Like the plants, animals evolved in the sea. In the eukaryote cell's cytoplasm and like chloroplasts they areĮnclosed by a double membrane as would be expected if they derivedįrom bacterial cells engulfed by another cell. In the form of a single circular DNA molecule their ribosomesĪre more similar to those of bacteria than to the ribosomes found
There is considerable evidence that mitochondriaĮvolved from free-living aerobic bacteria: they are the size of bacterial cells they divide independently To produce the energy-carrying molecule ATP. Both plant and animal rely on structures called mitochondria to release energy in their cells, using aerobic respiration The evidence for this lies in the way their cellsįunction. Plants and animals both owe their origins to endosymbiosis,Ī process where one cell ingests another, but for some reason thenįails to digest it. In fact, the name "Proterozoic" means "early life". Organisms are found in abundance in rocks from this period Thatĭate from the Proterozoic Era, the final Era of the Precambrian.įossils of both simple unicellular and more complex multicellular
Prokaryotes, between 25 million years ago. Large numbers of cells, and microscopic inspection of theseĬells reveals that they contain a nucleus and a number ofĬompared to prokaryotic organisms such as bacteria, plantsĪnd animals have a relatively recent evolutionary origin.ĭNA evidence suggests that the first eukaryotes evolved from As such, we have a number of features in common with all the organisms placed in the animal kingdom, and these common features indicate that we have a shared evolutionary history.Īll animals and plants are classified as multicellular
This may be because we are animals ourselves. For many people animals are perhaps the most familiar, and most interesting, of living things.
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