Chapter 37 Section 1 The Insect World Objectives

Chapter 37 Section 1 The Insect World

Objectives • Relate the major characteristics of insects to insects’ biological success. • List both harmful and beneficial effects of insects on human society. • Describe the external structure and organ systems of a grasshopper. • Compare incomplete and complete metamorphosis in insects. • Describe defensive adaptations in insects. #

The body is divided into three tagmata: • 1. Head- mandibles and one pair of unbranched antennae • 2. Thorax- 3 pairs of jointed legs, or two pairs of wings • 3. abdomen- 9 -11 segments no wings or legs in adults. • #

• Entomologist – the study of insects and other terrestrial arthropods. • There are 25 orders bases on characteristics: – Structure of mouthparts – Number of wings – Type of development –#

Factors responsible for their success include: • • • Ability to fly Exoskeleton Jointed appendages Small size Short life span #

Insects negatively affect humans by: • Competing for food • Transmitting diseases • Destroying building and other manufactured products • #

Insects benefit humans by: • • • Serving as food for other animals Pollinating flowers Making valuable products such as honey Recycling nutrients in ecosystems #

External Structure • Three tagmata: • 1. head – Mouthparts – Unbranched antennae – Simple and compound eyes –#

• 2. thorax – Prothorax – Mesothorax – Metathorax #

• 3. abdomen – Upper and lower plates The exoskeleton and waxy cuticle covering are adaptations for a terrestrial life. #

Feeding and Digestion • Grasshoppers feed on plants, and their mouthparts are modified for cutting and chewing leaves and blades of grass. • The Labrum and labium – upper and lower lips • #

Circulation, Respiration, and Excretion • Open circulatory system • Gas exchange- air-filled tracheae • Malpighian tubules – remove cellular wastes, and conserve water • #

Neural Control • Contains a brain and ventral nerve cord with ganglia located in each body segment. • Sensory structures include: – Simple and compound eyes – Sensory hairs on antennae and other body parts – In some species, a sound-sensing tympanum –#

Reproduction • All insects have separate sexes • Male deposits sperm into the female’s seminal receptacle, eggs are fertilized internally • The female’s last segment of the abdomen forms the ovipositor, she uses to lay fertilized eggs. • #

Insect Development • Most go through metamorphosis • Incomplete metamorphosis- nymph hatches from an egg and looks like the adult. – Undeveloped reproductive organs – No wings – Must molt several times to become and adult –#

• Complete metamorphosis –wormlike larva called a caterpillar hatches from and egg • Molts several times, becomes a pupa • Molts to produce the adult • The adult does not resemble the larva or the pupa. • #

Importance of Metamorphosis • Allows larvae and adults of the same species to avoid competing for space and food • Allows insects to survive periods of harsh weather or scant resources • #

Insect Defense • Defend themselves by: – Stinging – Using camouflage – Releasing noxious chemicals –#

• Dangerous insects or the ones that taste bad, they have warning coloration that predators recognize • Some harmless species may be mimicked the warning coloration to elude predators. • #

Section 2 Insect Behavior • Identify three ways that insects communicate • Describe the social organization of honeybees • Explain how honeybees communicate information about the location of food • #

Communication • Releasing pheromones • Producing sounds • Producing flashes of light • #

Behavior in Honey Bees • Social insects- live in groups or colonies • Division of labor- creates interdependence and a need to communicate • Colonies- mostly of female worker bees – Perform all of the duties, do not reproduce their own offspring. –#

• Reproduction- function of one queen bee and a few hundred male drones. • Worker bees live about six weeks • At one stage, worker bees are called nurse bees. – Secrete royal jelly-feed to the queen and youngest larvae –#

• Queen bee will develop when fed royal jelly • When a new queen matures, she secretes queen factor, this prevents other female larvae from developing into queens. • #

The Dances of the Bees • Honeybees use two types of dances: • The round dance- indicates a food source is nearby • The waggle dance- the direction of food and the distance from the hive. • #

Altruistic Behavior • In defending the colony, worker bees who altruistic behavior toward their close relatives in the colony. The unselfish concern for the welfare of others. • By working for the colony, the worker bees increase the propagation of their own genes. • #