Classifying Life Flashcards
What are the three domains of life?
Bacteria, Archaea and Eukarya
What are the kingdoms of life, in each domains?
Bacteria = Eubacteria, Archaea = archaebacteria, and eukarya = protista, fungi, animals, plants
Why do bacteria and archaea have 70s ribosomes and eukarya have 80s ribosomes?
Bacteria and archaea need to have smaller ribosomes, because their cells are smaller.
What are ribosomes?
The place in the cell where proteins are synthesized
How are archaea and bacteria different?
Archaea can live in more extreme conditions than bacteria. Their cell membranes are made of phospholipids(chains of fatty acids) (L-glycerol in ester linkages) that are more resistant than the phospholipids of bacteria which are made of D-glycerol in ester linkages. Some of the genes of archaea have introns whereas introns are absent in bacteria. There is peptidoglycan, a protein, in the cell wall of bacteria but not in archaea.
How are archaea and bacteria alike?
They are prokaryotes, so they do not have organelles with internal membranes, they do not have a nucleus and they are unicellular organisms. They have 70s ribosomes. They can be both autotrophs or heterotrophs. Mostly are heterotrophs. However, archaea cannot photosynthesize. They all reproduce asexually by binary fission and share their genes in three ways: transformation, transduction and conjugation.
Did bacteria or archaea come first?
It is unclear, but scientists tend to agree that bacteria came first and that archaea are strong evolutions of bacteria. One thing is sure, they came before eukaryotes. Because of that, they had the time to evolve so that biomass of prokaryotes > all biomass of animals and maybe plants even if they are smaller. Archaea are still unknown because they were discovered only 40ya.
What is the role of archaea in ecosystems?
They form methane, so they are producers. Some of them are decomposers.
What is the role of bacteria in ecosystems?
They are producers, decomposers and consumers. They have a role to play in biochemical cycling.
What are introns?
They are small pieces of DNA within a gene that are not used to make a gene product. Animals and some archaea have introns.
What are differences between prokaryotic and eukaryotic cells?
Eukaryotic cells have more organelles and those organelles are membrane-bound. They have a nucleus that contains the genetic material, like many rod-shaped chromosomes when condensation of chromatin fiber. In prokaryotes, the genetic material is in a central region called the nucleoid. Eukaryotic cells are thus more complex (organisms also) bc. the membranes of organelles allows different functions to be compartmentalized in different areas of the cell.
What is likely the origin of some eukaryotic organelles? What are those organelles?
Mitochondria and chloroplasts likely emerged from endosymbiosis in which an organism engulfed a smaller one, without digesting it. The little one was safe and the bigger one could gain some attribute (like aerobic respiration or photosynthesis). It was mutually beneficial for both of them.
What evidence is there for endosymbiosis?
There are similarities between prokaryotes, mitochondria and chloroplasts. They have similar membrane transport systems, they divide by binary fission as independent organisms synchronously with mitosis, they have circular DNA, similar ribosomes, similar DNA sequences.
What are examples of symbiotic relationships?
Mitochondria and chloroplasts in the cells. Bacteria in human gut. Coral polyps. Bacteria in termites.
What are possible origins of the nucleus?
Like mitochondria and chloroplasts, there is endosymbiosis. Also, there is infolding. Just like if the cell membrane had folded on itself, compressing the DNA inside it and enjailing tools to use the DNA.
What is the first sign that you have an eukaryotic cell?
There is a nucleus and membrane-bound organelles
