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