Tag: the origin of cells and cell division
Questions Related to the origin of cells and cell division
Which of the following gases probably least abundant in the early atmosphere?
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$H _2$
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$0 _2$
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$NH _3$
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CO
Most of the history of life concerns the evolution of
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Prokaryotes
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Photosynthesizers
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Plants and animals
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Eukaryotes
- Cells are divided into two main classes, initially defined by whether they contain a nucleus.
- Prokaryotic cells (bacteria) lack a nuclear envelope.
- Prokaryotic cells are generally smaller and simpler than eukaryotic cells; in addition to the absence of a nucleus, their genomes are less complex and they do not contain cytoplasmic organelles or a cytoskeleton.
- Phospholipids are the basic components of all present-day biological membranes, including the plasma membranes of both prokaryotic and eukaryotic cells.
- The key characteristic of the phospholipids that form membranes is that they are amphipathic molecules, meaning that one portion of the molecule is soluble in water and another portion is not.
Which of the following statements is true?
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True cell evolved before the protocell
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Prokaryotes evolved before eukaryotes
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Eukaryotes evolved before prokaryotes
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Prokaryotes didnt evolve until 1.5 billion years ago
- Scientists have concluded that prokaryotic life forms preceded the more complex eukaryotes.
- All organisms on Earth are classified into two basic cell types. "Kary" means nucleus, "Pro" means "before," and prokaryotes have DNA in a freely floating ring that is not encased in a nucleus.
- "Eu" means "true," and eukaryotes have DNA arranged in chromosomes and encased in a nucleus.
- Fossil evidence indicates that prokaryotic cells first existed on the earth, prior to the arrival of the eukaryotes.
- Though they lack skeletons, a few groups of single-celled organisms have hard portions or secrete hard shells and so appear in the fossil record.
- This record is the best indication of prokaryotes' and eukaryotes' relative ages.
The term, reducing atmosphere for the early earth means that the atmosphere
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Was much thinner around the surface of the earth than now
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Contained only two or three kinds of gases
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Contained little or no free oxygen
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Contained little or no free nitrogen
Members of biologic species are potentially able to
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compete
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introgress
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interbreed
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express all the same genes
Species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups. Interbreeding also called as hybrid is the result of combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.
Who first proposed the term and concept of species?
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John Ray and Ernst Mayr
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John Ray
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Lamarck and Darwin
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Ernst Mayr
Which was absent in the atmosphere at the time of origin of life?
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$NH _3$
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$H _2$
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$O _2$
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$CH _2$
The first person who proposed that small organic molecules can be formed in and oxygen-deprived environment was
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Stanley Miller
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Thomas Cech
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Aleksander
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Sidney Fox
In 1924, the Russian biochemist Aleksandr Oparin proposed that life could have developed through gradual chemical evolution in a “primordial soup.” This theory was independently proposed by English geneticist J.B.S. Haldane, also in the 1920s. This theory states that a mixture of organic molecules could form in an oxygen-deprived environment through the random interactions of small molecules, with energy provided by sunlight and lightning. This theory is not without controversy.
During which of the following intervals did life originate on the Earth?
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Mesozoic era
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Proterozoic eon
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Cambrian period
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Archean eon
- The Archean (or Archaean) eon is an interval of geologic time of about 1.4 billion years, beginning with the formation of Earth's crust and the oldest Earth rocks 3,960-3,800 million years ago (mya) and continuing until its boundary at 2,500 mya, with the Proterozoic eon.
- The origin of life has been traced to the Archean eon, with fossils of prokaryotes.
- During the Archean eon, prokaryotes spread over much of Earth's surface, often in mats comprising myriads of collaborating bacteria differentiated by the type of biochemistry each performed.
- During the Archean eon some prokaryotes developed the molecular structures for achieving photosynthesis, which permitted them initially to use sunlight for capturing hydrogen from the atmosphere and later to use it for capturing carbon from atmospheric carbon dioxide with the release of oxygen, thus helping to prepare an environment that could support eukaryotic cells and multicellular forms of life.
The first genes may have developed when
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Protobionts grew and divided
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Short RNA strands self-replicated
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DNA molecules produced RNA molecules
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Polypeptides became catalytic
RNA is capable of catalyzing a number of chemical reactions, including the polymerization of nucleotides. RNA is uniquely able both to serve as a template for and to catalyze its own replication. Consequently, RNA is generally believed to have been the initial genetic system, and an early stage of chemical evolution is thought to have been based on self-replicating RNA molecules—a period of evolution known as the RNA world.