AP Bio Chapter 25

Explain how index fossils can be used to determine the relative age of fossil-bearing rock strata. Explain how radiometric dating can be used to determine the absolute age of rock strata. Explain how magnetism can be used to date rock strata.

Index fossils are a starting point for the relative age of the fossils and rock around them. Radiometric dating is based on the decay of radioactive isotopes. The rate of decay is expressed by the half life, the time required for 50% of the parent isotope to decay. The ratio of carbon-14, which decays, compared to how much carbon-12 is in a fossil can determine its age. The less carbon-14 the older it is. Magnetism dating is used when other methods are unavailable. It dates the rocks around a fossil, based on the alignment of iron particles. The alignment of iron particles throughout history changes repeatedly due to the north and south magnetic poles reversing.

Describe the evidence that suggests that RNA was the first genetic material. Explain the significance of the discovery of ribozymes

RNA is central to information transfer in a cell. RNA can be copied abiotically. Ribozymes have a variety of catalytic functions; pre-date enzymes

Describe the key evolutionary adaptations that arose as life colonized land.

Tetrapods became more common as organisms adapted to land. There was more diversity as plants adapted in different ways. There was a lot of adaptive radiation to fill the ecological niches.

Explain the endosymbiotic theory for the evolution of the eukaryotic cell. Describe the evidence that supports this theory.

The endosymbiotic theory says that cells engulfed bacteria, didn't digest them and eventually the bacteria became organelles because the relationship between the two became mutually beneficial. The evidence to support this is that mitochondria and chloroplasts are self sufficient, independent, and do many things similar to prokaryotes today.

Describe the four stages of the hypothesis for the origin of life on Earth by chemical evolution.

1.The abiotic (nonliving) synthesis of small organic molecules, such as amino acids and nucleotides. 2. The joining of these small molecules into macromolecules, including proteins and nucleic acids. 3. The packaging of these molecules into "protobionts", droplets with membranes that maintained an internal chemistry different from that of their surroundings. 4. The origin of self-replicating molecules that eventually made inheritance possible.

Describe how natural selection may have favored the proliferation of stable protobionts with self-replicating, catalytic RNA

A protobiont with self-replicating, catalytic RNA would be different than neighbors without those characteristics. If the protobiont could grow, split and pass on its RNA to its "daughters" its limited inherited characteristics could be acted on by natural selection. Although very rare are those few protobionts, out of the trillions in a body of water, with a limited capacity for inheritance would have had a huge advantage over the rest.

Describe how chemiosmotic ATP production may have arisen.

Chemiosmosis in an energy coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, like the synthesis of ATP. It mostly likely arose before there was any free oxygen in the environment and before the appearance of photosynthesis; the organisms that used it would have required a plentiful supply of energy-rich compounds such as molecular hydrogen, methane, and hydrogen sulfide. Since there was very little oxygen at the time, chemiosmosis would have used other more abundant elements.

Describe the major events in Earth's history from its origin until 2 billion years ago. In particular, note when Earth first formed, when life first evolved, and what forms of life existed in each eon.

From 3.5 billion years ago comes fossilized stromatolites. Stromatolites are layered rocks that form when certain prokaryotes bind thin films of sediment together. It is reasonable to hypothesize that single-celled organisms originated perhaps as early as 3.9 billion years ago if microbial communities complex enough to form stromatolites existed 3.5 billion years ago. Early prokaryotes were Earth's sole inhabitants from 3.5 to 2.1 billion years ago. Photosynthesis and the oxygen revolution left the earth with an oxygenated atmosphere. A few hundred million years later, the rise in O2 accelerated. It is believed that this is because of the evolution of eukaryotic cells containing chloroplasts from about 2.1 billion years ago. Endosymbiosis is a model that explains how eukaryotic features evolved from prokaryotic cells which posits that mitochondria, plastids, and other organelles were formerly small prokaryotes. Serial endosymbiosis supports that mitochondria evolved before plastids through a sequence of endosymbiotic events. Archaen eon-- prokaryotes Proterozoic eon-- first eukaryotic cells, soft-bodied invertebrates & algae Phanerozoic eon: Paleozoic era-- first animals, diverse forests, first tetrapods Mesozoic era-- origin of mammal-like reptiles, dinosaur age, flowering plants Cenozoic era-- mammals, birds, pollinating insects, prime ates, ice age, humans

Explain how the snowball-Earth hypothesis explains why multicellular eukaryotes were so limited in size, diversity, and distribution until the late Proterozoic.

The freezing temperatures of the snowball-Earth make it difficult for multicellular eukaryotes to adapt to another except freezing temperatures or travel very far because of the climate.

Explain how the histories of Earth and life are inseparable.

The histories of Earth and life are inseparable because geological events affect biological evolution; similarly, organisms cause major chemical changes on Earth. Taken together, such changes provide a grand view of the evolutionary history of life on Earth.

Describe the timing and significance of the evolution of oxygenic photosynthesis.

The oxygenic revolution was a result of cyanobacteria, photosynthetic prokaryotes, who slowly led to plants. Eventually, earth was filled with oxygen which led to cellular respiration and life as we know it today.

Describe the mass extinctions of the Permian and Cretaceous periods. Discuss a hypothesis that accounts for each of these mass extinctions.

he Permian mass extinction defines the boundary between the Paleozoic and Mesozoic eras, claimed about 96% of life on earth.

Explain how continental drift explains Australia's unique flora and fauna

Australia is very separated from the rest of the continents on earth in climate and ecology. A continental drift separates every continent in various ways. Since Australia is so far from other pieces of land with such a different climate, the flora and fauna have had to adapt to widely different environmental challenges than the organisms around the rest of the world.

Explain how genetic annealing may have led to modern eukaryotic genomes.

Genetic annealing is the production of a new genome through the transfer of part of the genome of one organism to another organism. By sharing genetic material between organisms, the genetic material became more complex and similar to modern eukaryotes.

Describe how natural selection may have worked in an early RNA world.

Natural selection on the molecular level has produced ribozymes capable of self application in the laboratory. Unlike the doubled stranded DNA, which takes the form of a uniform helix, single stranded RNA molecules pursue a variety of specific three-dimensional shapes mandated by their nucleotide sequences. In a particular environment, RNA molecules with certain base sequences are more stable and replicate faster and with fewer errors and other sequences. The RNA molecules whose sequence is best suited to the surrounding environment and has greatest ability to replicate self believe the most to send it molecules. Its descendents will not be a single species but instead will be a family of sequences that differ slightly because of copying errors.

Describe the contributions that A. I. Oparin, J.B.S. Haldane, and Stanley Miller made toward developing a model for the abiotic synthesis of organic molecules. Describe the conditions and locations where most of these chemical reactions probably occurred on Earth.

Oparin and Haldane independently hypothesized that Earth's early atmosphere was a reducing (electron-adding) environment, in which organic compounds could have formed from simple molecules. The energy for this organic synthesis could have come from lightning and intense UV radiation. Thirty years later, Miller and Urey tested the Oparin-Haldane Hypothesis by creating laboratory conditions comparable to those that scientists at the time thought existed on early Earth. It is likely in any case that small "pockets" of the early atmosphere - perhaps near volcanic openings -were reducing. Perhaps instead of forming in the atmosphere, the first organic compounds formed near submerged volcanoes and deep see vents, where hot water and minerals gush into the ocean from the Earth's interior.