1. Topic 2 - Biotic and Abiotic Influences on Terrestrial and Aquatic Ecosystems
Introduction questions:
What part of this picture is aquatic and what parts are terrestrial?
What are some of the biotic components of this lake ecosystem? What are some of the abiotic components in this lake ecosystem?
How do you think humans impact the terrestrial ecosystem? What are some ways humans can impact the aquatic ecosystem?

2. Biotic and Abiotic Influences on 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

3. Abiotic Limiting Factors – Terrestrial
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

4. Temperature Nutrients
Global warming reduces habitat for animals adapted to cold temperature
Nutrients
Adding fertilizer to soil increases available nutrients

5. Abiotic Limiting Factors – Aquatic
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
Picture: sediment plumes from bottom trawler fishing boats

6. Temperature Nutrients Acidity
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
- Algal blooms form when excess phosphorus and nitrogen from fertilizers run off from farms. The fertilizer encourages the growth of naturally occurring algae. Eventually, the algae decomposes. The decomposition of algae and the bacteria involved in the decomposition process use up the oxygen present in the body of water. Organisms in the lake suffocate and die due to lack of oxygen.
- The algal bloom also prevents sunlight from reaching aquatic plants and slow down photosynthesis, which further decreases the concentrations of oxygen in the body of water

7. Biotic Limiting Factors – Species Interactions
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…)

8. A male lion with his cub eating a water buffalo
INSERT VIDEO LINK
A male lion with his cub eating a water buffalo
Praying Mantis eating a grasshopper
Indian python attempting to swallow a deer
Lynx and a hare

9. Biotic Limiting Factors – Species Interactions
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
Flower 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.
Other notes:
- While the orchid isn’t considered a parasitic plants, there are many other plant species (ex. strangler fig tree) that IS parasitic. It uses its host for support while draining nutrients from the host, eventually killing the host tree.
- Cuckoo birds also are a good example of a species of bird that practices brood parasitism
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

10. 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.

11. Red-billed oxpecker and the Impala Cleaner wrasses and whale shark
Egyptian Plover and Nile crocodile
Cow (or other ungulates) and E.coli bacteria

12. Buffalo and Cattle Egrets
Commensalism (+ and 0)
Shark and a remora fish
Ramora gets free ride + food
Buffalo and Cattle Egrets
Cattle Egrets and Livestock – as livestock (ex. buffalo) graze in the fields, their movements stir up insects which the egrets eat. The egrets benefit from the interaction while the livestock is unharmed.
Remora Fish and Shark – the remora (also sometimes called a “suckerfish”) attaches to the shark for transportation. In this way, the remora travels much farther than it would otherwise be able to without the shark.
Whales and Barnacles – the barnacles attach to the whale for transportation and is exposed to new food sources it would not otherwise be able to access.
Whales and barnacles

13. A roundworm inside a person’s eye… EWWW!!!
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!!

14. Human head lice feeds on blood from the scalp
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