Invertebrate Animals

Course CodeBEN218
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

Learn about the anatomy, behaviour, and physiology of Invertebrate Animals.

The largest group of animals on the planet, invertebrates comprise everything from snails and snakes to giant squid. In this course, you'll learn about these fascinating animals, studying their taxonomy in conjunction with many of their adaptations, necessary to survive the world around us. You'll also learn how some groups -- such as insects -- are significant to human survival as we know it. 

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
    • Class 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.

Learn about Arachnids and many other types of Invertebrates.

Arachnida is the largest class or arthropods comprising more than 60,000 described species and, presumably, an extensive number of undescribed species. The arachnids are predominantly made up of spiders. Mites and ticks are the second largest group of arachnids; and scorpions, whip scorpions, pseudoscorpions, palpigrades, harvestmen and solpugids make up the rest. 

Characteristics of the class Arachnida are:

  1. Cephalothorax unsegmented and partly or completely enclosed by a carapace (shield)
      Chelicerae have a short, thick base and a movable, often poisonous, fang 
      Pedipalps look like legs but are not used for locomotion
  2. Abdomen may be segmented or unsegmented
      Appendages on abdomen are absent or modified
  3. Simple eyes (no compound eyes)
  4. Respiration by book lungs, trachea or cutaneous in many small arachnids
  5. Wings are absent

Most arachnids are terrestrial; however, many mite species live in fresh water and a few, in the sea. Most arachnids are carnivorous (excluding mites which are typically herbivorous). The majority of arachnids secrete digestive enzymes into their prey as they can usually only consume pre-liquified food. This allows them to easily suck up the externally digested food using the pumping action of their muscular pharynx.

Order Scorpiones (Scorpions) 
Members of this order of arachnids are commonly known as scorpions. 
Characteristics of the order Scorpiones are:

  • Pedipalps modified as pincers used to manipulate food.
  • Distinctive elongated, jointed abdomen (note: most chelicerates have fused abdominal segments giving the impression that it is a single segment). 
  • Appendages on abdomen are modified as sensory appendages (pectines).
  • Terminal segment of abdomen bears a poisonous sting to stun prey.

Scorpions are an ancient terrestrial arthropod known from 425 million years ago. Ranging in size from 1 – 18cm in length, scorpions are found all over the world and typically found in tropical, subtropical, and desert areas. 

Order Araneae (Spiders) 
Members of this order of arachnids are commonly known as spiders. 
Characteristics of the order Araneae are:

  • Chelicerae are pointed with a poison duct on terminal claw functioning to bite and paralyse prey.  
  • Appendages on abdomen are modified as spinnerets that secrete a fluid protein to form silk.
  • Pedipalps are specialised reproductive organs.

Order Acari (Mites and Ticks) 
Members of this order of arachnids are commonly known as mites and ticks. 
Characteristics of the order Acari are:

  • Cephalothorax and abdomen are usually fused to form an unsegmented, oval body. 
  • Respiration by trachea or cutaneous. 

This group is highly diverse and contains the most numbers of described species of the arachnid orders, with possibly more than one million undescribed species. Mites and ticks are found in found in both terrestrial and aquatic (fresh and marine) habitats and feed on animals (predatory or parasitic), plants and fungi. 
Ticks are ectoparasites, living externally on animals such as cattle, horses, sheep and dogs or humans, and feeding on the host’s blood.
Mites are very small, normally not exceeding 1mm in length. Mites have numerous stages in their life cycle, typically starting as inactive, 8-legged pre-larva; followed by an active 6-legged larva; followed by three 8-legged stages before reaching and adult male or female. Mites live in hair follicles and wax glands of humans where they, usually, cause no problems. However, a mite bite can cause irritation and mites also carry diseases that affect humans.  

An ideal course for

This is a great course for any wishing to learn more about invertebrates, whether for personal studies or professional development.  It is an ideal course for:

  • Students of Biology
  • Farmers
  • Gardeners
  • Pest Controllers
  • Environmental Managements
  • Veterinarians
  • People working in human health

You can enrol and start studying Invertebrate Animals at any time.  The course requires around 100 hours of study, although as our courses are self-paced you determine how long you take.  We provide full tutor support for the duration of your studies.

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