Ecology PDF

BIOL S103F ESSENTIAL BIOLOGY ECOSYSTEMS AND ECOLOGY Week 11 Introduction 2  Species seldom lives alone  Different species live together in an habitat forms an ecosystem  This thus involves    Organisms behaviour and Interspecific relationship Interaction between organisms and abiotic environme...

BIOL S103F ESSENTIAL BIOLOGY ECOSYSTEMS AND ECOLOGY Week 11 Introduction 2  Species seldom lives alone  Different species live together in an habitat forms an ecosystem  This thus involves    Organisms behaviour and Interspecific relationship Interaction between organisms and abiotic environment Matter and energy flow Properties of Community 3   Species richness  Number of species Primary productivity  The amount of energy produced  The higher the productivity, the higher is the population Properties of Community 4  Environment influences the two properties Abundance of tree species along a moisture gradient. Each line represents the abundance of a different tree species. The species’ patterns of abundance are independent of one another. Community composition changes continually along the gradient. Properties of Community 5  Environment influences the two properties The plant communities on normal and serpentine soils are greatly different. Transition from one community to another occurs over a short distance. The Ecological Niche Concept 6  The differences in the species pattern in different localities suggest that different species is most suitable to grow in certain conditions (ecological niches)  Types of niches  Fundamental niches  The entire niches that a species is capable of using based on its physiological tolerance limits and resources needs  Realised niches  The niche that a species can establish a stable population 7 Realised Niches Fundamental Niches Competition 8   Species can interact with one another in a number of ways and these interactions can have either positive or negative effects. Interspecific competition  Occurs when two species use the same resource and there is not enough to satisfy both  Interference competition – physical interactions over access to resources  Exploitative competition – consume the same resources Exclusion Co-exist (for now) Resource partitioning Principle of Competitive Exclusion 10  If two species are competing for a limited resource, the species that uses the resource more efficiently will eventually eliminate the other locally Predator-Prey Relationship 11 Predator-Prey Relationship 12  Uncontrolled predation led to extinction of the predator  The population size of the prey was much larger than that of the predator  If prey is provided by shelter, the prey and the predator will sustain at a low level  Eg. Elimination of large carnivores in Eastern US led to population explosion of deer, which consumed all edible plants Symbiosis 13  Symbiosis refers to the elaborated and more-or-less permanent relationships between two or more interacting species  It is the often the result of the coevolution of the predator and prey. Eg. Bees and flowers  Three major types of symbiosis  Mutualism – all interacting species are benefited  Parasitism – one is benefited but one is harmed  Commensalism – one is benefited but one is neither benefited nor harmed Interspecific Interaction Drives Natural Selection 14  Competition, predation, parasitism, commensalism and mutualism exert selective pressures or provide reproductive/survival advantages to a species 15 Dynamics of Ecosystem - Matter and Energy Definition 16  All the living organisms that live in a particular place and the abiotic environment at that location  The major concern in the study of ecosystem is the flow of energy and materials Matter and Energy 17  Matter – Relatively a closed system in the Earth (no net output or input from the universe)  Energy – Open system in the Earth as constantly receiving sunlight Biogeochemical Cycles 18 Carbon cycle  Water cycle  Nitrogen cycle  Phosphate cycle  Carbon Cycle 19 Terrestrial ecosystem Anaerobic Respiration by methanogenic bacteria Aquatic ecosystem Carbon Cycle 20  Major sources of inorganic carbon  Atmospheric carbon dioxide  Aqueous bicarbonate  Major sink of organic carbon  Organism  Fossil fuels  The speed of the generation and removal of inorganic carbon should be similar Water Cycle 21 Aquifers Water Cycle 22  Groundwater  Aquifer – permeable, underground layers of rocks, sand, and gravel saturated with water  Water table – accessible by plant and flows into stream  Confined groundwater  Why is plant crucial to the balance of water cycle? Nitrogen Cycle 23 Nitrogen Cycle 24  Nitrates and ammonia are the sources of nitrogen of organisms  Nitrogen fixation – N2  NH3  Nitrification – NH3  NO3 Denitrification - NO3- / NH3  N2  Nitrogen fixing bacteria  Fixing (metabolic process of making nongaseous compound from gaseous compound) Phosphate Cycle 25 Phosphate Cycle 26  The only cycle without gaseous form  Flows from rocks to ocean sediment in general Energy Flow 27  Energy cannot be recycle  Because of increase of entropy (the order of chaos)  Organism cannot convert heat energy into other form of energy  As a result, energy used by organisms cannot be recycled and the Earth has to function as an open-system with regard to energy Flow of Energy in an Ecosystem 28 Flow of Energy in an Ecosystem 29 Energy flows through tropic levels Some bacteria is also detritivores (decomposer) 30 Energy flows through tropic levels Energy, Tropic Level, Productivity 31  Productivity – the rate at which organisms in a tropic level collectively synthesize new organic matter  Photosynthesis minus cellular respiration  Each tropic level has its productivity ⊷ Gross primary productivity – cellular respiration = Net primary productivity ⊷ Secondary productivity  Number of tropic level is dependent on energy availability Biodiversity 32  Biodiversity is crucial to the survival of top consumers  Diverse sources species provide multiple alternative of food