namely bacteria and archaea, which reproduce asexually by simple cell division); followed around 2 billion years ago by larger, relatively more complex single-celled organisms (eukaryotes, such as protozoa; eukaryotes contain a nucleus and organelles and reproduce sexually, ...
How did life on Earth begin and evolve?The many different species of living things on Earth (and many species that are now extinct) evolved from very simple living things.Life on Earth began about 3500 million years ago.Evidence for evolution is provided by fossils and from analysis of ...
Eventually, these simple life forms split and began to evolve separately. All animals, plants, and fungi trace back to this time. It’s difficult to pinpoint what order and the exact way this occurred. When did multicellular organisms first appear? Around 900 million years ago multicellular lif...
A new idea about the origin of complex life turns current theories inside out. In the open access journalBMC Biology, cousins Buzz and David Baum explain their 'inside-out' theory of how eukaryotic cells, which all multicellular life - including us - are formed of, might have evolved. Scien...
A large fraction of the protein-coding genes of multicellular organisms are alternatively spliced, although no regulated splicing has been detected in unicellular eukaryotes such as yeasts. A comparative analysis of unicellular and multicellular eukaryotic 5′ splice sites has revealed important differences...
All complex multicellular organisms are eukaryotes. How did the evolution of the highly complex architecture of the eukaryotic cell arise? I discuss the differences between bacteria and archaea (prokaryotes) and eukaryotes in terms of chemistry, cellular structure, energetic and genetics. Chemistry and ...
剪接如何选择选择性剪接Howdid选择剪接选择剪接的 系统标签: splicingalternative剪接evolve选择性exons REVIEWS NATUREREVIEWS|GENETICSVOLUME5|OCTOBER2004|773 5′splicesite(5′ss)signalthatonlysupportedconstitu- tivesplicingaccumulatedmutations.Theeffectofthe mutationswastosub-optimizethatsite,allowingitto beusedinalte...
We've probably all heard of mitochondria, and we may even remember learning in school that they are the "powerhouses of the cell" – but what does that actually mean, and how did they evolve? To answer this question, we have to go back about two billion years to a time when none of...
Millions of years later, eukaryotic cells began to band together in groups, forming multicellular organisms. So advantageous was this symbiosis that it appears to have happened multiple times. These multicellular organisms then competed with each other and suppressed competition internally. (We have a ...
For comparison, Earth is about 4.5 billion years old, and multicellular organisms developed relatively recently compared to unicellular, microbial life [source: Nature]. Classifying Extremophiles These depictions of single-celled organisms fall in the Monera kingdom, home of prokaryotes. Harnett/...