Freshwater habitats Flashcards
Why are freshwater habitats considered rare and ecologically significant
Freshwater makes up only ~0.8% of Earth’s total water volume, with much of it locked in glaciers, ice caps, groundwater, or permafrost. Despite this, these habitats cover just ~2% of Earth’s surface, making them both rare and crucial to study
How are freshwater habitats physically diverse
Freshwater systems vary widely, including temporary streams, wetlands, ponds, and vast deep lakes. This physical diversity creates a wide range of environmental conditions and niches
Why are freshwater habitats considered biodiversity hotspots
They support a huge range of life, including 25% of all described mollusc species and 55% of all fish species, as well as many microbes, invertebrates, amphibians, and mammals
Why are freshwater ecosystems particularly vulnerable to environmental threats
Their small size and direct reliance on surrounding human activities (e.g. pollution, land use)
What essential ecosystem services do freshwater habitats provide to humans
They offer critical services such as clean drinking water, food (e.g. fish), flood regulation, water purification, and recreational opportunities - making their protection vital to human well-being
What vertebrates live in freshwater
Fish (e.g. trout, salmon), amphibians (frogs, salamanders), reptiles (turtles, crocodiles), mammals (otters, beavers, river dolphins)
What invertebrates live in freshwater
Crustaceans (crayfish, shrimp), insects (dragonflies, mosquitoes), molluscs (snails, mussels)
What microorganisms are found in freshwater
Cyanobacteria (photosynthetic), Proteobacteria, Methanobacterium (Archaea)
How do freshwater species survive in cold environments like the Arctic
Cold-adapted fish produce antifreeze proteins to prevent ice crystal formation; some, like icefish, lack haemoglobin to improve circulation in near-freezing water
How do freshwater organisms survive extreme heat
Thermophilic species, such as Thermus aquaticus, thrive in geothermal springs over 70°C. Brine flies are another example of heat-adapted freshwater species
How do freshwater organisms adapt to low-oxygen environments
Some breathe air (lungfish), store oxygen with haemoglobin-like proteins (midge larvae), or use modified gills/surface breathing (certain fish) to extract oxygen efficiently
What adaptations help freshwater organisms survive in fast-flowing rivers
hey develop flattened bodies (e.g. mayfly larvae) to reduce drag or use suction structures (e.g. snails, algae-grazing fish) to cling to rocks
How are organisms adapted to still-water environments like lakes and ponds
Plankton have gas vacuoles for buoyancy, and floating plants like duckweed access light by staying on the water’s surface
What are euryhaline species and how do they adapt to salinity changes
Euryhaline species, such as salmon and eels, can tolerate a wide range of salinities and undergo physiological changes to move between freshwater and saltwater
How do microorganisms adapt to extreme pH in freshwater environments
Alkaliphilic bacteria thrive in highly basic lakes, while acidophilic microbes can live in acidic conditions with pH as low as 2
How do rotifers survive in temporary water sources
Adult rotifers can enter a dormant state with little body water and resume activity within hours after rehydration
What survival strategy do crustacean zooplankton use in ephemeral waters
Their eggs can remain dormant during dry periods and hatch when exposed to water again
How do aquatic insects disperse between temporary water bodies
Many have aquatic larvae and terrestrial adult stages, allowing them to move between habitats during dry spells
How do killfish survive in short lived ponds
They mature rapidly - within two weeks - and die young (3–9 months), leaving behind dormant embryos
How do biocides threaten freshwater ecosystems
Insecticides and herbicides enter waterways, harming non-target species and disrupting food webs by eliminating prey or predators
What are the effects of organic pollution on freshwater habitats
Nutrients from sewage and fertilisers cause algal blooms, leading to eutrophication, oxygen depletion, and fish die-offs
What human activities cause freshwater habitat loss
Deforestation, urbanisation, and pollution reduce habitat quality and destroy vital ecosystems
How do dams affect freshwater ecosystems
Dams block sediment flow and fish migration. Only 37% of rivers remain free-flowing from source to mouth
How does human exploitation harm freshwater systems
Overfishing and water abstraction for agriculture or cities lead to resource depletion and ecosystem imbalance
