chapter one: exploring life. biology is the scientific study of life biologists are moving closer to...
TRANSCRIPT
Chapter One:
Exploring Life
Biology is the scientific study of life Biologists are moving closer to
understanding: How a single cell develops into an organism How plants convert sunlight to chemical
energy How the human mind works How living things interact in communities How life’s diversity evolved from the first
microbes
What is Biology
Life’s basic characteristic is a high degree of order
Each level of biological organization has emergent properties
Video: Seahorse CamouflageVideo: Seahorse Camouflage
Concept 1.1: Biologists explore life from the microscopic to the global scale
The study of life extends from molecules and cells to the entire living planet
Biological organization is based on a hierarchy of structural levels
A Hierarchy of Biological Organization
1. Biosphere: all environments on Earth2. Ecosystem: all living and nonliving things
in a particular area3. Community: all organisms in an ecosystem4. Population: all individuals of a species
in a particular area5. Organism: an individual living thing
A Hierarchy of Biological Organization (continued)
6. Organ and organ systems: specialized body parts made up of tissues
7. Tissue: a group of similar cells8. Cell: life’s fundamental unit of structure
and function9. Organelle: a structural component of a cell10. Molecule: a chemical structure consisting of
atoms
Ecosystems
The biosphere
Organisms
Populations
Communities
Cells
Organelles
Molecules
Tissues
Organs and organ systems
Cell1 µm
Atoms
10 µm
50 µm
A Closer Look at Ecosystems
Each organism interacts with its environment Both organism and environment affect each other
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
Energy Conversion
Activities of life require work Work depends on sources of energy Energy exchange between an organism and
environment often involves energy transformations
In transformations, some energy is lost as heat
Energy flows through an ecosystem, usually entering as light and exiting as heat
LE 1-4
Sunlight
Ecosystem
Heat
Heat
Chemicalenergy
Consumers(including animals)
Producers(plants and otherphotosynthetic
organisms)
A Closer Look at Cells
The cell is the lowest level of organization that can perform all activities of life
The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms
LE 1-5
25 µm
The Cell’s Heritable Information
Cells contain DNA, the heritable information that directs the cell’s activities
DNA is the substance of genes Genes are the units of inheritance that transmit
information from parents to offspring
LE 1-6
Sperm cell
NucleicontainingDNA
Egg cell
Fertilized eggwith DNA fromboth parents
Embryo’s cells With copies of inherited DNA
Offspring with traits inherited from both parents
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
LE 1-7
DNA double helix Single strand of DNA
Nucleotide
Cell
Nucleus DNA
Two Main Forms of Cells Characteristics shared by all cells:
Enclosed by a membrane Use DNA as genetic information
Two main forms of cells: Eukaryotic: divided into organelles; DNA in
nucleus Prokaryotic: lack organelles; DNA not
separated in a nucleus
LE 1-8
Membrane
Cytoplasm
EUKARYOTIC CELL PROKARYOTIC CELL
DNA(no nucleus)
Membrane
1 µm
Organelles
Nucleus (contains DNA)
Concept 1.2: Biological systems are much more than the sum of their parts
A system is a combination of components that form a more complex organization
Cells, organisms, and ecosystems are some examples of biological systems
The Emergent Properties of Systems
Emergent properties result from arrangements and interactions within systems
New properties emerge with each step upward in the hierarchy of biological order
The Power and Limitations of Reductionism
Reductionism is reducing complex systems to simpler components that are easier to study
The studies of DNA structure and the Human Genome Project are examples of reductionism
Systems Biology
Systems biology seeks to create models of the dynamic behavior of whole biological systems
An example is a systems map of interactions between proteins in a fruit fly cell
Such models may predict how a change in one part of a system will affect the rest of the system
LE 1-10
CELL
Nucleus
Cytoplasm
Outer membraneand cell surface
Systems biology uses three key research developments: High-throughput technology: methods to
generate large data sets rapidly Bioinformatics: using computers and
software to process and integrate large data sets
Interdisciplinary research teams
Feedback Regulation in Biological Systems
Regulatory systems ensure a dynamic balance in living systems
Chemical processes are catalyzed (accelerated) by enzymes
Many biological processes are self-regulating: the product regulates the process itself
In negative feedback, the accumulation of a product slows down the process itself
In positive feedback (less common), the product speeds up its own production
Animation: Negative Feedback Animation: Positive Feedback
LE 1-11
Enzyme 1
A A
BB
C C
DD
D
DD
D
D
D
DDD
Enzyme 2
Enzyme 3
Negativefeedback
Enzyme 1
LE 1-12
W
Enzyme 4
W
XX
Y Y
ZZ
ZZ
Z ZZ
ZZ Z
Enzyme 5
Enzyme 6
Positivefeedback
Enzyme 4
Enzyme 6
Enzyme 5
Z
Z Z Z
Z
Z
Z
ZZ
Concept 1.3: Biologists explore life across its great diversity of species
Biologists have named about 1.8 million species
Estimates of total species range from 10 million to over 200 million
Grouping Species: The Basic Idea
Taxonomy is the branch of biology that names and classifies species into a hierarchical order
Kingdoms and domains are the broadest units of classification
LE 1-14
Ursidae
Ursus
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Species Genus Family Order Class Phylum Kingdom DomainUrsusamericanus(Americanblack bear)
The Three Domains of Life
At the highest level, life is classified into three domains: Bacteria (prokaryotes) Archaea (prokaryotes) Eukarya (eukaryotes)
Eukaryotes include protists and the kingdoms Plantae, Fungi, and Animalia
LE 1-15
Bacteria 4 µm 100 µm
0.5 µm
Kingdom PlantaeProtists
Kingdom AnimaliaKingdom FungiArchaea
Unity in the Diversity of Life
Underlying life’s diversity is a striking unity, especially at lower levels of organization
In eukaryotes, unity is evident in details of cell structure
LE 1-16a
Cilia of windpipe cellsCilia of Paramecium
15 µm 5 µm
LE 1-16b
Cilia of windpipe cellsCilia of Paramecium
Cross section of cilium,as viewed with anelectron microscope
0.1 µm
Concept 1.4: Evolution accounts for life’s unity and diversity
The history of life is a saga of a changing Earth billions of years old
The evolutionary view of life came into sharp focus in 1859, when Charles Darwin published On the Origin of Species by Natural Selection
“Darwinism” became almost synonymous with the concept of evolution
The Origin of Species articulated two main points: Descent with modification (the view that
contemporary species arose from a succession of ancestors)
Natural selection (a proposed mechanism for descent with modification)
• Some examples of descent with modification are unity and diversity in the orchid family
Natural Selection
Darwin inferred natural selection by connecting two observations: Observation: Individual variation in heritable
traits Observation: Overpopulation and
competition Inference: Unequal reproductive success Inference: Evolutionary adaptation
LE 1-20
Evolution of adaptationsin the population
Differences inreproductive success
Overproductionand competition
Populationof organisms
Hereditaryvariations
Natural selection can “edit” a population’s heritable variations
An example is the effect of birds preying on a beetle population
LE 1-21
Population with varied inherited traits
Elimination of individuals with certain traits
Reproduction of survivors
Increasing frequency of traits that enhancesurvival and reproductive success
Natural selection is often evident in adaptations of organisms to their way of life and environment
Bat wings are an example of adaptation
Video: Soaring HawkVideo: Soaring Hawk
The Tree of Life
• Many related organisms have similar features adapted for specific ways of life
Such kinships connect life’s unity and diversity to descent with modification
Natural selection eventually produces new species from ancestral species
Biologists often show evolutionary relationships in a treelike diagram
[Videos on slide following the figure]
LE 1-23
Largeground finch
Large cactusground finch
Sharp-beakedground finch
Geospizamagnirostris
Geospizaconirostris
Mediumground finch
Geospizafuliginosa
Smallground finch
Woodpecker finch
Camarhynchuspsittacula
Large tree finch
Medium tree finch
Cactusground finch
Geospizadifficilis
Cactus flowereaters
Geospizascandens
Seed eater
Ground finches
Seed eaters
Tree finches
Common ancestor fromSouth American mainland
Insect eaters Bud eater
Warbler finches
Mangrove finchGeospiza
fortis
Cactospizapallida Small
tree finch
Camarhynchuspauper
Camarhynchusparvulus
Greenwarblerfinch
Graywarblerfinch
Certhideaolivacea
Certhideafusca
Vegetarianfinch
Platyspizacrassirostris
Cactospizaheliobates
Video: Albatross Courtship RitualVideo: Albatross Courtship Ritual
Video: Blue-footed Boobies Courtship RitualVideo: Blue-footed Boobies Courtship Ritual
Video: GalapVideo: Galapáágos Islands Overviewgos Islands Overview
Video Galapágos Marine Iguanagos Marine Iguana
Video: Galapágos Sea LionVideo: Galapágos Sea Lion
Video: Galapágos TortoiseVideo: Galapágos Tortoise
Concept 1.5: Biologists use various forms of inquiry to explore life
Inquiry is a search for information and explanation, often focusing on specific questions
The process of science blends two main processes of scientific inquiry: Discovery science: describing nature Hypothesis-based science: explaining nature
Discovery Science
Discovery science describes nature through careful observation and data analysis
Examples of discovery science: understanding cell structure expanding databases of genomes
Types of Data
Data are recorded observations Two types of data:
Quantitative data: numerical measurements Qualitative data: recorded descriptions
Induction in Discovery Science
Inductive reasoning involves generalizing based on many specific observations
Hypothesis-Based Science
In science, inquiry usually involves proposing and testing hypotheses
Hypotheses are hypothetical explanations
The Role of Hypotheses in Inquiry
In science, a hypothesis is a tentative answer to a well-framed question
A hypothesis is an explanation on trial, making a prediction that can be tested
LE 1-25a
Hypothesis #1:Dead batteries
Hypothesis #2:Burnt-out bulb
Observations
Question
LE 1-25b
Hypothesis #1:Dead batteries
Hypothesis #2:Burnt-out bulb
Test prediction
Test falsifies hypothesis
Prediction:Replacing batterieswill fix problem
Prediction:Replacing bulbwill fix problem
Test prediction
Test does not falsify hypothesis
Deduction: The “If…then” Logic of Hypothesis-Based Science
In deductive reasoning, the logic flows from the general to the specific
If a hypothesis is correct, then we can expect a particular outcome
A Closer Look at Hypotheses in Scientific Inquiry
A scientific hypothesis must have two important qualities: It must be testable It must be falsifiable
The Myth of the Scientific Method The scientific method is an idealized
process of inquiry Very few scientific inquiries adhere
rigidly to the “textbook” scientific method
In mimicry, a harmless species resembles a harmful species
An example of mimicry is a stinging honeybee and a nonstinging mimic, a flower fly
A Case Study in Scientific Inquiry: Investigating Mimicry in Snake
Populations
LE 1-26
Flower fly (nonstinging)
Honeybee (stinging)
This case study examines king snakes’ mimicry of poisonous coral snakes
The hypothesis states that mimics benefit when predators mistake them for harmful species
The mimicry hypothesis predicts that predators in non–coral snake areas will attack king snakes more frequently than will predators that live where coral snakes are present
LE 1-27
Scarlet king snake
Eastern coralsnake
Scarlet king snake
Key
Range of scarlet king snake
NorthCarolina
Range of easterncoral snake
SouthCarolina
Field Experiments with Artificial Snakes
To test this mimicry hypothesis, researchers made hundreds of artificial snakes: An experimental group resembling king snakes A control group resembling plain brown snakes
• Equal numbers of both types were placed at field sites, including areas without coral snakes
• After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks
• The data fit the predictions of the mimicry hypothesis
LE 1-28
(a) Artificial king snake
(b) Artificial brown snake that has been attacked
In areas where coral snakes were present, most attacks were on brown artificial snakes.
In areas where coral snakeswere absent, most attacks
were on artificial king snakes.
LE 1-29
% of attacks onartificial king snakes
% of attacks onbrown artificial snakes
Field site withartificial snakes
83%
NorthCarolina
SouthCarolina
17%
16%
84%
Key
Designing Controlled Experiments
Scientists do not control the experimental environment by keeping all variables constant
Researchers usually “control” unwanted variables by using control groups to cancel their effects
Limitations of Science
The limitations of science are set by its naturalism Science seeks natural causes for natural
phenomena Science cannot support or falsify
supernatural explanations, which are outside the bounds of science
Theories in Science
A scientific theory is much broader than a hypothesis
A scientific theory is: broad in scope general enough to generate new
hypotheses supported by a large body of evidence
Model Building in Science
Models are representations of ideas, structures, or processes
Models may range from lifelike representations to symbolic schematics
LE 1-30Frombody
Fromlungs
Rightatrium
Leftatrium
Rightventricle
Leftventricle
To lungs To body
The Culture of Science
Science is an intensely social activity Both cooperation and competition
characterize scientific culture
Science, Technology, and Society
The goal of science is to understand natural phenomena
Technology applies scientific knowledge for some specific purpose
Concept 1.6: A set of themes connects the concepts of biology
Biology is the science most connected to the humanities and social sciences
Underlying themes provide a framework for understanding biology