3.8.7Additional lessons
Community: Interspecific Relationships — IB Biology HL Revision Notes & Topical Questions
5 min read 4 parts Lesson 16 of 101
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Feeding Relationships
Members of different species in a community interact in ways that affect one or both.
Herbivory
- Herbivory An animal feeds on a plant or part of a plant, usually without killing it at once, so the plant is harmed and the herbivore benefits.
Predation
- Predation A predator kills and eats another animal, the prey, so the predator gains and the prey individual is lost.
Parasitism
- Parasitism A parasite lives on or in a host and takes nutrients from it, usually harming the host without killing it quickly.
Pathogenicity
- Pathogenicity Disease-causing organisms such as bacteria and fungi are parasites that cause illness in the host.
Part 2 of 5Mutualism and Competition
Mutualism and Competition
Mutualism
- Mutualism Both species benefit from the relationship, so each gains something it could not easily obtain alone.
Coral and algae
- Coral and algae Reef-building corals house photosynthetic algae, which supply organic compounds, while the coral provides shelter and nutrients.
Mycorrhizae
- Mycorrhizae Fungal hyphae around plant roots increase water and mineral uptake, and the plant gives the fungus sugars.
Competition
- Competition Two species use the same limited resource, and each reduces the survival or reproduction of the other.
Part 3 of 5Summary of Effects
1
Identify the two species involved and decide what each gains from the interaction.
2
If both gain, the relationship is mutualism; if one gains and the other is harmed, it is feeding or parasitism.
3
If both lose because they use a shared resource, the interaction is interspecific competition.
4
Describe the relationship in terms of benefit or harm to each species, as exam questions require.
| Relationship | Species 1 | Species 2 |
|---|---|---|
| Herbivory | Benefits | Harmed |
| Predation | Benefits | Harmed |
| Parasitism | Benefits | Harmed |
| Mutualism | Benefits | Benefits |
| Competition | Harmed | Harmed |
Part 4 of 5Examples Worth Knowing
Herbivory example
- Herbivory example Caterpillars feeding on leaves reduce a plant's photosynthetic area, and many plants respond with thorns or toxic chemicals.
Predation example
- Predation example Lions hunting zebra remove individuals from the zebra population and influence its age structure and behaviour.
Parasitism example
- Parasitism example Tapeworms live in the gut of vertebrates and absorb digested food, so the host receives less nutrition.
Why it matters
- Why it matters Interactions shape the structure of the community, since the numbers of one species often depend on the presence of others.
Part 5 of 5Exam Checklist & Tips
3.8.7 – Key Points for the Exam
- Interspecific Occurring between members of different species.
- Predation A predator killing and eating prey.
- Parasitism A relationship where the parasite benefits and the host is harmed.
- Mutualism A relationship where both species benefit.
- Herbivory Consumption of plant material by an animal.
Common Mistakes
- Saying a parasite quickly kills its host, since it usually depends on the host staying alive.
- Calling all feeding relationships predation, ignoring herbivory and parasitism.
- Describing mutualism as one-sided, though both partners must gain.
- Confusing interspecific with intraspecific.
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