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3.7.6Additional lessons

Populations: Intraspecific Relationships — IB Biology SL Revision Notes & Topical Questions

5 min read 5 parts Lesson 87 of 142

📚 IB Biology SL Hub / Topical Revision
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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.
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Part 1 of 5Intraspecific Relationships

Meaning
  • Meaning Intraspecific means within one species, so these are interactions between members of the same species.
Cooperation
  • Cooperation Individuals benefit from working together, as in group hunting or shared defence.
Competition
  • Competition Individuals use the same limited resources, so one benefits at the expense of another.
Strength
  • Strength Because members of a species have identical needs, intraspecific competition is often intense.

Part 2 of 5Cooperation

Cooperation
Orcas
  • Orcas They hunt together, which increases the chance of catching prey that one animal could not take alone.
Meerkats
  • Meerkats Roles are shared, so some individuals watch for predators while others forage or care for young.
Ants
  • Ants Large groups build nests and provide food for developing young.
Benefit
  • Benefit Cooperation improves survival and reproductive success of the group.

Part 3 of 5Competition

Plants
  • Plants Plants compete for light, water, minerals and space.
Animals
  • Animals Animals compete for food, mates and territory.
Red deer
  • Red deer Males fight for access to females, so the dominant males gain more matings.
Robins
  • Robins They defend territories aggressively to protect food supply.
Hidden competition
  • Hidden competition Competition does not require visible conflict, since food eaten by one individual is no longer available to another.
ResourceOrganismExample
LightOak treesNeighbouring trees compete for light
FoodRobinsTerritory defended to secure food
MatesRed deerMales fight for access to females

Part 4 of 5Effects on Populations

1
As density rises, competition for resources increases.
2
Some individuals obtain fewer resources and may die or fail to reproduce.
3
Individuals best adapted to competition leave more offspring, which is natural selection.
4
This density-dependent effect helps to keep populations near the carrying capacity.

Part 5 of 5Exam Checklist & Tips

3.7.6 – Key Points for the Exam

  • Intraspecific Between members of the same species.
  • Cooperation An interaction in which individuals benefit from working together.
  • Competition Use of the same limited resource by two or more individuals.
  • Territory An area defended by an animal to secure resources.

Common Mistakes

  • Mixing up intraspecific and interspecific.
  • Saying competition always involves fighting.
  • Thinking cooperation means every individual benefits equally.
  • Forgetting that competition reduces the survival of some members of the population.

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