Oxygen and carbon dioxide move across a cell membrane due to diffusion. Diffusion is a passive process as it requires no energy to move particles down the concentration gradient.
Answer: One of the characteristics used to place organisms into kingdoms is their ability to make food. Other characteristics used are the cell structure that is whether prokaryote or eukaryote, absence or presence of cell wall, presence or absence of other organelles, cellularity may also be used such as whether unicellular or multicellular, and lastly the mode of nutrition such as whether heterotrophs or autotrophs, e.t.c
Catastrophism is associated with major changes that occurs once at a time in a species while gradualism is associated with tiny changes that occurs over a period of time that finally contributes a bigger evolutionary change.
<u>Explanation:</u>
The events that are sudden, short-lived, violent occurring worldwide thereby changing the shape of the Earth is Catastrophic. This process is opposite to contrast to gradualism which is also called as uniformitarianism. This process is associated with slow and also incremental changes. Erosion is the best example for this process.
The formation of major mountain chains and great floods are some of the examples of Catastrophism. Both are associated with the changes that occurs in a species by the time taken for the changes determines whether it is Catastrophism or gradualism.
Answer:
because our solar-system's vantage point is inside one of the galaxy's spiral arms. When we observe the Milky Way, we usually are looking toward the center of the galaxy, about 25,000 light-years away.