🌍 Why Do Insects Rule the World? Factors for Their Abundance
Have you ever wondered why insects are everywhere? From the freezing cold to the scorching heat, they seem to be the most dominant group of animals on our planet. here is a detailed breakdown of the factors responsible for the incredible abundance and dominance of insects.
📊 Measures of Dominance
The dominance of insects isn't just a feeling; it's backed by staggering numbers and history:
More Number of Species: Insects make up more than 85% of the species in the animal kingdom. So far, more than 9 lakh (900,000) insect species have been described
. Large Number of Individuals: A single species can have a massive population. For example, a Locust swarm can comprise $10^9$ individuals, occupying a large area
. Great Variety of Habitats: Insects thrive well under varied conditions
. Long Geological History: Insects have occupied the earth for more than 350 million years. This impressive track record has allowed them to evolve a great variety of adaptations under different conditions
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🚀 Reasons for Dominance
What specific biological traits give insects the upper hand? Let's explore the key factors:
1. Capacity for Flight ✈️
Insects are the earliest animals and the only flying invertebrates. Wings are lateral extensions of the exoskeleton. Flight serves several critical purposes:
To seek food, mates, shelter, and oviposition (egg-laying) sites
. To colonize new habitats and exchange habitats
. To escape from enemies and unfavourable conditions
. To migrate over long distances (e.g., Locusts)
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2. Adaptability or Universality 🌐
Insects were the earliest groups to occupy vast habitats of soil and water. Their adaptability is unmatched:
Climatic Range: Found in conditions ranging from -50 oC to 40 oC.
Extreme Habitats:
Psilopa petroli is found in crude petroleum wells
. Ephydra fly lives in the Great Salt Lake
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Diverse Diet:
Phytophagous: Every flowering plant provides food for one or many insects
. Saprophagous: Feed on decomposing materials
. Carnivorous: Many are parasitic on other animals and insects
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3. Small Size 🐜
The majority of insects are small, which offers physiological and ecological advantages:
Exploitation of numerous ecological niches that are inaccessible to other animals
. Less space, food, time, and energy are required for development and sustaining life
. Maximum energy utilization and less gravitational effect
. More effective muscular action and tracheal respiration
. Easy escape from enemies
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4. Exoskeleton 🛡️
The insect body is covered with an outer cuticle called the exoskeleton, made of a protein called Chitin. It is light, strong, rigid, and flexible.
Functions: Acts as external armour, provides space for muscle attachment, and prevents water loss
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5. Resistance to Desiccation 💧
Insects have mastered the art of minimizing water loss:
Prevention of Water Loss:
Lipids and polyphenols in the Epicuticle act as water-proofing
. A wax layer with closely packed wax molecules prevents the escape of water
. Spiracles close to restrict water loss
. Eggshells prevent the desiccation of inner embryos
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Conservation of Water:
Utilization of metabolic water
. Rectal resorption of water from faeces
. Excretion of nitrogenous waste as Uric acid (water-insoluble), requiring less water for removal
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6. Tracheal System of Respiration 🫁
This system ensures the direct transfer of adequate oxygen to actively breathing tissues. The spiracles' closing mechanism admits air while restricting water loss
7. High Reproductive Potential 🥚
Insects reproduce rapidly due to:
High Fecundity: e.g., A Queen termite lays 6,000–7,000 eggs per day for 15 years
. Short Development Period: e.g., Corn aphid produces 16 nymphs per female, reaching adulthood in just 16 days. This allows for quicker genetic changes, such as insecticide resistance
. Parental Care: Progressive provisioning (e.g., bees) and mass provisioning (e.g., wasps)
. Special Types of Reproduction:
Polyembryony: Many individuals from a single egg (e.g., parasitic wasps)
. Parthenogenesis: Reproduction without fertilization (e.g., aphids)
. Paedogenesis: Reproduction by immature stages (e.g., certain flies)
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8. Complete Metamorphosis 🐛🦋
More than 82% of insects undergo complete metamorphosis (Holometabolous), involving four stages: Egg, Larva, Pupa, and Adult.
Advantage: Since larval and adult food sources are often different, competition for food is reduced
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9. Defense Mechanisms ⚔️
Insects use various methods to increase survival:
Behavioural: Thanatosis (pretending to be dead, e.g., some beetles)
. Structural: Hardened forewings (elytra) protect beetles from birds
. Colourational: Protective colors (e.g., Stick insects)
. Chemical: Defensive chemicals (e.g., Bees producing venom)
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10. Hexapod Locomotion 🦵
Insects use 3 legs at a time during locomotion while the remaining 3 are static, providing greater stability
🧠 Knowledge Check: MCQs
Test your understanding of the factors behind insect abundance!
1. Which insect is known to live in crude petroleum wells?
A. Ephydra fly
B. Psilopa petroli
C. Corn aphid
D. Stick insect
2. What is the phenomenon called where an insect pretends to be dead to escape enemies?
A. Parthenogenesis
B. Polyembryony
C. Thanatosis
D. Metamorphosis
3. Which nitrogenous waste product do terrestrial insects excrete to conserve water?
A. Urea
B. Ammonia
C. Uric acid
D. Amino acid
4. How many eggs can a Queen termite lay per day?
A. 600-700
B. 1,000-2,000
C. 6,000-7,000
D. 10,000-15,000
5. Which percentage of insects undergo complete metamorphosis?
A. More than 50%
B. More than 82%
C. Less than 40%
D. 100%
Answers:
B (Psilopa petroli)
C (Thanatosis)
C (Uric acid)
C (6,000-7,000)
B (More than 82%)
