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Flashcards in Size and Scale Deck (12):

Smallest and largest organisms

-Smallest organisms = frogs and lizards
-Largest Vertebrate = Blue whale (30m and 170 tonnes)
*is massive variations across and w/in species


What happens when a body gets bigger? (2)

-Movement and body shape become restricted
-if you double size, you triple (cube) its mass
-Means need greater support - as bones increase in length they increase in width proportionally more
-5x longer bone needs to be 40x thicker to support
-Stresses on bones greatest at edges (means hollow tubes for bones are stronger)


Forces acting on body (3)

1. Compressive Forces: tend to collapse structures (e.g. weight)
2. Tensile Forces: tend to pull apart
e.g. muscles on tendons
3. Shear Forces: Twisting and sliding of one section on another
e.g. rotation of spine


Consequences of large size (6)

-Reduced trunk flexibility
-Reduced limb flexion
-Skeletal modification (major support shifts from muscle to bone)
-Limb bones pillar-like, vertical (w/ proximal portions longer than distal)
-Feet large, may be padded (digits usu retained for stability)
-Safety (size protects from most predators)


Metabolism and mass

-Many processes involve exchange across surface (respiration, digestion) -> SA is limiting factor
-large animals have to increase relative metabolic areas (e.g. length of digestive tract)


Energy and body mass

-Large bodies easier to maintain (per kilo of body weight)
-small animals require much more energy
-need to maintain body heat (has more heat loss if smaller)
-heat loss proportionate to SA
-Larger animals have proportionately more bone


Types of Growth - Isometric and Allometric growth

-Isometric Growth: All parts grow at relatively the same speed
-geometric similarity retained
-unusual in living organisms (factors of size, gravity and body part functions normally operate)
-Allometric growth: parts do not grow equally
-e.g. human babies -> head doesn't remain as big in comparison to rest of body)


Allometry -what is it

-Positive allometry, isometry and negative allometry

e.g. of kangaroos - male and female muscle

-Relative or differential growth of a part in relation to an entire organism or to a standard
-is the study and measure of such growth
-Positive Allometry - where Variable 1 (e.g. height) increases faster than variable 2 (e.g. head size)
-Isometry: constant ratio (both increase at same rate)
-Negative allometry: head size may double, but head size increases by 1.5

e.g. Females have iometry of muscles in limb, whereas males have positive alometry; 2 x bigger male = 2.5 x bigger muscle


Bergmann's Rule and Allen's Rule

-Bergmann's Rule: Homeothermic animals from higher altitudes and latitudes (or bred at lower temps), tend to be larger
-SA decreased therefore less heat loss
-Allen's Rule: The size of extremities increases from colder to warmer climates in same species (or closely related)
-allows body heat to disperse more readily

*both rules apply to people too


Ecological Influences on size

-Island Dwarfism

-Island Giantism


-Island Dwarfism: on smaller islands, where less food/resources
-e.g. elephants on Malta and Sicily are smaller than African elephants
-Island Giantism: occurs when there are fewer predators on island so that once small animals can become larger (due to loss of predation pressure)
-e.g. Komodo Dragon, Dodo, larger turtoise


Continental size and body size

-Maximal body mass relates to size of landmass -> larger animals need larger territories
-Migration from large to small territories results in loss of body mass w/ time


Climate change and reducing Body size

-38 of 85 animal and plant species showed reduction in size over decades
-include scottish sheep (5% smaller than 1985)
-Cotton, corn, strawberries, shrimp,l crayfish, Atlantic salmon, frogs, toads