Answer: C. 30 - 50 million years ago
Explanation:
Fossils found in layer Y formed 30 million years ago according to the graph above. Similarly, fossils found in layer Z formed 50 million years ago.
If a fossil (fern fossil) is found between layer Y and layer Z, it means that it formed between the years that the fossils in layers Y and Z formed which is 30 - 50 million years ago.
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Answer: According to Darwin theory of evolution the struggle for existence is considered as major part for competition among living things.
Explanation:
Coexisting species that belong to the same genera compete for same kind of resources for their survival. Some phenotypic variations gives an survival advantage over others. The superior ones dominate the inferior ones and compete for resources. The one who receives the resources like mates, food, shelter, and others the chances of survival also increases considerably.
_______________ reactions transfer energy to the surroundings, usually as heat.
C. Exothermic
Answer:
Humoral immunity involves <u>B cells</u> and<u> recognize antigens or pathogens in the lymph or blood.</u>
Explanation:
Humoral immunity is defined as the immunity which is mediated by several macromolecules presnet in the extracellular fluids such as antibodies, certain antimicrobial peptides, and complement proteins.
Humoral immunity allows to distinguishes two groups of foreign substances. it involves <u>B cells</u> and<u> recognize antigens or pathogens in the lymph or blood. </u>
Humoral immunity begins when an antigens bind to B cells. Interleukins or helper T cells provides a secondary signal to the B cells that activates a B cell and allows B cell proliferation. which roduces produce plasma cells. The plasma cell then produces antibodies which are identical to the specific antigen. The antibodies are the released and circulate through the body, binding to antigens. B cells the further produces memory cellss for future immunity.
So, Humoral immunity involves <u>B cells</u> and<u> recognize antigens or pathogens in the lymph or blood.</u>
