Succession, Shoaling, and Biodiversity Based on the interrelationships among organisms, what makes some organisms more successful than others at surviving?

What is a Shoal? Large numbers of fish of the SAME species and approximately the SAME size. Referred to as a ‘school’ when the group of fish is swimming together in a coordinated way.

Benefits of Shoaling Hydrodynamic efficiency Groups of fish save energy when swimming together Individuals obtain reduction in drag by following in “slip-stream” of neighbors

Benefits of Shoaling Predator avoidance: a) Confusion effect: It is difficult for predators to pick out individual prey from groups b) Many eyes effect as size of group increases, the task of scanning for predators can be spread out

Benefits of Shoaling Foraging Advantages : Time taken to find food is decreased Reproductive Advantages: Provides increased access to potential mates

Examples of shoalers Skipjack tuna and sardines When threatened, sardines form massive “bait balls” of hundreds or thousands! Skipjack tuna forms shoals of up to 50,000!

Types of shoalers Fish can be obligate or facultative shoalers: Obligate – spends all their time shoaling or schooling and may become agitated when separated from the group (examples: tuna, herring, anchovy) Facultative – shoal only some of the time, perhaps only for reproductive purposes (examples: Atlantic cod)

What is Succession? The gradual process of change that occurs in community structure over a period of time Example

Succession As plant communities change the animal communities change.

Succession at Hydrothermal Vents One of the first animal species to inhabit the area around a hydrothermal vent is the tube worm Tevnia. Tevnia is replaced by the larger and faster growing tube worm Riftia. Riftia tubeworms can grow up to two meters long. This adult tubeworm that has been removed from its white tube.

Riftia Tevnia Tevnia are usually white, but this clump of worms is stained brown from iron in the vent fluids. The largest worm in this clump (with more white color) is a different species - a Riftia tubeworm.

Biodiversity Takes into account: Examples: # of different species present Range of habitats and ecosystems Examples: CORAL REEFS High biodiversity w/ many species present SANDY SHORE Low biodiversity w/ few species present

Quadrat A square used in ecology and geography to isolate a sample, usually about 1m2 or 0.25m2 Used to investigate the diversity of organisms in a suitable habitat (example: rocky shore or sandy shore)

Extreme & Unstable Environments Tend to have LOW biodiversity! Example 1: Sand on a reef slope (unstable) Easily dries out Easily eroded by wind and water currents Animals here have to living in sediments in order to survive (Infauna) Worms, clams, sand fleas, crabs, etc. Example 2: Hydrothermal vents (extreme) Extremely high pressure High temperature Few organisms adapted to these conditions Lack of sunlight Bacteria, tube worms, crabs, fish, mussels, clams

Stable & Favorable Environments Tend to have HIGH biodiversity! Example: Coral Reefs Balance between predators and prey (sharks feed on sick & dying; keeps a strong healthy population of small reef fishes) Algae = primary producers (zooanthellae inside coral polyps & algae growing on the reef) Organisms found here: Sharks, groupers, snappers, worms, butterfly fish, urchins, sea stars, algae, corals, anemones, turtles, sponges, etc.

Specialized Niche Generalized Niche Exploit a wider range of food sources Live in wider range of habitats Ex: Tuna Migratory Feed on many different species of fish Narrow range of food requirements Live in specific habitat Example: Butterfly fish Territorial Live closely w/corals and anenomes

Why do habitats with high biodiversity tend to contain narrow ecological niches? Each species has its OWN niche within the ecosystem High biodiversity means that many different species live within one ecosystem. What would happen if the niches overlapped? INTERSPECIFIC COMPETITION and one species will die out! Narrow niches reduce overlap and therefore reduce competition