1. Exploring Life
Chapter 1

2. Unifying Themes of Biology
A hierarchy of organization
The cellular basis of life
Heritable information
The correlation between structure and function
The interaction of organisms with their environment
Unity in diversity
Evolution
Scientific process
Biology is an enormous scope—it is your job to identify how the information we discuss fits into these themes.

3. Life’s Hierarchical Order
Atoms ↓
Biological molecules
Organelles
Cells
Tissues
Organs
Organ systems
Complex organisms
(Beyond the individual organism)
Population
Community
Ecosystem
Biomes
Biosphere
The living world is a hierarchy, with each level of biological structure building on the level below it.
Each level of biological organization has emergent propertiesproperty that emerges as a result of interactions between components

4. Holism and Reductionism
Because properties of life emerge from complex organization, it is impossible to fully explain a higher level of order by breaking it into its partsHolism
Reductionismthe principle that a complex system can be understood by studying its component parts
Watson and Crick used reductionism to understand how DNA is inherited by studying its molecular structure.

5. Cell Theory
Cells are an organism’s basic units of structure and function
Lowest level of structure capable of performing all activities of life
All organisms are composed of cells
May be unicellular or multicellular

6. Cell Theory
Microscopes and the discovery of the cell helped form the cell theory:
Robert Hookelooked at dead cells—cork
Antonie van Leeuwenhoklooked at living cells
Schleiden and Schwannreasoned that all living things are made of cells
Electron microscopes have revealed the complex ultrastructure of cells.

7. Cell Theory Two major kinds of cells Prokaryotic Eukaryotic Bacteria
All other kingdoms
No membrane bound nucleus
Membrane bound nucleus
Lacks membrane bound organelles
Subdivided by internal membranes into functional compartments called organelles
Almost all have tough external walls
Some cells have tough cell walls, animal cells lack cell walls

8. Continuity of life is based on heritable information in the form of DNA
Biological instructions are encoded in DNA
DNA is made of nucleotides
Phosphate │
Sugar—Base (A,G,C,T)
Inheritance is based on mechanism for copying DNA and the passing of this information from the parent to offspringheredity
All forms of life essentially use the same genetic codedifferences in organisms reflect differences in nucleotide sequence

9. Structure and function are correlated at all levels of biological organization
Structure gives clues about what it does and how it works
Apparent at many levels of biological organization
If you know the function, this can help to understand the structure

10. Includes other organisms as well as abiotic factors
Organisms are open systems that interact continuously with their environments
Includes other organisms as well as abiotic factors
Abioticnot living

11. Homeostasis
Regulation of biological processes is critical for maintaining the ordered state of life
Feedback
Positive feedback speeds up a process
Increased uterine contractions, increases childbirth
Negative feedback slows a process down
Constriction of blood vessels, decreased heat loss

12. Evolution, Unity and Diversity
Biological diversity is enormous
To make this diversity more comprehensible, biologist classify species into categoriestaxonomy
Taxonomy is constantly changing—
5 Kingdoms—
Monera, Protista, Fungi, Plantae, Animalia
6 Kingdom—
breaks Monera down into two groups Eubacteria and Archaebacteria

13. Evolution, Unity and Diversity
At the lower levels of diversity and at the lower levels of organization
Universal genetic code
Similar metabolic pathways
Cell structure

14. Evolution, Unity and Diversity
Evolution is the core theme of biology
Life evolves—can be described as a branching tree of life
Species that are very similar share a common ancestor at a recent branch point on the phylogenetic tree
Less closely related organisms share a more ancient common ancestor
All life is connected and can be traced back to primeval prokaryotes that existed more than three billion years ago

15. Evolution, Unity and Diversity
Evolution accounts for both the unity and diversity of life
Similarities between two species may be a reflection of their descent from a common ancestor
Differences between species may be the result of natural selection

16. Scientific Process
Scientific Methodprocess which outlines a series of steps used to answer questions

17. Scientific Process
Hypothesiseducated guess proposed as a tentative answer to a specific question or problem
Inductive reasoningmaking an inference from a set of specific observations to reach a general conclusion
Deductive reasoningmaking an inference from general premises to specific consequences
usually takes the form of if…then logic
deductive reasoning usually involves predicting experimental results that are expected if the hypothesis is true.

18. Scientific Process
Useful hypotheses have the following characteristics:
Hypotheses are possible causes
Hypotheses reflect past experience with similar questions
Multiple hypotheses should be proposed whenever possible
Hypotheses must be testable
Hypotheses can be eliminated, but not confirmed with absolute certainty

19. Scientific Process Controlled experiment
Control groupgroup in which all variables are held constant
Variablecondition of an experiment that is subject to change and that may influence an experiment’s outcome
Experimental groupthe group in which one factor or treatment is varied

20. Scientific Process
Collect data
Make observations
Take measurements

21. Scientific Process Analyze dataPutting data into a usable form Graph
Interpret the datarecognize trends

22. Scientific Process Make a conclusion
Support or disprove your hypothesis ↓
modify experiments
test again
conclusion

23. Science and Technology
Technology extends our ability to observe and measure, which enables scientists to work on new questions that were previously unapproachable