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Assignment 2: History of Earth

Across
Eukaryotes first appear during this eon.
Organisms that lack membrane bound organelles
Fossils where body parts have been replaced by minerals.
Name of the body that collided with earth
Organic matter produced by photosynthesis has a ________ ratio of carbon-12 to carbon-13.
Event that occurred 541-506 million years ago.
550 million year old fossil that was confirmed as an animal by identifying breakdown products of cholesterol.
Period when there was widespread appearance of multicellular fauna.
Down
The theory that life had a chemical origin on earth.
The period dating from 4.54 billion years ago to 541 million years ago.
Species that was placed in the phylum problematica, before being identified as an arthropod.
The group that Haikouichthys ercaicunensis from the Cambrian explosion belongs.
RNA molecules that have catalytic activity.
Bun-shaped structures dating to around 3.5 billion years ago.
A sudden increase in _______. may have contributed to the Cambrian explosion.
The hypothesis that suggests that life on earth was seeded from another planet.
Country where the Burgess Shale is located.