2.9.1Inquiry Process
Habitats — IB Biology HL Revision Notes & Topical Questions
5 min read 4 parts Lesson 92 of 160
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 4Describing a Habitat
A habitat is described by where it is and by what kind of ecosystem it is.
Habitat
- Habitat The place where an organism lives, which supplies the food, shelter and physical conditions that the species needs to survive and reproduce.
Community
- Community All the populations of different species living together in one habitat;
- a single habitat therefore contains many species interacting with one another.
Location
- Location A habitat can be named by where it is on Earth, for example a polar habitat at the Arctic or Antarctic, a coastal strip or a mountain slope.
Ecosystem type
- Ecosystem type A habitat can also be named by its general type,
- such as grassland, desert, wetland or woodland,
- and the same type may occur on several continents.
Abiotic setting
- Abiotic setting Non-living conditions such as light, temperature, water, salinity, pH and oxygen define a habitat and decide which species can live there.
| Description used | Example habitat | What it tells you |
|---|---|---|
| Geographical location | Arctic polar habitat | Where on Earth the habitat is found |
| Ecosystem type | Grassland (prairie or savannah) | The general structure and dominant plants |
| Both together | North American grassland | Location and ecosystem type combined |
Part 2 of 4Marram Grass on Sand Dunes
Marram Grass on Sand Dunes
Challenges
- Challenges Dune sand drains quickly, the air is dry and windy, salt spray is common and nutrients are scarce,
- so water is hard to obtain and easy to lose.
Rolled leaves
- Rolled leaves Rolling the leaf traps a pocket of humid air inside and reduces the surface exposed to wind,
- so the water vapour gradient out of the leaf is smaller.
Sunken stomata and hairs
- Sunken stomata and hairs Stomata sit in pits lined with tiny hairs that trap water vapour, raising local humidity and slowing the loss of water by evaporation.
Thick waxy cuticle
- Thick waxy cuticle A waterproof layer on the outer surface of the leaf greatly reduces evaporation through the epidermis itself.
Xerophyte
- Xerophyte A plant adapted to survive in dry conditions;
- marram grass is a standard example because several features all reduce transpiration.
Part 3 of 4Mangroves in Salt Water
Challenges
- Challenges Mangrove swamps are tropical coastal habitats often flooded by sea water,
- so they combine high salinity, little fresh water and very low oxygen in the mud.
Aerial roots
- Aerial roots Parts of the root system rise above the water or mud so that tissues can take in oxygen for aerobic respiration,
- which submerged roots cannot do.
Red mangrove
- Red mangrove Prop roots support the tree in soft mud, and root cells exclude salt so that fresh water can be taken up without losing water by osmosis.
Black mangrove
- Black mangrove Pneumatophores grow upwards out of waterlogged soil to collect air, and salt taken up is excreted through salt glands on the leaves.
Osmotic risk
- Osmotic risk Sea water has a higher solute concentration than root cells, so unprotected roots would lose water by osmosis instead of gaining it.
| Feature | Marram grass | Mangrove |
|---|---|---|
| Main problem | Water shortage | Salt and lack of oxygen |
| Key adaptation | Rolled leaf, sunken stomata | Aerial roots, salt exclusion or excretion |
| Overall effect | Reduces water loss | Allows respiration and water uptake |
Part 4 of 4Exam Checklist & Tips
2.9.1 – Key Points for the Exam
- Habitat The place where an organism lives.
- Community All the populations of different species living together in one habitat.
- Abiotic factor A non-living part of the environment, such as temperature, light or salinity.
- Xerophyte A plant adapted to survive in dry conditions.
- Pneumatophore A root that grows upwards out of waterlogged soil to take in air.
Common Mistakes
- Confusing a habitat with a niche or an ecosystem; a habitat is simply where an organism lives.
- Writing that marram grass has no stomata; it has stomata, but they are sunken in pits that trap humid air.
- Saying mangroves absorb salt water freely; red mangroves exclude salt and black mangroves excrete it.
- Describing adaptations without linking each one to the abiotic factor that selects for it.
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