Q1: how long has teh earth exist?
A1:about 4.6 billion years ago
Q2:what is the earlest evident of life on earth?
A2:about 3.5 billion years old.
Q3: what is the first genetic material?why?
A3: RNA, because RNA molecule sequences are more stable and replicate faster and with fewer errors than other sequences.
Five Facts:
1. conditions on early earth made the origin of life possible
2. the fossil record documents the history of life
3. ket events in life's history include the origins of single-celled and multicelled organisms and the colonization of land
4. the rise and fall of dominant groups reflect continental drift, mass extinctions, and adaptive radiations
5. major changes in body form can result from changes in the sequences and regulation of developmental genes
Figure:
heterochrony is an evolutionary change in the rate or timing of developmental events. heterochrony can also alter the timing of reproductive development relative to the development of nonreproductive organs.
Summary:
Life arose consists of four main stages: small organic molecules were synthesized; small molecules joined into macromolecules, such as protein and nucleic acids; all these molecules were packaged into protobionts, membrane containing droplets, whose internal chemistry differed from that of the external environment; self-replicating molecules emerged that made inheritance possible. The fossil record is the sequence in which fossile appear in the layers of sedimentary rock that consistitue earth's surface. relative dating uses the order of rock strata to determine the relative age of fossils. Radiometric dating uses the decay of radioactive isotopes to determine the age of the rocks or fossiles. It is based on the rate of decay, or halflife of the isotope. the earliest livig organisms were prokaryotes. About 2.7 billion years ago, oxygen began to accumulate in earth's atmosphere as a result of photosynthesis. eukaryotes appeared about 2.1 billlion years ago. the endosymbiotic hypothesis proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells. Multicellular eukaryotes evolved about 1.2 billion years ago. The colonization of land occurred about 500 million years ago, when plants, fungi, and a animals began to appear on earth.
Continental drift is the movement of earth's continents on great plates that float on the hot, underlying mantle. Mass extinxtions, loss of large numbers of species in a short period, have resulted from global environment. Adaptative radiations are periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological noches. Structures that evolve in one context but become co-opted for another function are sometimes called exaptations. Homeotic genes are master regulatory genes that determine tha location and organization of body parts. Hox genes are one class of homeotic genes.
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