Biology is the study of life at all levels of organization, from atoms to ecosystems. It seeks to understand the diversity of life forms and their unity through common traits like cells, DNA, and evolution. The scientific process involves making observations and developing hypotheses and theories, which are continually tested through experimentation and evidence. While facts are prerequisites, science advances when new theories tie together disparate findings or technologies answer old questions. Biology explores life through cooperative yet skeptical inquiry to build knowledge and address society's needs and problems.

2. Biology:
Exploring Life

3. Introduction
• Biology, the study of life, is rooted in the human
spirit.
• Biology is the scientific extension of the human
tendency to connect to and be curious about life.
• Biology is one of the sciences takes us:
– Into a variety of environments to investigate
ecosystems
– To the laboratory to examine how organisms
work
– Into the microscopic world to explore cells and
the submicroscopic to explore molecules in cells
– Back in time to investigate the history of life.

4. • Biology is both – a body of
knowledge &
an ongoing inquiry process to
enhance it.
• This is an exciting era for exploring
biology.
–The largest and best-equipped
community of scientists try to solve
problems that once seemed insolvable.

5. –Genetics and cell biology are
revolutionizing medicine and agriculture.
–Molecular biology provides new tools to
trace the origins and dispersal of early
humans.
–Ecology is helping evaluate
environmental issues.
–Neuroscience and evolutionary biology
are reshaping psychology and
sociology.

6. Unifying themes pervade all of biology
• Life’s basic characteristic is a high degree of
order build with materials based on carbon.
• Biological organization is based on a hierarchy
of structural levels, each building on the
levels below.

7. Hierarchical levels of life
• Atoms
• Molecules
• Organelles
• Cells
• Tissues & Organs
• Organisms
• Populations
• Communities
• Ecosystems & Biosphere Visible
Invisible

8. Atoms & Molecules
• At the lowest level are atoms of diverse
chemical elements.
• Atoms are ordered via
bonds into larger, complex
biological entities called
molecules.
• Many molecules are arranged into minute
structures called organelles, which are crucial
functional components of cells.

9.  Cells are the smallest living structures of
organisms; they are the living units of life.
 Some organisms consist of single cells, others
are multicellular aggregates of specialized cells.
 Whether multicellular or
unicellular, all organisms
must accomplish the
same functions:
uptake and processing of
nutrients, excretion of wastes, response to
environmental stimuli, and reproduction among
others.

10. Tissues
 Similar cells are grouped into tissues to fulfill
certain biological functions.
 In multicellular organisms several tissues coordinate to
form organs, and several organs form an organ system.
For example, to coordinate
locomotory movements,
sensory information travels
from sense organs to the brain,
where nervous tissues composed
of billions of interconnected neurons,
supported by connective tissue,
coordinate signals that travel via
other neurons to the individual muscle cells.

11. Organisms & Populations
 Biological organisms belong to larger populations,
i.e., a localized group of organisms belonging to
the same species.
 Populations of several species in the same
environment comprise a
biological community.
 These populations interact
with their physical
environment to form
an ecosystem.

12. Biology: The study of life
• Investigating life at its many levels is
fundamental to biology.
• Biological processes often involve several levels
of biological organization.
– The coordinated strike of a rattlesnake at a mouse
requires complex interactions at the molecular, cell,
tissue, and organ levels within its body.
• Many biologists study life at one level but gain a
broader perspective when integrating
discoveries with processes at other levels.

13. Life & Emergent properties
• While studying life, novel properties emerge at each step
upward in the biological hierarchy.
• These emergent properties result from interactions
between components.
– A cell is certainly much more than a bag of molecules.
• This theme of emergent properties accents the
importance of structural arrangement.
• The emergent properties of life are not supernatural, but
simply reflect a hierarchy of structural organization.

14. • Life resists a simple, one-sentence definition, but we can
recognize life by what living things do; life has defining
properties.

15. Is this “Fulgurite” alive?
• How do you know you deal with life?

16. The properties of life
1. Complex structures
- made of chemical elements, mostly carbon (C)
2. Metabolism
- the sum of all chemical reactions
- anabolism & catabolism
3. Homeostasis
- capacity to maintain internal balance
4. Responsiveness
- living organisms are able to react to external
stimuli, e.g. light, cold, heat, with the help of
sensory mechanisms, tissues or organs

17. The properties of life
5. Development & Growth
- living organisms develop from simple small
structures, e.g. spores, seeds, eggs, cells, into
more complex or multiple structures

18. Properties of life
6. Reproduction
- living organisms are able to form new (daughter)
organisms and
new generations
with the help of
the hereditary
molecule DNA
7. Capacity to evolve

19. The diversity of life
• Diversity is a hallmark of life.
– At present, biologists have identified and named
about 1.5 million species.
• This includes over 280,000 plants, almost 50,000
vertebrates, and over 750,000 insects.
– Thousands of newly identified species are added
each year.
• Estimates of the total diversity of life range
from about 5 million to over 30 million species.

20. • Biological diversity is something to relish and
preserve, but can be a bit overwhelming.
• Despite its complexity, biologists have categorized life
into a smaller number of groups through taxonomy.
• Taxonomy is the
branch of biology
that names and
classifies species
into a hierarchical
order.
Taxonomy

21. The diversity of life
• More than 1.5 million different species are known
• Biologists ordered - or classified – life’s huge diversity
into three domains and six major kingdoms

22. The six kingdoms of life

23. • New methods, including comparisons of DNA among
organisms, have led to a reassessment of the number
and
boundaries of the
kingdoms.
• Below the kingdom level
biologists introduced
phyla, classes, orders,
families and genera
• At the lowest level is
the species concept

24. Life: Unity in diversity
• Despite the enormous diversity there is much
unity in life.
• All life forms are made up from cells.
- prokaryotic & eukaryotic cell types exist
- cell theory postulates that all living things consist
of cells.
• The hereditary molecule
of all forms of life is DNA.
- DNA is the substance of genes,
the units of inheritance that
transmit information from parents
to offspring.

25. • All forms of life employ the same genetic code
made up from 64 chemical codons.
- The diversity of life is generated by different
expressions of a common chemical language for
programming biological order.
• All life forms assure growth by performing
highly similar DNA copying and cell division
processes.
- DNA replication, mitosis (eukaryotic) & binary
fission (prokaryotic)
• All life forms use ribosomes to translate the
genetic code of genes into proteins

26. • All life forms use biological catalysts called
enzymes to drive their many chemical reactions,
i.e. metabolism.
• All life forms posses regulatory control
mechanisms which assure homeostasis.
- positive and negative feedback mechanisms
- negative feedback slows processes down

27. • All life forms exist as open systems that
exchange energy and materials with their
surrounding environment.
- leaves absorb carbon dioxide from the air, water
from the soil and capture
the energy of light to
drive photosynthesis; in
exchange oxygen is
released
- the exchange of energy
between an organism
and its surroundings
involves the transformation of energy from one
form to another while heat is released

28. • Strong correlation of structure and function in
life forms at all levels of biological organization
• E.g. structure-function relationship in the
aerodynamic efficiency in shape of bird wing.
– Honeycombed internal structure produces light but
strong bones.
– Neurons control
flight muscles.
– Many mitochondria
provide the energy
to power flight.

29. • All life forms evolve.
• Evolution is the key to understanding
biological diversity. Evolutionary connections
among all organisms explain the unity and
diversity of life.
• Evolution is the core
theme of biology.
• It accounts for this
combination of unity
in diversity of life.

30. • Since life evolves, each species is one twig on a
branching tree of life extending back through
ancestral species, living and extinct.
• The history of life is a
saga of a restless
Earth billions of years
old, inhabited by a
changing cast of living
forms.

31. • Species that are very similar share a common
ancestor that represents a relatively recent branch
point on the tree of life.
– Brown bears and polar bears share a recent
common ancestor.
• Both bears are also related through older common
ancestors to other organisms.
– The presence of hair and milk-producing
mammary glands indicates that bears are related
to other mammals.
• Similarities in cellular structure, like cilia, indicate a
common ancestor for all eukaryotes.
• All life is connected through evolution.

32. • Charles Darwin brought evolutionary biology into
focus in 1859 when he presented two main
concepts in The Origin of Species.
• 1. Contemporary species
arose from a succession
of ancestors through
“descent with modification”
(evolution).
• 2. The mechanism of
evolution is natural
selection.

33. The process of science
• The word science is derived from the Latin
verb ‘scientia’ meaning “to know”.
• At the heart of science are people asking
questions about nature and believing that
those questions are answerable.
• The process of science blends two types of
exploration: discovery science and
hypothetico-deductive science.

34. • Science seeks natural causes for natural
phenomena.
• The scope of science is limited to the study of
structures and processes that we can observe
and measure, either directly or indirectly, e.g.
through
experimentation.
• Verifiable observations
and measurements are
the data of discovery
science.

35. • Discovery science can lead to important
conclusions via inductive reasoning.
• An inductive conclusion is a generalization that
summarizes many concurrent observations.
• The observations of discovery science lead to
further questions and the search for
additional explanations via the scientific
method.

36. Scientific inquiry process
• The scientific method consists of a series of steps.
• Few scientists adhere
rigidly to this prescription,
but at its heart the
scientific method employs
hypothetico-deductive
reasoning.

37. Role of hypothesis
• A hypothesis is a tentative answer to some
question (“proposed explanation”).
• The deductive part in hypothetico-deductive
reasoning refers to the use of deductive logic
to test hypotheses.
• Most hypothesis are tested by performing a
scientific experiment to see whether or not
the results are as predicted.
• Deductive logic takes the form of “If…then”
logic.
– Reasoning flows from general to specific.

38. Experimental controls
• A “good” scientific hypothesis has to be testable
(‘verifiable’), falsifiable and based on causality.
• Scientists use controlled experiments to make
comparisons between two sets of subjects, e.g.
patients +/- drug.
– The set that receives the experimental treatment (drug) is
the experimental group.
– The control group receives all variables as the
experimental group except the control variable (= drug).
• Controlled experiments enable scientists to focus on
responses to the change of a single variable.

39. Scientific theory
• Facts, in the form of verifiable observations and
repeatable experimental results, are the
prerequisites of science.
• Science advances when several observations and
experimental results that seemed unrelated are
tied together in a theory.
• A scientific theory is broader in scope, more
comprehensive, than a hypothesis.
– They are only widely accepted in science if they are
supported by the accumulation of extensive and
varied evidence.

40. • Scientific theories are not the only way of
“knowing nature”.
– Various religions present diverse legends that tell of
a supernatural creation of Earth and its life.
– Science and religion are two very different ways of
trying to make sense of nature.
– Art is another way.
• Biology showcases life in the scientific context of
evolution, the one theme that continues to hold
biology together no matter how big or complex
the subject becomes.

41. • Facts, in the form of verifiable observations and
repeatable experimental results, are the prerequisites of
science.
• Science advances when:
1. A new theory ties together several observations
and experimental results that seemed unrelated
previously.
2. New technologies are applied to answer old
questions.
• A scientific theory is broader in scope, more
comprehensive, than a hypothesis.
– Both are only accepted in science if they are
supported by accumulation of extensive and varied
evidence.

42. • It is not unusual that several scientists are asking
the same questions using different approaches,
e.g. techniques.
– Scientists build on earlier research and pay close
attention to contemporary scientists in the same field.
– They share information through publications, seminars,
meetings, and personal communication.
• Both cooperation and competition characterize
the scientific culture.
– Scientists check each other’s claims by attempting to
repeat experiments.
– Scientists are generally skeptics.

43. • Some philosophers of science argue that scientists are
so influenced by cultural and political values that
science is no more objective than other ways of
“knowing nature”.
• At the other extreme are those who view scientific
theories as though they were natural laws.
• The reality of science is somewhere in between.
• The cultural milieu affects scientific fashion, but need
for repeatability in observation and hypothesis testing
distinguishes science from other fields.
• If there is “truth” in science, it is based on a
preponderance of the available scientific evidence.

44. Science & Technology
• Are associated and are functions of society.
• Technology results from scientific discoveries
applied to the development of goods and
services.
• DNA technology and biotechnology has
revolutionized the pharmaceutical industry.
• It also has an important impact on agriculture
and the legal profession.
– E.g. genetic engineering enables scientists to
transplant foreign genes into microorganisms and
mass-produce valuable products.

45. • Not all of technology is applied science.
– Technology predates science, driven by inventive
humans who designed inventions without
necessarily understanding why their inventions
worked.
– The direction that technology takes depends less on
science than it does on the needs of humans and the
values of society.
• Technology has improved our standard of living,
but also introduced new problems.
– Science can help us identify problems and provide
insight about courses of action that prevent further
damage.

46. • Both science and technology have become
powerful functions of society.
• It is important to distinguish “what we would like
to know” from “what we would like to build.”
• Scientists should try to influence how scientific
discoveries are applied.
• Scientists should educate politicians,
bureaucrats, corporate leaders, and voters about
how science works and about the potential
benefits and hazards of specific technologies.