Because most but not all 13 yrs olds and older smoke already and they just want to know if you have already smoked before
Independent variable: is the UV light exposure
Control group: people not exposed (sample b)
Dependent variable: skin cancer
Experimental group: (sample A)
Hummingbird predators would not have a food source, therefore competitive exclusion would occur and there'd be a decrease in hummingbird predators. There would also be an increase in the number of the hummingbird's prey since the hummingbird wouldn't be there to consume them. The absence of the species would mess up the rest of the ecosystem
Hey friends
The answer to the question would be A
Hope i helped
~Katie
Answer:
The cell membrane is semi-permeable. It allows some molecules to enter easily inside the cell whereas some molecules are blocked from entering the cell.
Small, polar molecules and hydrophobic molecules enter easily through the cell membrane. But large molecules and ions cannot easily move inside the cell membrane.
A hydrophilic substance like the substance L mentioned in the question enters the cell membrane through the help of carrier proteins. The substance attached to the large protein might enter through active or passive diffusion but it can only enter the cell by attaching to carrier proteins.
