Answer - It is a Great Concern because microbes such as a hydra can consume some of that mercury which then a shrimp can consume that microbes which then transfer into the mouth of a trout which then when humans fish they consume the fish which later we get Mercury poisoning.
Reasoning - There are more concern but these are a few and some reasoning.
Answer:
It becomes something like that
It becomes firm/turgid if it were an animal cell it would've burst but the cell wall prevents it from doing so.
eukaryote is a single celled organism, so that is almost like every organism on earth (except for bacteria). so actually there are many examples
1. bananas
2. algae
3. a spider
4. a lion
5. mushroom
4. tress, grass, flowers, pines....etc
5. humans
6. cancer cells, animal cells, sperm cells, muscle cells, plant cells...etc
5. flies almost every type of fly
6. fish
so yeah you get it almost every organism is a single celled organism :D
(except for bacteria and virus)