Tags & Description
Macroevolution
the pattern of evolution over large time scales
Protobionts
collections of abiotically produced molecules surrounded by a membrane-like structure. Internal chemical environment is different from that of their surroundings
Ribozyme
an RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing
Radiometric dating
a method for determining the absolute ages of rocks and fossils, based on the half-life of radioactive isotopes
Half-life
the amount of time it takes for 50% of a sample of a radioactive isotope to decay
Geological record
the division of Earth's history into time periods, grouped into 3 eras (Archaean, Proterozoic, Phanerozoic) and further subdivided into eras, periods, and epochs
Stromatolite
layered rock that results from the activities of prokaryotes that bind thin films of sediment together
Endosymbiosis
a process in which a unicellular organism (the host) engulfs another cell, which lives within the host cell and ultimately becomes and organelle in the host cell; also refers to the hypothesis that mitochondria and plastids were formerly small prokaryotes that began living within larger cells
Serial endosymbiosis
a hypothesis for the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells
Cambrian explosion
a relatively brief time in geological history when rage, hard-bodied forms of animals with most of the major body plans known today appeared in the fossil record. This burst of evolutionary change occurred about 535-525 million years ago
Continental drift
the slow movement of the continental plates across Earth's surface
Pangaea
the supercontinent that formed near the end of the Paleozoic era, when plate movement brought all the landmasses of Earth together
Adaptive radiations
periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles, or niches, in their communities
Paedomorphosis
the retention in and adult organism of the juvenile features of its evolutionary ancestors
Homeotic genes
any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells
What are the challenges of estimating the absolute ages of old fossils? How can these be overcome?
Organisms don't use radioisotopes that have long half-lives to build their bones on shells; so fossils older than 75000 years can't be dated directly. Sediment that contains fossils usually contains sediments of different ages. These can be overcome when geologists date layers of volcanic rock that surround old fossils and that use radioisotopes with long half-lives.
Why is the Cambrian explosion significant?
The evolutionary changes that occurred during this time, such as the appearance of large predators and well-defended prey, were important because they set the stage for many of the key events in the history of life over the last 500 million years
Explain how broad evolutionary changes seen in the fossil record are the cumulative result of speciation and extinction events.
The changes reflect the rise and fall of major groups of organisms. In turn, the rise or fall of any particular group results from a balance between speciation and extinction rates: a group increases in size when the rate at which its members produce new species is greater than the rate at which its member species are lost to extinction, while a group shrinks in size if extinction rates are greater than speciation rates
How could changes in a single gene or DNA region ultimately lead to the origin of a new group of organisms?
Morphological changes may enable organisms to perform new functions or live in new environments, thus potentially leading to an adaptive radiation and the formation of a new group of organisms
Explain what "evolution is not goal oriented" means.
Evolutionary change results from interactions between organisms and their current environments, no goal is involved in this process. As environments change over time, the features of organisms favored by natural selection may also change, and what once may have seemed like a "goal" of evolution, can cease to be beneficial.
Fossilized stromatolites resemble...
structures formed by bacterial communities that are found today in some warm, shallow, salty bays
The oxygen revolution changed Earth's environment dramatically; what took advantage of the presence of free oxygen in the oceans and atmosphere?
the evolution of of cellular respiration, which used oxygen to help harvest energy from organic molecules
What factor most likely caused animals and plants in India to differ greatly from species nearby in southeast Asia?
India was a separate continent until 45 mya
Adaptive radiation can be a direct consequence of what four factors?
vacant ecological niches; colonization of an isolated region that contains suitable habitat and few competitor species; evolutionary innovation; an adaptive radiation in a group of organisms that another group uses as food
What step has not been accomplished by scientists studying the origin of life?
formation of protocells that use DNA to direct the polymerization of amino acids