Size and Scale

Question 1

Smallest and largest organisms

Answer 1

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

Question 2

What happens when a body gets bigger? (2)

Answer 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)

Question 3

Forces acting on body (3)

Answer 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

Question 4

Consequences of large size (6)

Answer 4

• 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)

Question 5

Metabolism and mass

Answer 5

• 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)

Question 6

Energy and body mass

Answer 6

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

Question 7

Types of Growth - Isometric and Allometric growth

Answer 7

• 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)

Question 8

Allometry -what is it

• Positive allometry, isometry and negative allometry
  e. g. of kangaroos - male and female muscle

Answer 8

• 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

Question 9

Bergmann’s Rule and Allen’s Rule

Answer 9

• 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

Question 10

Ecological Influences on size

• Island Dwarfism
• Island Giantism
• e.g.

Answer 10

• 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

Question 11

Continental size and body size

Answer 11

• 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

Question 12

Climate change and reducing Body size

Answer 12

• 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