Chapter 25 Flashcards
(22 cards)
Four stages that produced a simple cell
1- the abiotic (non living) synthesis of organic molecules, such as amino acid and nitrogenous base
2- the joining of small molecules into macromolecules such as protein and nucleic acid.
3-the packing of these molecules into photocell droplets with membrane that maintained an internal chemistry different from that of their surrounding
4-the origin of self replication molecules that eventually made inheritance possible
Synthesis of Organic Compounds on Early Eart
A hypothesis suggests: organic compounds formed near volcanoes
Another hypothesis: organic compounds were first produced in deep-sea hydrothermal vents, areas on the seafloor where heated water and minerals gush from
Moreover Studies related to the volcanic-atmosphere and alkaline- vent hypotheses show that the abiotic synthesis of organic molecules is possible under various condition.
Another source may be meteorite
Abiotic Synthesis of Macromolecules
1-the abiotic synthesis of RNA monomers, can occur spontaneously from simple precursor molecules without enzymes or ribosomes.
Protocell
Amino acids and RNA nucleotides polymerize when dripped onto
hot sand, clay, or rock. Organic compounds can spontaneously assemble into protocells, membrane-bounded droplets that have some properties of cells.
Self replicating RNA
- first genetic material was RNA
- play role in protein synthesis and carry enzyme like function
- Some ribozymes can make comple- mentary copies of short pieces of RNA,
- A vesicle with self-replicating, catalytic RNA would dif- fer from its many neighbours that lacked such molecules.
The fossil record
- Sedimentary rocks are the richest source of fossils.
- Useful information is also provided by other types of fossils, such as insects preserved in tree sap and mammals frozen in ice.
- many fossil are not in right place or have been destroyed as result fossil record is bias
How rocks of fossil are dates
Technique radiometer dating and half life is used to find dates and time
Radiometer dating
Method based on decay of radioactive isotopes
Half life
the time required for 50% of the parent isotope to decay. Each radioactive isotope are characterised bye half life which is not affect by temperature or Pressure.
The origin of new group of organism
- Along with amphibians and reptiles, mammals belong to the group of animals called tetrapods;named for having four limbs.
- scientist matches unique fossil bones of mammal like lower jaw , three ear bones (hammer anvil and stirrup) and polar and premolar
Stromatolites
layered rocks that form when certain prokaryotes bind thin films of sediment together. Present-
day stromatolites are found in a
few warm, shallow, salty bay
Endosymbiotic theory
posits that mitochondria and plastids (a general term for chloroplasts and related organelles) were formerly small prokaryotes that began living within larger cells. The term endosymbiont refers to a cell that lives within another cell, called the host cell. Began as prey or parasites came to have a mutually beneficial relationship with the host in as little as five years.
Serial endosymbiosis
supposes that mito- chondria evolved before plastids through a sequence of endosymbiotic even
evidence that supports the endosymbiotic ori- gin of mitochondria and plastid
The inner membranes of both organelles have enzymes and transport systems that are homologous to those found in the plasma membranes of living prokaryotes.
• Mitochondria and plastids replicate by a splitting process that is similar to that of certain prokaryotes. In addition, each of these organelles contains circular DNA molecules that, like the chromosomes of bacteria, are not associated with histones or large amounts of other proteins.
• As might be expected of organelles descended from free- living organisms, mitochondria and plastids also have the cellular machinery (including ribosomes) needed to tran- scribe and translate their DNA into proteins.
• Finally, in terms of size, RNA sequences, and sensitiv- ity to certain antibiotics, the ribosomes of mitochondria and plastids are more similar to prokaryotic ribosomes than they are to the cytoplasmic ribosomes of eukaryotic cells.
Cambrian explosion
Many present-day animal phyla appear suddenly in fossils formed early in the Cambrian period (535– 525 million years ago), a phenom- enon referred to as the Cambrian explosion.
Mutually beneficial relationship f plant and fungi
ngi that aid in the absorption of water and minerals from the soil
(see Chapter 31). These root fungi (or mycorrhizae), in turn, obtain their organic nutrients from the plants.
genetic assimilation
when
a phenotype is no longer dependent on environmental conditions.
Plate tectonics
the conti- nents are part of great plates of Earth’s crust that essentially
float on the hot, underlying por- tion of the mantle
Continental drift
Movements in the mantle cause the plates to move over time
Consequence of drift theory
- continental drift alters the habitats in which organisms live
- Organisms are also affected by the climate change that occurs when a continent changes location
- Continental drift also promotes allopatric speciation on a grand scale.
- Finally, continental drift can help explain puzzles about the geographic distribution of extinct organisms
Mass extinctions
large numbers of species become extinct worldwide.
adaptive radiation
Period of evolutionary in which groups of organism from many new specieswhose adaptation allow them to fill ecological role or niche
