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Topic 2 - Biotic and Abiotic Influences on Terrestrial and Aquatic Ecosystems
• Limiting Factor = any factor that limits the size of a population or where it can live
• Tolerance Range = the range of abiotic conditions which a species can survive
Biotic and Abiotic Influences on Ecosystems
• Examples of how humans affect abiotic factors in a terrestrial ecosystem:
• Light– Cutting trees to expose plants
underneath to more light
• Water– Damming rivers decreases
water available– Irrigating fields increases
water available in an ecosystem
Abiotic Limiting Factors – Terrestrial
• Temperature– Global warming
reduces habitat for animals adapted to cold temperature
• Nutrients– Adding fertilizer
to soil increases available nutrients
• Examples of how humans affect abiotic factors in an aquatic ecosystem:
• Light– Stirring up sediment at the
bottom of a lake decreases amount of light reaching plants
• Salinity (Salt Levels)– Run-off from salting high ways
in the winter increases salt concentration in rivers and lakes
Abiotic Limiting Factors – Aquatic
• Temperature– Industries release
heated water into lakes and rivers killing fish and other organisms
• Nutrients– Fertilizer can run-off
causing algal blooms
• Acidity– Burning of fossil fuels
creates acid rain which makes bodies of water more acidic
• Examples of biotic factors in ecosystems: – Competition• Organisms compete for the
same limited resources: food, water, habitat, light, mates
– Predation• Predator (the organism that
hunts) kills and eats its prey (the organism that is attacked)• The populations of the predator
and prey depend on each other (more on this topic next day…)
Biotic Limiting Factors – Species Interactions
Lynx and a hare
Indian python attempting to swallow a deer
A male lion with his cub eating a water buffalo
Praying Mantis eating a grasshopper
INSERT VIDEO LINK
• Symbiotic Relationships between organisms:
Mutualism (+ and +)• Two organisms benefit from
each other
Commensalism (+ and 0)• One organism benefits and
the other neither benefits nor is harmed
Parasitism (+ and -)• One individual lives on or in a
host organism and feeds on it
Biotic Limiting Factors – Species InteractionsFlower provides the bee
with nectar, the bee helps the flower spread its pollen
Orchids grow on the trunks or branches of trees to receive more light. As long as the plant is not
too heavy, the tree is not affected.
The cowbird lays their eggs in the nests of other birds (like the reed warbler). The
reed warbler mother must spend more time feeding the larger and
more demanding cowbird
Mutualism (+ and +)
Stinging anemone tentacles provide the clownfish with protection from predators. The clownfish defend
anemones against butterflyfish which eat the anemones. Bacteria live in the nodules of
legumes (ex. soybeans) and provide nitrogen for the plant. The plant
provides sugars for the bacteria.
Cleaner wrasses and whale shark
Egyptian Plover and Nile crocodile
Red-billed oxpecker and the Impala
Cow (or other ungulates) and E.coli bacteria
Commensalism (+ and 0)
Ramora gets free ride + food
Shark and a remora fish
Buffalo and Cattle Egrets
Whales and barnacles
Parasitism (+ and -)• Parasite receives nourishment from host– Parasites don’t normally kill host but the host is
harmed
A roundworm inside a person’s eye… EWWW!!!
Numerous roundworms from the bowel of a dog post-surgery…. DOUBLE EWWW!!
Bed bugs… inside a mattress… do you see the bed bug fecal
matter?!? EW!
Caribbean soldierfish host to a parasitic isopod, which feeds on
its body tissues
Human head lice feeds on blood from the scalp