BIO113 Lecture 15 (Exam 3)

Allometry and scaling laws

quantitative relationship between size, shape, rates, etc. within and between organisms

• as body size increases something might change faster or slower

Y=AX^Y

Log Y = Log A + blogX

Mammalian metabolic rate

Larger size = greater metabolic rate

Total vs Specific metabolic rate (homeotherms and pokilo therms)

Total metabolic rate is in Watts Body mass M (in Kg)

Homeotherms = 4.1M^.75 Pokilotherms 0.14M^0.75

Specfic metabolic rate = total metabolic rate/M

BMR is rought matched to rate of

heat loss which is… M^.67 to 0.75

Compare the total and specific metabolic rates of an aligator and bird

An aligator would have greater total metabolic rate but lower specific metabolic rate (W/kg).

How do smaller animals achieve higher rate of oxygen delivery to tissues

By making the heart work harder in smmaler animals Heart rate = 241 M^-0.25

Oxyhemoglobin dissociation curves and animal size

Hemoglobin of smaller mammals has lower oxygen affinity, and unload O2 at higher partial pressures. →Greater O2 delivery associated with greater metabolic demands.

Fick’s equation (concept)

Rate of movement of a subastance through diffusion can be changed by changing the area of the concentration gradient. (which is the diff in partial pressures over how thick the barrier is)

Q=DA(P1-P2)/L

Delivery and removal systems for gases and nutrients and waste (6)

1. Diffusion

2. Gills (counter current exchange)

3. Lungs

4. Tracheal system

Diffusion (delivery and removal systems) effects

1. Low metabolic demands

2. Optimal if →All tissues near surface; steep concentration gradiant

Gills and counter current exchange

evaginations into the external medium

countercurrent exchange - oxygen flows from oxygen-rich blood to oxygen-low blood as it gets less and less concentrated.

High O2 (high blood o2) as it decreases, it goes to lower blood o2 areas with less oxygen.

Fills in gaps

Lungs

Invagination into body cavity, increase concetration gradient Lungfish through mammals

Birds and One-way airflow in bird lungs

No “dead space” →less O2 concentrations different mixing (greater gradient)

Have air sacs and lungs.

Inhalation Air sacxs fill → Exhalation Air sacs empty lungs fill.

Tracheal system

Direct delivery of O2 and removal of CO2 through tiny “Trachea throughout the insects body

Limits insect size b/c trachael density increases exponential faster than body size

Carbiniferous period (why and the end of it)

360-300 MYA, high levels of O2 giant insects

why? → High rates of photosythesis low rates of decomposition photosynthesis,

End →Extensive lowlands at continental margins → the majority of coal deposits today

BMR is lower in..

larger animals

Feedback systems

Are used to inhibit or stimulate certain system components

-positive feedback

-negative feedback

positive feedback

amplification of intial disturbance → all or nothing response. larger reponses

examples:

1. Quorum sensing in bacteria → more bacteria more toxins more bacteria

2. Shoaling in Atalantic herring

3. Childbirth and oxytoxicin release

4. Blood clotting

5. Lactation

Negative feedback (Homeostasis)

Maintenance of same state despite enviormental pertuburbations

Examples:

1. Blood sugar

2. Blood PH

3. Body Temp

Stages s of Homeostasis

Detection: A receptor detects the change from the stable state

Counteraction: An effector counteracts the changes from the stable state

Homeostasis components

Receptor- receives a stimuli →detection

Integrator - processes the information from the stimuli “regulatory center”
Effector - carries out a response to the stimuli

Control Theory

State of the system→sensor→controller→effector→state of the system

Mammalian thermal regulation

Metabolic processes are temp dependant (examples) and temperature performance curve

Reaction rates

Binding affinities →different enzymes gave different optimal temperatures

Temperature performance curve→ critical thermal miminimum - 80% breadth - critical maximum)

Poikilothermic vs Homeothermic

Internal tmeperature varies considerable vs An organisms that maintains thermal homeostasis

Ectothermic vs Endothermic

Do not purpose generate heat internally vs Maintain high body temp. By internal heat production

Heat balance 4 ways

Radiation, Evaporation, Convection, Conduction

Radiation

Heat transfer between objects not in direct contact]

Increase heat: rest in sunlight

Decrease heat: rest in shady area

Evaporation

Removal of heat from the surfance as water evaporates\

Increase heat: Allow water to condense

Decrease heat: Allow water to evaporate

Convection

Transfer of heat by the movmenet of air or liquid past a surface

Increase heat: Allow hot air to blow by

Decrease heat: Allow cool air to blow by —shady ravine

Conduction

Direct transfer of heat between molecules of objects in direct contact

Increase heat: rest on warm rock

Decrease heat: rest on cool rock

Cold tolerance methods

1. Super cooling,

2. Freeze tolerance,

3. Migration,

4. Dormancy/hibernation,

5. Staying warm

Freeze tolerance example

Amphibians freeze and lose their heartbeat and circulation, but all vital functions return after thawing

Benefits →Early spring emergence, predator avoidance, range extension

Supercooling and antifreeze proteins

Found in arctic ice fish, budworms

Prevents freezing and cell damage by limiting the size of the ice crystals that can form

→ high polyols, glucose, glycerol, sorbitol → prevents larger ice crystals

Antifreeze proteins compistion

Flat, hydrophilic, threonine rich face adsorbs to surface of ice crystals

Hydrophobic face repels liquid water molecules further inhibiting crystal growth

Hibernation = long term torpor

Adaptation to winter cold and food scarcity during which the animals’s body temeperature declines →often multiple arousal stages and lower metabolic rates

Maintenence of high temperature

1. Basking - basking in sun

2. Insulation - fat and blubber

3. Countercurrent exchange - heat transferred between arteries and veins makes sure all the blood near core is hot, surface is cold

4. shivering

Prevention of overheating

→ evaporative cooling - Sweating, panting

→ Insulation →larger body sizes larger to heat up

Bergmann’s Rule

For homeothermic species, greater body size at higher latitudes