BOI102 Ecosystem lecture 7.pdf

07/04/2024 BOI102 Ecology Ecosystem metabolism Instructor: Dr Sébastien Lavoué 1...

07/04/2024 BOI102 Ecology Ecosystem metabolism Instructor: Dr Sébastien Lavoué 1 BOI102 Ecology 1- Introduction to ecology: Definitions of ecology and ecosystem. 2- Ecosystem ecology: Definitions of components, structures and ecosystem processes. The role of abiotic and biotic factors. 3- Ecosystem ecology: Definitions of energy flow, food chain, food web and trophic structure. 4- General background on aquatic ecosystem and factors influencing the ecosystem. Mon., Apr. 8, 2024 BOI102 Lecture 7 2 2 1  07/04/2024 Ecosystem ecology: Definitions of energy flow, food chain, food web and trophic structure. 1- Energy flow, trophic level and food chain 2- Food web, proprieties, keystone species 3- Ecosystem Metabolism I: Primary Production 4- Ecosystem Metabolism II: Secondary Production 3 Ecosystem ecology: Definitions of energy flow, food chain, food web and trophic structure. 1- Energy flow, trophic level and food chain 2- Food web, proprieties, keystone species 3- Ecosystem Metabolism I: Primary Production 4- Ecosystem Metabolism II: Secondary Production 4 2  07/04/2024 Energy flow in ecosystems Life represents a local increase in order (decrease in entropy) powered by energy: In ecosystems, energy from sun passes to plants, then herbivores, then carnivores Energy lost at each level Ecosystems need constant input Entropy: the degree of disorder or randomness in the system Mon., Apr. 8, 2024 BOI102 Lecture 7 5 5 Energy flow in ecosystems The biosphere is dependent on solar energy that reaches the earth’s surface as solar radiation. How sunlight reaches the Earth’s surface? How and how much the plants utilize sunlight for new production (primary production) of organic matter that form the basis of energy for the ecosystem food chains? How is energy transferred? Mon., Apr. 8, 2024 BOI102 Lecture 7 6 6 3  07/04/2024 Solar radiation Solar radiation consists of electromagnetic waves which are created when hydrogen nuclei in the sun fusion at very high temperatures. The sunbeam spectrum is very wide, but almost all the radiation energy is in the visible light [400- 700 nm] between the ultraviolet and the infrared spectrum Mon., Apr. 8, 2024 BOI102 Lecture 7 7 7 Sunlight levels Communities process solar energy through green plants, and the resulting energy fixed via photosynthesis sustains all the trophic levels in the food web. Only 1-2% of solar energy hitting Earth enters ecosystems Tropical regions receive 2.5 times more energy than poles Poles and temperate regions have seasonal fluctuations: this affects their ecologies Mon., Apr. 8, 2024 BOI102 Lecture 7 8 8 4  07/04/2024 Global energy balance On average, the Earth emits a similar amount of radiation energy into space as the atmosphere and Earth’s surface absorb incoming solar radiation. This energy balance keeps the global average temperature to about 15 °C 1-2% is the part of the spectrum (especially the red and blue light) that the green plants can utilize for photosynthesis. Mon., Apr. 8, 2024 BOI102 Lecture 7 9 9 Trophic level and food chains The first step in the study of ecosystem metabolism is to identify the food web of the community. The transfer of energy from plants to animals is done through several links called a food chain. Organisms located at the same step in relation to the food source are said to be on the same trophic level. Trophic level: A feeding level in an ecosystem Trophic: relating to feeding and nutrition Mon., Apr. 8, 2024 BOI102 Lecture 7 10 10 5  07/04/2024 Modes of nutrition Autotrophs use solar energy and materials from nonliving sources. Green plants are autotrophs. Heterotrophs pick up energy and materials by eating living matter (Heterotrophs consume other organisms). Herbivores are heterotrophs (eat plants) Carnivores are heterotrophs (eat other heterotrophs) Heterotrophs are either consumers (herbivores, carnivores and scavengers) or decomposers (saprophytes and detritivores) Mon., Apr. 8, 2024 BOI102 Lecture 7 11 11 Modes of nutrition Mixotrophy? Mon., Apr. 8, 2024 BOI102 Lecture 7 12 12 6  07/04/2024 Trophic levels Levels of producers/consumers are trophic levels: First trophic level- producers – Autotrophs Second trophic level – Primary consumers – Herbivores Third trophic level – Secondary consumers – Carnivores (mesopredators) Fourth trophic level – Tertiary consumers – Top level carnivores (apex predators) Omnivores eat at many levels Mon., Apr. 8, 2024 BOI102 Lecture 7 13 13 Food chain Transfer of food from one trophic level to another through series of organisms with repeated eating and being eaten is called a food chain. Food chain is the linear unidirectional flow of energy and materials through the food from one trophic level to the other. In a food chain, each stage represents a trophic level. Food chains are interconnected Mon., Apr. 8, 2024 BOI102 Lecture 7 14 14 7  07/04/2024 Food chain Animals of successive trophic levels in a food chain tend to be larger Mon., Apr. 8, 2024 BOI102 Lecture 7 15 15 Food chain