Final answer:
The coastal redwood is the largest life-form in the Northern California coastal forests, reaching over 115 meters tall, while the bristlecone pine is the longest-lived, capable of living for over 4,500 years.
Step-by-step explanation:
The largest life-form and longest-lived life form on Earth found in the coniferous forest along the northern California coast is the coastal redwood (Sequoia sempervirens), also known as the sequoia. These trees, some of the tallest living vascular plants, can grow to over 115 meters tall and, due to their ability to obtain moisture from coastal fog, they thrive in the unique environmental conditions along the coast. In contrast, the oldest life form in these forests is the bristlecone pine (Pinus longaeva), which can live for more than 4,500 years, as found in the White Mountains of eastern California.