Presentation on theme: "University of Khartoum Institute of Environmental Sciences Dip/ M.Sc in Enviromental Sciences Fundamentals of Environmental Science By: Dr. Zeinab Osman."— Presentation transcript:
University of Khartoum Institute of Environmental Sciences Dip/ M.Sc in Enviromental Sciences Fundamentals of Environmental Science By: Dr. Zeinab Osman Saeed
LECTURE NU 3 DR: ZEINAB OSMAN SAEED Ecological Energetic
Ecological Energetics Solar radiation. Photosynthetic radiation. The flow of energy in the biosphere.
The sun observed by SUMER instrument on the SOHO satellite
Solar Energy Almost all of the energy that drives the various systems (climate systems, ecosystems, hydrologic systems, etc.) found on the Earth originates from the sun. Solar energy is created at the core of the sun when hydrogen atoms are fused into helium by nuclear fusion. The core occupies an area from the sun’s center to about a quarter of the star’s radius. At the core, gravity pulls all of the mass of the sun inward and creates intense pressure. This pressure is high enough to force the fusion of atomic masses.hydrogenhelium
Major parts of the Sun
Solar energy Solar energy is produced at the core of the sun by nuclear fusion. This energy is then radiated to the convection zone, where mixing transfers the energy to the photosphere. The photosphere is the surface that emits solar radiation to space. On the photosphere, localized cool areas called sunspots occur. Erupting from the photosphere, are solar flares composed of gas, electrons, and radiation. The corona is the upper portion of the sun’s atmosphere.
The Nature of Light White light is separated into the different colors (=wavelengths) of light by passing it through a prism. Wavelength is defined as the distance from peak to peak (or trough to trough). The energy of light is inversely porportional to the wavelength: longer wavelengths have less energy than do shorter ones.
The Nature of Light
The order of colors is determined by the wavelength of light. Visible light is one small part of the electromagnetic spectrum. The longer the wavelength of visible light, the more red the color. Likewise the shorter wavelengths are towards the violet side of the spectrum. Wavelengths longer than red are referred to as infrared, while those shorter than violet are ultraviolet.
The Nature of Light
Solar Radiation Solar radiation describes the visible and near-visible (ultraviolet and near-infrared) radiation emitted from the sun. The different regions are described by their wavelength range within the broad band range of 0.20 to 4.0 µm (microns). Terrestrial radiation is a term used to describe infrared radiation emitted from the atmosphere.
Approximately 99% of solar, or short- wave, radiation at the earth's surface is contained in the region from 0.3 to 3.0 µm while most of terrestrial, or long- wave, radiation is contained in the region from 3.5 to 50 µm.
Solar Radiation Outside the earth's atmosphere, solar radiation has an intensity of approximately 1370 watts/meter2. This is the value at mean earth-sun distance at the top of the atmosphere and is referred to as the Solar Constant. On the surface of the earth on a clear day, at noon, the direct beam radiation will be approximately 1000 watts/meter2 for many locations.
Solar Radiation The availability of energy is affected by location (including latitude and elevation), season, and time of day. All of which can be readily determined. However, the biggest factors affecting the available energy are cloud cover and other meteorological conditions which vary with location and time.
Basic Principles Every location on Earth receives sunlight at least part of the year. The amount of solar radiation that reaches any one "spot" on the Earth's surface varies according to these factors: Geographic location Time of day Season Local landscape Local weather.
Solar Radiation Because the Earth is round, the sun strikes the surface at different angles ranging from 0º (just above the horizon) to 90º (directly overhead). When the sun's rays are vertical, the Earth's surface gets all the energy possible. The more slanted the sun's rays are, the longer they travel through the atmosphere, becoming more scattered and diffuse. Because the Earth is round, the frigid polar regions never get a high sun, and because of the tilted axis of rotation, these areas receive no sun at all during part of the year.
Solar Radiation The Earth revolves around the sun in an elliptical orbit and is closer to the sun during part of the year. When the sun is nearer the Earth, the Earth's surface receives a little more solar energy. The Earth is nearer the sun when it's summer in the southern hemisphere and winter in the northern hemisphere. However the presence of vast oceans moderates the hotter summers and colder winters one would expect to see in the southern hemisphere as a result of this difference.
Solar Radiation The 23.5º tilt in the Earth's axis of rotation is a more significant factor in determining the amount of sunlight striking the Earth at a particular location. Tilting results in longer days in the northern hemisphere from the spring (vernal) equinox to the fall (autumnal) equinox and longer days in the southern hemisphere during the other six months. Days and nights are both exactly 12 hours long on the equinoxes, which occur each year on or around March 23 and September 22.
Diffuse and Direct Solar Radiation As sunlight passes through the atmosphere, some of it is absorbed, scattered, and reflected by the following: Air molecules Water vapor Clouds Dust Pollutants Forest fires Volcanoes. This is called diffuse solar radiation.
Direct Solar Radiation The solar radiation that reaches the Earth's surface without being diffused is called direct beam solar radiation. The sum of the diffuse and direct solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam radiation by 10% on clear, dry days and by 100% during thick, cloudy days
Albedo Albedo is known as surface reflectivity of sun’s radiation. The term has its origins from a Latin word albus, meaning “white”. It is quantified as the proportion, or percentage of solar radiation of all wavelengths reflected by a body or surface to the amount incident upon it. An ideal white body has an albedo of 100% and an ideal black body, 0%.
Albedo On average the Earth and its atmosphere typically reflect about 4% and 26%, respectively, of the sun’s incoming radiation back to space over the course of one year. As a result, the earth-atmosphere system has a combined albedo of about 30%, a number highly dependent on the local surface makeup, cover, and cloud distribution.
Photosynthesis and plant growth depend on the energy in radiation but only specific wavelengths of radiation cause photosynthesis.
Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the "fuel" used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive
Photosynthesis We can write the overall reaction of this process as: 6H 2 O + 6CO 2 ----------> C 6 H 12 O 6 + 6O 2
Diagram of a typical plant, showing the inputs and outputs of the photosynthetic process.
Photosynthesis Chlorophyll is a complex molecule. Several modifications of chlorophyll occur among plants and other photosynthetic organisms. All photosynthetic organisms (plants, certain protistans, prochlorobacteria, and cyanobacteria) have chlorophyll a. Chlorophyll a absorbs its energy from the Violet- Blue and Reddish orange-Red wavelengths, and little from the intermediate (Green-Yellow-Orange) wavelengths.
Molecular model of chlorophyll
The structure of the chloroplast and photosynthetic membranes The thylakoid is the structural unit of photosynthesis. Both photosynthetic prokaryotes and eukaryotes have these flattened sacs/vesicles containing photosynthetic chemicals. Only eukaryotes have chloroplasts with a surrounding membrane. Thylakoids are stacked like pancakes in stacks known collectively as grana. The areas between grana are referred to as stroma. While the mitochondrion has two membrane systems, the chloroplast has three, forming three compartments.
Structure of a chloroplast
Stages of Photosynthesis Photosynthesis is a two stage process. The first process is the Light Dependent Process (Light Reactions), requires the direct energy of light to make energy carrier molecules that are used in the second process. The Light Independent Process (or Dark Reactions) occurs when the products of the Light Reaction are used to form C-C covalent bonds of carbohydrates. The Dark Reactions can usually occur in the dark, if the energy carriers from the light process are present. The Light Reactions occur in the grana and the Dark Reactions take place in the stroma of the chloroplasts.Light Reactions Dark Reactions
Overview of the two steps in the photosynthesis process
Light Reactions In the Light Dependent Processes (Light Reactions) light strikes chlorophyll a in such a way as to excite electrons to a higher energy state. In a series of reactions the energy is converted (along an electron transport process) into ATP and NADPH. Water is split in the process, releasing oxygen as a by-product of the reaction. The ATP and NADPH are used to make C-C bonds in the Light Independent Process (Dark Reactions).ATPNADPH
Dark Reactions In the Light Independent Process, carbon dioxide from the atmosphere (or water for aquatic/marine organisms) is captured and modified by the addition of Hydrogen to form carbohydrates (general formula of carbohydrates is [CH 2 O] n ). The incorporation of carbon dioxide into organic compounds is known as carbon fixation. The energy for this comes from the first phase of the photosynthetic process. Living systems cannot directly utilize light energy, but can, through a complicated series of reactions, convert it into C-C bond energy that can be released by glycolysis and other metabolic processes.
The flow of energy in the biosphere
Components of ecosystems Ecosystems have four basic components: The abiotic environment Producers Consumers Decomposers
Producers (autotrophs) utilize energy from the sun and nutrients from the abiotic environment (carbon dioxide from the air or water, other nutrients from the soil or water) to perform photosynthesis and grow. Producers are generally green plants (those with chlorophyll) Consumers (heterotrophs) are organisms that feed on other organisms. Decomposers and detritivores utilize energy from wastes or dead organisms, and so complete the cycle by returning nutrients to the soil or water, and carbon dioxide to the air and water.
Food chain Food chains, also called food webs, food networks and/or trophic networks, describe the feeding relationships between species within an ecosystem. Organisms are connected to the organisms they consume by arrows representing the direction of biomass transfer. It also shows how the energy from the producer is given to the consumer.
Food chain Typically a food chain or food web refers to a graph where only connections are recorded, and a food network or ecosystem network refers to a network where the connections are given weights representing the quantity of nutrients or energy being transferred.
Organisms represented in food chains Primary producers, commonly called autotrophs, produce complex organic substances (essentially "food") from an energy source and inorganic materials. These organisms are typically photosynthetic plants, which use sunlight as their energy source. A few, such as those organisms forming the base of deep-sea vent food webs, are chemotrophic, using chemical energy instead.
Autotrophy Autotrophy is the ability to be self-sustained by producing food from inorganic compounds. Some bacteria and some archaea have this ability. Inorganic compounds are oxidized directly without sunlight to yield energy. This metabolic mode also requires energy for CO2 reduction, like photosynthesis, but no lipid-mediated processes are involved. This metabolic mode has also been called chemotrophy, chemoautotrophy, or chemolithotrophy. bacteriaarchaea
Heterotrophs Organisms that get their energy by consuming organic substances are called heterotrophs. Heterotrophs include: herbivores which obtain their energy by consuming live plants;plants carnivores, which obtain energy from eating live animals; as well asanimals detritivores, scavengers and decomposers, which all consume dead biomass.
Food chain A food chain is the flow of energy from one organism to the next and to the next and to the next. Organisms in a food chain are grouped into trophic levels, based on how many links they are removed from the primary producers. Trophic levels may contain either a single species or a group of species that are presumed to share both predators and prey. They usually start with a primary producer and end with a carnivore.
food web A food web extends the food chain concept from a simple linear pathway to a complex network of interactions. Food sources of most species in an ecosystem are much more diverse, resulting in a complex web of relationships.
Energy enters the food chain from the sun. Some energy and/or biomass is lost at each stage of the food chain as; feces (solid waste), movement energy and heat energy (especially by warm-blooded creatures). Therefore, only a small amount of energy and biomass is incorporated into the consumer's body and transferred to the next feeding level, thus showing a Pyramid of Biomass.