2. Scientific Method
• 1. Observation
• Using senses
• Learning from other scientists in the field
• 2. Create Hypothesis
• Based on existing knowledge
• If not supported, it can be
– Modified
– Rejected
• Must be testable
– Morals and religious beliefs are not always testable
3. • 3. Experiments and more observations
• Experimental variable
– What is changed in experiment
• Test groups
– Exposed to experimental variable
• Control group
– Not exposed to experimental variable
• Model
– Sometimes used in place of actual object
» Computer software
» Mice instead of humans
• Data
– Results of experiments and observations
– Correlation does not indicate causation
4. • 4. Conclusion
• Is hypothesis supported by data or not
• If not supported, propose new hypothesis
• CANNOT prove anything in science, only support
• Experiments and observations must be repeatable
by other scientists
• Scientific Theory
• Ultimate goal of science
• Accepted explanations for how the world works
6. Sample Experiment – Growing
plants in presence of salt
• Observation – Previous research, fields irrigated
with saltwater are lifeless
• Hypothesis – As the concentration of salt in the
soil increases, the amount of plant growth will
decrease
• Experiment – Include replicates
Control Pots Test Pots I Test Pots II
Water Only 5% Saltwater 10% Saltwater
7. • Results
Average Growth of Plants watered
with Varying Salt Concentrations
25
20
15
10
5
0
h wo G na P ega ev A
Control 5% Saltwater 10% Saltwater
r
Treatment
t r t l
8. • Conclusion – Hypothesis is supported.
Data illustrates that as salt concentration of
water increased, plant growth decreased.
• Follow-up Experiment – Perform the same
experiment with plants that live along the
ocean shore.
9. • Follow-up Results
Average Growth of Plants watered
with Varying Salt Concentrations
25
Average Plant Growth (mm)
20
15
10
5
0
Control 5% Saltwater 10% Saltwater
Treatment
10. • Follow-up Conclusion – Possible that
different plants are affected in different
ways when exposed to salt. Native
environment may play a large role.
11. Five Basic Theories of Biology
Theory Concept
• Cell • All organisms are composed of cells, and
new cells only come from preexisting cells
• Gene • All organisms contain coded information that
dictates their form, function, and behavior
• All organisms have a common ancestor, but
• Evolution each is adapted to a particular way of life
• All organisms have an internal environment
• Homeostasis that must stay relatively constant within a
range protective of life
• All organisms are members of populations
• Ecosystem that interact with each other and with the
physical environment within a particular
locale
12. Levels of Biological Organization
• Atom
– Smallest unit of an element (protons, electrons, neutrons)
• Molecule
– Two or more atoms of same or different elements
• Cell
– Structural and functional unit of all living things
• Tissue
– Group of cells with a common structure and function
• Organ
– Tissues functioning together for a specific purpose
• Organ System
– Several organs working together
13. • Organism
– Individual complex individual containing organ
systems
• Population
– Organisms of same species in particular area
• Community
– Interacting populations in a particular area
• Ecosystem
– Community plus physical environment
• Biosphere
– Crust, water, and atmosphere inhabited by living
things
14.
15. Cells are the Fundamental Unit of
Living Things
• Cell Theory
– Cells are the fundamental unit of living things
– Cells come from other cells
• Split
• Sexual reproduction
– Cells use materials and energy
• Sun is the ultimate source of energy – allows
plants to grow, which provides animals with food
16. Organisms have a Genetic
Inheritance
• Gregor Mendel
– Father of genetics
– Performed experiments with pea plants and
inheritance
– Genes – units of heredity
• James Watson and
Francis Crick
– Genes are composed
of DNA
17. • Gene Theory
– Genes are hereditary units composed of DNA
– Genes control the structure and function of
cells and organisms
• Gene theory applications
– Study metabolism at molecular level
– Who is related to whom
– Species conservation
– Genetic testing for diseases
18. Organisms Regulate their Internal
Environment
• Theory of Homeostasis
– Cells and organisms have an internal
environment
– Cells regulate this environment so that it stays
fairly constant
• Examples
– Body maintaining blood sugar levels
– Reptiles using sun to regulate temperature
– Plants bending towards sunlight
19. • Response to stimuli – this ability assists
the homeostatic ability of organism
– Vulture detecting carcass
• For food
– Monarch butterfly sensing fall
• Time to migrate
– Plant bending towards sun
• For photosynthesis
– Animal running away from danger
• For survival
20. The Biosphere is Divided into
Ecosystems
• Theory of Ecosystems
– Organisms form units in which they interact
with the biotic (living) and abiotic (nonliving)
components of the environment
• Biosphere
– Climate (temperature and precipitation)
determines where ecosystems are found in
biosphere
21. • Ecosystems characterized by
– Chemical cycling
• Chemicals move from one population to another in
a food chain
• Death and decomposition return nutrients back to
the soil to be used by plants again
– Energy flow
• From sun to plants to other members of the food
chain
• Gradually dissipates, does not cycle
• Photosynthesizers required to absorb energy
22.
23. The Ancestry of Species can be
Determined
• Theory of Evolution
– Organisms have shared characteristics due to common descent
– Evolutionary tree
• Traces the ancestry of a group to a common ancestor
– Ways to trace evolution
• Molecular data
• Fossil record
• Anatomy and physiology of
organism
• Embryonic development of
organism
Remember: species evolve,
not individuals
24. Evolutionary Relationships help
Biologists Group Organisms
• Organizing Diversity
– Taxonomy
• Identifying and grouping organisms according to
certain rules
– Classification categories
• Least inclusive to most inclusive
• Species, genus, family, order, class, phylum,
kingdom, and domain
25. • Domains – 3 domains
– Archaea
• Live in harsh environments
• Prokaryotes
– Bacteria
• Live in more common
environments
• Prokaryotes
– Eukarya
• Eukaryotes
• Protists, fungi, plants, and animals
26. • Scientific Names
– Binomial nomenclature
• 2 part name
• Genus and specific epithet (descriptive term)
• Phoradendron tomentosum or P. tomentosum
• Scientific names are Latin and universally used to
avoid confusion
27. Evolution through Natural Selection Results
in Adaptation to the Environment
• Charles Darwin
– Father of evolution
– Concluded that natural selection
is the process that makes modification
(adaptation) possible
• Natural selection
– Some aspects of the environment selects which traits
are more apt to be passed on to the next generation
– Mutations fuel natural selection because they produce
variation
28. Plant typically produces
smooth leaves
Mutation causes leaves
to be covered with hairs
Deer prefer to eat
smooth leaves
Hairy leaves have an
advantage
Generations later, most
of those plants produce
hairy leaves
29. Evolution’s Many Applications
• Agriculture
– Artificial selection of crops and livestock for high yield
in a short amount of time
– Pesticide use selects for resistant insects
• Medicine
– Antibiotic use selects for resistant bacteria
• Conservation
– Bacteria converting corn to ethanol, select for most
efficient
– Endangered species breeding
30. Evolution from a Common Ancestor
Accounts for the Characteristics of Life
1. Life is organized
2. Life uses materials and energy
3. Life reproduces
4. Life is homeostatic
5. Life responds to stimuli
6. Life forms ecosystems
7. Life evolves
