7/2014 Environmental Science Ch # 5. INTERACTIONS : ORGANISMS AND ENVIRONMENT 5 – 1 ECOLOGICAL CONCEPTS Energy Flow Dependence – Increase energy/benefit/services Ecology- The subject/Interactions Molded by surroundings Makes use of surroundings Surroundings impacted Environment Limiting factors/abiotic/biotic Physical/ Energy/Processes Habitat and Niche ROLE of NATURAL SELECTION Mechanism – Genes. (Camouflage, # off-springs, Food , time. Evolutionary Patterns Speciation – Extinction KINDS OF ORGANISM INTERACTIONS results in Adaptations & Coevolution Predation Competition - Intraspecific Interspecific Symbiotic Relationships- long lasting, physical two or more species Parasitism – Ecto /Endo Commensalism Mutualism Other Relationships COMMUNITY AND ECOSYSTEM INTERACTIONS To Understand the ecosystem: 1)Major roles of Organisms Producers Consumers – Herbivores/Carnivores/ Omnivores. Decomposers Keystone Species 2)Energy Flow through Ecosystems – Tropic Levels (Biomass) Food chains/webs 3)Nutrient Cycles in Ecosystems – (all organisms) Carbon Cycle- Photosynthesis starts. Nitrogen Cycle- source (nitrates) protein- fertilizer Phosphorous Cycle- rock or animal waste source for fruit/flower 1 Fertilizers Human Impact on Nutrient cycles Case Studies Contaminants in Great Lakes Fish The Reintroduction of Moose into Michigan 2 INTERACTIONS: Environment and Organisms 5 -1. Ecological Concepts Living things require a constant flow of energy to assure survival All organisms are dependent on others in some way for their survival. eg. one eats another to increase its energy; uses another temporarily for its own benefit without harm; provides service to another (spread seeds/ fertilize). Ecology: The study of how organisms interact with each other and their surroundings. Interact means: (a) How they are molded by their surroundings (b) How they make use of these surroundings (c) How an area is impacted by the organisms and their activities. Everything that affects an organism during its lifetime is its ENVIRONMENT. These "things" fall into two categories * Abiotic factors – 1)non-living, physical matter. 2)energy (includes the sun which is the ultimate source of energy) and 3)processes that involve the interactions of non living matter and energy. Examples : Climate, soil, space (energy flow is necessary to maintain the organism, atoms of C. N2. Water, and Air). b) Biotic (living) factors: all forms of life (plants and animals, bacteria, fungus and parasites). Limiting Factors The limiting factors are those which determine the success of a species, maybe biotic or abiotic (Milk weed - monarch butterflies; Reptiles - warm climate). The limiting factors can be quite different from one species to another. Some fish species may require more dissolved Oxygen than others and or, can tolerate warmer water. 3 Range Of Tolerance. Each species has a specific Range of Tolerance Habitat and Niche. It is almost impossible to understand an organism outside its environment, because the environment influences the organism and the organism affects the environment. Habitat: the physical space, with its characteristics, e.g. the grasses on the wide open prairie. Niche is the functional role an organism has in its surroundings. How it affects and modifies its surroundings, eg. the beaver builds dams, in which ducks and other birds and fish survive. 5 -2. THE ROLE OF NATURAL SELECTION How does each organism fit so precisely into the scheme of things? The process that leads to such a close fit is known as NATURAL SELECTION. The mechanisms of natural selection are: Genes, Populations and Species Genes are distinct pieces of DNA that determine the characteristics that an individual displays (color, shape, behavior). Each individual has a particular set of genes. Population is all the organisms of the same kind in a specific area. The individuals have similar sets of genes, but with individual variations. Reproduction is the process by which the genes are passed on from one to another generation. Species is a group that can interbreed and reproduce fertile offsprings. Each species requires specific conditions to reproduce. Those that reproduce successfully will pass on to the next generation the characteristics that make them more successful. Charles Darwin - The Origin of Species. (1859) Darwin concluded that there are several factors that can interact to allow natural selection to occur. Over time natural selection is known as Evolution. 4 Natural Selection What allows genes to be passed from one generation to another? 1. Local species camouflage. Individuals within a species show variations. Genetically determined variations. 2. Typically produce many more off springs than would survive. The XS number of individuals struggle for survival (food) leads to competition and shortages. 3. As time passes, the % of individuals showing favorable variations will increase. Because of variations, some individuals have a greater chance of surviving and reproducing. The gradual change in genes and characteristics displayed by successive generations over millions of years is known as EVOLUTION. Evolutionary Patterns A physical separation within a species can lead to groups subjected to natural selection, eventually becoming incapable of interbreeding. Speciation (The production of a new species from a previously existing species). It may require millions of years or months. Sub- populations in different environments may develop several sets of chromosomes – POLYPLOIDY or two sets of chromosomes – DIPLOID. Some organisms will evolve to the changing environments while others will be affected adversely, and may become extinct. Extinction is the loss of an entire species. Most species that have ever existed are now extinct. Estimated 500 million species have existed since life began on earth. Today, 5 to 10 million are active. Humans have had a significant impact on the extinction of many species. Co-evolution: two or more species evolutionary direction of the other. can influence the 5 -3. KINDS OF ORGANISM INTERACTIONS The way organisms interact varies. There are several types of interactions: 5 Predation: One organism kills and eats another (predator-prey). Only strong survive in the prey population while only the strong predator will pass on its genes. Additionally, prey population (usually high reproductive rate) is kept in check. Plants – the Venus flytrap. Competition: Organisms strive to obtain the same limited resources. Between members of the same species, competition is INTRASPECIFIC. Between different species, it is INTERSPECIFIC. Competition contributes to survival of the fittest and to better adaptation to the environment. The weakest leaves (Competitive Exclusion Principle). The winner emerges better adapted to the environment. Symbiotic Relationships: a close long lasting physical relationship between two different species. 1. Parasitism - the parasite does not kill, but harms. It gets its food from the host. Ecto-parasites (fleas, lice) live outside the body. Endo-parasites (tape worms) (Vectors are animals that carry a parasite from one host to another). Plants - mistletoe 2. Commensalism - one organism benefits, but the other is not affected. eg. Orchids on a tree or Remora around a shark’s mouth. 3. Mutualism - both organisms benefit e.g. the moth and the Yucca plant; nitrogen fixing bacteria on plant roots. Other Root fungus- mycorrhizae Relationships – categorization It is not always easy to categorize relationships (Temporary parasites, blood predators) 6 5 -4. COMMUNITY AND ECOSYSTEM INTERACTIONS Interacting groups of different species in an area is a community. Ecosystem - a defined space in which interactions occur. To 1. 2. 3. understand fully the ECOSYSTEM, look at it from 3 viewpoints Role of the organism How energy is utilized through the system How atoms are recycled from one organism to another Major roles of Organisms in ecosystems 1. Producers - trap energy, manufacture food, algae, plants, phytoplankton. 2. Consumers – Primary (herbivores) break down organic to inorganic matter - respiration. They Provide energy for self. (leaf-eating insects, seed eating birds). Secondary (carnivores)animals that eat other animals. Tertiary (Omnivores) diet of plants and animals 3. Decomposers (fungi, bacteria) complete the final break down. They are extremely important in the recycling process. Keystone Species Some species have a more central role than others in the ecosystem. The central role player is the Keystone species. Example: The bison in the American prairie. Energy flow through Ecosystems For an ecosystem to maintain itself, it must have a continuous flow of energy - source is sunlight. Energy flows thru the system in steps, stored as chemical energy. Each step is a trophic level. (Second Law of Thermodynamics) Producers constitute the first Trophic level; herbivores the 2nd. When it passes from one trophic level to another, about 90 % of useful energy is lost. Biomass is the weight of living matter in a trophic level. (90% of energy is lost moving from one level to another). 7 Food Chains and Food Webs The food chain is the passage of energy from one trophic level to another. eg. It starts with the producer and ends with the decomposer. One organism consumes another. When an organism dies, the chemical energy of its body is released as heat or water or CO2 The food web is formed when several chains overlap and intersect. Small bits of non-living organic material are called Detritus. Nutrient Cycles in the Ecosystem – Biogeochemical systems All organisms contain atoms of C, N2, O2, H2, K. When they die, their atoms are recycled. These nutrient cycles are often called biogeochemical cycles- - cycling of atoms includes Biological, Geological and Chemical processes Organic molecules contain carbon atoms attached to one another initially manufactured from inorganic molecules by photosynthesis. Ultimately, they are broken down by respiration and decay to inorganic constituents and returned to the abiotic environment Carbon Cycle: Starts during photosynthesis (carbon molecules are converted to organic molecules). Plants use CO2 to produce organic molecules (fat, sugar, protein). The leaves are subsequently eaten and the animal eventually releases the carbon back into the environment. Role of Producers. They use the energy of sunlight to convert inorganic to organic molecules. Oxygen is a by-product of the process. The role of Consumers. Herbivores convert organic molecules to muscle, energy etc. Ultimately are broken down by respiration to obtain energy. Water and carbon dioxide are released The role of Decomposers. Organic matter is used as food. Water and carbon dioxide are released. Carbon Sinks. Situations which remove atoms from active short term nutrients are known as sinks. Photosynthesis and deposition of CaCO3 remove carbon from the atmosphere. Therefore vegetation and the oceans are very important carbon sinks. Cellular respiration and combustion release carbon 8 and are carbon sources. Human alteration of the carbon cycle. The cycle is modified in several ways. Examples are Burning fossil fuels Modifying the ecosystem. When organisms die, decomposers act on the carcass and CO2 is produced in the process Phosphorous Cycle: Its ultimate source is rock. Transported in an aqueous form. It is important in DNA cell structure, bones and teeth. Plants require the phosphorous, which is later consumed by animals. When an returned too much Guano is organism dies or excretes waste, the phosphorous is to the soil. It stimulates fruiting and flowering, however Phosphorous ties up other nutrients in the soil. a natural source of phosphorous. Mining on Nauru in the South Pacific has created problems. The primary source is the droppings of Sea birds and Bats. The Nitrogen Cycle: 78% of the air we breathe involves the flow of nitrogen atoms thru the ecosystem (produce proteins). Very few organisms can use the N2 as it occurs in the atm. Plants get it in the form of nitrates or ammonia. Atmospheric Nitrogen is converted by Nitrogen fixing bacteria to a form that plants can use to make protein and other compounds. Nitrogen stimulates green growth as in lawns, non-blooming trees. Plants use the nitrogen with the help of a Nitrogen fixing bacteria, a denitrifying bacteria, which live in the roots of legumes. The bacteria breaks down nitrates into N2 gases that are returned to the atmosphere. Plants produce protein, often eaten by animals which produce waste, die and decompose, releasing ammonia (NH3). Inorganic fertilizer (Ammonia or nitrate NH3-) is a N2 source. Farmers alternate crops (Corn requires much N2 and Soybeans produces N2). N2 reenters the environment after death, or as leaves are shed or as excrement or urinary waste. 9 In agricultural ecosystems, these elements are removed when a crop is harvested. Unique features of the Nitrogen cycle. Two significant differences from that of the Carbon Cycle. Chemical conversions made by bacteria and other micro organisms Nitrogen enters organisms by way of Nitrogen fixing bacteria and is released into the atm through denitrifying bacteria, but there is a secondary loop in the cycle that recycles nitrogen compounds directly from dead organisms and organic wastes directly back to producers. Nitrogen sinks – Sedimentary rocks release nitrogen during the weathering process Ecosystems with large amounts of dead organic matter. Human Impact on Nitrogen Cycle Significant alteration from burning fossil fuels releases CO2 into the atmosphere. Converting forests to agricultural lands - less carbon stored. Both affect climate N2 is also released into the atm. If fertilizer is applied in XS, it gets into the aquatic system, which causes growth of algae, bacteria and aquatic plants. Algae may be toxic, which causes fish kills. Algae and plants can lead to low O2 content in water. When plants die, decomposition uses up O2 from the water to break down the organic matter. Dead zones in the GOM may be due to fertilizers. Fertilizer contains N2, P, and K. It is written on the container eg. 6-24-24. Means it contains 6% N2; 24% Phosphorous and 24% Potassium (Potash) which helps with root growth and general health. 10 CASE STUDIES Reintroduction of the Moose into Michigan The area initially was the habitat of the moose. Due to industrialization, they became extinct. Times have changed. There is now only minor mining, etc. What value is there in reintroducing the moose to the area ? Contaminants in Great Lakes fishes Synthetic molecules in toxic wastes are released into the GW. for which there are no natural decomposers. As these molecules are ingested by the fish, they bio-accumulate in the fish without killing them. Some fish accumulate more than others depending on where they feed. On the other hand, humans who eat the fish may be affected adversely. Hence, the reason for Fish Advisories. eg. Don't Don't Avoid Limit eat the bottom dwelling fish (cat fish) eat the old fish fatty tissue in fish by deep frying the amount of fish eaten. 11