Relationships Between Organisms
In an ecosystem, no organism lives alone. They interact in various ways to survive, find food, or reproduce.
1. Feeding Relationships
The most basic interaction is “Who eats whom?”
- Predation: One organism (Predator) hunts and eats another (Prey). Example: Tiger eats Deer.
2. Competition
When resources like food, water, or space are limited, organisms fight for them.
- Intraspecific Competition: Between members of the same species (two deer fighting for grass).
- Interspecific Competition: Between different species (lions and hyenas fighting for the same kill).
- Balance: Competition controls population size and prevents any single species from taking over.
3. Symbiosis (Living Together)
Some interactions involve close, long-term relationships between different species.
| Type | Definition | Effect on Species A | Effect on Species B | Example |
|---|---|---|---|---|
| Mutualism | Both benefit. | Happy (+) | Happy (+) | Honeybees & Flowers (Bees get nectar, Flowers get pollinated). |
| Commensalism | One benefits, the other is unaffected. | Happy (+) | Neutral (0) | Orchids on Trees (Orchids get sunlight/support, Tree is unharmed). |
| Parasitism | One benefits, the other is harmed. | Happy (+) | Sad (-) | Ticks on Dogs (Ticks suck blood, Dog gets irritation/disease). |
Warning
The Case of the Pond (Activity 12.3) Scientists found that ponds with fish had more seeds produced by nearby plants than ponds without fish. Why?
- Fish eat dragonfly larvae.
- Fewer dragonflies mean fewer predators for bees and butterflies.
- More bees/butterflies survive to pollinate the nearby flowers.
- More pollination = More seeds. This shows how connected nature is!