Marine Ecology and Evolution: Key Concepts and Relationships Lecture 3

This lecture introduces the principles of ecology and evolution in marine biology, focusing on how biotic and abiotic factors shape marine organisms' behaviors, adaptations, and interactions.
Core idea: ecology examines interactions between living components (biotic factors) and their environment (abiotic factors), and these interactions drive development and evolution.

Ecology examines interactions between organisms (biotic factors) and their environment (abiotic factors).
Biotic factors include all living components (e.g., predators, mates).
Abiotic factors include non-living elements (e.g., salinity, light, substrate).
These factors together drive organismal development and evolution.

Levels discussed: individual, population, community (not ecosystem or biosphere).
A niche is an organism's role, including its diet, habitat, predators, and interactions.
Interactions such as territoriality, predation, commensalism, mutualism, and parasitism help define niches.
Conceptual takeaway: the niche integrates how an organism uses resources and interacts with others, shaping its evolution.

Territoriality aids in resource (food, mates) protection, seen in damselfish, alligators, chimpanzees, and elephant seals.
Aggressive defense (e.g., damselfish) can make organisms vulnerable to predation.
Social structures and territorial spacing influence who competes with whom and how species partition resources.

Predators can be stationary (filter feeders, ambush predators) or active hunters.
Evolutionary pressure from predation shapes prey adaptations.
Starfish are keystone predators that shape entire marine communities.
Implication: removing or changing keystone predators can cascade through the ecosystem altering species composition.

Diet breadth model: abundant food leads to specialization; scarce food leads to a broader diet.
Time in patch model: organisms stay longer in food-rich areas if new food sources are distant.
Optimal foraging: animals balance energy gained vs. energy spent when selecting prey.
Conceptual takeaway: foraging strategies maximize net energy intake, influencing growth, reproduction, and survival.

Escape responses include speed, maneuverability, or seeking refuge.
Some fish (e.g., triggerfish) lodge themselves in crevices for protection.
Practical note: avoidance traits can drive habitat use and microhabitat selection, affecting distribution patterns.

Batesian mimicry: harmless species imitate dangerous ones to avoid predation.
Example: mimic octopus can impersonate multiple toxic species to deter predators.
Crypsis is camouflage; both prey and predators use it to blend with surroundings (e.g., frogfish, rockfish).
Insight: mimicry and camouflage reduce detectability, altering predator–prey dynamics and survival.

Keystone species have a disproportionately large effect on their environment (e.g., starfish as a keystone predator).
Changes to a keystone species can reorganize entire communities and resource webs.

Evolution by natural selection: predation pressure, niche definition, and interactions drive adaptive changes.
Community ecology: interactions (predation, mutualism, competition) shape biodiversity and ecosystem function.
Real-world relevance: understanding these concepts informs conservation, fisheries management, habitat protection, and responses to environmental change.
Hypothetical scenario: if a keystone predator (e.g., starfish) declines, prey populations may overgrow and alter habitat structure, potentially reducing biodiversity and changing nutrient cycling.
Foundational link: energy flow and trophic interactions underpin much of marine ecology; for example, changes in diet breadth or foraging efficiency can influence growth, reproduction, and population dynamics.

Ethical dimension: responsible stewardship of marine ecosystems requires recognizing interconnected roles (predators, prey, engineers like keystone species).
Practical implications: data on foraging and predation informs marine resource management, protected areas, and restoration efforts.
Philosophical reflection: studying the balance of interactions highlights the complexity and interdependence of life in marine environments.

Ecology links biotic and abiotic factors to organismal behavior and evolution.
The ecological hierarchy (individual, population, community) frames how organisms interact within their niches.
Territoriality, predation, and various interspecies interactions define niches and community structure.
Foraging theory explains how organisms optimize energy intake through diet breadth, patch choice, and profitability of prey.
Predation drives adaptation; keystone species like starfish can disproportionately shape communities.
Camouflage and mimicry reduce predation risk and influence predator–prey dynamics.
Understanding these concepts supports conservation and sustainable management of marine systems, with ethical considerations about human impact and stewardship.

Ecology: study of organism-environment interactions.
Biotic factors: living components affecting ecosystems.
Abiotic factors: non-living physical and chemical components.
Niche: organism’s functional role in its environment.
Territoriality: defense of space/resources.
Mutualism, Commensalism, Parasitism: interaction outcomes for the species involved.
Batesian mimicry: harmless species mimic harmful ones.
Crypsis: camouflage to blend with surroundings.
Keystone species: species with outsized influence on ecosystem structure.