Final answer:
Fossils provide essential evidence for the phylogenetic tree by showing evolutionary progression and common ancestry among different species. Genomic 'fossils' from DNA analysis bolster this evidence by elucidating relationships between extinct and extant species.
Step-by-step explanation:
Fossils are crucial in supporting the evidence of the phylogenetic tree as they provide a record of the gradual evolutionary changes that have occurred over millions of years. By determining the age and categorizing fossils from all over the world, scientists are able to understand when these organisms lived relative to each other.
For instance, detailed fossil records, such as those of humans and horses, indicate the progression of evolution and help scientists see the common ancestry among species, like the similarities observed in the morphology of whale flippers and bird and mammal appendages.
While DNA from organisms older than about 10,000 years is often too damaged for direct analysis, researchers use the sequences from existing species to reconstruct the DNA of long-gone ancestors.
This genomic data supports the phylogenetic tree by providing a basis for the theoretical sequencing of genes from ancient bacteria, helping to understand when significant evolutionary developments such as the diversification of photosynthetic organisms occurred.
Nevertheless, there are challenges in interpreting the fossil record due to incomplete preservation. Still, instances like the evolving suture patterns in ammonite shells over time provide compelling evidence for the evolutionary theory and support the phylogenetic tree by showing developmental similarities between young individuals and their ancestors.