500 Million Years Ago Flashcards, test questions and answers

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What is 500 Million Years Ago?

500 million years ago marks the beginning of the Cambrian period, a time when some of the earliest complex forms of life appeared on earth. This was an incredibly important moment in Earth’s history and marked a major transition from primitive single-celled organisms to more complex multi-cellular creatures. The appearance of these first animals had far reaching implications for our planet, including significantly altering its atmosphere and climate. The abundance of oxygen released by these new creatures caused temperatures to rise, triggering drastic changes in the environment which allowed for further evolution and biodiversity. Animals during this time were quite different from those we know today many species had bodies made up entirely of soft tissues that lacked any type of hard skeletal support (such as shells). As such they were often very small and simple in form, typically having no eyes or limbs. They also lived almost exclusively underwater where food sources were plentiful, but competition was low due to their lack of mobility skills. Remarkably all living animal phyla today can trace their origins back to this era 500 million years ago; an astonishing amount given how much life has changed since then. From trilobites to jellyfish – it is remarkable to consider that every creature alive today evolved from these early ancestors during such a comparatively short span on geologic time scale.