The following diagram shows an oceanic food web. At what trophic level do the killer whales primarily feed?

The killer whales primarily feed on the secondary consumers in the oceanic food web.

Explanation:

Killer whales are the tertiary consumers and occupy the highest position in the ocean food web. They are predating carnivores and feed on secondary consumers like other fishes, marine animals like leopard seals, sea turtles, dolphins, sea birds, etc. These secondary consumers in turn feed on primary consumers like zooplanktons, small fishes etc which feed on the primary producers like phytoplanktons. The energy flow is highest at the primary producer level and decreases as it goes up to the consumer levels.

interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle