Introductory Biology

12.2 Complex Organisms Developed

The Earth attracted oceans/water from the volcanoes, which contain water vapors, and also from the commits that pass by. Prokaryotes are the oldest group of organisms and fossils have shown that the earliest prokaryotes had been around, 3.5 billion years ago. What’s living now all come from the common ancestor (LUCA): Last Universal Common Ancestor. All of the oxygen in the atmosphere is produced from photosynthesis. Oxygen is very important because it creates an ozone layer, which protects us from ultraviolet radiation. Billions of years ago, organisms had to hide underwater in order to protect itself from ultraviolet radiation.

Bacteria can reproduce very rapidly. Archea and eukarya are more closely related to each other than they are to bacteria.  Prokaryotes have 2 main groups: archaebacteria and eubacteria. Archaebacteria are thought to be related to the earliest organisms on Earth. Eubacteria have a huge variety (consumers = Escherichia coli and photosynthesizers = cyanobacteria). Archaebacteria and eubacteria came from a common ancestor 2 billion years ago.

Archaebacteria:
  • lack peptidoglycan in their cell walls
  • have unique lipids in the cell membrane
  • DNA contains introns
  • ribosomes are similar to eukaryotic ribosomes: RNA polymerase & transcription starts at methionine, just like us
  • 1st eukaryotes are thought to have evolved from archaebacteria
Eubacteria:
  • contain peptidoglycan in their cell walls
  • have lipid membranes (like eukaryotes)
  • DNA lacks introns
  • ribosomes differ from eukaryotes
3 major ways eukaryotes differ from prokaryotes are; DNA is inside the nucleus, organelles separate the cytoplasm into compartments, and they have chloroplast & mitochondria (provides ATP). Plant cells have both chloroplast AND mitochondria. Mitochondria and chloroplast both have DNA and ribosomes. They are like little organisms that make their own protein. They evolved by the endosymbiotic origin of the eukaryotic cells. Some evidence was proven that they evolved by endosymbiosis from eubacteria:
  • mitochondria are about the same size & structure as most eubacteria
  • they have circular DNA + lack introns (like eubacteria)
  • mitochondrial & chloroplast ribosomes are similar to the ones of eubacteria
  • they divide by binary fission just like eubacteria.
Eukaryotic organisms have 4 main kingdoms: protists, fungi, plants, and animals. A half of the biomass of life is made up of unicellular bacteria, protists and fungi. Unicellular organisms are limited to simpler lifestyles. Multicellularity helps perform cellular specialization, division of labor, and thus greater complexity & size. During the Cambrian Period (540~505 million years ago), all the basic body plans were made/ major groups of complex multicellular animals evolved. During the Ordovician Period (505~438 million years ago), animals continued to diversify (trilobites as well). Slime moles get together to form a blob and some become stock cells. These cells go through meiosis and scatter the cells at the top to repeat the process once again.
Mass extinctions have had a major impact on Earth and the history of life, which have been recorded in the fossil record. The 5 major mass extinctions occurred in the following period: Ordovician (438 mya), Devonilian (360 mya) , Permian (245 mya), Triassic (205 mya) , and Cretaceous (65 mya). **mya = million years ago** At the end of the Permian Period, 96% of all species were killed. At the end of the Cretaceous Period, 65% of terrestrial animals + dinosaurs were killed. A sixth mass extinction is currently occurring, as humans destroy habitat (esp. tropical rain forests).  Nearly all of the species are gone or extinct and the total species living today are 10-30 million, we only know 10% of them. Right now, 50 thousand species are being extinct because of human destruction of nature/forest.  Continents are constantly moving and producing volcanoes, which effect the entire climate. Some causes can be thought as dinosaurs, asteroids and plate tectonics. Asteroids created meteor crater and massive explosions (once the ecosystems + photosynthesis stopped because of the ash and etc. from the explosion).  Plate tectonics cause the movement on the Earths plates and can allow earthquakes to form.
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One thought on “12.2 Complex Organisms Developed

  1. Yurika,

    Excellent entry for 12.2 on the evolution of complex life on Earth. Great organization and very thorough.

    Mr. F.

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