AP Bio Ch 25: The History of Life on Earth

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