Habitats and Adaptations

Habitats have distinct physical and chemical characteristics that support biodiversity.

Examples:

Sand Dunes (Marram Grass):

• Drought tolerance
• Salt tolerance
• Deep roots for stability
• Curled leaves to reduce transpiration
• Sand-binding to prevent erosion
• Rhizomes for anchorage and spread

Mangrove (Rhizophora Apiculata):

• Salt tolerance
• Roots adapted to soft sediment (e.g. stilt roots)
• Flood and wave tolerance
• Propagation of floating seeds

Abiotic Factors Affecting Distribution

Abiotic factors shape the distribution of species and the range of tolerance.

Examples:

• Temperature
• Light
• Salinity
• Water clarity
• pH

Coral Reefs

Corals: tiny invertebrate animals with calcified skeletons, who provide habitat and ecosystem services.

Ideal Conditions:

• Shallow, clear water
• Stable pH
• Moderate salinity
• Warm temperatures

Biomes

Biomes are large ecological regions defined by abiotic factors, especially temperature and precipitation.

Hot Desert Biome Species (e.g. Gila Monster):

• Low metabolic rate
• Fat storage in tail
• Bumpy skin for moisture retention
• Powerful jaw and venom for defense

Tropical Rainforest Biome Species (e.g. Amazon Water Lily):

• Waxy, large leaves repel water
• Strong fragrance to attract pollinators
• Unique roots adapted to nutrient-poor, muddy soils

Ecological Niches: What is a Niche?

• A niche is the functional role of a species in an ecosystem
• Includes all biotic (e.g. competition, behavior) and abiotic (e.g. habitat, temperature) interactions
• Example: Bird niche = habitat + food source + predator interactions

Modes of Respiration

Organisms use different forms of respiration that can define their niche:

• Obligate Anaerobes: Cannot survive in oxygen (e.g. some gut bacteria)
• Obligate Aerobes: Require oxygen (e.g. animals, fungi)
• Facultative Anaerobes: Can respire with or without oxygen (e.g. yeast)

Modes of Nutrition

Organisms are either autotrophs (self-feeding) or heterotrophs (feeding on others):

Autotrophic:

• Photosynthesis: Light → organic molecules (plants, algae, cyanobacteria)
• Chemosynthesis: Chemical energy → organic molecules (some archaea)

Heterotrophic:

• Holozoic: Ingest and internally digest food (animals)
• Saprotrophic: Secrete enzymes and externally digest (fungi, bacteria)
• Mixotrophic: Use both methods (e.g. Euglena, dinoflagellates, coral)

Archaea:

• Highly diverse
• Includes phototrophs, lithotrophs (inorganic sources), and organotrophs

Dentition and Diet in Hominidae

Diet reflected in teeth structure:

• Herbivores: Larger molars, thicker enamel
• Carnivores: Narrow jaws, sharper teeth
• Humans show a shift to omnivory (e.g. Paranthropus vs. Homo)

Adaptations for Herbivory

Plant defenses:

• Spines/thorns
• Toxic/bitter chemicals

Herbivore traits:

• Specialized mouthparts (mandibles)
• Symbiotic gut bacteria
• Detoxification abilities
• Grinding molars

Adaptations for Predation and Avoidance

Prey adaptations:

• Camouflage, mimicry, shells
• Behavioral (e.g. playing dead)

Predator adaptations:

• Sharp teeth/claws
• Venoms and toxins
• Coordinated hunting strategies

Plant Adaptations for Light

Plants evolve structures for light capture:

• Lianas: Climbs toward sunlight
• Emergent Trees: Extends above canopy
• Understory Plants: Large leaves
• Shade-Tolerant Plants: Broader pigment range
• Epiphytes: Grows on other plants

Fundamental vs. Realised Niches

• Fundamental Niche: Where an organism could live


• Realized Niche: Where an organism actually lives due to competition

Competitive Exclusion

Competitive Exclusion Principle: No two species can share the same niche.

Outcomes:

• One outcompetes the other → local extinction


• Resource partitioning → species divide resources