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FOCUS ON THE BIOTA Metabolism, Ecosystems & Biodiversity The Earth is the only place in the solar systems that has documented proof of life CHARACATERISTICS OF LIFE Life spreads exponentially the rate of population growth depends on the number of individuals reproducing at any time Exponential Growth If each pair produces 4 offspring, the number of organisms increases exponentially If resources become limited, exponential growth ceases CHARACATERISTICS OF LIFE Life needs energy photosynthesizers use solar energy chemosynthesizers use chemical energy most other organisms use the energy stored as the bodies of the these two CHARACATERISTICS OF LIFE Life pollutes every organism has a metabolism that releases waste products other organisms may use these waste products or the waste products may accumulate in the environment CHARACATERISTICS OF LIFE Life is versatile organisms react with their environment and with each other in many ways microbes are particularly inventive they occupy an incredible range of environments their activities are important for all life on Earth AUTOTROPHS AND HETEROTROPHS In Earth System Science - more useful to classify organisms based on the way that they obtain their energy and metabolize it (rather than by traditional taxonomic classification system) AUTOTROPHS AND HETEROTROPHS AUTOTROPHS – grow using a source of energy to reduce CO2 to organic carbon These organisms produce organic matter from inorganic carbon sources using either the Sun’s energy or that of energy-releasing chemical reactions Plants, algae and photosynthetic microbes (cyanobacteria, purple and green sulfur bacteria) Most common Chemosynthetic bacteria make up most of the remainder of the pack (colorless sulfur bacteria) Chemosynthesis is the basis of the mid-ocean ridge food chain. AUTOTROPHS AND HETEROTROPHS HETEROTROPHS - organisms that grow by using organic matter produced by other organisms heterotrophs use autotrophs by breaking them down (and using their stored energy) at a higher rate than they would abiotically STRUCTURE OF THE BIOSPHERE Species – all closely related organisms that can potentially interbreed and produce fertile offspring Population – all members of a single species that live in a given area Community – characteristic assemblage of two or more groups of interacting species boreal forest and prairies of Saskatchewan Ecosystem – community of plants, animals, fungi, and microbes coupled with the environment (climate, soil and rock type, etc.) May include any combination of plants, animals, fungi, and microbes Biome – region with a characteristic plant community Species represent the smallest subunit of the biosphere Coral reef, tropical cloud forest, and arctic desert Biosphere – all ecosystems on Earth Ecosystems The physical environment (topography, soil type, atmosphere, climate) plays a strong role in establishing an ecosystem However, the organisms present may also play a strong role in altering the physical environment in a number of ways (creating soil, decreasing albedo, etc.). PHYSIOLOGY VS. ECOLOGY FOR MAXIMUM GROWTH C3 – trees, plants, cyanobacteria, algae C4 – grasses, corn, pineapple evolved in last 10-20 million years as CO2 levels dropped or climate became drier Skip in 2015 ECOTONE- A DIFFUSE BOUNDARY BETWEEN ECOSYSTEMS - MAY CONTAIN AN ASSEMBLAGE OF SPECIES THAT IS NOT FOUND IN EITHER ADJACENT ECOSYSTEM MAJOR TERRESTRIAL BIOMES Polar biomes – characterized by very low temperatures throughout the year, with the permanent presence of snow and ice. This eliminates the possibility of significant terrestrial vegetation, although microscopic algae, cryovegetation, may develop temporarily on the ice or snow. This lack of terrestrial producers results in very low diversity in polar biomes. Tundra biomes – develop in regions where MAT is low, but where a short summer season permits development of terrestrial vegetation Boreal Forest or Taiga biomes form where winters are long and cold, but the growing season is long enough to eliminate permafrost. Extensive, conifer-dominated forests develop. Landscapes tend to be flat, as a consequence of earlier glacial activity, and bogs, ponds, and lakes are common, often as a result of beaver activity in damming streams. FEEDBACKS BETWEEN THE BOREAL FOREST AND CLIMATE IN NORTH AMERICA AND ASIA Models predict that April temperatures might be 12°C (21.6°F) colder and even July temperatures may decrease by 5°C (9°F) if the boreal forest disappeared Cold Desert biome – typically dominated by dry-adapted shrubs, such as the sagebrush (Artemisia) and rabbit-bush (Chrysothamnus) shown here, along with arid grasses and seasonal herbaceous dicots. "Short-grass" Prairie biome – along the eastern front of the Rocky Mountains. Temperate Deciduous Forest biome – dominated by trees that drop their leaves during the winter (cold) months of the year. Temperate deciduous forest covers much of the United States, east of the Mississippi River. Tropical Rainforest biome – form where rainfall is abundant throughout the year Tropical Deciduous Forest biomes – form where generally rainy areas have a distinct dry season. Thorn Forest Scrub, Savanna, and Tropical Grassland biomes - form in the semi-arid tropics, where available rainfall will no longer support true forest vegetation, leading to the development of a mosaic of open biomes. Warm Desert biome – this is the particularly rich warm desert flora of Sonoran Desert. In very dry deserts like the Namib of Africa or the Atacama of South America, vegetation may be virtually absent, except following very rare rains. NUTRIENT RESIDENCE TIMES & NET PRIMARY PRODUCTIVITY Skip in 2015 SPECIES INTERACTIONS primary producers (algae, plants) are consumed by primary consumers (zooplankton, rodents) that are eaten by secondary consumers (fish, hawks), while decomposers (bacteria and fungi) and detritus feeders consume the organic matter of primary and secondary producers and consumers Food chain – charts which organisms feed on which Food web – interconnected food chains that can be ordered as trophic levels Biomass – the total combined weight of organic material in each trophic level. Biomass decreases with each increase in trophic level. In terrestrial ecosystems, the biomass decreases by 90-99% for each level. The exchange of biomass can be thought of as exploitation efficiency. Higher trophic levels– all carnivores 2nd trophic level – all herbivores 1st trophic level – all producers SPECIES INTERACTIONS Symbiosis – a relationship where two species benefit from living together in intimate contact. SPECIES INTERACTIONS Competition – a relationship where two species vie for the same resources Niche – describes an animal’s lifestyle (where, when, and what it eats, where it lives, where and when it nests, etc.) Most organisms have different niches to reduce competition ECOSYSTEM DISTURBANCE AND SUCCESSION Disturbance of an ecosystem generates a predictable sequence of response called succession. In the example of a forest fire the first species to appear are called opportunists or pioneer species. These spread fast by reproducing rapidly and are tolerant of disturbed environments. Return to original conditions may take hundreds of years (ex. New England forests, Mt. St. Helens). This is the biosphere’s way of healing after being wounded. IS RESILIENCE A GENERAL CHARACTERISTIC OF DIVERSE ECOSYSTEMS? A HEALTHY PLANET SHOULD . . . Transport nutrients from where they are to where they are needed Eliminate wastes Have stable environmental variables (temperature, composition) Be capable of responding to disturbances while minimizing consequences THE BIOTA PLAY AN IMPORTANT ROLE IN THE REGULATION OF THE EARTH SYSTEM - modifies greenhouse gas content - created O2-rich atmosphere EARTH’S HEALTH CAN BE MEASURED BY THE NUMBER OF SPECIES IT SUPPORTS Biodiversity Biodiversity is the number of species in a given area. However, there are other ways to look at biodiversity too. Biodiversity is the same in both plots. Community II is much more heterogeneous and therefore diverse. Simpson’s diversity index measures the likelihood that two individuals drawn from the same community will be of different species. SDI = 1- [(proportion of species A)2 + (proportion of species B)2 + …] 1 = Very High Diversity 0 = Very Low Diversity SDI for community I (1- (0.992 + 0.012) = 0.02 SDI for community II (1- (0.52 + 0.52) = 0.50 Diversity and Stability Time Stability Hypothesis- environmental stability like that seen in the tropics leads to high diversity Intermediate Disturbance Hypothesis- the high diversity in the tropics is the result of disturbances that occur with intermediate frequency and intensity Rainforests tend to show greatest diversity where some disturbance has occurred Coral reefs show maximum diversity where they are most likely to get trashed in storms. It may be that a world with greater biodiversity will recover more quickly from a disturbance and thus a more diverse world is a more stable world. Decreases in some species counterbalanced by increases in others DIVERSITY INDEX FOR THE EARTH SYSTEM SHOULD Capture the degree of interactions between biological and physical components Incorporate the attribute of redundancy Incorporate potential diversity A more biologically diverse Earth would be more stable and resilient Biodiversity does enhance environmental stability on a global scale DANGERS OF LOSS OF BIODIVERSITY An Gorta Mór- implications for low diversity Monocultures famine, disease, social breakdown