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Chapter 19: 19.1-19.3
Terms in this set (35)
something that has died out
What do fossils reveal about ancient life?
From the fossil record, paleontologists learn about the structure of ancient organisms, their environment, and the ways in which they lived
1. Usually forms when small particles of sand, silt, clay, or lime muds settle to the bottom of a river, lake, ocean, or other body of water
2. Can also form from compacted desert sands
3. Pressure from water over years can compress lower layers and, along with chemical activity, form rocks from the sediment
Fossils in Sedimentary rock
As sediments build up, they bury dead organisms that have sunk to the bottom. Over time the remains are buried deeper and deeper
Researchers who study fossils to learn about ancient life
What can researchers infer about fossils?
By comparing body structures from fossils to body structures in living organisms, researchers can infer evolutionary relationships and form hypotheses about how body structures and species have evolved
How do we date events in Earth's history?
1. Relative dating allows paleontologists to determine whether a fossil is older or younger than other fossils
2. Radiometric dating uses the proportion of radioactive to stable isotopes to calculate the age of a a sample
1. Places rock layers and their fossils in a temporal sequence. This allows paleontologists to determine whether a fossil is older or younger than other fossils
2. Doesn't provide any information about a fossil's absolute age in years
This uses the proportion of radioactive to stable isotopes to calculate the age of a a sample
1. Distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain.
2. Useful ones must be easily recognized and will only occur in a few rock layers (meaning the organism lived only for a short time), but these layers will be found in many places (meaning the organism was widely distributed)
3. Trilobites, a large group of distinctive marine organisms, are often used as these
Time required for half of the radioactive atoms in a sample to decay
1. After one half-life: half of the original radioactive atoms have decayed
2. After another half-life: another half of the remaining radioactive atoms will have decayed
Radioactive isotopes and half-lives
1. Different radioactive isotopes decay at different times, so they have different half-lives
2. An example of one is Carbon-14
How was the geologic time scale established, and what are its major divisions?
The geologic time scale is based on both relative and absolute dating. The major divisions of the geologic time scale are eons, eras, and periods
geologic time scale
a time line of Earth's history
eons are divided into these
Four of these:
1. Hadean Eon: from Earth's formation to about 4 million years ago
2. Archean Eon: followed Hadean
3. Proterozoic Eon: followed Archean
4. Phanerozoic Eon: followed Proterozoic
eras are subdivided into these
How have our planet's environment and living things affected each other to shape the history of life on Earth?
Building mountains, opening coastlines, changing climates, and geological forces have altered habitats of living organisms repeatedly throughout Earth history. The actions of living organisms over time have changed conditions in the land, water, and atmosphere of planet Earth
geologic processes, such as continental drift, volcanoes, and earthquakes, resulting from plate movement
changes in anatomy , phylogeny, ecology, and behavior that take place in clades larger than a single species
extinction caused by slow and steady process of natural selection
event during which many species become extinct during a relatively short period of time
the evolution of a species by gradual accumulation of small genetic changes over long periods of time
pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
process by which a single species or a small group of species evolves into several different forms that live in different ways
process by which unrelated organisms independently evolve similarities when adapting to similar environments
process by which two species evolve in response to changes in each other over time
What processes influence whether species and clades survive or become extinct?
If the rate of speciation in a clade is equal to or greater than the rate of extinction, the clade will continue to exist. If the rate of extinction in a clade is greater than the rate of speciation, the clade will eventually become extinct
How fast does evolution take place?
Evidence shows that evolution has often proceeded at different rates for different organisms at different times over the long history of life on Earth
What are two patterns of macroevolution?
Two important patterns of macroevolution are adaptive radiation and convergent evolution
What evolutionary characteristics are typical of coevolving species?
The relationship between two coevolving organisms often becomes so specific that neither organism can survive without the other. Thus, an evolutionary change in one organism is usually followed by a change in the other organism.
theory that propose that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic species
What do scientists hypothesize about early Earth and the origin of life?
1. Earth's early atmosphere contained little or no oxygen. It was principally composed of carbon dioxide, water vapor, and nitrogen, with lesser amounts of carbon monoxide hydrogen sulfide, and hydrogen cyanide.
2. Miller and Urey's experiment suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds on a primitive Earth.
3. The "RNA world" hypothesis proposes that RNA existed by itself before DNA. From this simple RNA-based system, several steps could have led to DNA-directed protein synthesis.
What theory explains the origin of eukaryotic cells?
The endosymbiotic theory proposes that a symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them.
What is the evolutionary significance of sexual reproduction?
The development of sexual reproduction sped up evolutionary change because sexual reproduction increases genetic variation
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