Fossils can be used to match up rock layers. As organisms change over time, they look different. Older fossils will look different than younger fossils. Some organisms only survived for a short time before going extinct. Knowing what organisms looked like at certain times also helps date rock layers. Some fossils are better than others for this use. The fossils that are very distinct at certain times of Earths history are called index fossils. Index fossils are commonly used to match rock layers. You can see how this works in Figure 2.30. If two rock layers have the same index fossils, then they're probably about the same age.

What key do index fossils play in dating rock layers?

The Glory of Melaka: In the early days, if you were not a pirate or a mosquito, Melaka was not much of a place to live. The land was infertile, just a swampy plain, the river small and sluggish. But it had a sheltered harbor, protected from the monsoons by neighboring Sumatra. Later, the strategic location and deep-water channel close to the coast brought in the bigger vessels of the trade-wind traffic crossing the Indian Ocean. The first to realize the larger commercial potential, as so often throughout the country's subsequent history, were the Chinese. In 1409, under a new directive from Emperor Chu Ti to pursue trade in the South Seas and the Indian Ocean, a Chinese fleet of 50 ships headed by Admiral Cheng Ho called in at Melaka. They made Parameswara an offer he could not refuse: port facilities and an annual financial tribute in exchange for Chinese protection against the marauding Thais. In 1411, Parameswara took the money to Beijing himself, and the emperor gratefully made him a vassal king. Twenty years later, the Chinese withdrew again from the South Seas trade. The new ruler of Melaka, Sri Maharajah, switched his allegiance to the Muslim trading fraternity by marrying into the Muslim faith, wedding the daughter of a sultan in Sumatra. Islam won its place in Malaya not by conquestas had been the case in North Africa and Europebut by trade, dynastic alliances, and peaceful preaching. Bengali peddlers had already brought the faith to the east coast. In Melaka and throughout the peninsula, Islam thrived as a strong, male-dominated religion of individuality, offering dynamic leadership and preaching brotherhood and self-relianceall qualities ideally suited to the coastal trade. At the same time, Sufi mystics synthesized Islamic teaching with local Malay traditions of animistic magic and charisma, though Islam did not become the state religion until Muzaffar Shah became sultan of Melaka (14461459). But the key figure in the sultanate was Tun Perak, bendahara (prime minister) and military commander. He expanded Melaka's power along the west coast and down to Singapore and the neighboring Bintan islands. He also had orang laut pirates patrolling the seas to extort tribute from passing ships. After Ailied district chiefs had repelled assaults from Thai-controlled armies from Pahang, Tun Perak personally led a famous victory over a Thai fleet off Batu Pahat in 1456.

What did Sri Maharajah do that contributed to Islam winning its place in Malaya?

Relying on an animal to come by is risky. A flower may have to wait a long time for the right animals to come by. What if one never passes close enough to the flower? Hoping the wind will blow is also risky for a plant. What if the wind does not blow? What if the blowing pollen does not land on another flower? The wind could even blow the pollen over the ocean where it is wasted. Giving free nectar is costly. It is not a good use of the plants energy. A plant uses a lot of energy to produce nectar. Some animals may just drink the nectar. They may not carry off any pollen in return. To improve their chances, plants evolved special traits. For example, they developed ways to hide their nectar. Only certain animals were able to get at the plants hidden nectar. These specific animals might be more likely to visit only flowers of the same species. This was also a benefit for some animals. Animals also evolved special traits to get to the nectar.
How do plants protect nectar?