Entomology: Hexapoda Overview

Entomology (Hexapoda)

• Kingdom: Animalia
• Phylum: Arthropoda
• Class: Insecta
• Subclass I: Apterygota
  • Primitive insects
  • Wingless
  • Ametabola (No metamorphosis)
  • Eggs → Young → Adult
• Subclass II: Pterygota
  • Not primitive
  • Wingless or winged
  • Incomplete or Complete Metamorphosis
  • Eggs → Nymph → Adult
  • Eggs → Larva → Pupa → Adult
• Physical Characteristics:
  • Exoskeleton
  • 3 pairs of legs
  • 1 pair of antennae
  • Body divided into three regions (Head-Thorax-Abdomen)
  • More than 1 million recorded species

Evolution of Flight and Feeding

• Insects experimented with membranous wings and modifications of mouthparts.
• Presence of membranous wings is a common characteristic of late Carboniferous fossil insects.
• Paranotal Lobe Theory:
  • Changes in thoracic segments for expansion and consolidation of sclerites which formed the sockets.
  • Enabled insects to raise themselves and move more quickly.
  • Paranotal lobes served as stabilizers.
  • Geared towards gliding planes.
  • Useful as means of localized mobility and wider spread by wind.
  • Enhances mate location and selection.

Posture of the Head and Modifications of Mouthparts

• Hypognathous: Mouthparts directed downward, suitable for feeding.
• Prognathous: Forward direction of mouthparts, better suited for tunneling or pursuit.
• Opithognathous: Feeding on plant juices by penetration and sucking.

Biodiversity

• Variety of habitats, living communities, and ecological processes in an ecosystem.
• Diversity of genetic characteristics within a species.
• Variety of species in a given area.
• Ecosystems depend on individual organisms' combined contributions.
• Loss of any species could disrupt an ecosystem's function.
• High biodiversity ecosystems are more resistant to environmental change.

Keystone Species

• disproportionately large effect on its natural environment relative to its abundance.
• Critical role in maintaining the structure and numbers of various other species.
• Ecosystems may shift dramatically if a keystone species is removed.

Indicator Species

• Species whose function, population, or status reveals the environment's status.
• Often used to monitor changes in an ecosystem.
• Can indicate problems within an ecosystem.
• Quantify environmental quality. Assess pollution level and intensity and extent of exposure.

Types of Biodiversity

• Genetic diversity
• Ecosystem or Ecological diversity
  • Biomes (Desert, Aquatic, Forests, Open lands, etc.)
  • Distinct climate
  • Certain species, especially vegetation
• Functional diversity (Energy flow, matters recycling)
• Species Diversity

Ecological Diversity

• Variety of terrestrial and aquatic ecosystems in an area or on earth.

Genetic Diversity

• Variety of genetic material within a species or a population.

Species Diversity

• Number and abundance of species present in different communities.
  • Species richness = number of species
  • Evenness = proportion of species
  • Calculation of evenness: p = n/N
  • Several indices for measuring species diversity such as Shannon's diversity index (H), Simpson diversity index (1 − D) Margalef's, & Menhinick indices

Indices of Similarity

• Jaccard's index (CJ) and Sorenson's index (CS) for comparing communities based on species compositions.

Index of Relative Rarity (IRR)

• Method of determining how common or rare a species is based on species richness and weights.

Sp-Effects and Level Covariates

• Categories of species with their local abundance, extent of geographical area and habitat specificity.

Conservation of Biodiversity

• Management of human use of the biosphere for sustainable benefits to the present and future generations.
  • In-situ Conservation
    • Protecting organisms in their natural habitats
    • Includes National Parks, Wildlife Sanctuaries, Biosphere reserves etc.
    • Protectorates • Over 287,000 protectorates globally.
  • Ex-situ Conservation
  • Protecting organisms outside their natural habitats. Included Botanical gardens, zoos and seed banks, etc
• Feeding Habits ("Habits") and Trophic Levels
• Autotrophs
• Heterotrophs
• Classifying Organisms by interaction methods
• Producers
• Consumers • Herbivores: Organisms that feed on plants, usually have adapted mouthparts for chewing or grinding • Carnivores: Organisms that feed on animals. • Predators: Hunt, kill and feed on prey • Omnivores: Survive on both plant and animal material • Parasites: Live on or in a host organism, getting nourishment at their expense. • Parasatoids: Develop on or in a host organism and eventually kills it.

Food Chain

• Interlocking linear feeding links among organisms, starting from producers (e.g., green plants).
• Measure of energy flow and index of ecological structure from the lowest to highest trophic levels.

Food Web

• Complex mesh of relationships between organisms, reflecting what eats what in an ecological community.

Ecological Pyramids

• Graphic representation of ecological parameters (number, biomass or energy) across trophic levels of a food chain (producers at base, carnivores at top)
• Pyramid of Numbers
• Pyramid of Biomass
• Pyramid of Energy

Insect Sociobiology

• Study of social behavior in insects.
• Includes insect societies and swarms, comparing and contrasting the social structures among them.
• Degrees of Sociality
• Solitary
• Subsocial
• Communal
• Quasisocial
• Semisocial
• Eusocial
• Size of Insect Societies (number of workers, queens etc in different insect communities)

Reproduction/Modes of Reproduction

• Details of reproduction process starting from mate location
• Courtship behaviour
• Copulation with male/female genital apparatus
• Ejaculation
• Insemination
• Fertilization
• Embryogenesis
• Oviposition
• Eclosion
• Viviparity
  • Young are nourished within the body of the female
• Ovoviviparity
  • Eggs are retained within the body of the female till they hatch, and then the young individuals are released.
• Paedogenesis
  • Reproduction of the juveniles or the young
• Parthenogenesis
  • Off spring is produced from the mother without needing to fertilize from a male