Ecosystems Chapter 16 Coach Fults

Interactions of Organisms and Their Environment All of Earth’s inhabitants are interwoven in a complex web of relationships 1866 Ernst Haeckel coined the term “ecology” Ecology- is the study of the interactions of living organisms with one another and their physical environment

Interactions of Organisms and Their Environment Habitat- where species live The many different species that live together in a habitat is called a community An ecosystem consists of a community and all the physical aspects of its habitat, such as soil, water, and weather The physical aspects of a habitat are called abiotic factors & the organisms are the biotic factors

Biodiversity The number of living species in a ecosystem is a measure of biodiversity

Ecosystem Boundaries Not all boundaries in an ecosystem are obvious A dead tree can be an ecosystem There could many species thriving inside The size is relative

Change of Ecosystems over Time Either a volcano forms a new island; a glacier melts and exposes bare rock; a forest burns down The 1 st organisms to colonize the new earth surface are usually small fast growing plants, called pioneer species The may make the ground hospitable for other species After time new species outcompete dominate over the pioneer species

Succession Succession- is a somewhat regular progression of species replacement Primary succession- succession that occurs where plants have not grown before Secondary succession- occurs where there has been previous growth, such as abandoned fields or forest clearings

Succession

Scientists previously thought that all succession was predictable But this is not the case; if 2 species are in competition, a sudden change in climate may favor 1 of the species more than the other No 2 successions are alike

Movement of Energy Through Ecosystems Everything an organism does requires energy The flow of energy is the most important factor that controls what kind of organisms live in an ecosystem and how many organisms the ecosystem can support

Primary Energy Source Most of the life on earth depends on photosynthetic organisms, which captures light from the sun and store it as chemical energy in organic molecules These organic molecules are what we call food The rate at which organic material is produced by autotrophs is called primary productivity

Primary Energy Source Primary productivity determines the amount of energy available in an ecosystem Most organisms can be thought as chemical machines that are fueled by autotrophs Organisms that 1 st capture energy are called producers; plants, some bacteria, and algae

Primary Energy Source Producers make energy-storing molecules that are consumed by consumers Consumers use that energy obtained to build their molecules

Trophic Levels Ecologists study how the energy flows in an ecosystem by assigning organisms in that ecosystem to a specific level, called a trophic level Food chain- path of energy through the trophic levels of an ecosystem 1 st level- are the producers (autotrophs) 2 nd level- are herbivores (primary consumers)

Trophic Levels 3 rd – these are carnivores, omnivores, detritivores, and decomposers Detritivores- obtain energy from the organic wastes and dead bodies produced at all trophic levels Decomposers- bacteria and fungi; release nutrients back into the environment Food web- many food chains linked together

Loss of Energy in a Food Chain A deer eats a leaf. Does all that energy get stored in the deer? No, most energy is given off as heat As the energy goes through the ecosystem most of it is lost

Energy Transfer When a plants harvests sunlight, it stores in chemical bonds only half of the energy captured When a herbivore uses plant molecules to make its own molecules, only 10% of the energy in the plant ends up in the herbivore’s molecules And when a carnivore eats the herbivore, about 90% of the energy is lost in making carnivore molecules At each trophic level, the energy stored by the organism in a level is 1/10 of that stored by the organism in the level below

The Pyramid of Energy

Limitations of Trophic Levels A large population of humans could not survive eating lions on the Serengeti Plain of Africa There are not enough lions to make this possible Not enough grass to support the enough zebras to support the lions, which results in the humans starving; but since we are omnivores we can eat plants The number of trophic levels that can be maintained in an ecosystem is limited by the loss of potential energy

Limitations of Trophic Levels To better determine the amount of energy present in trophic levels, ecologists measure biomass Biomass- is the dry weight of tissue and other organic matter found in an ecosystem Each higher level on the pyramid contains only 10% of the biomass found in the trophic level below it

Biogeochemical Cycles Humans throw away trash everyday. But nature does not throw away anything Many elements are recycled in nature; Carbon, Nitrogen, Sulfur, Calcium, and Phosphorus 4 substances that are very important to maintain the health of ecosystems are: water, carbon, nitrogen, and phosphorus

Biogeochemical Cycles Biogeochemical Cycles- a pathway forms when a substance enters living organisms such as trees from the atmosphere, water, or soil; stays for a time in the living organism; then returns to the non-living environment

The Water Cycle Groundwater- water under earth’s surface Transpiration- water passes through plants and evaporates through the leaf

The Carbon Cycle Carbon dioxide in the air or dissolved in water is used by autotrophs as a raw material to build organic molecules Carbon atoms may return to the pool of carbon dioxide in the air and water in 3 ways: 1. Respiration- nearly all living organisms, including plants engage in cellular respiration. They use oxygen to oxidize organic molecules during cellular respiration, and carbon dioxide is a byproduct of this reaction

The Carbon Cycle 2. Combustion- wood releases carbon when burned. Also, fossil fuels when burned 3. Erosion- marine organisms use CO 2 dissolved in seawater to make calcium carbonate for shells. Over millions of years, the shells of the dead organisms form sediments, which forms limestone. As the limestone becomes exposed and erodes, the carbon becomes available to other organisms

The Phosphorus and Nitrogen Cycles Organisms need nitrogen and phosphorus to build proteins and nucleic acids. Phosphorus is an essential part of both ATP and DNA Phosphorus is usually present in the soil and rock as calcium phosphate, which dissolves in water to form phosphate ions. This is absorbed by roots of plants and used to build organic molecules Animals eat this, then use the phosphorus

The Phosphorus and Nitrogen Cycles The atmosphere is 79% nitrogen N 2. However, most organisms are unable to use it in this form. The 2 nitrogen atoms are connected by a triple covalent bond that is hard to break But some bacteria have enzymes that can break it, and they bind to nitrogen and turn it into ammonia NH 3 The process of combining nitrogen with hydrogen to form ammonia is called nitrogen fixation

The Phosphorus and Nitrogen Cycles Nitrogen-fixing bacteria live in the soil and are also found within swellings, or nodules, on roots of beans, alder trees, and a few other kinds of plants

Nitrogen Fixation 1. Assimilation is the absorption and incorporation of nitrogen into plant and animal compounds 2. Ammonification is the production of ammonia by bacteria during the decay of nitrogen-containing urea (found in urine) 3. Nitrification production of nitrate from ammonia 4. Denitrification conversion of nitrate to nitrogen gas