Download Homeostasis External vs. Internal conditions

1/25/2017
Homeostasis
External vs. Internal conditions
• Regulation of internal body conditions
• Often regulated via negative feedback system
Thermostat
Input feedback
Furnace
Air
Conditioner
• Three general types of managing internal conditions
– Avoiders
– Conformers
– Regulators
• Prefix: Homeo or poikilo
• Suffix: thermo, haline etc…
Internal Environment
Hot or cold air
External Environment
Avoiders, Conformers and Regulators
Various methods for regulating, conforming or avoiding
Icefish:
Stenothermal or eurythermal?
Oligothermal or polythermal?
Homeothermic or poikilothermic?
Ectothermic or endothermic?
Avoider, conformer or regulator?
1
1/25/2017
Mechanisms of Adaptation
• DNA – genotype
• Phenotype – what
selection acts on.
• Review basics of protein
synthesis.
• Genes are expressed to
produce proteins. Proteins
perform most functions,
make up what the
phenotype is.
Overview - Control of Gene Expression
+ environment =
Proteins
• Protein diversity
– Number proteins= 20n (n=#
AA)
– Sequence of 10 AA -> ~10
trillion different proteins
• Structure and shape of proteins
• Ligand
• Allosteric effect
• Protein actions
– Pump
– Motor
– Enzyme
– Etc…
Gene Regulation
• Gene regulatory proteins (activators and repressors)
• Promoter region and transcription factors
2
1/25/2017
RNA Processing
Protein Evolution
• Point mutations -> fine tuning of existing
proteins
• Duplications
– Pseudogenes
– Gene families
• Intron-exon system – one gene can produce
multiple proteins through different splicing
(alternative splicing)
Protein Evolution
• Recombination
– Homologous (crossing over) or
non-homologous
• Protein complexes
– Form of quaternary structure
Hemoglobin is also a well known gene family…
• Multiple forms:
– Maternal vs. fetal
forms
– Can evolve
independently
• Expected to be under
strong selection
3
1/25/2017
Feedback loops
• Key course
concepts:
– Homeostasis
– Energetics
– Optima
Allometry
Allometry
• “The structural and functional consequences of
changes in size or scale among otherwise similar
organisms” – Schmidt-Nielsen
• Isometric geometric shapes:
Head width ~ 13% of height
Head width ~ 9% of height
4
1/25/2017
1000
1200
500
1000
200
50
100
Surface Area
Vol 1436.8 SA 615.8
400
– Very basic functionality (exchange with the
environment) works differently at those scales
800
• Bacteria – 10-13 grams
• Blue whale – 108 grams
• For a sphere (by definition, an isometric shape)
– Surface Area = 4πr2
– Volume = 4/3πr3
– As length increases, volume increases at greater rate
than total surface area
– Slope of the double log plot is 2/3
600
• Anything that does not change isometrically, changes
allometrically
– Isometry, negative and positive allometry
• Why it matters:
– Organisms vary in size over 21 magnitudes
Allometry
Surface Area
Allometry
20
200
Vol 523.6 SA 314.2
0
Vol 33.5 SA 50.3
0
1000
2000
3000
4000
5
10
20
50
Volume
• Surface area to volume ratio shows negative allometry
• Cellular level – physiological constraint on cell size
• Organism level - the rate of exchange with the
environment changes dramatically with size.
200
500
1000
2000
5000
Volume
Allometry
• Relationships can be easily described
mathematically
• Comparing lines tells us a lot about species
Morphological or Physiological Trait
Allometry of surface area
100
Body Size
5
1/25/2017
Allometry
Example allometric relationships
• Most of the time we will examine allometry in terms of body size
• Power function:
– Y=a Mb
• Not always linear
• Log form of equation
– Log Y = log a + b log M
20.0
10.0
2.0
log Y
5.0
• Hemoglobin concentration, cell size
– If something is isometric, b=1.0
• Eg. blood or lung volume in mammals
1.0
a=1.0 b=0.67
a=10 b=0.67
a=1.0 b=1.15
a=1.0 b=0.25
– Positive allometry (b>1) – mammal bone thickness b= 1.08
0.5
–
–
–
–
Y = trait of interest
a = proportionality constant
b = slope
M = mass
• Why? What does this mean biologically?
0.2
•
•
•
•
• The proportionality constant and mass exponent describe
allometric relationships.
• b – how something changes with size
– No relationship to size (technically, negative), b=0
0.1
0.5
1.0
5.0
log Mass
10.0
50.0
100.0
– Negative allometry (b<1) – human skull size, mammal
heart rate
• a – how the intercept changes among lines
6