Aliens on our planet Alexa Romersa

What are they? Are they rare? Do they live so far away that we would never find them? Are they dangerous? None of the above!

They are plants And some of them are tiny animals called Plankton

Where do they live? Right here

Plankton Microscopic: a cup of seawater contains thousands of these unicellular organisms (sometimes each plankton is only one cell) Primary producers: contain chlorophyll Photosynthesize (use up carbon dioxide and water to produce oxygen and sugar) Bottom of the food chain What they lack in size, they make up for in numbers

All other life in the ocean needs phytoplankton to survive. Plankton are at the base of a complex aquatic food web.

Phytoplankton get their energy directly from the sun using photosynthesis, just like plants. Zooplankton then feed on phytoplankton, and are then eaten by larger zooplankton, fish, larger fish, and so on.

Basically the same food web Small fish Big fish Energy flow

Why so different from land? The 3 rd dimension: depth Watery environment leads to increased mobility They don’t make lifejackets that small Therefore they are tiny Must avoid grazing by zooplankton Must have light and nutrients

Escaping grazers: Flagella Increased mobility to escape zooplankton Silica shells Glass-like armor for protection

Stay afloat Small size So small that water hold them up, like throwing confetti into a pool Gas bladder Little pockets of air inside organism to stay afloat

Abiotic Factors: Temperature, Sunlight, Nutrients Temperature is stable Sunlight only reaches top 20m (euphotic zone) Nutrients are quickly used up in the top 20m Therefore, nutrients are a Limiting Factor

Limiting factors In any particular environment, the growth and survival of organisms depend on the physical conditions.

Environmental factors that affect an organism’s ability to survive in its environment, such as food availability, predators, and temperature, are limiting factors.

Example Water is nutrient poor Plankton cannot photosynthesize Jellyfish starve Sea turtles die

Limiting factors affect phytoplankton population, which in turn affect zooplankton, then jellyfish, then fish, then sharks Every trophic level is affected if phytoplankton are out of commission because of the one way flow of energy

Marine Trophic levels