Lecture 1: Key Themes Flashcards
1
Q
What is physiology?
A
- how animals work
- not anatomy
- function not just structure
- how animals work in diff environmental contexts
- link structure and function
2
Q
Adaptive physiology
A
- how challenges in environment effect physiology
- e.g. pollution in rivers, climate change
Ecotoxicology: chemical toxicity & tolerance. How pollutants affect organisms.
3
Q
Integrative physiology
A
- no system / organ / tissue / cell / molecule exists in isolation
- all linked and working together
4
Q
What does an animal need?
A
- O2
- H2O
-nutrients - temp
- to reproduce
5
Q
Homeostasis
A
- ‘A self-regulating process by which biological systems maintain stability while adjusting to changing external conditions.’ (Bilman, 2013).
- not a fixed state, a similar state
- a dynamic, steady state
- responsive to feedback mechanisms
NEEDS: sensor, set point, integrator, effectors
6
Q
Feedback control
A
Negative feedback: response will reverse or cause opposite effect of original stimulus.
- Deviation in controlled variable e.g. fall in body temp below set point
- Detected by sensors e.g. temp monitoring nerve cells
- Informs integrator e.g. temp control centre
- Sends instructions to effectors e.g. skeletal muscles etc
- Brings about compensatory response e.g. increase heat production through shivering etc
- Variable restored to normal e.g. increased body temp to set point
- Leads to negative feedback to shut off system responsible for response.
7
Q
Not all processes regulated by negative feedback
A
-
Physiological reset (or restasis)
- temporary increase in set point
- e.g. fever, increase in body temp helps fight infection
- some are short lived or permanent
- e.g. puberty, set point for producing sex hormones elevated
8
Q
Not all processes regulated by negative feedback
A
-
Positive feedback loop
- e.g. during labour. Signal from mature fetus > uterus begins contractions > stretch sensors > mothers hypothalamus > pituitary gland > oxytocin secreted. > contractions are enhanced
- e.g. immune response, site of injury platelets produced & release clotting factors to recruit more platelets.
9
Q
Response to environment
A
- environment acting on physiology
- if effect of environment too strong = disruption of homeostasis.
- or can have adaptive response
10
Q
Adaptive responses
A
-
ACCLIMATISATION
- change occurs in individuals own lifetime = phenotypic plasticity (=one genotype in individual can produce can produce many different phenotypes depending on environmental influence).
- e.g. O2, temp
- increased sensitivity in early life, e.g. exposed to low O2 concentration, animal develops particular physiological adjustments to better tolerate low O2 environment.
- changes in early life often irreversible = ‘developmental plasticity’
- multiple unknown mechanisms responsible e.g. epigenetic
- rapid & usually not heritable
- when something occurs naturally in environment -
ACCLIMATION
- same changes as acclimatisation but induced in laboratory/experiment
11
Q
Adaptive responses
A
-
ADAPTATION
- evolution by natural selection (organism with advantageous traits more likely to survive & pass on traits to offspring).
- changes in underlying DNA sequence.
- gradual change over generations
- heritable genetic adaptation
12
Q
Example of ACCLIMATION
A
- carpe (fish) exposed to high levels of nitrate & temp
- these 2 stressors reduce available O2 (increased temp reduces O2 solubility)
- animal will acclimate
- physiological changes to allow animal to extract O2 more efficiently & carry more O2 around body
- carpe will increase gill surface area to allow more O2 transport from H2O into body tissue AND increase ventricular mass (increase in heart size & strength to pump blood cells around body)
13
Q
Example of ACCLIMATION & ADAPTATION
A
- copepods (small marine plankton) along west coast of America, Vancouver (lower temps) at top, California (higher temps) at bottom.
- huge range of temps along coast (lower at top, warmer at bottom)
- study collected popualtions from diff sites
- first tested their temp tolerance AND performed acclimation experiment
- took populations & reared them at 2 developmental temps (20˚C & 25˚C)
- showed it was genetic adaptations. From California there is increased survival than populations in Vancouver. So they genetically adapted.
- California populations better tolerate temp.
- also populations reared at 20˚C always had lower survival than those at 25˚C
- so rearing them at a higher temp further increases temp tolerance. = Acclimation (a more rapidly occurring adaptive response)
- reasons they can tolerate increased temps due to heat shock proteins, allow organisms to repair DNA damage under increased temps
- so the populations surviving produce more HSP
14
Q
Biological constraints
A
- limit course of adaptive evolution & animal physiology
- animals cannot continue getting bigger, faster, more fecund.
Due to trade-offs:
- energy use - having to enact physiological responses takes energy e.g. HSP.
- e.g. trade off between egg size & number of eggs in a clutch is down to energy
- e.g. trade off between speed & strength
- cost benefit analysis
15
Q
Example of biological constraint
A
Scaling
- size influences performance & is subject to constraints e.g. niche availability (is there niche available at that size?), food requirements (more food for larger species), environmental suitability, competition, predation.
16
Q
What determines body size limits?
A
-
Metabolic demands:
- larger body size = higher energetic demands, more food intake, expend more energy in day to day life.
- Kleiber’s law (1932) - increase in mass leads to increase in MR, but this doesn’t have a symmetric relationship (every time double mass do not double MR), when double mass get increase of MR only to 3/4 of what you’d expect, MR~Mass^3/4, this is Allometric scaling = larger organisms have a lower MR per unit of body mass compared to smaller organisms.
- metabolic demands also depend on life history
- amount of energy/MR required to regulate body temp elevates for endotherms & is less for ectotherms.
- endotherms generally not as small as ectotherms
17
Q
What determines body size limits?
A
-
Mechanical constraints
- Cube Law = 2 diff animals, on linear axis one is twice as big, SA is 4 times as big, vol is 8 times as big, there is gravitational FORCE acting on animal, force is 8 times as big, STRESS is what constraints size, stress = force/SA, stress is how the force is distributed across animals surface, there is twice the amount of stress acting on larger animals.
- mechanical stress doubles for every linear (length) doubling
- animals deal with that by increasing skeletal mass (increase strength of skeleton) to compensate.
- but this gets incapacitating (loose mobility as skeleton is dense & heavy)
18
Q
What determines body size limits?
A
-
Ability to thermoregulate
- Bergmann’s Law (1847) = increase in latitude (further from equator, lower temp) leads to an increase in body size of the Swedish moose
- larger animals occur at cooler temps (higher latitudes) as they have bigger SA to vol ratio, so warm blooded animals (endotherms)able to retain heat better (as they usually bigger)
- smaller animals loose heat well but struggle to keep warm.
19
Q
Small size VS large size animals
A
Small:
+ lower total food demand
+ lower skeletal pressure
+ easier to keep cool
Large:
+ easier to keep warm
+ more fat (energy) reserves
+ amount of food needed per Kg of mass is less
+ better defence against predators
+ wider range & search capacity
20
Q
Mammalian (endotherms)
A
- lower size limits set by energetic demands (when too small , require too much energy to keep warm & do daily activities)
- higher limits set by mechanical stress (terrestrial) (weight of skeleton & agility) AND total food demand (marine)
21
Q
Invertebrates (ectotherms)
A
- can be much smaller (do not need to use additional energy to keep warm)
- upper limits determined by structural constraints & O2 diffusion (insects don’t have circularly systems, O2 needs to diffuse into body)
