Overall premise: basic similarity in mechanisms between all animals.
Justification for reductionist approach: flies, simple animals.
Text- Fig 1.2: similarity in arm/dog foreleg/ seal flipper
Insect: similarity in basic mechanisms for appendage development
Basic cellular & developmental mechanisms, ie:
Cell death pathways [apotosis]; cell cycle
Segment identity; A/P [anterior/posterior]
D/V [dorsal/ventral] development
Related to: Immune regulation
Eye development; simple vs. compound: link to fly eye structure, development:
Ectopic eyes by ectopic expression of an eye development gene:
Czerny et al Molecular Cell, (1999) Vol. 3, 297–307
Neural development & physiology
Complexity in vertebrates: 4x genome duplication vs. flies/worms -> redundant genes
-> common lack of phenotypes in single gene knockouts
Earth: ~4.5 billion yrs old: early atmosphere reducing; no O2
First life: ~3.6 billion years ago; origin unclear: simple organic compounds throughout universe.
Simple prokaryotic cells in ocean environment; anaerobic; scum=slime=biofilm. A problem in medicine:
"Slime" May Be Cause of Common Childhood Ear Infection
~2.7 bya: blue-green algae: prokaryotes (cyanobacteria): photosynthesis -> O2 production: O2 accumulation by 2.3 bya; 400 million years of rust....
Conversion of anaerobic to aerobic metabolism; accumulation of O3 in last 800 myrs to provide UV protection.
Eukaryotes: single cell: ~1.7 byrs
Land plants: only ~400 myrs ago.
Homo sapiens: ~100K; oldest cave paintings: 35K yrs.
Life: cells: simple membranous compartments; reduced entropy; self replicating units containing carbohydrates, lipids, nuceic acids, proteins; early life: probably RNA based.
Prokayote cells: no internal membraneous organelles. Must survive in varied environments; biofilms=scum. Prokarya, Archaebacteria; To survive harshest conditions: spores
Multicellularity->specialization; sex vs. somatic cells: mitosis vs. meiosis.
Internal environments controlled: individual cells less able to survive varied environments.
Regulated growth: -> developmental mechanisms.
Diversity through speciation:
Diversity through imprecise replication! HIV
Biological studies at different levels:
Reductionist vs. holistic; extremes: bored vs scared to death
Common to all: hypothesis testing: validation or invalidation
Reproducibility: distinction from non-scientific studies.
Experimental approach: objectivity: Pons/Fleischmann