Invertebrate Animals

Course CodeBEN218
Fee CodeS1
Duration (approx)100 hours
QualificationStatement of Attainment

Insects, worms, and other invertebrates are significant to horticulture.

  • Some help plants and others hinder
  • Some are even critical to plants, facilitating pollination or other processes in the plants
  • Some are indirectly important, providing a food source to animals, which in turn are important to plants
  • Invertebrates are interwoven into the environment; integral but often unnoticed pieces of a much larger living ecosystem that is the farm, garden or broader landscape.

Whatever the effect; it is important to be able to identify and understand invertebrates if you are to be effective as a horticulturist.

This course helps you understand the many different types of invertebrate animals, from microscopic to relatively large species; the characteristics that differentiate one from the next, and the ways in which each fits into the wider ecosystem.

Lesson Structure

There are 9 lessons in this course:

  1. Scope and Nature of Invertebrate Animals
    • Introduction
    • Significance to humans
    • Comparative studies - invertebrate animals
    • Important terminology
    • Overview of Invertebrate Phyla
    • Microscopic phyla -Tardigrada, Kinorhyncha, Loricifera, Placozoa
    • Worms - Acanthocephala, Annelida, Hemichordata, etc
    • Corals and relatives - Cnidaria, Ctenophora, Ectoprocta, Porifera
    • Echinoderms and Molluscs - Echinodermata, Mollusca, Brachiopoda
    • Complex Invertebrates - Arthropoda
  2. Microscopic Animals
    • Protozoa or Animalia
    • Phylum Nematoda
    • Mites
    • Phylum Tardigrada
    • Adaptability and Survival
    • Anhydrobiosis
    • Cysts
    • Phylum Kinorhycha
    • Phylum Loricifera
    • Phylum Placozoa
  3. Worms & Worm Like Animals
    • True worms vs Worm like organisms
    • Worm evolution
    • Bilateral symmetry
    • Cephalisation
    • Body organisation
    • Characteristics and systems showing complexity
    • Phylum Platyhelminthes (Flatworms)
    • Free living flatworms
    • Parasitic flatworms
    • Significance to Humans - Liver fluke, blood flukes, tapeworms
    • Beef tapeworm
    • Phylum Nematoda (Roundworms)
    • Phylum Annelida (Segmented Worms)
    • Other Worm Like Animals - Acorn worms, ribbon worms, Spiny headed worms, etc.
    • Coelomate Worms
  4. Sponges, Corals, Anemones, Jellyfish
    • Introduction
    • Phylum Cnidaria
    • Hydrozoa
    • Scyphozoa
    • Cubozoa
    • Anthozoa
    • Cnidaria and Humans
    • Phylum Ctenophora
    • Phylum Porifera - Location, Internal & External Structures, Reproduction, Toxicity
    • Classes within Porifera
    • Finding food
  5. Molluscs and Echinoderms
    • Phylum Echinodermata
    • Crinoidea - Sea Lilies and Feather Stars
    • Ophiuroidea -Brittle stars, Basket Stars
    • Asteroidea - Sea stars or Starfish
    • Case Study - Crown of Thorns Starfish
    • Echinoidea -Sea urchins, Heart urchins, Sea dollars
    • Chass Holothuroidea - Sea Cucumbers
    • Phylum Mollusca - general characteristics and types
  6. Arthropods 1
    • Classification into Arachnida, Crustacea, Myriapoda and Insecta (insects)
    • Origin
    • Terminology
    • Characteristic body parts
    • Ecdysis
    • Digestion, Respiration, reproduction and other systems
    • Phylum Arthropoda
    • Chelicerata (Chelicerates)
    • Arachnida (Scorpions, Spiders, Mites and Ticks)
    • Scorpiones (Scorpions)
    • Araneae (Spiders)
    • Acari (Mites and Ticks)
    • Opiliones (Daddy Long-Legs)
    • Merostomata (Horseshoe crabs)
    • Pycnogonida (Sea spiders)
  7. Arthropods 2
    • Terminology
    • Crustacea (Crustaceans)
    • Class Malacostraca -Crayfish, Crabs, Shrimp etc
    • Branchiopoda - Fairy shrimp, Water fleas
    • Cephalocardia
    • Remipedia
    • Maxilopoda
    • Sessile Crustaceans
    • Sub Phylum Uniramia - millipedes, centipedes and insects
  8. Insects 1
    • Origin of insects - winged vs non winged
    • Class Entogantha -Collembola, Diplura, Protura
    • Class Insecta
    • Insect features
    • Mouthparts
    • Insect classification into 29 orders
    • Specialised organs
    • Reproduction
    • Lifecycle
    • Senses - vision, comminication
    • Odonata -Dragonflies and Damselflies
    • Mantodea - Mantises
    • Orthoptera - Grasshoppers, Crickets, Katydids
  9. Insects 2
    • Significance to man
    • Clean air and water
    • Pollination by insects
    • Edible insects
    • Case Study - Grasshoppers save lives
    • Order Diptera - Mosquitos and Flies
    • Order Hymentoptera - Bees, wasps, ants, sawflies
    • Order Coleoptera - Beetles, weevils


  • Describe the scope and nature of invertebrate animals; including similarities and differences between different groups of invertebrates.
  • Describe and compare the structure and function of animals that cannot be seen readily with the naked eye.
  • Describe and compare the structure and function of a variety of different worms and worm like animals.
  • Describe and compare the structure and function of a variety of different sponges, corals and anemones.
  • Describe and compare the structure and function of a variety of different molluscs and echinoderms.
  • Describe and compare the structure and function of a variety of different arthropods.
  • Explain the significance of arthropods to man
  • Describe and compare the structure and function of a variety of different insects.
  • Explain the significance of insects to man.

WORMS - much more than just earthworms!

Throughout the evolution of worms, an increasing complexity of the body structure is observed. Platyhelminth worms are slightly more complex than cnidarians. Worms are important in horticulture; some helping plant growth and others hindering it. 

Bilateral Symmetry
Bilateral symmetry is a major evolutionary advancement in invertebrate animals. Bilateral symmetry in animals evolved in the simplest worms, the platyhelminths. The evolution of the bilaterally symmetrical body plan has enabled parts of the invertebrate body to evolve independently of each other. The advantages of bilateral symmetry are:

  • The differentiation of organs (true organs) located in different parts of the body. 
  • Increased mobility (compared with the sessile or passive existence of invertebrates with a radially symmetric body plan), enabling greater efficiencies in obtaining food, seeking mates and avoiding predators.

Cephalisation is an evolutionary process associated with the evolution of bilateral symmetry in the platyhelminths. Cephalisation is a process where the anterior region has become specialised, with nervous tissue becoming concentrated in the anterior end, increasing in complexity over time and eventually producing a distinct head and sensory organs.

Body Organisation
Platyhelminths were the first invertebrates to evolve body organisation, which has formed the basis of all other animal evolution. While cnidarians only have two layers of cells, the endoderm (inner layer) and ectoderm (outer layer), platyhelminth worms have a middle layer of cells (mesoderm layer) between the endoderm and ectoderm. The evolution of the mesoderm enabled body organisation in the form of a basic body plan. The mesoderm functions to produce muscle tissue, which enables mobility in worms. All worms possess a mesoderm layer and have evolved muscular systems of increasing complexity. The organisation of endoderm and ectoderm cells is more complex in worms than cnidarians, where groups of tissues have evolved to form true organs. Accordingly, the features (e.g. organs) and systems (e.g. digestive, nervous and excretory systems) of worms have increased in complexity throughout evolution.   


More from ACS