Hybrids produced by invasive species

The ecological effects of invasive species are often well known, particularly their impact on native plants or animals. But the invaders sometimes make love as well as war: they mate with related local species, producing hybrids. And the effects of such hybridization have not been the subject of much study.

Now, research involving invasive and natives salamanders in the Salinas Valley of California shows how devastating this can be: the hybrids have voracious appetites and can practically wipe out other species.

Maureen E.Ryan and Jarrett R.Johnson of the University of California, Davis, and Benjamin M. Fitzpatrick of the University of Tennessee studied hybrids between native California tiger salamanders and barred tiger salamanders, brought in huge numbers from Texas beginning 60 years ago by California balit dealers. Tiger salamander larvae are high on a pond’s food chain, gulping down larvae of other species with their big mouths.

The researchers built artificial ponds, stocked them with salamanders and other species, notably the California newt and the Pacific chorus frog (both of which are found in the Salinas Valley) and monitored what happened. Their findings appear in the Proceedings of the National Academy of Sciences.

Hybrid larvae had a greater effect on the newts and frogs than native salamander larvae did, nearly wiping them out. Hybrids even affected the survival of native salamanders in the ponds.

The implication is they’re ecologically quite different than the native species,” Ryan said.

That could spell trouble for other third-party” species in the valley, like the California red-legged frog and the Santa Cruz long-toed salamander.

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Celestial Location

To locate the ecliptic, planets, or anything else in the sky, you need something to refer to, a referent system. A referent system is easily established by first imagining the sky to be a celestial sphere just as the ancient Greeks did. A coordinated system of lines can be visualized on this celestial sphere just as you think of the coordinate system of latitude and longitude lines on the earth’s surface. Imagine that you could inflate the earth until its surface touched the celestial sphere. If you now transfer the latitude and longitude lines to the celestial sphere, you will have a system of sky coordinates. The line of the equator of the earth on the celestial sphere is called the celestial equator. The North Pole of the earth touches the celestial sphere at a point called the north celestial pole. From the surface of the earth, you can see that the celestial equator is a line on the celestial sphere directly above the earth’s equator, and the north celestial pole is a point directly above the earth’s equator, and the north celestial pole is a point directly above the North Pole of the earth. Likewise, the south celestial pole is a point directly above the South Pole of the earth.

You can only see half of the overall celestial sphere from any one place on the surface of the earth. Imagine a point on the celestial sphere directly above where you are located. An imaginary line that passes through this point, then passes north through the north celestial pole, continuing all the wary around through the south celestial pole and back to the point directly above you makes a big circle called the celestial meridian. Note that the celestial meridian location is determined by where you are on the earth. The celestial equator and the celestial poles, on the other hand, are always in the same place no matter where you are.

Overall, the celestial sphere appears to spin, turning on an axis through the celestial poles. A photograph made by pointing a camera at the north celestial pole and leaving the shutter open for several hours will show the apparent motion of the celestial sphere with star trails. The moderately bright star near the center is the North Stat, Polaris. Polaris is almost, but not exactly, at the north celestial pole. You can locate Polaris by finding the Big Dipper. The two stars on the end of the dipper opposite the handle are called the pointers. Imagine a line moving from the bottom of the dipper upward through the two pointers. The first bright star that this line meets is Polaris. The angle that you see Northern Hemisphere. Shows the geometric relationships between your latitude and the angle of Polaris above the horizon.

If you observe the constellation night after night, you will see that the stars maintain their positions relative to one another as they turn counterclockwise around Polaris. Those near Polaris pivot around it and are called “circumpolar”. Those farther out rise in the east, move in an arc, then set in the west.

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Natural Radioactivity

Radioactivity was discovered in 1896 by Henri Becquerel, a French scientist who was very interested in the recent discovery of X- rays. Becquerel was experimenting with fluorescent minerals, minerals that give off visible light after being exposed to sunlight. He wondered if fluorescent minerals emitted X rays in addition to visible light. From previous work with X-rays, Becquerel knew that they would penetrate a wrapped, light-tight photographic plate, exposing it as visible light exposes an unprotected plate. Thus, Becquerel decided to place a fluorescent uranium mineral on the plate when it was developed. Believing the uranium mineral emitted X- rays, he continued his studies until the weather turned cloudy. Storing a wrapped, protected photographic plate and the uranium mineral together during the cloudy weather, Becquerel returned to the materials later and developed the photographic plate to again find an image of the mineral. He concluded that the mineral was emitting an “invisible radiation” that was not induced by sunlight. Becquerel named the emission of invisible radiation radioactivity. Materials that have the property of radioactivity are called radioactive materials.

Becquerel’s discovery led to the beginnings of the modern atomic theory and to the discovery of new elements. Ernest Rutherford studied the nature of radioactivity and found that there are three kinds, which are today known by the first three letters of the Greek alphabet-alpha (a), beta (b), and gamma. These Greek letters were used at first before the nature of the radiation was known. Today, an alpha particle (sometimes called an alpha ray) is known to be the nucleus of a helium atom, that is, two protons and two neutrons. A beta particle (or betaray) is a high-energy electron. A gamma ray is electromagnetic radiations, as is light, but of very short wavelength.

It was Rutherford’s work with alpha particles that resulted in the discovery of the nucleus and the proton. At Becquerel’s suggestion, Madame Marci Curie searched for other radioactive materials and in the process discovered two new elements, polonium and radium. More radioactive elements have been discovered since that time, and in fact, all the isotopes of all the elements with an atomic number greater than 83 (bismuth) are radioactive. Today, radioactivity is defined as the spontaneous emission of particles or energy from an atomic nucleus as it disintegrates. As a result of the disintegration, the nucleus of an atom often undergoes a change of identity, becoming a simpler nucleus. The spontaneous disintegration of a given nucleus is a purely natural process and cannot be controlled or influenced. The natural spontaneous disintegration or decomposition of a nucleus is also called radioactive decay. Although it is impossible to know when a given nucleus will undergo radioactive decay, as you will see later, it is possible to deal with the rate of decay for a given radioactive material with precision.

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Precipitation

Precipitation that falls on the land either evaporates, flows across the surface, or soaks into the ground. Water moving across the surface is called runoff. Water that moves across the land as a small body of running water is called stream. A stream drains an area of land known as the stream. A stream drains an area of land known as the stream drainage basin or watershed. The watershed of one stream is separated from the watershed of another by a line called a divide. Water that collects as a small body of standing water is called a pond, and a larger body is called a lake. A reservoir is a natural pond, a natural lake, or a lake or pond created by building a dam for water management or control. The water of streams, ponds, lakes, and reservoirs is collectively called surface water.

Precipitation that soaks into the ground percolates downward until it reaches a zone of saturation. Water from the saturated zone is called groundwater. The amount of water that a material will hold depends on its porosity, and how well the water can move through the material depends on its permeability. The surface of the zone of saturation is called the water table.

The ocean is the single, continuous body of salt water on the surface of the ocean with different characteristics. The dissolved materials in seawater are mostly the ions of six substances, but sodium ions and chlorine ions are the most abundant. Salinity is a measure of the mass of salts dissolved in 1,000 grams of seawater.

An ocean wave is a moving disturbance that travels across the surface of the ocean. In its simplest form a wave has a ridge called a crest and a depression called a trough. Waves have a characteristic wave height, wavelength, and wave period. The characteristics a of waves made by the wind depend on the wind speed, the time the wind blows, and the fetch. Regular groups of low-profile, long-wavelength waves are called swell. When swell approaches a shore, the time the wind blows, and the fetch. Regular groups of low-profile, long-wavelength waves are called swell. When swell approaches a shore, the waves so they approach the shore head-on. When the wave height becomes too steep, the top part breaks forward, forming breakers in the surf zone. Water accumulates at the shore from the breakers and returns to the sea as undertow, as longshore currents, or in rip currents.

Earthquakes or undersea landslides produce large, destructive waves called tsunamis. Tsunamis do not have a large wave height at open sea, but they can do tremendous damage when they reach a low coastal area. A tide moving in or out of a narrow bay can produce a wave called a tidal bore.

Ocean currents are streams of water that move through other seawater over large distances. Some ocean currents are density currents, which are caused by differences in water temperature, salinity, or suspended sediments. Each ocean has a great system of moving water called a gyre that is centered in mid-latitudes. Different parts of a gyre are given different names such as the Gulf Stream or the California Current.

The ocean floor is made up of the continental shelf, the continental slope, and the ocean basin. The ocean basin has two main parts, the abyssal plain and mountain chains called ridges.

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Water and the Atmosphere

Water exists on the earth in all three states: (1) as a liquid when the temperature is generally above the freezing point of 0 C (32F), (2) as a solid in the form of ice, snow, or hail when the temperature is generally below the freezing point, and (3) as the invisible, molecular form of water in the gaseous state, which is called water vapor.

Over 98 percent of all the water on the earth exists in the liquid state, mostly in the ocean, and only a small, variable amount of water vapor is in the atmosphere at any given time. Since so much water seems to falls as rain or snow at times, it may be a surprise that the overall atmosphere really does not contain very much water vapor. If the average amount of water vapor in the earth’s atmosphere were condensed to liquid form, the vapor and all the droplets present in clouds would form a uniform layer around the earth only 3 cm (about 1 in) thick. Nonetheless, it is this small amount of water vapor that is eventually responsible for (1) contributing to the greenhouse effect, which helps make the earth a warmer planet, (2) serving as one of the principal agents in the weathering and erosion of the land, which creates soils and sculptures the landscape, and (3) maintains life, for almost all plants and animals cannot survive without water. If is the ongoing cycling of water vapor into and out of the atmosphere that makes all this possible. Understanding this cycling possible. Understanding this cycling process and the energy exchanges involved is also closely related to understanding the earth’s weather patterns.

Water tends to undergo a liquid–to-gas or a gas-to-liquid phase change at any temperature. The temperature of liquid water and the temperature of water vapor are associated with the average kinetic energy of the water molecules. The word average implies that some of the molecules have a greater kinetic energy and some have less. If a molecule of water that has an exceptionally high kinetic energy is near the surface, and is headed in the right direction, it may overcome the attractive forces of the other water molecules and escape the liquid to become a gas. This is the process of evaporation. A supply of energy must be present to maintain the process of evaporation, and the water robs this energy from the surroundings. This explains why water at a higher temperature evaporates more rapidly than water at a lower temperature. More energy is a available at higher temperatures to maintain the process at a faster rate.

Water molecules that evaporate move about in all directions and some will strike the liquid surface. The same forces that it escaped from earlier now capture the molecule, returning it to the liquid state. This is called the process of condensation. Condensation is the opposite of evaporation. In evaporation, more molecules are leaving the liquid state than are returning. In condensation, more molecules are returning to the liquid state than are leaving. This is a dynamic, ongoing process with molecules leaving and returning continuously. If the air were perfectly dry and still, more molecules would leave (evaporate) the liquid state than would return (condense). Eventually, however, an equilibrium would be reached with as many molecules returning to the liquid state per unit of time as are leaving. An equilibrium condition between evaporation and condensation occurs in saturated as long as (1) the temperature remains constant and (2) the processes of evaporation and condensation remain balanced. Temperature influences the equilibrium condition of saturated air because increases or deceases in the temperature mean increases or decreases in the kinetic energy of water vapor molecules. Water vapor molecules. Water vapor molecules usually undergo condensation when attractive forces between the molecules can pull them together into the liquid state. Lower temperature means lower kinetic energies, and slow-moving water vapor molecules spend more time close to one another and close to the surface of liquid water. Spending more time close together means an increased likelihood of attractive forces pulling the molecules together. On the other hand, higher temperature means higher kinetic energies, and molecules with higher kinetic energy are less likely to be pulled together. As the temperature increases, there is therefore less tendency for water molecules to return to the liquid state. If the temperature is increased in an equilibrium condition, more water vapor must be added to the air to maintain the saturated condition. Warm air can therefore hold more water vapor than cooler air. In fact, warm air on a typical summer day can hold five times as much water vapor as cold air on a cold winter day.

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