Ecosystems, Food Chains, and Food Webs Ecosystem: A community of living things and the non-living components of their environment (things like weather, water, chemicals, etc) interacting as a system. Food Chain: A linear (simple) sequence of organisms within a food web. Food Web: A complex network of living organisms within an ecosystem whose predator/prey interactions are connected within an ecosystem.

- The different levels as you move through a food chain are referred to as trophic levels

Producers Phytoplankton – small autotrophic organisms who obtain their energy through photosynthesis. Photosynthesic – mainly algae in the marine environment. Marine plants are rare due to the salinity of the water. Chemosynthesic – bacteria in the deepest darkest areas of the ocean use methane and sulfur dioxide to create energy.

-Zooplankton – small heterotrophic organisms who feed on phytoplankton or filter nutrients and minerals out of the water. Consumers *Primary**Secondary* -Filter feeders – heterotrophic organisms which feed on zooplankton or other smaller filter feeders. -Can be large (whales/sunfish) or small (amphipods/small fish)

Consumers -Tertiary, quaternary, etc – The larger organisms that you are most familiar with. -Sharks, squid, tuna, swordfish, dolphins, seals.

-Decomposers – usually small bacteria (fungi on land) which break down decaying organic material. -Can also be scavengers, such as crabs and some deep water fish. -They are important in returning nutrients back into ecosystem that would otherwise be lost in the water column. -Zooplankton and filter-feeders are the primary predators of decomposers in marine environments. Decomposers

Affecting one part of a marine food web ends up impacting the population of every other level.

-Why are there so few top level predators and so many zooplankton and phytoplankton? A: Only 10% of an organisms energy is passed on to the next trophic level.

Top-down vs. Bottom-up These are the 2 theories attempting to explain how ecosystem populations change over time Organisms higher up in food webs determine the population size at each level. (ie sharks) Organisms lower in food webs determine the population size at each level. (ie kelp)

*Density-dependent factors – factors in an ecosystem that depend on the population size of the organisms involved. *Density-independent factors – factors in an ecosystem that are not a result of population size.

What factors could possibly affect the populations within an ecosystem? 1)Disease 2) Climate Change (Biggie for marine organisms) 3) Invasive Species 4) Human Impact 5) Death vs. Birth (Carrying Capacity) 6) Predator Prey Interaction 7) Natural Disasters 8) Immigration vs. emmigration

Carrying Capacity (K) – The maximum size a population can reach before factors force the population to stop growing.

Ecosystems from another perspective

Symbiotic Relationships **Translates to “living with” in Latin** Close interactions between two different biological species

Mutualism – both species involved benefit from the relationship (+,+) -Exchange oxygen and carbon dioxide -Provide a safe place to live zooxanthellae coral

Parasitism – the species performing the action benefits and the other is harmed (+,-) -Juvenile pearl fish swim into anus of sea cucumber to feed on digestive system and gonads Juvenile pearl fish Sea cucumber Anus

Commensalism – one species benefits, and the other species is not affected at all (+,0) -The barnacles hitch a free ride on the whale through nutrient rich waters, while the whale is unaffected.

Altruism – the species performing the action is harmed, and the other benefits (-,+) -This goes against typical evolutionary biology (survival of the fittest) -So why does it happen?

Identify the type of symbiotic relationship exhibited in each of the following examples.

Sea anemone/Hermit crab commensalism

Cleaner shrimp/zebra moray eel mutualism

Clam/Barnacle commensalism

Hermit Crab/egg sacs parasitism

Clownfish/sea anemone mutualism

Remora/shark, ray, turtle commensalism