Animal Kingdom: organisms that are eukaryotic multicellular, heterotrophic feed by ingestion The phylogenetic relationships shown below is largely based on DNA evidence because the fossil evidence is too poor to show the details. You need to know this hereditary tree and be able to explain the key criteria biologists use to organize the tree this way. This major apparent spurt in evolution occurred in just ~50 million years in the Cambrian period. Animal Evolution Multicellularity originated many times independently. It seems to have evolved simply by cells staying together after they have divided, rather than two different cells joining up. The advantage of multicellarity is that the organism is much larger and harder to capture as prey. Also, if cells stay together and live in groups they can specialize for different functions (e.g. eating, movement, reproduction, etc.). All phyla except the Porifera (Sponges) have specialized tissues or organs. What caused the Cambrian Explosion? The DNA evidence indicates that although many phyla suddenly appear for the first time in the Cambrian, they had really evolved well before this period but the groups were small and soft bodied and did not fossilize well. But what happened to cause the sudden appearance? Possible Causes of the Cambrian Explosion: (i.e. sudden appearance of large animals with skeletons) Environment:
Animal Kingdom: organisms that are eukaryotic multicellular, heterotrophic feed by ingestion The phylogenetic relationships shown below is largely based on DNA evidence because the fossil evidence is too poor to show the details. You need to know this hereditary tree and be able to explain the key criteria biologists use to organize the tree this way. This major apparent spurt in evolution occurred in just ~50 million years in the Cambrian period. Animal Evolution Multicellularity originated many times independently. It seems to have evolved simply by cells staying together after they have divided, rather than two different cells joining up. The advantage of multicellarity is that the organism is much larger and harder to capture as prey. Also, if cells stay together and live in groups they can specialize for different functions (e.g. eating, movement, reproduction, etc.). All phyla except the Porifera (Sponges) have specialized tissues or organs. What caused the Cambrian Explosion? The DNA evidence indicates that although many phyla suddenly appear for the first time in the Cambrian, they had really evolved well before this period but the groups were small and soft bodied and did not fossilize well. But what happened to cause the sudden appearance? Possible Causes of the Cambrian Explosion: (i.e. sudden appearance of large animals with skeletons) Environment: