Keeping it Simple

The Sidmouth Nature project and many other local wildlife groups use a simplified structure to help non-professionals organise their records and observations. This system divides the life we see every day into four approachable sections.

The Four Pillars of Everyday Observation

Section Scientific Meaning What's Included

Tetrapods Animals with an internal skeleton Amphibians, Reptiles, Birds, and Mammals.

Arthropods Animals with an external skeleton Insects, spiders, crabs, and scorpions

Angiosperms Plants that reproduce by seeds Flowering plants, from oak trees to grasses

Cryptogams "Plant-like" things that reproduce by spores Mosses, ferns, fungi, lichen and algae.

Understanding the "Informal" Groups

Some of these categories are formal scientific ranks, while others are "Clades" or "Informal Groups" used for convenience.

1. Tetrapods: The "Four-Footed" Ancestry

"Tetrapod" is not a Phylum; it is a Superclass sitting between Phylum and Class

• The Name: It literally means "four-footed"15.

• The Rule: Even creatures like whales (with fins) or snakes (with no legs) are considered Tetrapods because they evolved from ancestors with four limbs.

2. Arthropods: The Largest Phylum

This is a formal Phylum (Arthropoda) and the largest on Earth.

• Formal definition: Any animal with a segmented body, jointed legs, and an exoskeleton.

• Informal use: In casual observation, this group is often expanded to include other invertebrates like slugs, snails, and earthworms.

3. Angiosperms: The Seed-Bearers

In botany, the word Division is often used instead of Phylum.

• Definition: Plants that produce seeds enclosed within a flower or fruit.

• The Exception: Not all seed-plants are Angiosperms. Conifer trees (like pines) belong to a different group called Coniferophyta because of their seed structure.

4. Cryptogams: The Spore-Bearers

This is the "odd one out" because it is no longer a formal scientific rank.

• The Nickname: Biologists use it as a nickname for "spore-bearing things".

• The Issue: Historically, this group accidentally lumped together unrelated things like Ferns (Plants), Lichen (Fungi), and Cyanobacteria (Bacteria)25. While it has no place on the modern Tree of Life, it remains a helpful way for beginners to group "hidden reproduction" life forms.