heat.
An animal’s musclecells convertchemical energyfrom food to kineticenergy, the energyof motion. A plant’s cells use
chemical energy to dowork such as growingnew leaves.
6. Living things respond to their environment.a) Organisms detect and respond to
stimuli from their environment.b) A stimulus is a signal to which an
organism responds. c) External stimuli include
temperature and light.d) Internal stimuli come from within,
such as blood sugar level or feeling thirsty.
7. Living things maintain a stable internal environment.
a) Even though external environmental conditions may vary widely, most organisms must keep internal conditions, such as temperature and water content, fairly constant.
b) Maintaining a stable internal environment is called homeostasis (Greek, same condition).
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Feedback Mechanisms Regulate Biological Systems
Feedback mechanisms allow biological processes to self-regulate
Negative feedback means that as more of a product accumulates, the process that creates it slows and less of the product is produced
Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is produced
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Figure 1.13
Negativefeedback
A
B
C
D
C
Enzyme 1
Enzyme 2
Enzyme 3
D
W
Enzyme 4
X
DD
Excess Dblocks a step.
(a) Negative feedback
Positive feedback
Excess Zstimulates a step.
Y
Z
Z
Z
Z
(b) Positive feedback
Enzyme 5
Enzyme 6
8. Taken as a group, living things change over time (living things evolve).a) Plants have adapted to living in dry and hot deserts.b) Fossils of ancient organisms can be used to show how
organisms have changed over time.
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
Figure 1.4
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The biosphere
EcosystemsTissues
Organs andorgan systems
Communities
Populations
Organisms
OrganellesCells
Atoms
Molecules
Figure 1.4
Biological systems are much more than their biological parts Emergent
properties
result from the arrangement and interaction of parts within a system
Reductionism
is the reduction of complex systems to simpler components that are more manageable to study
For example, studying the molecular structure of DNA helps us to understand the chemical basis of inheritance
Systems Biology
A system is a combination of components that function together
Systems biology constructs models for the dynamic behavior of whole biological systems
The systems approach poses questions such as How does a drug for blood pressure affect
other organs? How does increasing CO2 alter the biosphere?
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Structure and Function Are Correlated at All Levels of Biological Organization
Structure and function of living organisms are closely related
For example, a leaf is thin and flat, maximizing the capture of light by chloroplasts
For example, the structure of a bird’s wing is adapted to flight
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The Cell Is an Organism’s Basic Unit 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
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Genes control protein production indirectlyDNA is transcribed into RNA then translated into a proteinGene expression is the process of converting information from gene to cellular product
Evolution, the Overarching Theme of Biology
Evolution makes sense of everything we know about biology
Organisms are modified descendants of common ancestors
Evolution explains patterns of unity and diversity in living organisms
Similar traits among organisms are explained by descent from common ancestors
Differences among organisms are explained by the accumulation of heritable changes
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Classifying the Diversity of Life
Approximately 1.8 million species have been identified and named to date, and thousands more are identified each year
Estimates of the total number of species that actually exist range from 10 million to over 100 million
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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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Binomial Nomenclature was developed by Carolus Linnaeus.
• The scientific name is always written in italics.
• The first work is capitalized, and the second word is lowercased.
Carolus von Linnaeus(1707-1778)
Kingdom
Largest and most inclusive group of closely related phyla
Phylum
group of closely related ClassesClass
group of similar OrdersOrder
group of similar FamiliesFamily
group of Genera that share characteristics
Genus
group of closely related species and the first part of the scientific name in binomial nomenclature
There are seven levels, or taxons, in the system of classification:
Speciesgroup of similar organisms that breed & produce
fertile offspring
Species
Ursus
Ursidae
Carnivora
Mammalia
Ursus americanus(American black bear)
Chordata
Animalia
Eukarya
Genus Family Order Class Phylum Kingdom DomainFigure 1.14
The Six-Kingdom system of classification includes the kingdoms:
Eubacteria Archeabacteria Protista Fungi Plantae Animalia
The Six-Kingdoms fall into categories called domains. Domains are made up of certain
kingdoms. Bacteria: eubacteria Archaea: archaebacteria Eukarya: protists, fungi, plants, and animals
Figure 1.15
(a) Domain Bacteria (b) Domain Archaea
(c) Domain Eukarya
2 m
2 m
100 m
Kingdom Plantae
Kingdom Fungi
Protists
Kingdom Animalia
Charles Darwin and the Theory of Natural Selection
Fossils and other evidence document the evolution of life on Earth over billions of years Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 Darwin made two main points Species showed evidence of “descent with modification” from common ancestors Natural selection is the mechanism behind “descent with modification”
Darwin’s theory explained the duality of unity and diversity
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Darwin’s Observations Individuals in a population vary in their traits, many
of which are heritable More offspring are produced than survive, and
competition is inevitable Species generally suit their environment
Darwin inferred that Individuals that are best suited to their environment
are more likely to survive and reproduce Over time, more individuals in a population will have
the advantageous traits Evolution occurs as the unequal reproductive success
of individuals
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In other words, the environment “selects” for the propagation of beneficial traits
Darwin called this process natural selection
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Figure 1.20
Population withvaried inheritedtraits
Elimination ofindividuals withcertain traits
Reproduction ofsurvivors
Increasing frequency oftraits thatenhancesurvival andreproductivesuccess
1 2 3 4
The Tree of Life
“Unity in diversity” arises from “descent with modification”
For example, the forelimb of the bat, human, and horse and the whale flipper all share a common skeletal architecture
Fossils provide additional evidence of anatomical unity from descent with modification
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COMMONANCESTOR
Green warbler finchCerthidea olivacea
Gray warbler finchCerthidea fusca
Sharp-beakedground finchGeospiza difficilis
Vegetarian finchPlatyspiza crassirostris
Mangrove finchCactospiza heliobates
Woodpecker finchCactospiza pallida
Medium tree finchCamarhynchus pauper
Large tree finchCamarhynchus psittacula
Small tree finchCamarhynchus parvulus
Large cactusground finchGeospiza conirostrisCactus ground finchGeospiza scandens
Small ground finchGeospiza fuliginosa
Medium ground finchGeospiza fortis
Large ground finchGeospiza magnirostris
Inse
ct-e
aters
See
d-e
ater Bu
d-e
ate
r
Inse
ct-e
aters
Tree
finch
es
Gro
un
d fin
che
s
See
d-e
aters
Cac
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-flow
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ters
Wa
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hes
Figure 1.22
Concept 1.3: In studying nature, scientists make observations and then form and test hypotheses
The word science is derived from Latin and means “to know”
Inquiry is the search for information and explanation
The scientific process includes making observations, forming logical hypotheses, and testing them
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Types of Data
Data are recorded observations or items of information; these fall into two categories
Qualitative data, or descriptions rather than measurements For example, Jane Goodall’s observations of
chimpanzee behavior
Quantitative data, or recorded measurements, which are sometimes organized into tables and graphs
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Questions That Can and Cannot Be Addressed by Science
A hypothesis must be testable and falsifiable
For example, a hypothesis that ghosts fooled with the flashlight cannot be tested
Supernatural and religious explanations are outside the bounds of science
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Figure 1.24
Observations
Question
Hypothesis #1:Dead batteries
Hypothesis #2:Burnt-out bulb
Prediction:Replacing bulbwill fix problem
Test of prediction Test of prediction
Test falsifies hypothesis Test does not falsify hypothesis
Prediction:Replacing batterieswill fix problem
In the context of science, a theory is Broader in scope than a hypothesis General, and can lead to new testable
hypotheses Supported by a large body of evidence in
comparison to a hypothesis
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Theories in Science
Science, Technology, and Society
The goal of science is to understand natural phenomena
The goal of technology is to apply scientific knowledge for some specific purpose
Science and technology are interdependentBiology is marked by “discoveries,” while
technology is marked by “inventions”
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The combination of science and technology has dramatic effects on society
For example, the discovery of DNA by James Watson and Francis Crick allowed for advances in DNA technology such as testing for hereditary diseases
Ethical issues can arise from new technology, but have as much to do with politics, economics, and cultural values as with science and technology
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