3.8.6Additional lessons
Populations: Intraspecific Relationships — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 15 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.
Section 1 of 5Intraspecific Competition
Competition occurs when a resource is in short supply and one individual's use of it reduces what is available to another.
Meaning
- Meaning Competition between members of the same species for the same limited resources, such as food, water, light, space and mates.
Why it is intense
- Why it is intense Members of one species have identical requirements,
- so they overlap completely in their niche and compete most strongly with each other.
Density-dependent
- Density-dependent The more individuals there are, the greater the competition per individual, so survival and reproduction fall as density rises.
Plants
- Plants Seedlings growing close together compete for light, water and mineral ions, and the weaker ones grow poorly or die.
Animals
- Animals Males may fight for mates, and individuals may compete for territories or for food at a shared site.
Section 2 of 5Intraspecific Cooperation
Intraspecific Cooperation
Group hunting
- Group hunting Wolves and lions hunt together and can take larger prey than a single animal could bring down.
Defence in groups
- Defence in groups Meerkats post sentries,
- and herding animals such as zebra gain protection because predators find it harder to single out one individual.
Rearing young
- Rearing young In some species helpers assist the breeding pair in feeding offspring, which improves survival of the young.
Benefit
- Benefit Cooperation increases the chance of survival and reproduction for group members, even though they still compete for food.
Section 3 of 5Effects on the Population
1
When a population is small, resources are plentiful and there is little competition among its members.
2
As numbers rise, competition for food and space grows and individuals obtain less on average.
3
Reduced resources lower the birth rate and raise the death rate, so growth slows.
4
The population settles near the carrying capacity, where competition and cooperation are in balance.
| Feature | Competition | Cooperation |
|---|---|---|
| Effect on individuals | Reduces resources obtained | Improves chance of food or safety |
| Typical example | Seedlings for light | Wolves hunting prey |
| Effect on population size | Limits it | Can allow larger prey or better defence |
Section 4 of 5Territory and Social Structure
Territorial behaviour
- Territorial behaviour Individuals defend an area that holds food or nest sites, which spaces animals out and reduces direct fighting later.
Dominance hierarchy
- Dominance hierarchy In some groups, a ranking decides which animals feed or breed first, so conflict is settled without repeated fights.
Benefits of limits
- Benefits of limits Territories ensure that the resident has enough resources, but animals without a territory may fail to breed.
Population regulation
- Population regulation Because the number of territories is limited, territorial behaviour keeps the size of a breeding population fairly stable.
Section 5 of 5Exam Checklist & Tips
3.8.6 – Key Points for the Exam
- Intraspecific Occurring between members of the same species.
- Competition Struggle between organisms for a resource in short supply.
- Cooperation Individuals working together for shared benefit.
- Niche The role and requirements of a species in its habitat.
- Territory A defended area that contains resources.
Common Mistakes
- Mixing up intraspecific and interspecific; intra means within one species.
- Saying competition always ends in the death of one individual, when it may only reduce growth or breeding success.
- Forgetting that cooperation can occur among members of the same species that also compete.
- Stating that competition does not occur if resources are abundant.
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