Energy and matter are essential constituents of living organisms. Matter is the material of which they are made, and energy provides a force to hold structures together, tear them apart, and move them.
Energy Types and Qualities
Energy is defined as the ability to do work and can take many forms (light, heat, electricity, etc.) and is measured in calories, BTUs, or joules.
The energy found in moving objects is called kinetic energy. Heat measures the total kinetic energy of atoms or molecules in a substance.
Temperature is the measure of the speed of motion of atoms or molecules in a substance. Heat and temperature are NOT the same.
Potential energy is stored energy that is latent but available for use.
Food and gasoline are examples of chemical energy.
Power is defined as the rate of doing work.
Energy can be low-quality or high quality.
Conservation of Matter
The principal of the conservation of matter states that matter is neither created nor destroyed.
Thermodynamics and Energy Transfers
The study of thermodynamics deals with how energy is transferred in natural processes.
The first law of thermodynamics states that energy is conserved; that is, it is neither created nor destroyed. It may change forms but the total amount does not increase nor decrease.
The second law of thermodynamics states that, with each successive energy transfer or transformation in a system, less energy is available to do work. Natural systems tend to move towards a higher state of entropy or disorder.
Energy for Life
Most organisms depend on the sun for the energy needed to create structures and carry out life processes.
Solar Energy: Warmth and Light
Solar energy is essential for life.
Most organisms survive within a narrow temperature range. The necessary heat is provided by the sun.
Organisms depend on solar radiation for life-sustaining energy, which is captured by green plants, algae, and some bacteria in a process called photosynthesis.
However, only about 1-2% of the total solar radiation hitting the earth is utilized by living organisms
Sun is a fiery ball of exploding hydrogen gas.
Radiant energy classified by wavelengths.Intense energy has short wavelengths.Lower energy has longer wavelengths. Solar energy that reaches the earth’s surface is in, or near, the visible light wavelengths.
Drive photosynthesis.
More than half of the incoming sunlight may be reflected or absorbed by atmospheric clouds, dust, or gases.Short wavelengths are filtered out by gases in the upper atmosphere.
The sun produces warmth and light, both of which are needed for living organisms.
• Most organisms live within a narrow temperature range.
• Light is composed of particles of energy that travel as waves.
• Light is part of the electromagnetic spectrum, the entire range of electromagnetic radiation.
Of the solar radiation that reaches the earth’s surface, 45% is visible light, 45% is infrared radiation and 10% is ultraviolet radiation.
• 30% is reflected back into space.
• 20% is absorbed by the atmosphere.
• 50% is absorbed by ground, water and vegetation.
Less than 1% of the absorbed energy is used in photosynthesis. This small percentage is the energy base for all life on the biosphere.
PHOTOSYNTHESIS AND RESPIRATION
Photosynthesis can be summed as
6H2O + 6CO2 + solar energy -> C6H12O6 + 6O2
Cellular respiration is the process in which glucose (the sugar) is split apart and its energy released for use by cellular metabolism.
C6H12O6+6O2 à 6H2O + 6CO2 + energy
Animals do not have chlorophyll and gain their energy by eating other plants or animals and breaking down their organic molecules for energy.
From Species to Ecosystems ·
Ecologists study interactions at the species, population, community, and ecosystem level.
· The word species refers to all organisms of the same kind that are genetically similar enough to breed in nature and produce live, fertile offspring.
Populations, Communities, and Ecosystems
A population consists of all the members of a species living in a given area at the same time.
All the populations of organisms living and interacting in a particular area make up a biological community.
An ecosystem is composed of a biological community and its physical environment. Food Chains,
Food Webs, and Trophic Levels
Photosynthesis is the base of the energy economy of most ecosystems.
Productivity is the amount of biomass produced in a given area during a given period of time.
Photosynthesis is described as primary productivity because it is the basis for almost all other growth in an ecosystem. Manufacture of biomass by organisms that eat plants is termed secondary productivity.
A food chain is a linked feeding series of organisms. It is the transfer of food energy from the source (e.g. plants) through series food organisms, in the process of sequential or repeated eating and being eaten.
Individual food chains may be interconnected to form food webs.
Two (2) types:
1. Grazing food chain - start from the green plants from which the chain goes to grazing herbivores and then to carnivores
2. Detritus food chain - from dead organic matter into microorganisms and then to detritus-feeding organisms and their predators.
· Producers (organisms that transform solar energy into chemical energy) and consumers (organisms that consume the chemical energy harnessed by producers) occupy different trophic levels.
· Organisms can be identified by their trophic level at which they feed and by what kinds of foods they eat (herbivores, carnivores, and omnivores).
o Herbivores - Eat plants.
o Carnivores - Eat animals.
o Omnivores - Eat plants and animals.
o Detritivores - Eat detritus.
o Decomposers - Breakdown complex organic matter into simpler compounds
· Scavengers, detritivores, and decomposers also occupy important places in the trophic levels.
Trophic Level refers to an individual’s feeding position in an ecosystem.
Ecological Pyramids
By arranging the organisms in a food web by trophic levels, an ecological pyramid can be formed with producers at the wide base and fewer and fewer individuals in the higher levels. This follows the second law of thermodynamics that less and less energy is available in succeeding trophic levels.
Second law of thermodynamics.
Ecosystems not 100% efficient.
10% Rule
This means that if there are 1000 calories in a certain weight of grass consumed, the grasshopper retains only100 calories of that, with 900 calories spent during its energy expending metabolic processes (like respiration) and the frog that eats the grasshopper will get only 10 calories of it, and the snake gets only 1 calorie. The total number of organisms and total biomass in each successive trophic level in an ecosystem may also form pyramids.
BIOGEOCHEMICAL CYCLES
The interaction between the organisms and the environment in an ecosystem is well illustrated in the cycling and recycling of essential nutrients and materials between them. Substances that organisms need to survive are called nutrients such as water, carbon, oxygen, nitrogen and sulfur. Nutrients move through the ecosystem in cycles.called BIOGEOCHEMICAL CYCLES where “BIO” refers to the living organisms, “GEO” refers to the inorganic molecules such as those found in rocks, air and water, and “CHEMICAL” refers to the interactions of elements between them.
The Water (Hydrologic) Cycle
This is the movement of water between ocean, atmosphere and land. It constantly purifies and redistributes fresh water.
Physical processes that make it possible are…
• Evaporation: liquid is changed to gas (vapor).
• Sublimation: change from solid to gas.
• Condensation: gas changes to liquid.
• Precipitation: falling of water in any of its phases upon the surface of the earth.
Air can support so much water vapor at a given temperature.
The Carbon Cycle
Carbon serves two purposes for organisms; 1) it is a structural component of organic molecules, and 2) the energy-holding chemical bonds it forms represent energy "storage".
The carbon cycle begins with the intake of carbon dioxide by photosynthetic organisms.
Carbon and oxygen are incorporated into sugar molecules.
These molecules are taken up by other organisms, and carbon dioxide is released following respiration, closing the cycle.
Not all carbon is cycled. Some forms (coal and oil) may be sequestered for millions of years without being released. Tying up carbon in the bodies and byproducts of organisms favorably affects the biosphere. It helps balance carbon dioxide generation and utilization and so regulates the greenhouse effect. Oceans and heavily vegetated areas are important carbon sinks.
The Nitrogen Cycle
Organisms cannot exist without amino acids, peptides, and proteins which are all molecules containing nitrogen.
Although nitrogen is the most abundant gas in the atmosphere about 78%, plants cannot use N2 gas.
Nitrogen-fixing bacteria convert nitrogen gas (N2) to ammonium (NH4+ ). Other bacteria oxidize the ammonium into nitrites (NO2-).
Another group converts nitrites to nitrates (NO3-) which can be absorbed and used by plants. Plants convert nitrates into ammonuim (NH4+) which is used to build amino acids.
Some plants (legumes) have nitrogen fixing bacteria living in their roots and so are especially useful to agriculture.
Animals assimilate nitrogen from plant proteins.
Excretion and egestion products of animals contain ammonia and other nitrogenous compounds. Nitrogen reenters the environment in several ways including the death of organisms and animal wastes.
Denitrifying bacteria break these down back into nitrogen gas which reenters the atmosphere. Synthetic fertilizers and fossil fuel combustion products may cause an excess of nitrogen in the environment leading to fertilization or acidification of lakes and rivers, blooms of toxic algae, loss of soil nutrients, and rising atmospheric concentrations of the greenhouse gas nitrous oxide.
The Phosphorus Cycle
Minerals are available to organisms after they have been released from rocks. Phosphorus and sulfur are two examples of this. Phosphorus is important because it is an essential component of many high energy compounds such as ATP. The phosphorus cycle begins when phosphorus compounds are leached from rocks and minerals. Inorganic phosphorus is taken in by producer organisms, incorporated into organic molecules, and passed on to consumer organisms. High concentrations of phosphorus in aquatic systems may lead to algal blooms, suffocating other life in lakes and streams.
The Sulfur Cycle
Sulfur compounds are a minor but essential portion of protein molecules.Sulfur compounds are important determinants of the acidity of water.Particulates may also act as critical regulators of global climate.Inorganic sulfur stored in rocks is released into the air and water by weathering, volcanic eruptions, and seafloor vent emissions. The sulfur cycle is complicated by the large number of oxidation states sulfur can assume. Which of the states it is found in depends on oxygen concentrations, pH, and light levels. Human activities resulting in the release of large quantities of sulfur contribute to problems such as acid rain, the greenhouse effect, and human health problems. Release of dimethylsulfide (DMS) by oceanic phytoplankton could be a feedback mechanism that keeps temperature within a suitable range for life.
