2.9.4Additional lessons
Nutrition: Adaptations of Organisms — IB Biology SL Revision Notes & Topical Questions
5 min read 6 parts Lesson 48 of 142
Part 1 of 6Adaptations in Animals
Carnivore teeth
- Sharp canines and carnassial teeth grip prey and shear flesh, as in cats and dogs.
Herbivore teeth
- Broad, flat molars grind tough plant material, and many lack upper incisors and use a horny pad.
Gut microbes
- Herbivores such as cattle host microorganisms that digest cellulose in a specialised stomach or caecum.
Filter feeding
- Baleen whales strain small organisms from the water using plates in the mouth.
Behaviour
- Hunting in groups, stalking and storing food are behavioural adaptations that improve feeding success.
Part 2 of 6Adaptations in Plants and Microbes
Adaptations in Plants and Microbes
Carnivorous plants
- Plants such as the Venus flytrap trap insects to obtain nitrogen in poor soils.
Root nodules
- Nitrogen-fixing bacteria live in root nodules of legumes and supply nitrogen compounds in exchange for sugars.
Fungal hyphae
- Fine hyphae spread through the substrate, increasing surface area for enzymes and absorption.
Vent bacteria
- Chemoautotrophic bacteria at deep sea vents use chemical energy to make organic compounds.
Part 3 of 6Linking Structure to Diet
1
Identify the food source and how it must be captured or processed.
2
Match features such as teeth, gut length or mouthparts to the properties of that food.
3
Explain how the feature increases the chance of obtaining food or absorbing nutrients.
4
State how this improves survival and reproduction, so the feature is favoured by natural selection.
Part 4 of 6Evaluating Adaptations
Evaluating Adaptations
Trade-offs
- A feature that helps with one food source may be less useful for another, so adaptations involve compromise.
Evidence
- Comparing the teeth or gut of related species with different diets supports a link between structure and diet.
Variation
- Individuals vary, and those whose features suit the food supply leave more offspring.
Part 5 of 6Further Examples
Further Examples
Anteaters
- Long sticky tongues and strong claws let them collect ants and termites from nests.
Hummingbirds
- Long beaks and a hovering flight allow them to feed on nectar from flowers.
Fungus-farming ants
- Leaf-cutter ants use leaves to grow a fungus, which they eat;
- this behaviour is an example of an adaptation to obtain food.
Part 6 of 6Exam Checklist & Tips
2.9.4 – Key Points for the Exam
- Adaptation A feature that helps an organism survive and reproduce in its environment.
- Mutualism A relationship in which both species benefit.
- Carnassial teeth Large cheek teeth in carnivores that slice flesh.
- Nitrogen fixation Conversion of atmospheric nitrogen into compounds usable by plants.
Common Mistakes
- Saying that an individual develops a feature because it needs it;
- adaptations arise through natural selection.
- Stating that carnivorous plants do not photosynthesise; they do, and trap prey to get nitrogen.
- Confusing mutualism with parasitism, where only one partner benefits.
- Describing every herbivore gut as the same, ignoring microbial digestion of cellulose.
Last updated:
\n