题型:阅读理解 题类: 难易度:普通
四川省遂宁市 2024届高三下学期第三次诊断考试英语试题
It's breathtaking to watch the delicate spring wildflowers come out from their blanket of leaves, bloom, develop and disperse (传播) fruit, all in a matter of a few short days or weeks.
Although they look fragile, these are tough little plants, each focusing its efforts on spreading its species. They have evolved to have a wide range of flower structures and colors, some with fragrances, attracting many different insect species to assist them in pollination (授粉).
There is one strategy that a surprising number of spring blooming native plants have evolved in common: seed dispersal by ants. As many as thirty percent of the spring flowering plant species in the forests of eastern North America have evolved to take advantage of this situation to benefit themselves. These species have evolved to provide food attached to their seeds to encourage ants to disperse those seeds. This food, called an elaiosome(油质体), is a specialized fat body whose chemical composition more closely matches that of the insects that ants prefer than it does that of a seed.
When a fruit opens to disperse its seeds, the elaiosomes are an instant attraction for ants. They take the seed with its attached elaiosome back to their nests for consumption there, but they just eat the elaiosome, their preferred food, and dispose of the seed on their trash pile. This tends to be an environment that is rich in nutrients, and will benefit the growth of the new plant. Just to make sure the ants don't eat the seeds in addition to the elaiosome, some plant species have hard seed coatings that ants can't really bite through.
This evolutionary adaptation is somewhat similar to the strategy of plants that have evolved to surround their seeds with fleshy fruits to attract birds to assist them with seed dispersal. Given the fact that there are fewer birds available in early spring to help with seed dispersal, it makes sense that the early blooming plants evolved to partner instead with the ants for this service.
Did you ever wonder how your Spring Beauty managed to pop up in new locations in your lawn or garden? Thank an ant!
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