Final answer:
The notion that current species have evolved to look different from their ancestors through 'descent with modification' is true and is a fundamental concept in evolutionary biology, supported by fossil evidence and genetic data.
Step-by-step explanation:
The statement that species today look different from their ancestors because of the concept of descent with modification is true. This evolutionary principle suggests that all organisms are related through descent from a common ancestor and have undergone changes over time. This theory is backed by various forms of evidence, including the fossil record, genetic data, and the observation of homologous and vestigial structures. An example of this evidence can be seen in the fossil of Archaeopteryx, which shares traits with both reptiles and birds, suggesting it is a transitional form and supports the common ancestry and modification over time.