Interactions Among Organisms

Study Notes

Interactions among organisms are crucial for the health and balance of ecosystems. These interactions can be beneficial, harmful, or neutral.

Competition: Organisms compete for limited resources like food, water, or shelter. This can negatively affect both participants.
- Example: Two types of birds fighting over a food source.
Predation: One organism (predator) hunts and kills another (prey) for food.
- Example: A lion hunting a zebra.
Symbiosis: Close relationships where two species live together. The interactions can be positive, negative, or neutral.
- Mutualism: Both species benefit from the interaction.
  - Example: Bees pollinating flowers. The bees get nectar, and the flowers get their pollen spread.
- Commensalism: One species benefits, and the other is neither harmed nor helped.
  - Example: A bird building a nest in a tree. The bird benefits, the tree is neither harmed nor helped.
- Parasitism: One species (parasite) benefits at the expense of the other (host).
  - Example: A tick feeding on a dog. The tick benefits, the dog is harmed.

Assessing the effects of interactions requires understanding the needs of each organism and how they influence each other.

Interactions affect population size and distribution. Predation can reduce prey populations, for instance. Mutualistic relationships can support growth in both species' populations.

Consider the following hypothetical interaction: A type of bird feeds on insects that live on a specific type of tree. The insects are the bird's prey, and the tree is a source of shelter and food for both the birds and insects. A decrease in insects due to a severe drought would most likely result in:
- A) An increase in the bird population
- B) A decrease in the bird population
- C) No change in the bird population
- D) The bird population migrating to a new habitat
If a lion hunts a zebra, what type of interaction is taking place?
- A) Mutualism
- B) Commensalism
- C) Parasitism
- D) Predation
Flowers and bees have a mutualistic relationship. What does this mean?
- A) The bees are harmful to the flowers.
- B) Both the bees and flowers benefit from the relationship.
- C) The flowers are harmed, and the bees are helped.
- D) The bees eat the flowers.
Consider a species of fish that lives in a coral reef and eats algae from coral. How does this affect the coral?
- A) The coral is helped.
- B) The coral is harmed.
- C) The coral is neither helped nor harmed.
- D) The fish leaves the coral reef.

Changes in the environment or availability of resources can impact the strength or type of interactions among organisms. For example, if a key food source disappears, the animals that depend on it will likely struggle and experience decreased population growth.

Remember to consider the impact on both interacting species when evaluating interactions.
Environmental factors like drought or temperature shifts can alter interactions.
Focus on identifying whether organisms are helped, harmed, or neither in a particular interaction.