Final answer:
Pangaea was a supercontinent that existed from about 300 to 200 million years ago, comprising all of Earth's land masses. It provided the framework for Alfred Wegener's theory of continental drift, which explained evidence of similar fossils and climatic patterns across different continents.
Step-by-step explanation:
The hypothetical landmass in which all the continents were joined approximately 300-200 million years ago is called Pangaea. This supercontinent included all of Earth's continental crust, and its existence has been supported by evidence such as similar fossils found on different continents and patterns of ancient climate. The formation and subsequent fragmentation of Pangaea were due to the movement of the Earth's tectonic plates, a process first theorized by Alfred Wegener when he proposed the idea of continental drift.
During the time of Pangaea, extreme climates and dry conditions prevailed. These conditions led to evolutionary adaptations in plants and animals, such as waxy leaves and leathery skin to prevent water loss. The break-up of Pangaea into smaller continents created the diverse geological and biological landscapes we see today.