Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• A niche is the role of a species in a community • It includes habitat, activity, feeding, reproduction, and biotic and abiotic interactions • Cormorants and shags illustrate different niches through diet and behaviour despite similar habitat
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Learning objective
• Oxygen availability shapes microbial niches and respiration strategy • Obligate aerobes require oxygen, such as Mycobacterium tuberculosis • Obligate anaerobes are poisoned by oxygen; facultative anaerobes such as E. coli can switch pathways
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Learning objective
• Photoautotrophs use light energy to make organic molecules from carbon dioxide • Plants, algae, and cyanobacteria contain photosynthetic pigments • Cyanobacteria were early oxygen-producing photosynthetic organisms
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Learning objective
• Holozoic nutrition is heterotrophic feeding by ingestion of organic matter • Food is digested internally, absorbed, and assimilated • Herbivores, carnivores, and omnivores are consumers with holozoic nutrition
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Learning objective
• Mixotrophs combine autotrophic and heterotrophic nutrition • Euglena photosynthesizes using chloroplasts and can ingest bacteria by phagocytosis • Mixotrophy may be obligate or facultative, including some plankton and symbioses
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Learning objective
• Saprotrophs secrete enzymes onto dead organic matter and absorb digestion products • Many fungi and bacteria are saprotrophic decomposers • Saprotrophs recycle inorganic nutrients, but energy is lost as heat through respiration
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Learning objective
• Archaea include photoheterotrophic, chemoautotrophic, and heterotrophic nutrition • Halobacteria use light-driven ion pumps rather than oxygenic photosynthesis • Methanogens and hydrogen-dependent archaea illustrate chemosynthesis and anaerobic niches
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Learning objective
• Incisors slice, canines tear, and premolars and molars grind food • Gorillas and Paranthropus robustus have robust jaws and large grinding teeth for tough vegetation • Humans have smaller canines, smaller molars, and more gracile skulls linked to omnivorous diet
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Learning objective
• Herbivores have adaptations such as chewing mouthparts, aphid stylets, or detoxifying gut bacteria • Plants resist herbivory with spines, stinging hairs, or toxic compounds • Examples include cacti, stinging nettles, deadly nightshade, oleander, and cassava
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Learning objective
• Predators use binocular vision, specialized senses, speed, stealth, or venom to find and kill prey • Prey use wide fields of view, camouflage, mimicry, armour, aposematic colouration, or toxins • Examples include peregrine falcons, hedgehogs, chameleons, coral snake mimicry, poison dart frogs, and bombardier beetles
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Learning objective
• Forest strata create intense competition for light from canopy to ground layer • Canopy trees, lianas, epiphytes, and strangler figs reach light using different forms • Shade-tolerant plants may have large leaves, different pigments, bright flowers, or strong scent
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Learning objective
• Fundamental niche is where a species could live based on adaptations and tolerance limits • Realized niche is where it actually lives after biotic and abiotic interactions • Competition, predation, mutualism, dispersal, and climate can narrow realized niches
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Learning objective
• Competitive exclusion occurs when one species outcompetes another for the same limiting resource • Niche overlap increases interspecific competition • Gause's Paramecium experiments showed P. aurelia excluding P. caudatum in mixed culture
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