Insect size and consequences

Question 1

Big Vs Small

Answer 1

Bigger…
+make better predators
+can cope with environmental fluctuations better
-big investment but bigger = greater lifespan, more investment into body to mature
-slow reproduction
Smaller…
+rapid development
+adaptable populations - persistence and resilience due to genetic and phenotypic D
-prone to adverse events of environment fluctuations

Question 2

Constraints on size (other than tracheal system)

Answer 2

1. Exoskeleton - relating to the fact they are terrestrial

2. Flight and tracheal system - flight is costly so needs lots of energy

Question 3

Exoskeleton constraints

Answer 3

• can get much larger marine organisms with their exoskeleton (crustaceans)
• combination of soft exoskeleton and terrestrial habitat may set upper size limit
• need to be able to support own weight with gravity acting
• large immobile soft insects would make very vulnerable to predation (longer to regrow and more conspicuous)

Question 4

Flight and tracheal system

Answer 4

•insect flight muscles most metabolically active tissue known to science
-60% proportion of flight muscle
•all supplied by tracheal system…
•power requirement very high

Question 5

Costs of being small due to SA:V

Answer 5

•smaller = relative SA up = large SA:V
Costs:
-more vulnerable to water loss
-heat gain/loss happens quicker, thermoregulatory mechanisms conquer this
-air resistance, viscosity of air increases as you get smaller - more fluid like

Question 6

Benefits of being small

Answer 6

• cross-sectional area/volume ratio greater in insects, proportional to muscle power = greater if smaller
• kinetic energy and gravity effects
• ecological opportunities
• living room - can fit more individuals in smaller space than bigger animals - smaller resource requirement, colonising potential greater

Question 7

Benefits of size relating to muscles

Answer 7

Muscle moves mass!
•muscles become relatively much more powerful
•moving objects more efficient
•move own bulk more easily, dispersion and colonisation better
•good at digging (exploit more niches)
•good at foraging - jaw musculature enhanced
=better predation, herbivory etc.

Question 8

Benefits of size relating to kinetic energy and gravity

Answer 8

•geometry important…
-effects of kinetic energy obey 10 to power of 5 laws, benefits smaller organisms
•incredibly resilient to impacts of damage so can move at high speeds with little consequence
-why they smack into walls etc. and are fine

Question 9

Ecological opportunities relating to size

Answer 9

• smaller food requirements and short generations times = high reproductive outputs and large populations
• high genetic heterogeneity as large genetic D
• can respond to selection much more rapidly
• more persistent populations more likely to speciate