Module 74
When do the first cells appear in the fossil record?
3.5 billion years ago
Explain how species evolved adaptations to life on land.
About 500 million years ago, some organisms moved from the oceans to land. Based on fossil, developmental, and anatomical evidence, scientists think humans and other mammals evolved from fish and lungs evolved from gills.
After Lynn Margulis's endosymbiont theory met opposition, what new evidence emerged in support of the theory?
DNA sequencing
What is the main distinction between prokaryotes and eukaryotes?
Eukaryotes have a nuclear membrane.
Relate endosymbiont theory to the evolution of eukaryotes.
Mitochondria and chloroplasts are widely believed to have evolved from bacteria that entered eukaryotic cells through endosymbiosis. These organelles not only have their own circular DNA, like bacteria, but contribute DNA to the nuclear genome, have double membranes and make their own proteins. Researchers are investigating this process and its effects.
Which of the following would NOT likely have occurred without the evolution of photosynthetic organisms? 1.Life would be much less diverse. 2.Most organisms would have gone extinct due to the increase in oxygen. 3.Mitochondria-containing cells would not have evolved. 4.There would be no oxygen on Earth. 5.All of the other choices are potential consequences of a photosynthesis-free world.
Most organisms would have gone extinct due to the increase in oxygen.
Describe the geologic and biologic effects of the evolution of photosynthesis.
Photosynthetic organisms dramatically increased atmospheric oxygen levels between 2 and 2.5 billion years ago. This change created selective pressure favoring organisms that used oxygen to produce energy-containing molecules.
Give the date the first prokaryotes appear in the fossil record and how they were identified.
Single-celled prokaryotes, the first sign of life on Earth, appear in the fossil record as stromatolites about 3.5 billion years ago. The best evidence is the stromatolites, fossilized layers of these organisms trapped in sediment.
serial endosymbiosis
Theory that multiple endosymbiotic events occur in the same cell.
Which of the following is NOT a way in which mitochondria and bacteria are similar? 1.Mitochondrial genes resemble proteobacterial genes. 2.Their ribosomal structures and RNA are similar. 3.They both produce all the proteins they need. 4.They are similar in size. 5.They both have DNA arranged in circular chromosomes.
They both produce all the proteins they need.
How did photosynthetic prokaryotes dramatically change Earth's atmosphere?
They increased oxygen levels through photosynthesis.
endosymbiotic theory
Widely accepted theory that states mitochondria and chloroplasts were once free-living prokaryotes prior to incorporation inside cells.
