Final answer:
Examples 1), 2), and 4) illustrate evolution through natural selection, where environmental pressures lead to adaptations, and 3) exemplifies artificial selection, where humans breed organisms with desirable traits.
Step-by-step explanation:
Examples 1), 2), and 4) describe potential evolution by natural selection, while example 3) describes evolution by artificial selection. In 1), non-native grasses evolving seeds of similar size and weight to native ones to compete for the same resources is an instance of natural selection. In scenario 2), birds developing longer beaks to access food sources is another example of natural selection, where adaptations beneficial for survival and reproduction are favored. In example 4), a virus evolving resistance to antiviral medication exemplifies natural selection because only those viruses with resistant traits survive and reproduce.
However, in the third example, where a farmer selectively breeds cows with high milk production, artificial selection is at play. Artificial selection is a process where humans intentionally select and breed individuals with desirable traits to produce offspring with those specific traits. It differs from natural selection in that humans guide the selection process rather than environmental pressures.