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Remote Ready Biology Learning Activities

Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.

Biology 103; Fall, 1997

Science? ..... Life?

Science = Life


Scientific method: hypothesis -> experiment -> proof or disproof ...?

hypothesis = summary of observations
experiment = new observation
hypotheses not provable, only disprovable
process infinitely recursive

Start from where one is, accept value of (ideally enjoy) being wrong.


Summaries of observations critical:

Science = a long standing and apparently quite successful effort to make sense of the world, an effort

Life .... ?

Living organism? How tell? Start with preconceptions ....
Practical problem .... life elsewhere in universe? ... how recognize?

A living organism is a ... And if see just one ...?

LIFE is an interacting and interdependent array of diverse living organisms at multiple scales

with substantial "fit" to its surroundings
and substantial variation both at any given time and over time.

Where does "fit" come from? Why persisting variability and change? Accident ...imperfection?

LIFE is an ongoing process of exploration, of generating and testing hypotheses about the surroundings.



seek to account for characteristics of life in terms of interactions of elements at multiple levels of scale over varying periods of time.

Patterns in space?

Diversity and Scale

How "make sense" of diversity?

Arrange in order of size

Technology dependence of observations
Limited range of observations? of sizes of organisms?

Size scales

1. Improbable assemblies exist at a most scales (though see Alvarez)
2. Different features apparent at different scales; at larger scales, smaller wholes become invisible parts
3. There exist lower and upper(?) bounds for living organisms ... as we currently know them
4. Existing observations are greater than in past, but clearly incomplete
5. Can distinguish smaller, single-celled from larger, multicellular organisms
(Why no big unicellular organisms? - need for communication/integration?)

Other ways of making sense of diversity?

Taking advantage of technology: Eukaryotes (Protists) vs Prokaryotes (Monerans: eubacteria and archaea) (Why no multicellular prokaryotes?)

Back to preconceptions: what things LOOK like and do

Plants versus animals versus fungi(?)

Autotrophs versus heterotrophs (interdependence)
With correlates (e.g. cell wall versus no cell wall)
Fungi have cell walls, but different molecular constituents, are heterotrophs but with external digestion
Can use molecules, like any other feature, to evaluate similarities/differences

(Why no autotrophs without cell walls?)

Five (or six, or more) Kingdoms:

Why "clumpiness"? Things like small number of other things, some kinds of things absent?

Look more carefully at animals (metazoans)

More patterns (level of internal complexity, embryology)
More clumpiness

Why no ventral nervous system with endoskeleton?
Humans a small part of life, as life (as we know it) a small part of universe

Other ways of making sense of diversity?
Great chain of being - ordering of organisms along some scale?

Evolution as way of making sense of diversity?

Patterns in time

Scale and Evolution

Time scales?

Human - seconds to years, perhaps three generations (100 years)

Shorter important - milliseconds, nanoseconds (change where not aware of it)
Longer also important (there too change where not aware of it):

Humans young, as yet restricted experience, small part of life
LOTS of time for evolution

Long, slow, inexorable, inevitable continuous change, progressive improvement?

Earliest life - prokaryotes (> 3 billion years, and getting older)

Plenty of time for subsequent development of improbable assemblies, but ...?
Consistent with progression, but changing what adapted to, and persisting

Next steps? How soon?

Eukaryotes - 1-2 billion years ago (last quarter of life's history to date)
much more improbable than prokaryotes?

Multicellular Organisms - ~600 million years ago (last sixteenth of life's history to date)
VERY improbable?

Stasis and change - THEN slow progressive improvement?

Nope, continued fits and starts

Well then ... humans at least?

Nope - diversification and extinction here too
Though there are here, as elsewhere, some reasonably slow, continuous changes

Different time scales reveal different patterns, just as different space scales do
Clumpiness understandable in terms of evolution, but (and) raises new questions

Evolution includes both slow, continuous change and rapid change
  • The latter because exploring some possibilities depends on having explored prior possibilities?
  • Would help explain how highly improbable things come into existence.
  • Indicates very strong history dependence in accounting for life.
Evolution involves "chance", and hence likely to proceed somewhat differently elsewhere or if repeated
  • meteor collisions (and the like)
  • dependence on random variation within biological systems
Evolution does include some directionality, but is not toward "perfection" or "better" but rather toward having explored more (increased "complexity"?)
  • All existing organisms (including ones that have long evolutionary histories) equally adapted ("successful").

Need to account for patterns in space and time at multiple scales
Improbable assemblies, adaptiveness, diversity, change
Can get that from improbable assemblies of physical elements (atoms)?

Remarkable generalization - dissociate ANYTHING, get out elements = atoms

ElementSymbolAtomic numberPercent in universePercent in earthPercent in human

Living, non-living assemblies not distinguishable by identity of constituents at atomic level
Fewer kinds of constituents than of assemblies
Living assemblies are distinctive in proportions of atomic constituents (improbable assemblies)

What are atoms? How get more from less?

Atoms -themelves combinations of still smaller and fewer constituents

Periodic table - another related remarkable generalization

Vastly more possible different molecules than numbers of different atoms - diversity by combinatorial expansion
Combinatorial rules also create 3-D shapes, central to biological processes

Electron, electron affinities key to many biological processes

Water, central to living system as known, example of "emergent properties"

combinations of simple parts (atoms, elements) yield in assemblies (molecules) new properties

keep eyes on electrons, oxygen, charge
on polar vs. non polar
on water
remember three-dimensionality, flux

Overwhelming diversity of molecules (like life)
Any way to make sense of it? Any other useful things to learn at this level?

"Inorganic" versus "organic" molecules?

Carbon based versus non-carbon based, but no longer a good distinction for small molecules (large?)

Functional groups help to make sense of both small and large molecules

Classes of biological(?) macromolecules (and related constituents): lipids, carbohydrates, nucleic acids, proteins

From hydrocarbons to lipids

Carbohydrates: monomers (saccharides) to polymers (polysaccharides)

Nucleic acids, from nucleotides

Proteins, from amino acids

Molecules, macromolecules as smallest boxes, relevant properties, rudiments of life properties from interactions
Macromolecules as clumpy diversity (like organisms)
Why these? How come into existence?
Highly improbable, energy dependent, need cells? (chicken and egg problem?)
Lipids, carbohydrates from proteins
Proteins from nucleic acids
Nucleic acids from evolution?
Clearly history dependent

How get macromolecules? Improbable assemblies? Flux/energy/information?
Assembly rules define possible things that can be, not what IS, nor what leads to change from one thing to another ...

First Law of Thermodynamics - matter/energy remains constant

Second Law of Thermodynamics - change is from less probable to more probable states Diffusion as the archetype of life - improbability and flux driving inpredictably increasing improbability Sun (plus?) as source of driving improbability
Need to capture, use improbablity to make improbability
Take advantage of "quasi-stable" improbability, "energy" in chemical bonds

Why can't eat cellulose? Why doesn't cellulose fall apart?

Enzymes as regulatable rate regulators in flux

"Energy flows" (improbability increases) - metabolism
Catabolism - more to less improbable ("energy yielding")
Coupled to anabolism - less to more improbable ("energy requring")
The driving force: second law, random movement
The constraint: assembly rules plus surroundings
Enzymes as flux organizers

Cells as energy-dependent, semi-autonomous, semi-homeostatic, reproducing, bounded improbable assemblies (scale: microns, tens of microns, a minimum size?)

Prelude: The "cell theory", cell size limitations?

Cell components

The role of the nucleus

Matter and energy flux - energy dependent and energy independent processes


Chloroplasts - photosynthesis - half of life's energy flow cycle

Mitochondria - cellular respiration - the other half

Cell reproduction - Amoeba

Cells as bounded semi-etc improbable assemblies of different interacting molecules
Multi-cellular organisms as bounded semi-etc assemblies of different interacting cells
Similar as well in having internal bounded spaces

Tissues as intermediate levels of organization

Functions of parts of cells served by assemblies of specialized cells
LOTS of different specialized cells in specific, complex three dimensional arrangement (tissues, organs, organ systems)
How get that way (development)? How both work as individual cells, and work together (physiology)?
How get reproduction with variability (genetics)?

Reproduction in multicellular organsims


Relation of meiosis to Mendelian genetics

Development - from single cell to multicellular organism

Genetic identity - cloning and how it was done

Induction (cell interactions)

Cytoplasmic determinants

Extraembryonic influences

Bottom line: complex improbable assembly based on initial information, cell interactions, external influences ... cooperating coordinated system without "boss", influenced by but not determined by genetic information

Multicellular organization the same (abbreviated look)
(From molecules to cells to human experience, some examples, with much left as an exercise for the student)

Need for circulatory system (diffusion vs. bulk flow)

Sex hormones: a case study in interacting parts and the underlying mechanisms

Immune system: more variance

Multiorganismal organization the same (even more abbreviated look): interacting improbable assembly with both homeostatic and autonomous properties

Homeostasis and autonomy in population size

(The Animal Ecology Group at Leiden University has a much more extensive array of population models in Java format)

Bottom line

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