B4.2 Ecological niches

Form and function—Ecosystems
Standard level and higher level: 4 hours

Guiding questions

Linking questions

• What are the advantages of specialized modes of nutrition to living organisms?
• How are the adaptations of a species related to its niche in an ecosystem?

• What are the relative advantges of specificity and versatility?
• For each form of nutrition, what are the unique inputs, processes and outputs?

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B4.2.1—Ecological niche as the role of a species in an ecosystem

Include the biotic and abiotic interactions that influence growth, survival and reproduction, including how a species obtains food.

B4.2.2—Differences between organisms that are obligate anaerobes, facultative anaerobes and obligate aerobes

Limit to the tolerance of these groups of organisms to the presence or absence of oxygen gas in their environment.

B4.2.3—Photosynthesis as the mode of nutrition in plants, algae and several groups of photosynthetic prokaryotes

Details of different types of photosynthesis in prokaryotes are not required.

B4.2.4—Holozoic nutrition in animals

Students should understand that all animals are heterotrophic. In holozoic nutrition food is ingested, digested internally, absorbed and assimilated.

B4.2.5—Mixotrophic nutrition in some protists

Euglena is a well-known freshwater example of a protist that is both autotrophic and heterotrophic, but many other mixotrophic species are part of oceanic plankton. Students should understand that some mixotrophs are obligate and others are facultative

B4.2.6 – Saprotrophic nutrition in some fungi and bacteria

Fungi and bacteria with this mode of heterotrophic nutrition can be referred to as decomposers.

B4.2.7—Diversity of nutrition in archaea

Students should understand that archaea are one of the three domains of life and appreciate that they are metabolically very diverse. Archaea species use either light, oxidation of inorganic chemicals or oxidation of carbon compounds to provide energy for ATP production. Students are not required to name examples.

B4.2.8—Relationship between dentition and the diet of omnivorous and herbivorous representative members of the family Hominidae

Application of skills: Students should examine models or digital collections of skulls to infer diet from the anatomical features. Examples may include Homo sapiens (humans), Homo floresiensis and Paranthropus robustus.

NOS: Deductions can be made from theories. In this example, observation of living mammals led to theories relating dentition to herbivorous or carnivorous diets. These theories allowed the diet of extinct organisms to be deduced.

B4.2.9—Adaptations of herbivores for feeding on plants and of plants for resisting herbivory

For herbivore adaptations, include piercing and chewing mouthparts of leaf-eating insects. Plants resist herbivory using thorns and other physical structures. Plants also produce toxic secondary compounds in seeds and leaves. Some animals have metabolic adaptations for detoxifying these toxins.

B4.2.10—Adaptations of predators for finding, catching and killing prey and of prey animals for resisting predation

Students should be aware of chemical, physical and behavioural adaptations in predators and prey.

B4.2.11—Adaptations of plant form for harvesting light

Include examples from forest ecosystems to illustrate how plants in forests use different strategies to reach light sources, including trees that reach the canopy, lianas, epiphytes growing on branches of trees, strangler epiphytes, shade-tolerant shrubs and herbs growing on the forest floor.

B4.2.12—Fundamental and realized niches

Students should appreciate that fundamental niche is the potential of a species based on adaptations and tolerance limits and that realized niche is the actual extent of a species niche when in competition with other species.

B4.2.13—Competitive exclusion and the uniqueness of ecological niches

Include elimination of one of the competing species or the restriction of both to a part of their fundamental niche as possible outcomes of competition between two species.

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