1. Chapter 1
Exploring Life

2. Overview: Biology’s Most Exciting Era
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

4. Video: Seahorse Camouflage
Life’s basic characteristic is a high degree of order
Each level of biological organization has emergent properties
Video: Seahorse Camouflage

6. 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

7. A Hierarchy of Biological Organization
Biosphere: all environments on Earth
Ecosystem: all living and nonliving things in a particular area
Community: all organisms in an ecosystem
Population: all individuals of a species in a particular area
Organism: an individual living thing

8. A Hierarchy of Biological Organization (continued)
Organ and organ systems: specialized body parts made up of tissues
Tissue: a group of similar cells
Cell: life’s fundamental unit of structure and function
Organelle: a structural component of a cell
Molecule: a chemical structure consisting of atoms

9. Organs and organ systems Organisms
The biosphere
Organelles
1 µm
Cell
Ecosystems
Cells
Atoms
Molecules
10 µm
Communities
Tissues
50 µm
Populations
Organs and organ systems
Organisms

10. A Closer Look at Ecosystems
Each organism interacts with its environment
Both organism and environment affect each other

11. 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

12. 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

13. LE 1-4 Sunlight Ecosystem Producers (plants and other photosynthetic
organisms)
Heat
Chemical
energy
Consumers
(including animals)
Heat

14. 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

15. LE 1-5
25 µm

16. 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

17. LE 1-6 Sperm cell Nuclei containing DNA Fertilized egg Embryo’s cells
with DNA from
both parents
Embryo’s cells
With copies of
inherited DNA
Egg cell
Offspring with traits
inherited from both parents

18. 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

19. Nucleus DNA Nucleotide Cell DNA double helix Single strand of DNA

20. 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

21. LE 1-8
EUKARYOTIC CELL
PROKARYOTIC CELL
DNA
(no nucleus)
Membrane
Membrane
Cytoplasm
Organelles
Nucleus (contains DNA)
1 µm

22. 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

23. 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

24. 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

26. 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

27. LE 1-10
Outer membrane
and cell surface
CELL
Cytoplasm
Nucleus

28. 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

29. 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

30. Animation: Negative Feedback Animation: Positive Feedback
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

31. A A Negative feedback Enzyme 1 Enzyme 1 B B Enzyme 2 C C Enzyme 3 D D
LE 1-11 A A
Negative
feedback
Enzyme 1
Enzyme 1 B B
Enzyme 2 C C
Enzyme 3 D D D D D D D D D D D

32. W W Enzyme 4 Enzyme 4 X X Positive feedback Enzyme 5 Enzyme 5 Y Y
LE 1-12 W W
Enzyme 4
Enzyme 4 X X
Positive
feedback
Enzyme 5
Enzyme 5 Y Y
Enzyme 6
Enzyme 6 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z

33. 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

35. 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

36. LE 1-14
Species
Genus
Family
Order
Class
Phylum
Kingdom
Domain
Ursus
americanus
(American
black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya

37. 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

38. LE 1-15 Bacteria Protists Kingdom Plantae Archaea Kingdom Fungi
Kingdom Animalia

39. 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

40. Cilia of windpipe cells
LE 1-16a
15 µm
5 µm
Cilia of Paramecium
Cilia of windpipe cells

41. Cross section of cilium, as viewed with an electron microscope
LE 1-16b
0.1 µm
Cross section of cilium,
as viewed with an
electron microscope
Cilia of Paramecium
Cilia of windpipe cells

42. 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

44. 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

46. 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

48. 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

49. LE 1-20 Population of organisms Hereditary Overproduction variations
and competition
Differences in
reproductive success
Evolution of adaptations
in the population

50. Natural selection can “edit” a population’s heritable variations
An example is the effect of birds preying on a beetle population

51. LE 1-21 Population with varied inherited traits
Elimination of individuals with certain traits
Reproduction of survivors
Increasing frequency of traits that enhance
survival and reproductive success

52. Bat wings are an example of adaptation
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 Hawk

54. 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]

55. South American mainland
LE 1-23
Large
ground finch
Large
tree finch
Small
ground
finch
Large cactus
ground finch
Camarhynchus
psittacula
Geospiza
magnirostris
Geospiza
fuliginosa
Green
warbler
finch
Gray
warbler
finch
Sharp-beaked
ground finch
Woodpecker
finch
Medium
tree finch
Geospiza
conirostris
Medium
ground
finch
Certhidea
olivacea
Certhidea
fusca
Geospiza
difficilis
Cactus
ground finch
Camarhynchus
pauper
Cactospiza
pallida
Small
tree finch
Mangrove
finch
Geospiza
fortis
Geospiza
scandens
Camarhynchus
parvulus
Cactospiza
heliobates
Seed eater
Vegetarian
finch
Cactus flower
eaters
Seed eaters
Platyspiza
crassirostris
Insect eaters
Bud eater
Ground finches
Tree finches
Warbler finches
Common ancestor from
South American mainland

56. Video: Albatross Courtship Ritual
Video: Blue-footed Boobies Courtship Ritual
Video: Galapágos Islands Overview
Video Galapágos Marine Iguana
Video: Galapágos Sea Lion
Video: Galapágos Tortoise

57. 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

58. Discovery Science
Discovery science describes nature through careful observation and data analysis
Examples of discovery science:
understanding cell structure
expanding databases of genomes

59. Types of Data Data are recorded observations Two types of data:
Quantitative data: numerical measurements
Qualitative data: recorded descriptions

61. Induction in Discovery Science
Inductive reasoning involves generalizing based on many specific observations

62. Hypothesis-Based Science
In science, inquiry usually involves proposing and testing hypotheses
Hypotheses are hypothetical explanations

63. 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

64. Observations Question Hypothesis #1: Dead batteries Hypothesis #2:
LE 1-25a
Observations
Question
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb

65. Test falsifies hypothesis Test does not falsify hypothesis
LE 1-25b
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test prediction
Test prediction
Test falsifies hypothesis
Test does not falsify hypothesis

66. 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

67. A Closer Look at Hypotheses in Scientific Inquiry
A scientific hypothesis must have two important qualities:
It must be testable
It must be falsifiable

68. 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

69. A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations
In mimicry, a harmless species resembles a harmful species
An example of mimicry is a stinging honeybee and a nonstinging mimic, a flower fly

70. Flower fly (nonstinging)
LE 1-26
Flower fly (nonstinging)
Honeybee (stinging)

71. 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

72. LE 1-27 Scarlet king snake Key Range of scarlet king snake
Range of eastern
coral snake
Eastern coral
snake
North
Carolina
South
Carolina
Scarlet king snake

73. 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

74. (a) Artificial king snake
LE 1-28
(a) Artificial king snake
(b) Artificial brown snake that has been attacked

75. North Carolina South Carolina
LE 1-29
17%
In areas where coral snakes
were absent, most attacks
were on artificial king snakes.
83%
Key
North
Carolina
% of attacks on
artificial king snakes
% of attacks on
brown artificial snakes
South
Carolina
Field site with
artificial snakes
16%
84%
In areas where coral
snakes were present,
most attacks were on
brown artificial snakes.

76. 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

77. 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

78. 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

79. Model Building in Science
Models are representations of ideas, structures, or processes
Models may range from lifelike representations to symbolic schematics

80. From body From lungs Right atrium Left atrium Right ventricle Left
To lungs
To body

81. The Culture of Science Science is an intensely social activity
Both cooperation and competition characterize scientific culture

83. Science, Technology, and Society
The goal of science is to understand natural phenomena
Technology applies scientific knowledge for some specific purpose

85. 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