This topic examines the animal species known collectively as tetrapods, focusing on their evolutionary journey from aquatic ancestors to the diverse terrestrial and semi-aquatic forms seen today. The threads explain the defining characteristics and diversification of the four main tetrapod classes: mammals, reptiles, amphibians, and birds. They provide a detailed local examination of these animal groups within the Sid Valley, highlighting specific species, their preferred habitats, and the significant threats they face, such as habitat loss and invasive species. Ultimately, the topic underscores the interconnectedness of these species within their ecosystems and the critical importance of conservation efforts for their survival.

This thread aims to answer the following questions:

• What are the two defining characteristics of a tetrapod?

• Describe the key difference in reproduction that allowed reptiles to fully adapt to terrestrial life compared to amphibians.

• What is the unique characteristic of birds, and what significant evolutionary group are they descended from?

• Name the three main groups of mammals and provide a distinguishing feature for each group.

• Why is the evolution of tetrapods from lobe-finned fishes considered a pivotal moment in the history of life on Earth? Briefly explain the significance of this transition.

• Explain why the low number of mammal species recorded in the formal Sidmouth Nature project surveys might not reflect the true mammal diversity of the area. Give at least two reasons.

• What are the defining metabolic characteristics of reptiles, and what bodily feature do they typically possess? Name at least three of the main groups of reptiles.

• Describe two crucial ecological roles that amphibians play in their environments, highlighting their importance within food webs and broader ecosystem functions.

• Identify two key biological features of birds that are adaptations for flight. Briefly explain how each feature aids in aerial locomotion.

• Explain why amphibians are often considered indicators of environmental health. What specific characteristic makes them particularly vulnerable to environmental changes?