BIOL 102 Lecture 30: Insect Success PDF

BIOL 102 – Lecture 30 Swarming hordes – insect success Learning outcomes Why are insects regarded successful Positive and negative sides Different strategies to avoid predation Significance of complete metamorphosis  Insects rule! Most successful animals on Ear...

BIOL 102 – Lecture 30 Swarming hordes – insect success Learning outcomes Why are insects regarded successful Positive and negative sides Different strategies to avoid predation Significance of complete metamorphosis  Insects rule! Most successful animals on Earth – More species than any other life form (species richness) – More individuals than anything else (abundance) – Make up most biomass – Occur everywhere on land in diversity of habitats – Diverse feeding habits – Huge impact on other life forms  Why are insects successful? Small size due to tracheal breathing system – Can colonize more niches Short generation times & high genetic variability – Respond rapidly to environmental change Aquatic immatures Metamorphosis – Adults & immature stages exploit different niches Flight confers many advantages Dragonflies = predators  Flight Dragonfly: among 1st insect to fly Modification: those evolved later Bees and wasp wings: hooked together-move as single pair Butterfly: anterior pair overlaps the posterior Beetles: posterior wings-flight – Anterior wings-protection when walking or burrowing  Insect metamorphosis Involves change from one body form to another during same life cycle 2 main types – Incomplete (gradual) = most primitive – Complete (abrupt) = most advanced Metamorphosis advantages – Allows specialization between stages  Incomplete metamorphosis 3 stages = egg, nymph & adult Immature stages = nymphs – Resemble adults but smaller & wings not fully developed – Occupy same habitat & feed on same food as adults Found in locusts, bugs, termites, mantids etc Life cycle of bug  Complete metamorphosis 4 stages = egg, larva, pupa & adult Immature stages = larvae – Do not resemble adults – Pupal stage aids transition from larva to adult – Occupy very different habitats to adults & feed on different food types Found in butterflies beetles, flies, bees etc Life cycle of fly Significance of complete metamorphosis 85% of insects have complete metamorphosis – Adults & larvae evolve different adaptations & lifestyles (e.g. tiger beetles) – Reduces competition between larvae & adults for Tiger food, shelter & space beetles = – Reduces mortality since aggressive predators as larvae & adults attacked by adults & different predators larvae  Specialization between stages Egg = embryonic stage Larva = major feeding stage – Soft body allows expansion with food intake – Vulnerable to predators Pupa = re-construction stage – Larval tissues broken down & converted into adult tissues Adult = reproductive & Life cycle of a butterfly dispersal stage  Mopani worm: Imbrasia belina Adult moths: don’t feed are short-lived (3-4 days) During which they mate and the female lays her eggs.  Protection from predation Different life stages are Leaf mimic vulnerable to predators Many strategies for protection – Camouflage (crypsis) = body shape & colours that allow concealment – Aposematism = colours that Poison spines warn of distasteful (toxic) features – Mimicry = colours that falsely suggest distasteful features (copy toxic species)  Reproduction in insects Reproduce sexually Identify members of own species – Bright colours, sounds or odours. Fertilization is internal Eggs laid on food sources