Larger eukaryotes such as vertebrates contain much more noncoding DNA compared to smaller eukaryotes such as yeast. This means every time a vertebrate cell divides, it must spend more time and more energy replicating a large genome. What may this potentially high cost of having a bigger genome suggest about the selective pressures acting on organisms with smaller and larger genomes?

non-coding DNA sequences confer a key adaptive advantage associated with the ability to control a higher number of transcriptional programs  

Explanation:

A selective pressure can be defined as any type of external agent that affects an organism with certain genetic/phenotypic features, thereby exhibiting differential survival. Some examples of phenotypic selective pressure features include resistance to pollutants, diseases, illnesses, climate change, etc, while genetic selective features include, among others, a higher number of genes, higher non-coding DNA information, etc. Non-coding DNA sequences were originally thought to be selfish junk DNA without function. However, it has recently been shown that non-coding DNA sequences have critical regulatory roles, thereby it is expected that multicellular organisms with bigger genomes contain a higher amount of these sequences in order to modulate more transcriptional programs compared to organisms with smaller genomes, thereby being able to produce a higher number of cell types.

"a scientist studying a whale and its surroundings would need to understand the structure of atoms in case something was negatively affecting the whale or its surroundings."

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answer: after carbon dioxide enters the leaf through stomata it moves into the mesophyll cells where photosynthesis occurs and glucose is constructed. respiration occurs when glucose (sugar produced during photosynthesis) combines with oxygen to produce useable cellular energy.

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