Final answer:
Heritable traits are encoded in the genetic material and can be passed on to offspring, which means both living and deceased phenotypes can contribute to their offspring's genetics. Variation among offspring is due to different combinations of alleles. Offspring will have a combination of genes that may reflect the sizes of the parents’ beaks or exhibit new variations.
Step-by-step explanation:
If a trait is heritable, it means that it is encoded in an organism's genetic material and can be passed on to their offspring. The offspring will inherit variations of these heritable traits through the genetic material contributed by the parents. In the example provided about beak sizes in birds, assuming beak size is a heritable trait, the offspring would inherit genes that determine beak size from both of their parents. Although two of the original phenotypes have died, their genetic contribution can still be passed to the offspring if they reproduced before dying. It's important to understand that phenotypes are the observable characteristics, and while they are influenced by genetics, the environment can also play a role. Therefore, the offspring's beak sizes will be a result of the genetic combination received from their parents as well as potential environmental influences.
Populations of species share a gene pool, which is a collection of all the gene variants in the species. Heritable traits contained in the genes are passed along to an organism's offspring, ensuring that they belong to the same species and have similar characteristics. However, variation exists among offspring in terms of their characteristics. These variations can be due to different combinations of alleles, which are different versions of a gene. Natural selection can only act on heritable traits, meaning that characteristics such as body strength gained through exercise are not passed down to offspring. Only those traits with a genetic basis can be heritable and thus evolve over time through reproduction.
For the beak size example specifically, the offspring will have a combination of genes determining beak size that may reflect the sizes of the parents' beaks or exhibit new variations due to the genetic recombination during sexual reproduction. This is because only heritable traits that are part of an organism's genetic code can be passed down and potentially subject to evolutionary processes such as natural selection.