In an Antarctic ecosystem, phytoplankton are the main producers. A
species of zooplankton, called krill, are the primary consumers. To some
extent, fish, penguins, seals, whales, and other animals of the ecosystem
depend on krill to survive. Which of these is a biotic factor in this
ecosystem?
A. the amount of ice at any given time
B. che amount of salt in the ocean water
C. the temperature of the air and water
D. the size of the krill population

Fill in the blank 1. digestion occurs in the small intestine through the action of enzymes. 2. urea, excess water, and other waste materials are eliminated in a water fluid called 3. can cause infections by injecting dna or rna into hosts. 4. the human immune system produces in response to a vaccine, which later can bind to and destroy a pathogen if it invades. 5. are structures that link bone to bone at a joint 6. in the heart, blood flows from the right atrium to the right ventricle, where it is pumped to the the words i can use are: lymphocytes gliding pivot gas urine absorption dermis fulcrum lungs chemical viruses capillary vertebrae esophagus tendons antibodies synapses ligaments kidneys pathogens