7_Ecosystems.pdf

BIO 211 Organismal Biology This presentation has been composed for educational purposes only. I do not clai...

BIO 211 Organismal Biology This presentation has been composed for educational purposes only. I do not claim to hold any ownership and/or copyright to the images or content displayed here. I have tried to provide the original source and/or copyright holder’s details wherever applicable.  BIO 211 Lecture 7 Ecosystems Yashraj Chavhan What is an ecosystem? A system formed by an ecological community and its abiotic environment through their multifaceted interactions. Ecosystem ecology is the study of how the interactions of the biotic and abiotic components of an ecosystem shape its energy composition, energy flux, stability, etc.  Ecosystems show a diverse range of size A tidal pool The Amazon rainforest in Brazil Source: https://openstax.org/books/biology/pages/46-1-ecology-of-ecosystems#fig-ch46_01_07; credit pic 1: modification of work by “takomabibelot”/Flickr; credit pic 2: modification of work by Ivan Mlinaric) Three broad categories of ecosystems 1. Ocean water 2. Freshwater 3. Terrestrial Ocean water ecosystems The most common ecosystems on the planet Comprise ~75% of the Earth’s surface Three basic types of ocean water ecosystems: 1. Shallow ocean (high biodiversity; example: coral reefs) 2. Deep ocean surface (high biodiversity; example: plankton and krill) 3. Deep ocean water (no access to sunlight; relatively low biodiversity) Coral reefs One of the most diverse ecosystems on the planet Corals are cnidarians and exhibit radial symmetry (e.g., jellyfish, hydroids, and sea anemones) Corals have colonial polyps that share resources Beneath their soft bodies, polyps secrete a calcium carbonate skeleton that forms the foundation of the reef ecosystem, which supports a large amount of biodiversity. https://www.nature.com/scitable/knowledge/library/coral-reefs-15786954/ Global distribution of coral reefs Source: Henkel 2010 Nature Education Knowledge https://www.nature.com/scitable/knowledge/library/coral-reefs-15786954/ Freshwater ecosystems The rarest ecosystems on the planet Comprise ~1.8% of the Earth’s surface Include rivers, lakes, streams, and springs. Terrestrial ecosystems Can show a wide range of biological diversity Grouped into large categories known as biomes Examples of biomes: tropical rain forests, savannas, deserts, coniferous forests, tundra, etc. The distribution of biomes as a function of temperature and precipitation Source: Forseth 2010 Nature Education KNowledge (https://www.nature.com/scitable/knowledge/library/terrestrial-biomes-13236757/) There is tremendous variation within biome categories Source: https://openstax.org/books/biology/pages/46-1-ecology-of-ecosystems#fig-ch46_01_07 Food chains A linear sequence of interdependent organisms within an ecosystem through which nutrients and energy flux (pass). Within a food chain, each organism occupies a trophic level that denotes its role and position relative to the other members of the ecosystem. Examples of trophic levels: Primary producers, primary consumers, secondary consumers, etc.  Example: The trophic levels of a food chain in Lake Ontario https://openstax.org/apps/archive/20240725.163813/resources/d2b636a215efb1ec7f1a55221e684d1410da22 e3 No trophic interactions are completely efficient Energy is inevitably lost as heat between each trophic level. Hence, after only a few trophic energy transfers, the available energy left within the food chain may not be sufficient to support a higher trophic level. https://openstax.org/apps/archive/20240725.163813/resources/fed8946489d8206798f34d6a82a7d7cd2cc49493 Food chains may be overly simplistic in most ecosystems Some organisms tend to feed on more than one trophic level. Some organisms are fed upon by organisms from more than one trophic level. A more holistic (and realistic) representation is offered by food webs. An example of a food web The Lake Ontario Ecosystem https://openstax.org/apps/archive/20240725.163813/resources/74e37436206adabb8f303fd8c60afcb17ff1d7ae Credit: Cohen et al. 2003 PNAS Components of an organism’s mass balance Credit: Sterner et al. 2011 Nature Education Knowledge Productivity within trophic levels Biomass: The total mass of living or previously living organisms within a trophic level per unit area. https://openstax.org/books/biology/pages/46-1-ecology-of-ecosystems#fig-ch46_01_07 Gross primary productivity: The rate at which the primary producers incorporate energy from the sun. Net primary productivity: The energy that remains in the primary producers after losses due to respiration and heat.  Trophic level transfer efficiency (TLTE) https://openstax.org/books/biology/pages/46-1-ecology-of-ecosystems#fig-ch46_01_07 The Net Production Efficiency Net consumer productivity: The energy content available to the organisms of the next trophic level. Assimilation: The biomass (energy content generated per unit area) of the present trophic level after accounting for the energy lost due to various processes. The NPE for ectotherms is ~10-fold higher than that for endotherms. Ecological pyramids The pyramids of biomass and numbers can be inverted or upright. The pyramids of energy can never be inverted. Why? https://openstax.org/apps/archive/20240725.163813/resources/95af711419a8c5ec02c1e4bc5aeb618a29cb5d15 Reference material for this module Book: Clark, M. A., M. Douglas, and J. Choi. (2018) Biology 2e | OpenStax: Unit 8 (Ecology: Chapters 45 and 46) Link: https://openstax.org/books/biology/