Sun as Energy Source
The sun is the primary source of energy for almost all life on Earth.
Energy enters ecosystems through photosynthesis predominantly conducted by green plants, termed producers or autotrophs.
Energy Dynamics in Ecosystems
Understanding food chains, food pyramids, and food webs is essential as they illustrate how energy flows through different trophic levels.
Trophic pyramids feature a wide base due to high biomass at the producer level, decreasing as we progress to higher levels (i.e., primary consumers to top predators).
Top predators are rare due to low biomass availability at those trophic levels, complicating food webs and feeding interactions.
Species Interaction Strength
Not all species in ecosystems have equal feeding interactions; some species exhibit strong connections while others are weak links.
Keystone Species: Species whose impact on a community or ecosystem is disproportionate relative to their abundance or size.
Example: Pacific Sea Otters
Historically hunted to near extinction, their numbers rebounded after hunting bans were implemented in 1911.
They play a crucial role in maintaining the health of kelp forest ecosystems by controlling sea urchin populations.
Excessive sea urchins, unchecked by otters, lead to significant kelp loss, demonstrating a phenomenon known as a trophic cascade.
Trophic Cascade Example
Without sea otters, sea urchin populations expand, causing kelp forests to decline.
The return of sea otters leads to the decline of sea urchins, allowing kelp forests to flourish.
Similar dynamics observed with Yellowstone Wolves and elk populations.
Transition to Competition and Disturbance
Shift in focus to how competition and disturbance shape ecological communities, particularly with corals as a case study.
Coral Reef Ecosystems
Coral reefs form in warm, shallow, nutrient-poor waters and are among the most productive ecosystems on Earth.
Coral comprises both animal (cnidarians) and plant (algae) components, allowing for unique symbiotic relationships and energy production through photosynthesis.
The balance of oxygen production by the plant and carbon dioxide release by the animal creates a mutually beneficial relationship.
Ecological Interactions
Corals compete intensely for sunlight, leading to phenomena such as competitive dominance.
Over time,