The answer is natural killer cells.
Natural killer cells are a type of lymphocytes and they are important for the innate immune system. They recognise stressed cells much faster than other immune cells. Their response is rapid and usually only a few days after a viral infection. They also respond to <span>cancer cell </span>formation. While other immune cells can detect only those harmful cells that have specific markers on the surface of the cell membrane, natural killer cells can even detect those cells that miss markers for apoptosis.
The phylogenetic tree is commonly used by biologists to study evolutionary relationships between organisms and their ancestors. To add up, it is a diagram that branches the "phylogeny" of a single organism which could be very significant and determining on how genetically different or similar they are to their ancestors.
Answer:this is definitely a covalent bond
:)