Why was the evolution of the extraembryonic membranes crucial for colonization of land by the vertebrates? extraembryonic membranes
a. provide nutrients that produce energy for development
b. direct morphogenesis within the embryo
c. give rise to crucial organ systems, like the heart and brain
d. provide an aqueous environment for embryo development

Competition. interaction among organisms that compete for the same natural resource (food, shelter, water, space) in an ecosystem. predation. an interaction in which one organism kills another for food. predator. prey. symbiosis. mutualisum. commensalisum. parasitisum.

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The higher you go up the less oxygen there is 

Cuz i said so. which gives it to b

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.