Koalas are marsupials that are found in eastern Australia. Although their ancestors lived mostly on the ground, modern koalas spend most of their time in eucalyptus trees. This is possible because their hands and feet have
strong claws and opposable digits.
What other adaptation could have helped koalas as they evolved from land dwellers to tree dwellers?

List two new traits (structural or behavioral) that each new species of rat might demonstrate as it adapts to the conditions on two of the four islands. choose only two islands that are described in the lesson. record the island latter and the major habitat feature of the island. then list two new traits each rat subspecies might demonstrate in order to survive the habitat on that island. note: new traits should be unique to that island and be in response to that island’s habitat feature. i cannot remember islands that were names in the lesson so only answer if you have done the lesson (5.13 life science 7b) choose 2 of the islands and describe a structural and a behavioral trait for a rat on each island so 4 total answers, 2 different structurals and 2 different behaviorals, one for each rat for each island

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?