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Did animals evolve from plants? Did animals' ancestors have chloroplasts in their cells?

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Why do you think that animals evolved from plants? –  Michael Kuhn May 7 '12 at 8:45
    
@Michael Kuhn because animals and fungi (uniconts) evolved from biconts. Biconts currently represented only by plants. –  Anixx May 7 '12 at 10:06
    
I see! The relation of the eukaryote ancestor to the unikont/bikont split is still debated. Here's one option supported by rare genomic changes: ncbi.nlm.nih.gov/pmc/articles/PMC2817406/figure/fig4 where a chloroplast-less ancestor acquires a chloroplast on the way to plants –  Michael Kuhn May 7 '12 at 11:25
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Based on your comments to the answers and above... it seems that your question is "Did the common ancestor of plants and animals have chloroplasts?" In my opinion, this is quite distinct from "Did animals evolve from plants?" –  KennyPeanuts May 7 '12 at 12:09

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up vote 19 down vote accepted

See this paper "Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi" for information on the divergence estimates (I'm not sure if there are more recent papers discussing this).

Plants, animals and fungi are eukaryotes, distinct from eubacteria and archaebacteria, which are prokaryotes. The difference being in the composition of the cell, particularly a nucleus contained within a membrane for eukaryotes, along with other membrane bound organelles, e.g. chloroplasts. They all share a common ancestor, according to this paper, that split 1.576 Bya (billion years ago) +/- 88 Mya (although it states the relationships are unresolved - it is often difficult to resolve relationships so deep in a tree). They form distinct groups known as Kingdoms under Linnaean based biological classification; the Fungi, Plantae and Animalia. Thus, in answer to your question, no, animals did not evolve from plants.

Plants have chloroplasts in their cells, which provide the ability to produce energy via photosynthesis. It is thought that the chloroplast resulted from a symbiotic relationship between early plants and a cyanobacteria in that they both relied on each other for survival and so coevolved. Animals don't contain chloroplasts and instead contain an organelle called the mitochondria (although most plants also have mitochondria), which is also thought to have been a bacterial endosymbiont, probably related to rikettsias.

Protists also contain chloroplasts. The protists are intermediate between all three groups and have been notoriously difficult to classify, being placed into a fourth Kingdom, the Protozoa, although this grouping has been contested. The current Cavalier-Smith system was proposed in 2004 and classifies life into 6 Kingdoms.

Chloroplasts are thought to have evolved from a single endosymbiotic event in Archaeplastida, although there are evidence to suggest some secondary endosymbiotic events. Check out this paper for more information; figure 1 shows the relationships between the different groups and the endosymbiotic events. The Opisthokonts are the origin of the Fungi and Animalia kingdoms.

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This does not answer the question: did ancestors of animals have chloroplasts? –  Anixx May 7 '12 at 10:04
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Ancestors of animals had mitochondria (hence the "animal equivalent of the chloroplast is the mitochondria), as did the ancestors of plants have chloroplasts. Although, it is a common misconception, that plants don't respire and in fact most plants also have mitochondria. –  gawbul May 7 '12 at 10:25
    
Edited my question to include chloroplast origin information. Hope that helps? –  gawbul May 7 '12 at 11:01
    
Thanks, the linked diagram is very useful. –  Anixx May 7 '12 at 11:43
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Here's a cool phylogenomics paper by Eugene Koonin "The origin and early evolution of eukaryotes in the light of phylogenomics" - genomebiology.com/2010/11/5/209 –  gawbul May 7 '12 at 12:20

No. Animals form the kingdom Animalia (or Metazoa) which is distinct from the Plantae kingdom.

Both evolved independently from single-celled eukaryotes.

In fact, animals are more closely related to fungi than to plants.

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Did those single-celled eukariotes have chloroplasts? –  Anixx May 7 '12 at 10:09
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@Anixx No. Chloroplasts originally developed in green algae, after divergence from the single-celled common ancestor of plants and metazoa. –  Konrad Rudolph May 7 '12 at 10:33
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Which implies that multi-cellularity evolved independently at least twice, once in plants and once in animals (and possibly in fungi as well). Interesting. –  Keith Thompson Jul 2 at 20:05
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@KeithThompson Indeed, it does have these implications: There are potential hard-to-cross thresholds to higher life forms, which prevents their abundance in the Universe (and may help explain the Fermi paradox), but evolution of multicellularity is not one of them. –  Konrad Rudolph Jul 2 at 20:52

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