Topic 2 Ecology

At the end of this subtopic 2.1 you should understand:

• The biosphere is an ecological system composed of individuals, populations, communities, and ecosystems. (2.1.1)

• An individual organism is a member of a species. (2.1.2)

• Classification of organisms allows for efficient identification and prediction of characteristics. (2.1.3)

• Taxonomists use a variety of tools to identify an organism. (2.1.4)

• A population is a group of organisms of the same species living in the same area at the same time, and are capable of interbreeding. (2.1.5)

• Factors that determine the distribution of a population can be abiotic or biotic. (2.1.6)

• Temperature, sunlight, pH, salinity, dissolved oxygen, and soil texture are examples of many abiotic factors that affect species distributions in ecosystems. (2.1.7)

• A niche describes the particular set of abiotic and biotic conditions and resources on which an organism or a population depends. (2.1.8)

• Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease, and competition, with ecological, behavioural, and evolutionary consequences. (2.1.9)

• Carrying capacity is the maximum population size of a species that can be sustainably supported and determined by competition for limited resources. (2.1.10)

• Population size is regulated by density-dependent factors and negative feedback mechanisms. (2.1.11)

• Population growth can be either exponential or limited by carrying capacity. (2.1.12)

• Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems. (2.1.13)

• Carrying capacity cannot be easily assessed for human populations. (2.1.14)

• Population abundance can be estimated using random sampling, systematic sampling, or transect sampling. (2.1.15)

• Random quadrat sampling can be used to estimate population size for non-motile organisms. (2.1.16)

• Capture-mark-release-recapture and the Lincoln Index can be used to estimate population size for motile organisms. (2.1.17)

• A community is a collection of interacting populations within an ecosystem. (2.1.18)

• Habitat is the location in which a community, species, population, or organism lives. (2.1.19)

• Ecosystems are open systems in which both energy and matter can enter and exit. (2.1.20)

• Sustainability is a natural property of ecosystems. (2.1.21)

• Keystone species play a role in the sustainability of ecosystems. (2.1.23)

• Human activity can lead to tipping points in ecosystem stability. (2.1.22)

• The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold. (2.1.24)

• To avoid critical tipping points, loss of biosphere integrity needs to be reversed. (2.1.25)

At the end of this subtopic 2.2 you should understand:

• Producers form the first trophic level in a food chain. (2.2.5)

• Consumers gain chemical energy from carbon (organic) compounds obtained from other organisms. Consumers have diverse strategies for obtaining energy-containing carbon compounds. (2.2.9)

• Because producers in ecosystems make their own carbon compounds by photosynthesis, they are at the start of food chains. Consumers obtain carbon compounds from producers or other consumers, so form the subsequent trophic levels. (2.2.10)

• Carbon compounds and the energy they contain are passed from one organism to the next in a food chain. The stages in a food chain are called trophic levels. (2.2.11)

• Ecosystems are sustained by supplies of energy and matter. (2.2.1)

• The first law of thermodynamics states that as energy flows through ecosystems, it can be transformed from one form to another but cannot be created or destroyed. (2.2.2)

• The second law of thermodynamics states that energy transformations in ecosystems are inefficient. (2.2.8)

• Photosynthesis and cell respiration or cellular respiration transform energy and matter in ecosystems. (2.2.3)

• Photosynthesis is the conversion of light energy to chemical energy in the form of glucose, some of which can be stored as biomass by autotrophs. (2.2.4)

• Cell respiration or cellular respiration releases energy from glucose by converting it into a chemical form that can easily be used in carrying out active processes within living cells. (2.2.6)

• Some of the chemical energy released during cell respiration or cellular respiration is transformed into heat. (2.2.7)

• Food webs show the complexity of trophic relationships in communities. (2.2.15)

• There are losses of energy and organic matter as food is transferred along a food chain. (2.2.12)

• The number of trophic levels in ecosystems is limited due to energy losses. (2.2.14)

• Biomass of a trophic level can be measured by collecting and drying samples. (2.2.16)

• Ecological pyramids are used to represent relative numbers, biomass, or energy of trophic levels in an ecosystem. (2.2.17)

• Gross productivity (GP) is the total gain in biomass by an organism. Net productivity (NP) is the amount remaining after losses due to cell respiration or cellular respiration. (2.2.13)

• Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT), and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification. (2.2.18)

• Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain. (2.2.19)

• Human activities, such as burning fossil fuels, deforestation, urbanisation, and agriculture, have impacts on flows of energy and transfers of matter in ecosystems. (2.2.20)

At the end of this subtopic 2.3 you should understand:

• Biogeochemical cycles ensure chemical elements continue to be available to living organisms. (2.3.1)

• Biogeochemical cycles have stores, sinks, and sources. (2.3.2)

• Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form. (2.3.5)

• Fossil fuels are stores of carbon with unlimited residence times. They were formed when ecosystems acted as carbon sinks in past eras and become carbon sources when burned. (2.3.7)

• Organisms, crude oil, and natural gas contain organic stores of carbon. Inorganic stores can be found in the atmosphere, soil, and oceans. (2.3.3)

• Ecosystems can act as stores, sinks, or sources of carbon. (2.3.6)

• Carbon flows between stores in ecosystems by photosynthesis, feeding, defecation, cell respiration or cellular respiration, death, and decomposition. (2.3.4)

• Agricultural systems can act as carbon stores, sources, and sinks, depending on the techniques used. (2.3.8)

• Carbon dioxide is absorbed into oceans by dissolving and is released as a gas when it comes out of a solution. (2.3.9)

• Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals. (2.3.10)

• Measures are required to alleviate the effects of human activities on the carbon cycle. (2.3.11)

At the end of this subtopic 2.4 you should understand:

• Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time. (2.4.1)

• A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur. (2.4.2)

• Abiotic factors are the determinants of terrestrial biome distribution. (2.4.3)

• Biomes can be grouped into various different types that include freshwater, marine, forest, grassland, desert, and tundra. Each of these classes has characteristic abiotic limiting factors, productivity, and diversity. They may be further classed into many subcategories (for example, temperate forests, tropical rainforests, and boreal forests). (2.4.4)

• Global warming is leading to changing climates and shifts in biomes. (2.4.7)

• The tricellular model of atmospheric circulation explains the behaviour of atmospheric systems and the distribution of precipitation and temperature at different latitudes. It also explains how these factors influence the structure and relative productivity of different terrestrial biomes. (2.4.5)

• The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world. (2.4.6)

By the end of this section you should understand the following:

• Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables. (2.5.3)

• Each seral community (sere) in a succession causes changes in environmental conditions that allow the next community to replace it through competition until a stable climax community is reached. (2.5.4)

• Primary successions happen on newly formed substrata where there is no soil or pre-existing community, such as rock newly formed by volcanism, moraines revealed by retreating glaciers, wind-blown sand, or waterborne silt. (2.5.5)

• Secondary successions happen on bare soil where there has been a pre-existing community, such as a field where agriculture has ceased or a forest after an intense firestorm. (2.5.6)

• Energy flow, productivity, species diversity, soil depth, and nutrient cycling change over time during succession. (2.5.7)