Cambrian explosion Flashcards
What are metazoans?
Multicellular animals with three embryonic layers
What characteristics do metazoans share?
Multicellular body formed of specialised cells
Ability to manufacture collagen
reproductive cycle wit gametes from meiosis
Nervous system
What are diploblastic animals?
A body derived form two embryonic cell later
What are triploblastic animals?
a body derived from three embryonic cell layers
What where the ediacaran biota?
An early group of multicellular eukaryotes, some are sponges, no guts, limbs or mouth. May have fed using photosynthetic algae
What is the evidence for life in the precambrian?
The ediacaran fossils,
Trace fossils of triploblastic organisms
Eggs cases containing embryos
What life existed in the early Cambrian?
small shelly fossils - disarticulated elements of early shell
Extinct phylum close to molluscs
What life is there in the middle Cambrian?
The Cambrian explosion, fossilised hard parts evolve and soft parts exceptionally preserved. All modern animal phyla now present
What caused the Cambrian explosion?
The environment - Breakup of supercontinent, Atmospheric O2 levels
The Ecology - development of eyes and predation, new selection pressures cause life to rapidly diversify and adapt
What happened in the late precambrian?
Ediacaran animals inhabit sea floor, unprotected but have no predators , triploblastic evolve
Middle Cambrian:
Triploblastic predators with teeth evolve, ediacaran mostly become extinct, Protection with armour evolves
Late Cambrian:
Predators more efficient with eyes, more burrowing and armour evolves.
