This document provides an overview of biology and the scientific method. It discusses that biology is the study of life and its key characteristics, including being made up of cells and organic molecules like DNA and proteins. It also outlines the hierarchical organization of life from subatomic particles to ecosystems. Additionally, it describes the scientific method as a process of making observations, developing hypotheses, conducting experiments to test predictions, analyzing data, and re-evaluating hypotheses based on experimental evidence.

1. Introducing Biology
• Nature of Biology: The Characteristics of
Life
• The Scientific Method

2. The Nature of Biology
• Biology is the study of life
– Life defines animate from inanimate
• Humans from Rocks
• A Donkey from a Chair

3. Universal similarities
• Humans, cats, bacteria, stones, gravel and
brick are all made up of atoms – the
building blocks of matter
• All have their very basic components in the
subatomic particles: protons, electrons and
neutrons.

4. How do we differ?
• The key difference is the difference between
matter and molecules
– Stones and gravel consist of matter
– Biological living beings are made up of organic
molecules

5. Organic molecules: the basic
cellular components:
• DNA and RNA
• Proteins
• Lipids
• Carbohydrates

6. The cell is the smallest unit
having the capacity for life and
ALL living things consist of one
or more cells

7. And all cells are made up of
organic molecules

8. The Characteristics of Life
• Organisms consist of one or more cells
– Assembled by same kinds of atoms and
molecules according to the same laws of energy

9. The Characteristics of Life
• Organisms produce and expend energy
(=metabolism)
– Cells obtain and convert energy from their
surroundings (photosynthesis and aerobic
respiration)
– Cells use energy to maintain themselves
(assemble, stockpile, breakdown and dispose of
necessary cellular materials)

10. The Characteristics of Life
• Organisms sense changes to their
environment and make controlled responses
– Each organism has receptors (molecules and
structures that can detect specific stimuli)
– A stimulus is any energy change in the
environment (light, heat, etc.)

11. The Characteristics of Life
• Organisms have the capacity for growth
– Development occurs in higher organisms
(zygote to multicellular)
– Growth is regulated (not unlimited)

12. The Characteristics of Life
• Organisms have capacity for reproduction
– Based on heritable instructions encoded in the
molecular structure of their DNA
– Sexual reproduction provides the diversity of
organisms

13. The Characteristics of Life
• Organisms die
– Sad but true

14. Biological systems
are organized into a
series of levels,
with the units at one
level forming the
components or
building blocks of
the next.

15. Hierarchy of Life
• Subatomic particles
– Protons, electrons, neutrons
• Atom
– Smallest unit of an element
• Molecule
– Two or more atoms bonded together

16. Hierarchy of Life
• Organelle
– Membrane bound sac or compartment
found inside all cells but bacteria
• Cell
– Smallest unit that can live and reproduce
independently

17. Hierarchy of Life
• Tissue
– An organized group of cells and
surrounding substances functioning
together in a specialized activity
• Organ
– A group of specialized tissues that
together provide a specific function

18. Hierarchy of Life
• Organ system
– 1 of more organs which interact
chemically and/or physically
• Multicellular organism (e.g., us, dog)
– An individual composed of specialized,
interdependent cells

19. Hierarchy of Life
• Population
– A group of individuals of same species
occupying a given area
• Community
– The populations of all species occupying
a given area

20. Hierarchy of Life
• Ecosystem
– A community and its physical
environment
• Biosphere (EARTH)

21. Hierarchy of Life
• Organisms connect with one another by a
one-way flow of energy through them and a
cycling of materials among them.
• The flow of energy starts with the producers
– plants and other organisms capable of
making their own food via photosynthesis.

22. Hierarchy of Life
• Consumers (animals) depend on the energy
obtained by producers (either directly by
eating plants or indirectly by eating animals
that eat plants).
• Decomposers break down biological
molecules and this energy is available to the
producers (nutrients).

23. Hierarchy of Life
• The interconnectedness of organisms affects
the structure, size, and composition of
populations and communities – which
affects ecosystems and the biosphere.

24. The Scientific Method
How we know what we know

25. The Nature of Biological Inquiry
• SCIENTIFIC METHOD in the study of
biological and physical phenomena: The
process involves observing phenomena,
asking questions based on these
observations, devising a tentative
explanation, and performing experiments to
support or refute this explanation.

26. Scientific method involves:
• Make an observation - noting a specific
phenomenon in nature.
– The observations must be systematic and
objective.
• Devise a working hypothesis - coming up
with a tentative explanation for the specific
phenomenon.
– One must explain observations using only
known chemical and physical laws.

27. Scientific method involves:
• Make a testable and falsifiable prediction
- making a claim about what can be
expected based on your hypothesis
– Note: For statistical reasons, we actually test
hypotheses by constructing and testing their
converse, the null hypothesis. Rejecting a null
hypothesis supports the working hypotheses.
By contrast, accepting a null hypothesis
suggests there that our hypotheses is invalid.

28. Scientific method involves:
• Testing the hypothesis/prediction - an
attempt to produce actual observations that
match predicted observation
– involves defining variables to test and
collecting unbiased data.
= Experimental Design

29. Experimental Design
• clearly define independent, dependent and
standardized variables:
– independent variable: the factor being
manipulated in the experiment
– dependent variable: that variable which
responds to the manipulation
– standardized variable: all the variables that are
held constant between the variables.

30. Experimental Design
• Define the experimental treatment:
– A treatment is a test group of individuals that
are subjected to the same levels of the
independent variable.
• Define the control group:
– The control group consists of individuals that
receive no treatment but are held to the same
standardized variables.

31. Experimental Design
• Select materials and identify experimental
methods and methods of data collection.
• Use replications – scientific conclusions are
statistical

32. Scientific method involves:
• Perform experiments and collect data in a
precise and unbiased manner.
• Analyze Data Statistically
– Because results are never absolute, we must
determine the probability that our null
hypothesis is true or false. That is, we attempt
to generalize from our finite sample to the
world at large. This relies on statistical analysis
of the data.

33. Scientific method involves:
• Re-Evaluate Hypotheses and Report
– We can never prove that a hypothesis is true.
Instead, hypotheses are supported when a
number of experiments do not falsify it.

34. If we reject our hypothesis:
• Error in data
• Missing observations
• Predictions based on hypothesis may be
flawed
• Hypothesis itself may be flawed – data do
not support hypothesis (therefore must alter
hypothesis and continue experimentation).

35. Key Elements of a Scientific
Approach
• Criteria for an explanation to be
considered scientific:
– Must explain observations using only known
chemical and physical laws
– Must make testable predictions
– Must be falsifiable

36. Key Elements of a Scientific
Approach
• Important components of the scientific
method:
– Working hypothesis
– Null hypothesis
– Experimental design