INTRODUCTION: CH1
What is Biology
Biology is the scientific study of life
Such ?’s as:
How do plants interact with one another?
How does the human mind work?
Life is categorized by what living things do
Thus it can be somewhat quantified by ‘us’
Chapter 1
Ten Themes in the “study of life”
Emergent Properties
The Cell
Heritable Information
Structure & Function
Interaction with the environment
Regulation
Unity & Diversity
Evolution
Scientific Inquiry
Science – Technology - Society
Emergent properties
New themes in biology arise at each level of biological organization
Emergent properties
Emergent properties result from the arrangement and interaction of parts within a system
Emergent properties characterize nonbiological entities as well
For example, a functioning bicycle emerges only when all of the necessary parts connect in the
correct way
Reductionism & Emergent Properties
Reductionism – reducing complex systems to simpler components which are easier to study.
Systems Biology
Attempts to model behavior of biological systems based on interactions among the systems parts.
This approach allows us to pose new kinds of questions.
How might CO2 increases in the atmosphere alter ecosystem processes?
The Cell
The lowest unit of organization for any organism that can perform all activities required for life.
All cells
Enclosed by a membrane
Use DNA as genetic information
Eukaryotic Cells
Membrane-bound organelles
Largest is usually the nucleus
Contains DNA
Prokaryotic Cells
Simpler, usually smaller
No nucleus
DNA is not separated by membrane-bounded nucleus
Heritable Information
Continuity of life is based on heritable information in the form of DNA.
DNA is the substance of genes
These units of inheritance are passed from parents to offspring.
The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular
organisms.
DNA Structure & Function
Each chromosome has one long DNA molecule which contains 100’s or 1000’s of genes.
Genes encode for protein building.
DNA Structure & Function
Genes control protein production indirectly
Transcribed into RNA then translated to protein
Gene expressionProcess of converting information from gene to cellular product
Genomics & Bioinformatics
Genomics – study of genes within and between species.
Bioinformatics – uses computational tools to process huge amounts of data.
Organisms interact with their environment
These interactions are regulated by feedback mechanisms
Negative Feedback
Positive Feedback
Negative Feedback
As more of a product accumulates, the process that creates it slows and less of the product is
produced.
Positive Feedback
As more of a product accumulates, the process that creates it speeds up and more of the product
is produced.
Positive Feedback
Climate Change
Unity & Diversity
Evolution is the core theme in all branches of biology.
Theodosius Dobzhansky (one founder of evolutionary biology) “Nothing in biology makes sense
except in the light of evolution”
Diversity
~ 1.8 million species identified and named.
New species found each day.
Estimated diversity ranges from 10 – 100 million species.
Classifying diversity: the basics
Taxonomy is the branch of science that names and classifies species into groups.
Domains followed by kingdoms are the broadest units of biological classification.
Three Domains of Life
Organisms are divided into three domains.
Bacteria and Archaea compose the prokaryotes.
Prokaryotes are mostly single-celled and microscopic.
Domain Eukarya
Includes all eukaryotes
Includes 3 multicellular groups
Plants – make own food by photosynthesis.
Fungi – detritus (absorb dead material).
Animals – ingest food.
Unity in the diversity of life
A striking unity underlies the diversity of life
DNA is the universal genetic language of all organisms
Unity is evident in many features of cell structure
Natural Selection & Evolution
Fossils and other evidence document the evolution of life over billions of years.
Two great thinkers developed this theory.
Alfred Russell Wallace
1823 - 1913
British naturalist
Same viewpoints of Charles Darwin
Acutally preempted Darwin’s ideas (just didn’t publish them)
Believed that environmental pressures forced species to adapt
Infamous for biogeography and the roles humans have on animal distribution
Charles Darwin
1809 - 1882
“On the Origin of Species by Means of Natural Selection” published 1859.
Species showed evidence of “descent with modification” from common ancestors.
Natural Selection is the mechanism behind ‘descent with modification’.
Natural Selection
Individuals in a population vary in their traits, many of which are heritable.
More offspring are produced than survive, thus competition is inevitable.
Species are usually suited to their environment.
Inferences made by Darwin
Individuals that are best suited to their environment are more likely to survive and reproduce
Over time, more individuals in a population will have the advantageous traits
Thus, evolution occurs as the unequal reproductive success of individuals.
Natural Selection at Work
Peppered Moth
Light Morph favored on trees with lichens
Industrial revolution caused lichens to die and soot to cover trees
Now dark moths favored
Tree of Life
“Unity in diversity” results from ‘descent with modification’
For example the forelimb of a bat, human, and horse all share a common ancestor.
Scientific Inquiry
Science is derived from Latin and means “to know”
Inquiry is the search for information and explanation
The scientific process includes
Making observations
Forming testable hypotheses
Actually testing them
Types of data collected
Qualitative data
Descriptions rather than measurements.
Researcher’s studying behavior of zoo animals.
Quantitative data
Recorded measurements.
Measuring total biomass of a plant following a flood treatment.
Inductive Reasoning and Hypothesis formation
Inductive reasoning draws conclusions through the logical process of induction.
Repeated observations lead to generalizations
Ex. “The sun always rises in the east”
Ex. “All organisms are made of cells”
Hypotheses
Hypotheses are tentative answers to well-framed questions.
A scientific hypothesis leads to predictions that can be tested by observation or experimentation.
Example
Observation
Flashlight doesn’t work
Question
Why doesn’t my flashlight work?
Hyp1: Batteries are dead
Hyp2: Bulb is burnt out
Both of which are testable
Deductive Reasoning
Example
If organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans
are composed of cells (deductive prediction)
Hypotheses
Hypothesis-based science usually has more than two alternative hypotheses.
You never prove a hypothesis to be true
Failure to falsify a hypothesis does not prove that hypothesis.
Hypotheses must be testable and falsifiable.
No supernatural or religious thoughts should be brought into hypothesis testing.
Case study in Mimicry
Many venomous snakes are brightly colored.
Mimics are harmless snakes that “mimic” their venomous counterparts.
Henry Bates hypothesized that mimicry evolved in harmless individuals as an evolutionary
adaptation to reduce the chances of being eaten
Hypothesis was tested with venomous coral snake and non-venomous kingsnake.
Both species live in the Carolinas, but the kingsnake is also found in regions without venomous
coral snakes.
If predators inherit an avoidance of the coral snake’s coloration, then the colorful kingsnake will
be attacked less often in the regions.
To test this mimicry hypothesis, researchers made hundreds of artificial snakes:
An experimental group resembling kingsnakes
A control group resembling plain brown snakes
Equal numbers of both types were placed at field sites, including areas without poisonous coral
snakes
Experiments must be controlled and repeatable
A controlled experiment compares an experimental group (the artificial kingsnakes) with a
control group (the artificial brown snakes).
Ideally, only the variable of interest (the effect of coloration on the behavior of predators) differs
between the control and experimental groups.
A controlled experiment means that control groups are used to cancel the effects of unwanted
variables.
A controlled experiment does not mean that all unwanted variables are kept constant.
Viewpoints in Science are diverse
Most scientists work in teams, which often include graduate and undergraduate students.
Good communication is important in order to share results through seminars, publications, and
websites.
Science is building on previous knowledge
Scientists check each others’ claims by performing similar experiments.
It is not unusual for different scientists to work on the same research question.
Scientists cooperate by sharing data about model organisms (e.g., the fruit fly Drosophila
melanogaster).
Science, Technology, and Society
The goal of science is to understand natural phenomena.
The goal of technology is to apply scientific knowledge for some specific purpose.
Science and technology are interdependent.
Biology is marked by “discoveries,” while technology is marked by “inventions”.
Ethical issues can arise from new technology, but have as much to do with politics, economics,
and cultural values as with science and technology.
Science benefits from diverse views from different racial and ethnic groups, and from both
women and men.