Answer:
The force of surface tension in the lungs is so great that without something to reduce the surface tension, the airways would collapse after exhalation, making re-inflation during inhalation much more difficult and less effective. Collapse of the lungs is called alectasis.
Explanation:
Answer: D
Explanation:
Because the heavy plow and its traction team was expensive tool and individual peasant farmers were not able to own it, it brought collective ownership and patterns of communal agriculture and communal animal husbandry.
The heavy plough required more energy to pull this resulted several families coming together to pool their oxen to form a team large and strong enough to pull the heavy plow. The resulting “ox-gangs” became an important social group.
Answer:
Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes, which is less than one percent of the total are slightly different between people.
Explanation:
I believe the biggest space mission of the twenty-first century will be a manned mission to Mars, and the colonization that follows. This is the stated goal of several nations, companies, and individuals, all with considerably deep pockets. This mission will not only be a huge leap forward in space exploration, it will usher in a new era in human history in which the human race is an interplanetary civilization, a natural milestone as humanity continues to progress and advance.
Significant challenges are many and overwhelming. In terms of getting to mars, we need efficient, powerful propulsion systems and a spaceship that can not only accommodate a full crew for a mission that would likely last years, but withstand the various hazards that a long trip through space and entrance into the Martian atmosphere will entail. In terms of colonization, significant challenges will include establishing efficient and frequent travel/transport between the planets, and in the longer term, the necessity to terraform the planet (make it more like Earth) so that humans can more easily live there.
