Ecosystems Communities Organisms Populations Biosphere A Hierarchy of Biological Organization
8 Cells 6 Organs and organ systems 7 Tissues 10 Molecules 9 Organelles 50 µm 10 µm 1 µm Atoms
New properties emerge with each step up in hierarchy of biological order Structural arrangement and interaction of parts is important to function!
EMERGENT PROPERTIES ~ the sum is greater than the parts Individual amino acids don ’ t catalyze chemical reactions… but proteins do!
11 MAJOR THEMES that unify biology Connect concepts and provide a framework for understanding
Unifying Themes in Biology connect concepts & provide framework for understanding Evolution ~ biology’s core theme; differential reproductive success Emergent Properties ~ the sum is greater than the parts The Cell ~ basic structure of all organisms Heritable Information ~ DNA Structure & Function ~ form follows function Environmental Interaction ~ organisms are open systems Energy and life ~ work requires energy that flows from sunlight to producers to consumers Regulation ~ feedback mechanisms Unity & Diversity ~ universal genetic code Scientific Inquiry ~ observation; testing; repeatability Science, Technology & Society ~ functions of our world
Evolution – Evolution, biology’s core theme, explains both the unity and diversity of life. The Darwinian theory of natural selection accounts for adaptation of populations to their environment through the differential reproductive success of varying individuals. 11 MAJOR THEMES that unify biology
EVOLUTION is the CORE THEME SLIDE FROM BIOLOGY ZONE by Kim B. Foglia
... as diverse as life is, there is also evidence of remarkable unity Cilia of Paramecium. The cilia of Paramecium propel the cell through pond water. Cross section of cilium, as viewed with an electron microscope 15 µm 1.0 µm 5 µm Cilia of windpipe cells. The cells that line the human windpipe are equipped with cilia that help keep the lungs clean by moving a film of debris- trapping mucus upward.
11 MAJOR THEMES that unify biology Regulation - Everything from cells to organisms to ecosystems is in a state of dynamic balance that must be controlled by positive or negative feedback mechanisms.
In feedback regulation – The output, or product, of a process regulates that very process
In negative feedback – An accumulation of an end product slows the process that produces that product B A C D Enzyme 1 Enzyme 2 Enzyme 3 D D D D D D D D DD C B A Negative feedback Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway
In positive feedback (less common) – The end product speeds up production WW X Y Z Z Z Z Z Z Z Z Z Z Z ZZ Z ZZ Z Z Z Y X Enzyme 4 Enzyme 5 Enzyme 6 Enzyme 4 Enzyme 5 Enzyme 6 Positive feedback EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.
11 MAJOR THEMES that unify biology Image from BIOLOGY ZONE by Kim B. Foglia Interdependence in Nature – No organism “is an island”. Organisms are open systems that exchange materials and energy with their surroundings.
11 MAJOR THEMES that unify biology HERITABLE INFORMATION- The continuity of life depends on the inheritance of biological information in the form of DNA molecules. This genetic information in encoded in the nucleotide sequences of the DNA
How can we understand biological systems? DILEMMA: Because of EMERGENT PROPERTIES we can ’ t fully explain a higher level of order by breaking it into parts, but... organisms are too complex to analyze without taking them apart! TWO STRATEGIES : REDUCTIONISM SYSTEMS BIOLOGY
REDUCTIONISM Reducing complex systems to simpler components that are more manageable to study EXAMPLE: By studying the molecular structure of DNA, James Watson & Francis Crick were able to infer how this molecule could serve as the chemical basis of inheritance
Concept 1.5: Biologists use various forms of inquiry to explore life At the heart of science is inquiry – A search for information and explanation, often focusing on specific questions Biology blends two main processes of scientific inquiry – Discovery science – Hypothesis-based science
Induction in Discovery Science In inductive reasoning – Scientists derive generalizations based on a large number of specific observations EX: “ The sun always rises in the East. ” “ All living things are made of cells. ”
Hypothesis-Based Science (Deductive reasoning) Inquiry that asks specific questions – Usually involves the proposing and testing of hypothetical explanations, or hypotheses Hypothesis – Is a tentative answer to a well-framed question, an explanation on trial – Makes predictions that can be tested – Usually expressed as an: If…., then …. statement
Deduction: The “ If…then ” Logic of Hypothesis-Based Science In deductive reasoning – The logic flows from the general to the specific If a hypothesis is correct – Then we can expect a particular outcome
A Closer Look at Hypotheses in Scientific Inquiry A scientific hypothesis must have two important qualities – It must be testable – It must be falsifiable An hypothesis can only be proven to be FALSE, never proven to be TRUE!
The Myth of the Scientific Method The scientific method – is an idealized process of inquiry There is not “ ONE ” method May design experiment, then backtrack when realize need more observations May redirect research if realize been “ barking up wrong tree ” Hind sight is 20/20
EXPERIMENTAL DESIGN A CONTROLLED experiment must see the effect of ONE VARIABLE at a time Hard to do in field/lab Don ’ t eliminate unwanted variables…. cancel their effects by using a CONTROL GROUP Must be repeated (at least 3 X) Can ’ t ignore or rule out data which do not support the hypothesis
VARIABLES A variable is any factor, trait, or condition that can exist in differing amounts or types. – independent variable is the one that is changed by the scientist. – dependent variable is observed to see how it responds to the change made to the independent variable. The new value of the dependent variable is caused by and depends on the value of the independent variable. – controlled variables. are quantities that a scientist wants to remain constant, and must be observed as carefully as the dependent variables.
HYPOTHESISIndependent variable (What I change) Dependent variable (What I observe) Controlled variables (What I keep the same) If fertilizer is added, then a plant will grow bigger. Measure amount of fertilizer (grams) Growth of the plant measured by its height Growth of the plant measured by the number of leaves There are other ways to measure growth Same size pot Same type of plant Same type and amount of soil Same amount of water and light Make measurements of growth for each plant at the same time The many variables above can each change how fast a plant grows, so to insure a fair test of the fertilizer, each of them must be kept the same for every pot.
“ IT ’ S JUST A THEORY ” In every day conversation, a theory often implies an untested guess. In science, the word “ theory ” means something different than in common usage. Broader than a hypothesis General enough to spin off more hypotheses Supported by a massive body of evidence
“ IT ’ S JUST A THEORY ” A theory is a well supported, testable explanation of natural phenomena. EX: Cell Theory, Gravitational theory, or Atomic theory