EXAM 1

How do ecology and environmentalism differ? In what way does environmentalism depend on the science of ecology?

Environmentalism is activism with a stated aim of protecting the natural environment, particularly from the negative impacts of human activities. Environmentalism includes public education programs, advocacy, legislation, and treaties. Ecology is a science. Ecology is the economy of nature the investigation of the total relations of the animal both to its inorganic and to its organic; including above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contact. Ecology looks into the relationship of the environment with other animals. Humans are animals. One aspect of ecology is looking into the relationship that humans have with the environment. Environmentalist rely on the scientific findings of ecologists to form public education programs, advocacy, legislation, and treaties.

The concentration of which element is used to define the salinity of water?

The concentration of NaCl is what defines the salinity of water.

What is net radiation?

The difference between incoming (absorbed) and outgoing (emitted) electromagnetic radiation (both shortwave and longwave) for an object.

Assume that two forests have the same quantity of leaves (leaf area index). In one forest, however, the leaves are oriented horizontally (parallel to the forest floor). In the other forest, the leaves are positioned at an angle of 60 degrees. How would the availability of light at the forest floor differ for these two forests at noon? In which forest would the leaves at the bottom of the canopy (lower in the tree) receive more light at mid-morning?

At noon light fall vertically on the surfaces of the leaves. If the leaves are oriented horizontally, they will offer more leaf surface for intercepting light. Hence the light reaching the forest floor will be less in such a forest. When the leaves are oriented at an angle of 60 degrees, the leaf area receiving light is lower. Hence there is lesser attenuation when the leaves are placed at a 60 degree angle. More light passes through the canopy to the forest floor. Hence the forest floor will receive more light at noon this forest.

Define the terms population, community, ecosystem, landscape, and biosphere.

Population- A group of individuals of the same species living in a given area at a given time. Community- A group of interacting plants and animals inhabiting a given area. Ecosystem- The biotic community and its abiotic environment, functioning as a system. Landscape- An area of land (or water) composed of a patchwork of communities and ecosystems. Biosphere- Thin layer about Earth in which all living organisms exist.

Given the importance of ecological research in making political and economic decisions regarding current environmental issues such as global warming, how do you think scientists should communicate uncertainties in their results to policy makers and the public?

Scientist should be vocal and made clear on the uncertainties in their ecological researchers. Ecologist should also be vocal and clear on the consequences of what could occur in no action is taken place.

Explain why seasonal stratification of temperature and oxygen takes place in deep ponds and lakes.

Seasonal stratification of temperature and oxygen takes place in deep ponds and lakes because of the need to bring oxygen down to the decomposing sediments. Also, colder water increases so does oxygen solubility which can lead to formation of ice which is not positive because that reduces diffusion. The diffusion is necessary for the oxygen to reach the bottom of the deep waters.

What property of water allows aquatic organisms to function with far fewer supportive structures (tissues) than terrestrial organisms have?

Viscosity is the property of water that allows aquatic organisms to function with far fewer supportive structures than terrestrial organisms have. This is because viscosity is the property of a material that measures the force necessary to separate the molecules and allow an object to pass through the liquid and the viscosity of water is very low.

What causes the upwelling of deeper, cold waters in the equatorial zone of the oceans?

Winds blowing across the oceans surface that push water away causes the upwelling of deeper, cold waters in the equatorial zone of the oceans.

Name two constraints imposed on organisms in the transition of life from aquatic to terrestrial environments.

1. "Perhaps the greatest constrant imposed by terrestrial environments is desiccaion. Living cells, both plants and animal, contail 75-95% water. Unless the air is saturated with moisture, water readily evaporates from the surfaces of cells via the process of diffusion. The water that is lost to the air must be replaced if the cell is to remain hydrated and continue to function. Maintaining this balance of water between organisms and their surrounding environment has been a major factor in the evolution of life. 2. "Desiccation is not the only constraint imposed by the transition from water to land. Because air is less dense than water, it results in a much lower drag (frictional resistance) on the movement or organisms, but it greatly increases the constraint imposed by gravitational forces. The upward force of buoyancy due to the displacement of water helps organisms in aquatic environments overcome the constraints imposed by gravitational force in terrestrial environments results in a significant investment in structural materials such as skeletons (for animals) or cellulose (for plants) 3."Another characteristic of terrestrial environments is their high degree of variability, both in time and space. Temperature variations on land (air) are much greater than in water. The high specific heat of water prevents wide daily and seasonal fluctuations in the temperature of aquatic habitats. In contrast, such fluctuations are a characteristic of air temperatures. Likewise, the timing and quantity of precipitation received at a location constrain the availability of water for terrestrial plants and animals as well as their ability to maintain water balance. These fluctuations in temperature and moisture have both a short-term effect on metabolic processes and a long-term influence on the evolution and distribution of terrestrial plants and animals.

What five major factors affect soil formation?

2. Climate: Climate influences weathering. Temperature, precipitation and winds cause rock to disintegrate into smaller units by erosion. This is known as mechanical weathering. Water, oxygen and elements in the soil react to alter the chemical composition of the soil. This is known as chemical weathering. The presence of plants and microorganisms in soil also cause mechanical and chemical weathering. 3. Biotic factors: Plants help to hold the topsoil in place, thereby delaying erosion. Plant roots penetrate the bedrock, causing the soil to break up. They also extract minerals from the soil and bring them to the surface. Plant and animal life decay through microbial action into organic matter which forms part the soil surface. 4. Topograph: The nature of terrain, whether mountainous, hilly or level, the presence of rivers, forests and water bodies, all affect soil formation. Sloping terrain is subject to natural run off of water and earth due to gravity. Thus, there is accumulation of water and soil from slopes at the base of hills and mountains. Wind furthers the mechanical weathering of sloping areas and the formation of creep. 5. Time: Soil formation takes place over several thousand years. The processes of weathering and biotic action continue over time, to gradually convert the parent material into soil.

What is a hypothesis? What is the role of hypotheses in science?

A hypothesis is an educated guess about what the answer to the question may be. The role of hypotheses is to make a statement on cause and affect that can then be tested.

Suppose you were given the task of estimating the density of two plant species in a field. Based on the life histories of the two species, you expect that the spatial distribution of one of the species is approximately uniform, whereas the other is likely to be clumped. How might your approach to estimating the density of these two species differ?

Distribution of population mainly depends on the suitable conditions, For instance within in the geographic range the red maple (Acer rubrum) trees grow under a wide variety of soil types, soil moisture, acidity, and elevations. Distribution of population also describes different spatial scale for example Tetraphis pellucida has different spatial scales and it can grow only in the areas where the temperature, humidity and pH are suitable, and other different factors may be limiting at different spatial scales. Depending upon their growth conditions plant species will survive. Spatial distribution is different from one species to the other species.

Why are the coastal waters of the southeastern United States warmer than the coastal waters off the southwestern coast? (Assume the same latitude. Hint: Look at the direction of the prevailing surface currents presented in Figure 2.13).

Each ocean in dominated by two great circular water motions, or gyres. Within each gyre, the ocean current moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere (Figure 2.13). Along the equator, trade winds push warm surface waters westward. When these waters encounter the eastern margins of continents, they split into north- and south-flowing currents along the coasts, forming north and south gyres. As the currents move farther from the equator, the water cools. Eventually, they encounter the westerly winds at higher latitudes (30-60 degrees N and 30-60 degrees S), which produce eastward-moving currents. When these eastward-moving currents encounter the western margins of the continents, they form cool currents that flow along the coastline toward the equator. Just north of the Antarctic continent, ocean waters circulate unimpeded around the globe. On the east coast of the United Sates it is taking water up from the equator so it is warm. On the west coast of the United States it is taking water down to the equator so it is cold.

Use Figure 4.10 to answer this question: Which soil holds more moisture at field capacity: clay or sand? Which soil holds more moisture at wilting point: clay or sand? Which soil type has a greater availability of water for plant uptake when the water content of the soil is 3.0 in/ft (value on y-axis)?

Field Capacity At field capacity, the moisture content in sand is 2.1 inches per ft. The moisture content in clay soil at field capacity is 4.4 inches per ft. Hence, clay has more moisture in the soil at field capacity. The moisture content in sand at wilting capacity is 1.1 inches per ft. At wilting capacity, the moisture content in clay is 2.6 inches per ft. Hence clay holds more moisture at wilting capacity.

How might including the abiotic environment within the framework of the ecosystem help ecologists achieve the basic goals of understanding the interaction of organisms with their environment?

For example, the abiotic components of a forest include atmosphere, climate, soil, and water. Relationships are complex in that each organism not only responds to the abiotic environment but also modifies it and, in doing so, becomes part of the broader environment itself. The trees in the canopy of a forest intercept the sunlight and use this energy to fuel the process of photosynthesis. As a result, the trees modify the environment of the plants below them, reducing the sunlight and lowering air temperature.

Why is there less seasonal variation in temperature in aquatic compared to terrestrial environments (at the same latitude)?

Just as seasonal variation in the input of solar radiation to Earth's surface results in seasonal changes in surface temperatures, seasonal changes in the input of solar radiation of the water surface give rise to seasonal changes in the input of solar radiation to the water surface give rise to seasonal changes in the vertical profile to temperature in aquatic environments (Figure 3.9). Because of the relatively constant input of solar radiation to the water surface throughout the year, the thermocline is a permanent feature of tropical waters. In the waters to the temperate zone, a distinct thermocline exists during the summer months. By fall, conditions begin to change, and a turnabout take place. Air temperatures and sunlight decrease, and the surface water becomes denser and sinks, displacing the warmer water below to the surface, where it cools in turn. As the difference in water density between the epilimnion and hypolimnion continues to decrease, winds are able to mix the vertical profile to greater depths. This process continues until the temperature is uniform throughout the basin (see Figure 3.9). Now, pond and lake water circulate throughout the basin. This process of vertical circulation, called the turnover, is an important component of nutrient dynamics in open-water ecosystems (see Chapter 21). Stirred by wind, the process of vertical mixing may last until ice forms at the surface.

What is a model? What is the relationship between hypotheses and models?

Models are abstract, simplified representations of real systems. They allow us to predict some behavior or response using a set of explicit assumptions, and as with hypotheses, these predictions should be testable through further observation or experiments. Models may be mathematical, like computer simulations, or they may be verbally descriptive, like Darwin's theory of evolution by natural selection. Hypotheses are models, although the term model is typically reserved for circumstances in which the hypothesis has at least some limited support through observations and experimental results. For example, the hypothesis relating grass production to nitrogen availability is a model. It predicts that plant productivity will increase with increasing nitrogen availability. However, this prediction is qualitative-it does not predict how much plant productivity will increase. In contrast, mathematical models usually offer quantitative predictions. For example, from the data in Figure 1.5, we can develop a regression equation-a form of statistical model-to predict the amount of grassland productivity per unit of nitrogen in the soil.

How might the relative humidity of a parcel of air change as it moves up the side of a mountain? Why?

Mountains also influence patterns of precipitation. As an air mass reaches a mountain, it ascends, cools, relative humidity rises (because of lower saturation vapor pressure). When the temperature cools to the dew point temperature, precipitation occurs at the upper altitudes of the windward side. As the now cool, dry air descends the leeward side, it warms again and relative humidity declines. As a result, the windward side of a mountain supports denser, more vigorous vegetation and different species of plants and associated animals than does the leeward side, where in some areas dry, desert-like conditions exist. This phenomenon is called a rain shadow (Figure 2.21). Thus, in North America, the westerly winds that blow over the Sierra Nevada and Rocky Mountains, dropping their moisture on west-facing slopes, support vigorous forest growth. By contrast, the eastern slopes exhibit semidesert or desert conditions.

What is the Intertropical Convergence Zone (ITCZ), and why does it give rise to a distinct pattern of seasonality in precipitation in the tropical zone?

Near the equator, the northeasterly trade winds meet the southeasterly trade winds. This narrow region where the trade winds meet is the ITCZ, characterized by high amounts of precipitation. Where the two air masses meet, air piles up, and the warm humid air rises and cools. The ITCZ is not stationary but tends to migrate toward regions of the globe with the warmest surface temperature. Although tropical regions around the equator are always exposed to warm temperatures, the Sun is directly over the geographical equator only twice a year, at the spring and fall equinoxes. At the northern summer solstice, the Sun is directly over the Tropic of Cancer; at the winter solstice (which is summer in the Southern Hemisphere), the Sun is directly over the Tropic of Capricorn. As a result, the ITCZ moves poleward and invades the subtropical highs in northern summer; in the winter it moves southward, leaving clear, dry weather behind. As the ITCZ migrates southward, it brings rain to the southern summer. Thus, as the ITCZ shifts north and south, it brings on the wet and dry seasons in the tropics (Figure 2.19).

An ecologist observes that the diet of a bird species consists of primarily of large grass seeds (as opposed to smaller grass seeds or the seeds of other herbaceous plants found in the area). He hypothesizes that the birds are choosing the larger seeds because they have a higher concentration of nitrogen than do other types of seeds at the site. To test the hypothesis, the ecologist compares the large grass seeds with the other types of seeds, and the results clearly show that the large grass seeds do indeed have a much higher concentration of nitrogen. Did the ecologist prove the hypothesis to be true? Can he conclude that the birds select the larger grass seeds because of their higher concentration of nitrogen? Why or why not?

No, the ecologist did not prove the hypothesis to be true. The ecologist now has data that supports the hypothesis. The data suggests birds are choosing the larger seeds because they have a higher concentration of nitrogen than do the other types of seeds at the site, but this does not prove that this is the only factor contributing to birds choosing larger seeds. There could be various other factors contributing to birds eating larger seeds.

Why do equatorial regions receive more solar radiation than the polar regions? What is the consequence to latitudinal patterns to temperature?

On average, the amount of incoming shortwave radiation intercepted by Earth and the quantity of longwave radiation emitted by the planet back into space balance, and the average surface temperature of our planet remains approximately 15 degrees celcius. Note, however, from the global map of average annual surface net radiation presented in that there is a distinct latitudinal gradient of decreasing net surface radiation from the equator toward the poles. This decline is a direct function of the variation with latitude in the amount of shortwave radiation reaching the surface. Two factors influence this variation. First, at higher latitudes, solar radiation hits the surface at a steeper angle, spreading sunlight over a larger area. Second, solar radiation that penetrates the atmosphere at a steep angle must travel through a deeper layer of air. In the process, it encounters more particles in the atmosphere, which reflect more of the shortwave radiation back into space. The result of the decline in net radiation with latitude is a distinct gradient of decreasing mean annual temperature from the equator toward the poles.

Draw a simple diagram of the water cycle and then describe the processes involved.

Solar radiation, which heats Earth's atmosphere and provides energy for the evaporation of water, is the driving force behind the water cycle. Precipitation sets the water cycle in motion. Water vapor, circulating in the atmosphere, eventually falls in some form of precipitation. Some of the water falls directly on the soil and bodies of water. Some is intercepted by vegetation, dead organic matter on the ground, and urban structures and streets in a process known as interception. Because of interception, which can be considerable, various amounts of water never infiltrate the ground but evaporate directly back to the atmosphere. Precipitation that reaches the soil moves into the ground by infiltration. The rate of inflitration depends on the type of soil, slope, vegetation, and intensity of the precipitation. During heavy rains when the soil is saturated, excess water flows across the surface of the ground as surface runoff or overland flow. At places, it concentrates into depressions and gullies, and the flow changes from sheet to channelized flow-a process that can be observed on city streets as water moves across the pavement into gutters. Some water entering the soil seeps down to an impervious layer of clay or rock to collect as groundwater. From there, water finds its way into springs and streams. Through their roots, they take in water from the soil and lose it through their leaves and other organs in a process called transpiration. Transpiration is the evaporation of water from internal surfaces of leaves, stems, and other living parts. The total amount of evaporating water from the surfaces of the ground and vegetation (surface evaporation plus transpiration) is called evapotranspiration.

The air temperature at noon on January 20 was 45 degrees fahrenheit, and the air temperature at noon on July 20 at the same location was 85 degrees fahrenheit. The relative humidity on both days was 75 percent. On which of these two days was there more water vapor in the air?

The amount of water in a given volume of air is its absolute humidity. A more familiar measure of the water content of the air is relative humidity, or the amount of water vapor in the air expressed as a percentage of the saturation vapor pressure. At saturation vapor pressure, the relative humidity is 100 percent. If air cools while the actual moisture content (water vapor pressure) remains constant, then relative humidity increases as the value of saturation vapor pressure declines. If the air cools to a point where the actual vapor pressure is equal to the saturation vapor pressure, moisture in the air will condense. This is what occurs when a warm parcel of air at the surface becomes buoyant and rises. As it rises, it cools, and as it cools, the relative humidity increases. When the relative humidity reaches 100 percent, water vapor condenses and forms clouds. As soon as particles of water or ice in the air become too heavy to remain suspended, precipitation falls. For a given water content of a parcel of air (vapor pressure), the temperature at which saturation vapor pressure is achieved (relative humidity is 100 percent) is called dew point temperature. Think about finding dew or frost on a cool falling morning. As nightfall approaches, temperatures reach the dew point, water condenses and dew forms, lowering the amount of water in the air. As the sun rises, air temperature warms and the water vapor capacity (saturation vapor pressure) increases. As a result, the dew evaporates, increasing vapor pressure in the air.

What feature of global atmospheric circulation gives rise to the desert zones of the midlatitudes?

The arid regions of the midlatitudesAt the intertropical convergence zone (ITCZ), the moisture laden air loses moisture by precipitation or rainfall. This means that the air mass has cooled to reach its dewpoint. The cool air descends and splits up into the northerly and southerly tradewinds. These winds are depleted of moisture and as they pass over the land mass, they gather moisture from the surface of theland. Depletion of moisture from the surface of the earth results in dry and arid regions around 30° North and 30° South latitudes. Thus there is a belt of deserts and dry land in this region.

What is the fate of visible light in water?

The fate of visible light in water is that most of the light that is in water does not get through very deep. So, this results in most of the water being extremely dark. The reason that water appears blue is due to the wavelengths that actually have success coming through water.

What is the thermocline? What causes the development of a thermocline?

The thermocline is the region of the vertical depth profile where the temperature declines most rapidly. It develops from the input of solar radiation to the surface waters and on the degree of vertical mixing.

Spruce Knob (latitude 38.625 degrees N) in eastern West Virginia is named for the spruce trees dominating the forests at this site. Spruce trees dominating the forests at this site. Spruce trees are typically found in the colder forests of the more northern latitudes (northeastern United States and Canada). What does the presence of spruce trees at Spruce Knob tell you about this site?

The patterns of temporal variation in climate that we have discussed thus far occur at regular and predictable intervals: seasonal changes in temperature with the rotation of Earth around the Sun, and migration of the ITCZ with the resultant seasonality of rainfall in the tropics and moonsoons in Southeast Asia. Not all features of the climate system, however, occur so regularly. Earth's climate system is characterized by variability at both the regional and global scales. The Little Ice Age, a period of cooling that lasted from approximately the mid-14th to the mid-19th century, brought bitterly cold winters to many parts of the Northern Hemisphere, affecting agriculture, health, politics, economics, emigration, and even art and literature. In the mid-17th century, glaciers in the Swiss Alps advanced, gradually engulfing farms and crushing entire villages. In 1780, New York Harbor froze, allowing people to walk from Manhattan to Staten Island. In fact, the image of a white Christmas evoked by Charles Dickens and the New England poets of the 18th and 19th centuries is largely a product of the cold and snowy winters of the Little Ice Age. But the climate has since warmed to the point that a white Christmas in these regions is becoming an anomaly.

The 23.5 degrees tilt of Earth on its north-south axis gives rise to the seasons (review Figure 2.7). How would the pattern of seasons differ if the Earth's tilt were 90 degrees? How would this influence the diurnal (night-day) cycle?

There would be no pattern of seasons if the Earth's tilt were 90 degrees. Regions of Earth would constantly stay at the same temperature year round. There would still be night and day if the earth was tilted at a 90 degree angle. Yet the length of the day would be constant year round, there would be no extremes in day length like there are now at the arctic and antarctic circles ranging from 0 to 24 hours.

What is the greenhouse effect, and how does it influence the net radiation balance (and temperature of Earth?

This absorbed radiation is emitted downward toward the surface as longwave atmospheric radiation, which keeps near surface temperatures warmer than they would be without this blanket of gases. This is known as the "greenhouse gases." It is the difference between the incoming shortwave (solar) radiation and outgoing longwave (terrestrial) radiation that defines the net radiation and determines surface temperatures. If the amount of incoming shortwave radiation exceeds the amount of outgoing longwave radiation, surface temperature increases. Conversely, surface temperature declines if the if the quantity of outgoing longwave radiation exceeds the incoming shortwave radiation (as is the case during the night).

What causes the tides?

Tides are caused from the gravitational pull of the moon. The moons gravitational force is greater than the centrifugal force at a certain point so the force is directed away from the earth and causes a tidal bulge. Tides are also affected by water depth, winds on and off shore, shore contour and wave action.

What effect does increasing the carbon dioxide concentration of water have on its pH?

Water typically has a neutral pH because the dissociation of the water molecule produces the same amount of H+ and OH- ions. But, when CO2 is added into the mix the charges no longer cancel out. The pH lowers a little, ranging from 4-7 when free CO2 is added to water.

Which aspect of a slope, south- or north-facing, would receive the most solar radiation in the mountain ranges of the Southern Hemisphere?

the sun us directly above the equator, which receives max sunlight. In the southern hemisphere, the higher latitudes do not receive direct sunlight. Solar radiation hits surfaces at an angle, known as aspect. TLDR north facing slopes of a mountain on the southern hemi will receive more radiation.