They are a vital ancestor 他们是从古到今所有植物

72. They all feed off the earth's heat-
    他们都以地热为生
73. All except the cyanobacteria, or blue-green algae.
    除了蓝细菌即蓝绿水藻以外
74. They alone have the capacity to turn to the sun to capture the energy.
    他们能够独自俘获来自太阳的能量
75. They are a vital ancestor
    他们是从古到今所有植物
76. of all yesterday's and today's plant species.
    的关键祖先
77. These tiny bacteria...
    这些微小的细菌
78. And their billions of descendants...
    以及他们的亿万后代

来自《家园 第一部分 Home Part1》第 75 行