1. An Introduction to Life on Earth1
An Introduction to Life on Earth 1

2. Why Study Biology?
Biology helps you to understand your body.
How behavior affects health
How diseases do their damage
Biology helps you to become an informed citizen.
Pollution
Modified foods
Extinction
Cloning
Human stem cell research
Cures for diseases
Population control
Career opportunities
Biotechnology, pharmaceuticals, medical equipment
Allied health
Wild life manager, forester, environmental consultant
Law (environmental, patent, medical malpractice)
Research
Teaching
Biology can enrich your appreciation of the world.

3. Chapter 1 At a Glance 1.1 What Is Life? 1.2 What Is Evolution?
1.3 How Do Scientists Study Life?
1.4 What Is Science?

4. 1.1 What Is Life?
Biology comes from the Greek words “bio” meaning “life” and “logy” meaning “the study of.” Organisms share common characteristics that, taken together, define life. Organisms:
Acquire and use materials and energy
Actively maintain organized complexity
Perceive and respond to stimuli
Grow
Reproduce
Have the capacity to evolve, collectively

5. 1.1 What Is Life? Organisms acquire and use materials and energy
Materials and energy are required for organisms to maintain organization, to grow, and to reproduce
Important materials (minerals, water, & other simple chemical building blocks) are acquired from the air, water, soil, and bodies of other living things
Organisms use energy continuously to sustain themselves

6. Figure 1-2 Properties of life
The waterflea is alive.
Antennae and
eyes: living
things respond
to stimuli
Gut: living
things acquire
nutrients
Eggs: living
things
reproduce
This waterflea is both organized and complex. 6

7. 1.1 What Is Life? Characteristics of living things
This wave is complex but not organized.
It is not alive.

8. 1.1 What Is Life?
Organisms acquire and use materials and energy (continued)
Organisms obtain energy in two ways, coming directly or indirectly from the sun
Photosynthesis is the process by which plants and some single-celled organisms capture sunlight
Other organisms consume energy-rich molecules in the bodies of other organisms

9. Figure 1-3 The flow of energy and the recycling of nutrients9

10. 1.1 What Is Life? Organisms actively maintain organized complexity
Living things use energy on a continuous basis to self-sustain
Cells pump chemicals in and out for appropriate chemical reactions to occur
Organisms maintain relatively constant internal conditions or homeostasis

11. Figure 1-4 Organisms maintain relatively constant internal conditions11

12. 1.1 What Is Life? Organisms perceive and respond to stimuli
Organisms sense and respond to internal and external environmental stimuli
Sensory organs in animals can detect and respond to external stimuli such as light, sound, chemicals, etc.
Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical receptors
Plants and bacteria respond to stimuli as well (e.g., plants grow toward the light, and bacteria move toward available nutrients in a medium)

13. 1.1 What Is Life? Organisms grow
Every organism becomes larger over time
Plants, birds, and mammals grow by producing more cells to increase their mass
Bacteria grow by enlarging their cells; they divide in half to reproduce after genetic material is copied
Growth involves the conversion of acquired materials to molecules of the organism’s body

14. 1.1 What Is Life? Organisms reproduce
Organisms reproduce by dividing in half, producing seeds, bearing live young, and laying eggs
Organisms give rise to offspring of the same type
The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life

15. Figure 1-6 Organisms reproduce
Dividing Streptococcus
bacterium
Dandelion producing
seeds
Panda with its baby 15

16. Figure 1-7 DNA 16

17. 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

18. 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%

19. Figure 1-8 Chimps and people are closely related19

20. Levels of biological organization
Fig. 1-10

21. 1.3 How Do Scientists Study Life?
Life can be studied at different levels
All matter is formed of elements
An atom is the smallest particle of an element retaining the properties of an element
Atoms combine to form molecules
Molecules provide the building blocks for cells, the smallest unit of life

22. 1.1 What Is Life? The cell is the basic unit of life
It is separated from its surroundings by a membrane
It encloses a variety of structures and chemicals in a fluid environment

23. Figure 1-1 The cell is the smallest unit of life
nucleus
cell wall
plasma
membrane
organelles 23

24. 1.3 How Do Scientists Study Life?
Life can be studied at different levels (continued)
Some forms of life consist of single cells
In multicellular forms, cells combine to form tissues
Tissues combine to form organs, which can be united as organ systems
Multicellular organisms are composed of multiple organ systems

25. 1.3 How Do Scientists Study Life?
Life can be studied at different levels (continued)
Organisms of the same type that are capable of interacting and interbreeding are called a species
A group of organisms of the same species living in a given area is a population
Interacting populations make up a community
A community and its nonliving environment is an ecosystem
The entire surface of Earth, including living and nonliving components, is the biosphere

26. 1.3 How Do Scientists Study Life?
Biologists classify organisms based on their evolutionary relationships
Scientists generally categorize organisms into three major groups, or domains
Bacteria
Archaea
Eukarya
The fundamental differences among cell types in organisms are reflected in classifications

27. Figure 1-11 The domains and kingdoms of life
DOMAIN BACTERIA
FIRST CELLS
DOMAIN ARCHAEA
Protists
Plants
DOMAIN EUKARYA
Fungi
Animals 27

28. 1.3 How Do Scientists Study Life?
Biologists classify organisms based on their evolutionary relationships (continued)
Bacteria and Archaea are single, simple cells
Eukaryotic organisms have one or more extremely complex cells
The domain Eukarya contains four subdivisions or kingdoms
Fungi
Plantae
Animalia
Protists

29. 1.3 How Do Scientists Study Life?
Biologists classify organisms based on their evolutionary relationships (continued)
Three characteristics underlie the classification of an organism into a domain and kingdom
There are exceptions to any simple set of rules used to distinguish the domains and kingdoms, but three characteristics are particularly useful
Cell type—simple or complex
The number of cells in each organism—unicellular or multicellular
Energy acquisition

30. 1.3 How Do Scientists Study Life?
Cell type distinguishes the Bacteria and Archaea from the Eukarya
All cells share common features
Plasma membrane is a thin sheet of molecules surrounding the cell
Organelles are specialized structures that carry out specific functions
All cells contain DNA, the hereditary material

31. 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

32. 1.2 What Is Evolution? Three natural processes underlie evolution
Genetic variation among members of a population due to differences in their DNA
Inheritance of those variations by offspring of parents carrying the variation
Natural selection of individuals whose survival and enhanced reproduction are due to the favorable variations they carry

33. 1.2 What Is Evolution?
Mutations are the original source of differences in DNA
Variations are due to the differences in genes, which are components of DNA and the basic units of heredity
Mutations occur when changes in genes are mistakenly copied
Mutations can also result from DNA damaged by
UV rays from sunlight and toxic chemicals from cigarette smoke

34. 1.2 What Is Evolution?
Some inherited mutations help individuals survive and reproduce
Natural selection is the process by which organisms with certain inherited traits survive and reproduce better than others in a particular environment
Organisms that best meet environmental challenges leave the most offspring
Natural selection preserves genes that help organisms flourish

35. Figure 1-9 A fossil Tyrannosaurus rex35

36. 1.4 What Is Science?
Science is the systematic inquiry – through observation and experiment – into the origins, structure, and behavior of living and nonliving environments

37. 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

38. 1.4 What Is Science?
The scientific method is an important tool of scientific inquiry (continued)
Scientific inquiry is a rigorous method for making observations
The scientific method for inquiry follows six steps

39. 1.4 What Is Science? The six steps of scientific inquiry
1. Observation of a specific phenomenon
2. The observation, in turn, leads to a question
3. The question leads to formulation of a hypothesis, based on previous observations, which is offered as an answer to the question

40. 1.4 What Is Science? The six steps of scientific inquiry (continued)
The hypothesis leads to a prediction, which is the expected outcome of testing if the hypothesis is correct
The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments
The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion

41. 1.4 What Is Science?
Biologists test hypotheses using controlled experiments
Two types of situations are established
A baseline or control situation in which all possible variables are held at a constant
An experimental situation in which one factor, variable, is manipulated to test the hypothesis to determine that this variable is the cause of an observation
Science is useless unless communicated
The scientific method is illustrated by experiments by Francesco Redi and Malte Andersson

42. Obtain identical pieces of meat and two identical jars
Figure E1-1 The experiment of Francesco Redi illustrates the scientific method
Observation:
Flies swarm around meat left in the open; maggots appear on the meat.
Question:
Where do maggots on the meat come from?
Hypothesis:
Flies produce the maggots.
Prediction:
IF the hypothesis is correct, THEN keeping the flies away from the meat
will prevent the appearance of maggots.
Experiment:
Obtain identical pieces of
meat and two identical jars
Place meat
in each jar
Experimental variable:
Leave the jar
uncovered
Cover the jar
with gauze
gauze prevents the
entry of flies
Leave exposed
for several days
Controlled variables:
Leave covered
for several days
time, temperature,
place
Flies swarm around
and maggots appear
Results
Flies are kept from
the meat;
no maggots appear
Control situation
Experimental situation
Conclusion:
The experiment supports the hypothesis that flies are the source of
maggots and that spontaneous generation of maggots does not occur. 42

43. Figure E1-2 The experiment of Malte Andersson
Observation:
Male widowbirds have extremely long tails.
Question:
Why do males, but not females, have such long tails?
Hypothesis:
Males have long tails because females prefer to mate with long-tailed males.
Prediction:
IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates.
Experiment:
Divide male birds
into four groups
Manipulate the
tails of the males
Do not
change the tail
Cut the tail and
re-glue in place
Experimental
variable:
Cut the tail to half of
the original length
Add feathers to
double the tail length
length of tail
Release the males,
wait a week,
count the nests
Release the males,
wait a week,
count the nests
Controlled
variables:
Release the males,
wait a week,
count the nests
Release the males,
wait a week,
count the nests
location, season,
time, weather
Average of
about one nest
per male
Average of
about one nest
per male
Results
Average of less
than half a nest
per male
Average of
About two nests
per male
Control groups
Experimental groups
Conclusion:
The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to mate
with short-tailed males) is supported. 43

44. 1.4 What Is Science? Scientific theories have been thoroughly tested
A scientific theory is a general and reliable explanation of important natural phenomena that has been developed through extensive and reproducible observations and experiments
A scientific theory is best described as a natural law, a basic principle derived from the study of nature, which has never been disproven by scientific inquiry

45. 1.4 What Is Science?
Scientific theories are formulated in ways that can potentially be disproved
Basic principles of science are referred to as theories because theories can be disproved or falsified
Falsifying theories is distinctly different between scientific theories and faith-based beliefs
“Each creature on Earth was separately created” cannot be subjected to scientific inquiry because it is a belief rooted in faith

46. 1.4 What Is Science? Science is a human endeavor
Human personality traits are part of “real science”
Scientists, like other people, may be driven by pride, ambition, or fear
Scientists sometimes make mistakes
Accidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances

47. 1.4 What Is Science? Science is a human endeavor (continued)
In the 1920s, bacteriologist Alexander Fleming grew bacteria in cultures
One of the bacterial cultures became contaminated with a mold
Fleming was about to destroy the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture

48. 1.4 What Is Science? Science is a human endeavor (continued)
Fleming hypothesized that the mold produced an antibacterial substance
Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin

49. Figure 1-12 Penicillin kills bacteria
A Petri dish
contains solid
growth medium
Bacteria grow in
dense red colonies
on the growth medium
A substance diffuses
from the mold and
kills the bacterial
colonies, which lose
their color as they die
A colony of the
mold Penicillium 49

50. 1.4 What Is Science? Science is a human endeavor (continued)
Fleming continued beyond a lucky “accident” with further scientific investigation to a great discovery
“Chance favors the prepared mind” Louis Pasteur