Invertebrate Zoology

Invertebrates are important in so many ways - to both the environment, and to both the human and animal food chains.

• Invertebrates account for around 95% of all animals
• This is estimated at over 1 million named species.
• Invertebrates are significant in human and animal disease

Lesson Structure

There are 9 lessons in this course:

1. Scope and Nature of Invertebrate Animals
2. Microscopic Animals
3. Worms and Worm-Like Animals
4. Sponges, Corals, Anemones, and Jellyfish
5. Molluscs and Echinoderms
6. Arthropods 1
7. Arthropods 2
8. Insects 1
9. Insects 2

Why are there so many invertebrates ?

How do they maintain their high numbers? 

Many species can survive in the most extreme environments on Earth.  Some are deep within the depths of the ocean and some can survive within the freezing temperatures of Antarctica.  Some species are able to switch into dormant mode to enable their survival within these extreme conditions.  Invertebrate species are small which allows them to easily avoid predatory species and being small also takes less feeding.  Some species have wings which enhances their survival.  The reproduction rates of invertebrates are very high with many species producing hundreds of eggs at a time.  Some females store sperm and some species are parthenogenetic.  Some species can go through metamorphosis which also assists in their population survival.  Invertebrates are very adaptable, not only to their environment but also having a shorter life cycle with a high reproductive capacity.  

Approximately 95% of all species from the animal kingdom form part of this group, which accounts for over 1 million known species. We could also say that approximately 80% of the invertebrates belong to the Phylum Arthropoda.