Final answer:
True, natural selection is constrained by the laws of physics and chemistry, as it can only act on existing genetic variations within a population and is subject to the physical realities of biological systems.
Step-by-step explanation:
The statement that natural selection is limited in its effect on phenotypes by the laws of physics and chemistry is true. Natural selection can only act on the variation present within a population, which is constrained by existing genetic variance and the laws that govern how biological systems operate.
For example, a phenotype that confers a reproductive advantage may still be selected against if it is associated with a fatal genetic condition that prevents reproduction.
Moreover, because natural selection acts on whole organisms, not individual alleles, beneficial alleles can be lost and detrimental alleles can be retained due to the overall genetic makeup of the organisms carrying them.
Additionally, evolution acts on the phenotype, the observed characteristics driven by the genotype, but it is limited by the genotype's ability to produce variation. There might be physical or chemical constraints that prevent certain beneficial phenotypes from ever arising.
Thus, while natural selection drives populations toward better adaptation, it can be impeded by physical limitations rooted in an organism's genetic material and how it interacts with the environment.
Finally, natural selection is influenced by linkage disequilibrium, where certain alleles are physically close on the genome and tend to be inherited together.
This can lead to the retention of less optimal alleles if they are linked to beneficial ones, making the process of selection less efficient and more complex.