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History of Life


What trait did the earliest fish have that set them apart from all other organisms at the time? a primitive backbone
What are the distinguishing characteristics of arthropods? exoskeleton and jointed appendages
Which animals were the first vertebrates? fish
Why was the atmospheric oxygen level 30% lower in the Cambrian period than today? there were no plants on land
Which animals were the first to leave the water and walk on land? arthropods
What affect did the first forests have on the environment that made it more suitable for land-dwelling animals? Increased oxygen levels in the atmosphere
What adaptations made it possible for early amphibians to live on land? complex lungs and limbs
What characteristics limited the colonization of the land by early amphibians? moist skin and wet eggs
Why was the environment in the Carboniferous period able to support large arthropods? there was 40% more oxygen
What adaptations did reptiles have that gave them more stamina and speed? a complex heart
What adaptations allowed reptiles to live entirely on land? dry, scaly skin and hard-shell eggs
Why was life in the late Permian so difficult for amphibians? it was very hot and dry
What caused the oxygen levels in the Carboniferous period to go so high? there were vast forests on land
Created by: StudySkillz