On the nature trail at pennsylvania state university, tall pine trees have reduced the amount of sunlight that reaches the forest floor. while hardwood trees flourish in shaded regions, pine seedlings require sunlight. ecologists believe that over time, the hardwood trees will replace the pine trees. this scenario is an example of which concept? a. competition b. succession c. natural selection d. cross pollination

Aflashlight battery is an example of a) potential energy b) kinetic energy c) thermal energy d) solar energy

Guinea pig coat color is determined by a single gene. the allele for black coat color is dominant to brown. in a cross between twoblack-haired guinea pigs, 20 offspring are born. if both parents were heterozygous, probability would predict that approximately howmany of the 20 offspring would have brown hair?

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?