Ecological Niches and Nutrition in Organisms

Ecological Niches

Definition and Importance of Niches

• Habitat: The location where a species lives.

• Niche: Defined as the role of a species within its habitat, which encompasses various aspects:

  • What the species eats.

  • Which other species depend on it for food.

  • The activity patterns (time of day) of the species.

  • The specific locations within a habitat where the species lives and feeds.

  • The abiotic factors influencing the species (e.g. climate, temperature).

  • The biotic factors interacting with the species (e.g. competition, predation).

• Competitive Exclusion Principle: No two species can occupy the exact same niche in a habitat without incurring direct competition for resources, resulting in one species outcompeting or eliminating the other.

• Subtle Niche Differences: Species may appear to occupy the same niche but often have minor differences in roles, such as feeding at different times or utilizing different resources.

Feeding Niches

• Feeding Location: An example of how niches can differ among species.

Methods of Nutrition

Overview of Nutrition

• All living organisms perform some form of respiration to produce ATP (energy).

• The energy stored in ATP originates from organic molecules (like carbohydrates) transferred during respiration.

• Nutrition methods define how organisms obtain these organic molecules, falling into two main categories:

  • Autotrophy: Organisms that synthesize their own organic molecules from inorganic substances.

  • Photoautotrophs: Use light energy.

  • Chemoautotrophs: Use energy from the oxidation of chemicals.

  • Heterotrophy: Organisms that obtain organic molecules from the tissues of other organisms (e.g. animals).

Photosynthesis

• Photosynthetic organisms convert carbon dioxide into organic molecules (carbohydrates) using light energy through pigments like chlorophyll, making them producers.

• Importance of Photosynthesis: It bridges non-living matter and living organisms, releases oxygen for aerobic respiration, and sustains food chains.

• Examples of photosynthetic organisms:

  • Terrestrial and aquatic plants.

  • Algae (both single-celled and multicellular).

  • Photosynthetic bacteria (e.g., cyanobacteria).

Holozoic Nutrition

• Definition: A type of heterotrophic nutrition involving direct ingestion, digestion, absorption, and assimilation of organic molecules.

  • Ingestion: The act of eating.

  • Digestion: The breakdown of larger molecules into smaller ones.

  • Absorption: Transport of these molecules into cells.

  • Assimilation: Utilizing these molecules to build cellular structures.

• Example Organisms: Most animals; different from those that exhibit external digestion (e.g. house flies).

Mixotrophs

• Organisms utilizing multiple nutritional methods:

  • Obligate Mixotrophs: Must access both modes of nutrition.

  • Facultative Mixotrophs: Can survive primarily on one method, supplementing with the other.

  • Examples: Euglena (with both autotrophic and heterotrophic capabilities).

Nutrition in Archaea

Overview of Archaea

• Archaea comprise a diverse group of single-celled organisms across three metabolic categories:

  • Phototrophic Archaea: Utilize light for ATP production (e.g., Halobacteria).

  • Chemotrophic Archaea: Include chemoautotrophs and chemoheterotrophs.

  • Heterotrophic Archaea: Obtain carbon compounds from other organisms.

Specific Examples

• Phototrophic Archaea: Halobacteria use bacteriorhodopsin for ATP production, functioning similarly to oxidative phosphorylation but not producing oxygen.

• Chemotrophic Archaea: Gain energy from oxidizing external chemicals (e.g., hydrogen gas, ammonia).

Nutrition in Hominidae: Skills

Overview of Hominid Nutrition

• Hominidae includes humans, chimps, gorillas, orangutans, and gibbons, many of which are omnivores.

• Dietary Specializations:

  • Chimps: Primarily frugivores. Mainly consume fruits but also eat other plants and small mammals.

  • Gorillas: Herbivores focused on leafy vegetation but may occasionally consume insects.

Jaw and Dentition Adaptations

• Dentition Types:

  • Incisors: Chisel-shaped for biting and cutting.

  • Canines: Pointed and strong for holding and tearing.

  • Premolars and Molars: Flat and ridged for grinding tough materials.

• Adaptations reflect dietary needs; e.g. gorillas have strong jaw muscles for tough vegetation while chimps have jaws for softer foods.

Relationship Between Diet and Dentition

• The link between dentition and diet is essential for reconstructing diets of extinct hominids.

• Observations: Fossil teeth can show patterns of wear indicative of dietary habits.

• Example Species: Australopithecus, Paranthropus, and Homo species reveal distinct traits suggesting dietary preferences.

Adaptations of Organisms

Herbivore Adaptations

• Insects: Specialized mouthparts (e.g., stylets to pierce plant tissues for sap).

• Mammals: Grazers (e.g. horses) have flat teeth for grinding; ruminants have complex digestive systems for cellulose breakdown.

• Enzymatic Adaptations: Some animals like proboscis monkeys have gut flora that neutralizes plant toxins.

Plant Adaptations Against Herbivory

• Mechanical Defenses: Structures like thorns and tough bark prevent herbivory.

• Chemical Defenses: Production of toxins or unpleasant tastes to deter herbivores.

Predator and Prey Adaptations

• Predator Adaptations:

  • Chemical adaptations: Venoms to subdue prey (e.g., snakes).

  • Physical adaptations: Enhanced senses (e.g. sight, hearing) for detecting prey, specialized body structures for capturing prey (e.g. cheetah speed).

  • Behavioral adaptations: Ambush and cooperative hunting strategies.

• Prey Adaptations:

  • Chemical defenses: Production of toxins that deter predators.

  • Physical adaptations: Camouflage, mimicry, and tough exoskeletons for protection.

  • Behavioral strategies: Fleeing, grouping, and using warning calls or distracting maneuvers against predators.

Plant Light Harvesting Adaptations

• Structures of leaves and entire organisms that maximize sunlight absorption for photosynthesis:

  • Tall trees maximize access to light above the canopy.

  • Lianas and epiphytes use other trees for vertical growth, gaining sunlight without needing to grow extensively upright.

  • Shade-tolerant plants adapt to low light by evolving specialized pigments and larger leaves for improved light capture.

Competition Between Species

Niche Definitions

• Fundamental Niche: The complete range of conditions and resources a species can theoretically occupy.

• Realized Niche: The actual conditions and resources a species occupies due to interactions (e.g. competition).

Competitive Interactions

• Overlapping niches lead to competition; the outcome can result in:

  • One species outcompeting another (competitive exclusion).

  • Shared resource partitioning, where species adjust to utilize different resources or times.

Competitive Exclusion Example

• Paramecium aurelia vs Paramecium caudatum: Under controlled growth conditions, the former outpositions the latter when competing for resources.

Conclusion

• Understanding niches, competition, and adaptations is crucial in ecology, highlighting the intricate relationships among species and ecosystems that influence survival, adaptation, and evolution.