condensed notes 3
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BL1006 PART 3 – FULL SENTENCE CUTE NOTES (WORD FOR WORD STYLE)
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URBAN ECOSYSTEMS: Historical Development, Environmental Impacts, and Biodiversity Dynamics
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Preliminary Ecological Concepts
Tundra plants propagate primarily by vegetative or clonal growth 🌿.
Two major factors that make sand dunes inhospitable for plant growth include high salt spray or salinity and extreme water stress due to the low water-retention capacity of sand 🏖💧.
The term “aerenchyma” refers to a specialized plant tissue containing enlarged gas spaces or air channels, which allows for the exchange of gases between the shoot and the root, and is often found in plants in waterlogged or anaerobic environments 🫧🌱.
Desert soils are typically rich in minerals but poor in humus (organic matter) 🪨.
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Introduction to Urban Ecosystems
Urban areas currently account for approximately 3% of the Earth’s total land surface 🌎.
The expansion of the London built-over area illustrates the rapid growth of urban centres, beginning with initial core expansion in 1850, followed by continued expansion along the Thames River in 1860, outward growth in 1880, significant densification by 1900, and reaching a built area index of approximately 3317 by 1914, before expanding even further by 1929 📈🏙.
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Global Urbanisation Trends
There is a projected inversion of the world population, where the percentage of urban residents continues to rise while the percentage of rural residents declines 🌆.
The ten largest urban agglomerations have seen massive growth between 1950 and 2010, with Tokyo projected to reach a population of approximately 37 million people by the year 2025 🌏.
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Urban Heat Island Effect
Urban centres create localized heat islands where temperatures are significantly higher than in surrounding rural areas 🌡🔥.
Late afternoon temperature gradients show rural areas at approximately 30°C, suburban residential areas slightly higher, and commercial or downtown areas peaking at approximately 33°C, while urban parks show a localized temperature dip 🌳.
Materials such as stone, brick, concrete, and asphalt are impervious to water and highly efficient at trapping solar heat 🏢.
Standard roofs can reach temperatures near 80°C, whereas green roofs maintain significantly lower and more stable temperatures, rarely exceeding 40°C 🌿.
Sedum is frequently used for green roofs because it is exceptionally drought-tolerant.
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Biodiversity in Urban Areas
Urban environments support both native and exotic species across plants and birds 🌱🐦.
Cosmopolitan bird species found in more than 80% of cities worldwide include the
rock pigeon,
house sparrow,
starling, and
swallow 🐦.
Cosmopolitan plant species found in more than 90% of cities worldwide include
Poa annua,
Capsella bursa-pastoris,
Stellaria media,
Plantago lanceolata,
Phragmites australis 🌿.
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Urban Core Ecology
The urban core is characterized by a
high built-to-green space ratio,
low gross primary productivity,
and low carrying capacity for most wild animal populations 🏙.
Animals in the urban core are primarily scavengers, parasites, or predators, with mammals dominated by rodents such as rats and mice 🐀.
Many urban species depend on humans for food, which can be categorized as
autochthonous (produced within the ecosystem) or
allochthonous (imported from outside the ecosystem) 🍔.
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Predation by Domestic Cats
Domestic cat populations have risen significantly, reaching approximately 8 to 9 million in the UK 🐱.
Cats have a significant impact on urban bird populations and also cause sub-lethal effects such as stress and behavioural changes in prey species 🐦💔.
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GRASSLAND ECOLOGY AND THE POACEAE FAMILY
Grasslands are areas where the vegetation is dominated by perennial grasses, usually occurring in combination with evergreen non-woody perennials 🌾.
Grasslands represent 20% of all vegetation cover on Earth and account for 70% of the world’s agricultural land 🌍.
In Ireland, 80% of land area is categorized as grassland 🇮🇪.
Grasses belong to the family Poaceae and are monocotyledonous flowering plants 🌱.
Monocots have
one cotyledon,
parallel leaf veins,
complex vascular bundles,
floral parts in multiples of three,
and fibrous root systems 🌿.
Grasses typically have hollow stems and narrow, alternate leaves 🌾.
There are approximately 12,000 species of grasses, making it the fifth largest plant family 🌍.
Grasses have structural components including the blade, crown, ligule, collar, leaf sheath, stem, roots, and tiller 🌱.
Grasses have evolved to withstand grazing and fire because their growth points (meristems) are located below the ground or near the surface, protecting them from damage 🔥🐮.
Grasslands are characterized by
intermediate rainfall,
high evaporation,
and frequent drought,
with terrain generally flat and influenced by grazing and fire ☀
Grasslands are known by different regional names, including pampas, savanna, prairie, and steppe 🌍.
Grasslands store significant amounts of carbon, support biodiversity, and provide essential ecosystem services 🌱.
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ARCTIC, ANTARCTIC, AND TUNDRA ECOSYSTEMS
The Arctic has approximately 8 million km² of land area with 30% ice coverage, supports land mammals and birds, and has relatively high biodiversity compared to the Antarctic ❄.
The Antarctic has approximately 14 million km² of land area with 97% ice coverage, no terrestrial food, no land mammals, and very low biodiversity 🧊.
Tundra ecosystems occur in extreme near-polar climates, with low temperatures, low precipitation, and limited productivity 🌡.
Permafrost is a permanently frozen soil layer, with only a thin active layer thawing during summer ❄.
Tundra vegetation is low-growing,
mainly perennial, and
reproduces primarily through vegetative methods 🌱.
Animals in tundra ecosystems survive through migration, hibernation, insulation, and behavioural adaptations 🐾.
Climate change is causing melting ice, northward shifts in vegetation, and changes in biodiversity 🌍🔥.
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DESERT ECOSYSTEMS
A desert is defined as an area receiving less than 25 cm of annual precipitation ☀.
Deserts are characterized by extreme temperatures, high evaporation, low humidity, and high solar radiation 🌡.
Soils are rich in minerals but low in organic matter 🪨.
Plants have evolved adaptations such as deep roots, water storage, and CAM photosynthesis 🌵.
Animals are adapted through nocturnal behaviour, water conservation, and specialized morphology 🐫.
Desertification is caused by drought and human activity, leading to environmental degradation ⚠.
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SOIL ECOSYSTEMS
Soil provides essential ecosystem services including food production, water regulation, carbon storage, nutrient cycling, and habitat for organisms 🌍.
Soil forms through the breakdown of rock by physical, chemical, and biological processes 🪨.
Soil is composed of clay, silt, sand, and gravel particles of varying sizes 🌱.
The soil food web includes plants, microbes, invertebrates, and predators interacting across trophic levels 🐛.
Mycorrhizal fungi form symbiotic relationships with plants, aiding nutrient uptake 🌿.
Earthworms act as ecosystem engineers by improving soil structure and increasing porosity 🪱.
Soil ecosystems face threats such as pollution, erosion, land-use change, and climate change ⚠.
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SAND DUNE ECOSYSTEMS
Sand dunes form through the interaction of sand supply, wind transport, and obstacles such as vegetation 🌬.
Ecological succession in dunes progresses from pioneer species to intermediate plants and eventually to a climax community 🌱.
Early dune stages are characterized by harsh conditions including high salinity, low nutrients, and instability 🌊.
Later stages have increased organic matter, reduced salinity, and greater biodiversity 🌿.
Marram grass plays a key role in stabilizing dunes through specialized leaf, stem, and root adaptations 🌾.
Human activity, grazing, and climate change can impact dune ecosystems and biodiversity ⚠.
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WETLAND ECOSYSTEMS
Wetlands are ecosystems characterized by the presence of water, unique soils, and specialized plant and animal communities 💧.
Water is the primary factor controlling wetland environments and associated biota 🌊.
Wetlands occur where the water table is at or near the surface or where land is covered by shallow water 🌍.
Hydrology plays a key role in shaping
plant composition,
productivity,
nutrient cycling, and
biodiversity 🌱.
Wetland plants have adaptations such as aerenchyma, shallow roots, and oxygen transport systems 🫧.
Wetlands provide ecosystem services including water filtration, flood control, carbon storage, and habitat provision 🌿.
Wetlands are threatened by drainage, pollution, agriculture, and climate change ⚠.