Tertiary consumers are organisms that primarily eat secondary consumers and are typically at the top of the food chain in their respective ecosystems. Based on the provided list of organisms, the following can be identified as tertiary consumers:
- Seagull - Depending on the specific diet, seagulls can be tertiary consumers, particularly if they eat secondary consumers like fish or squid.
- Penguin - Penguins can also fit into the tertiary consumer category, especially when consuming prey like fish that have higher trophic levels.
- Elephant seal - These can be considered tertiary consumers when they eat fish or squid, which may be secondary consumers.
- Leopard seal - They are known to eat penguins and other seals, making them tertiary consumers.
- Blue whale - While primarily a filter feeder that consumes krill, blue whales can be classified as tertiary consumers in some contexts, especially since they are at the top of their food web.
- Killer whale (Orca) - These are apex predators and eat various animals, including seals and fish, classifying them as tertiary consumers.
- Squid - Generally, squids can be considered tertiary consumers, especially when consuming fish or other smaller marine animals.
The following organisms are not tertiary consumers:
- Fish - Typically considered secondary consumers or primary consumers depending on the type of fish.
- Krill - Usually classified as primary consumers as they feed on phytoplankton.
- Crab - Generally considered secondary consumers, depending on what they are feeding on.
- Seaweed - A primary producer, not a consumer.
- Phytoplankton - Primary producers, not consumers.
- Zooplankton - Primary consumers, typically feeding on phytoplankton.
In summary, the tertiary consumers from your list are:
- Seagull
- Penguin
- Elephant seal
- Leopard seal
- Blue whale
- Killer whale
- Squid