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What is the life in an ecosystem(生态系统)? You’re in the forest. From your place on the hill, you can see a pond below you and the sun shining above you. A pond is an area of water smaller than lake. A frog sings noisily through your binoculars(双筒望远镜), you see the cattails (香蒲）shaking in the wind. You close in on the dragonflies(蜻蜓) resting on them.
Look at a family of ducks swimming along noisily. The brothers and sisters at the end of the line hurry to keep up. At the other side of the pond, a long-legged bird, heron(苍鹭)waits patently in the reeds. Reeds are grass-liked plants in wet places. You watch carefully as the heron drops his head down into the water, when it pulls suddenly back up, you see the fish in in mouth. You may not realize it, but you are watching a great system(系统) in action.
What is a system?
A system is made up of many parts working together for a purpose(目的). But scientists divide them into two main parts, they are living and nonliving parts. Every part of system is important, if any part of system is lost, the whole system does not work.
Let’s take another look. The ducks and the herons are birds, the frog is an amphibian, which can live both on land and in water. The dragonflies are insects(昆虫)and the cattails are plants. They are all alive. What nonliving parts can you think of?Air, water sunlight, and land forms are all nonliving parts. All of these parts system are working together.
1．What does the writer want us to find in the first paragraph(段落)?| A．The sun shining above. |
| B．A frog singing noisily. |
| C．The dragonflies resting on cattails. |
| D．The life in an ecosystem. |
| A．A heron is a small bird with short legs. |
| B．A heron is a big bird with long legs. |
| C．A heron is a kind of frogs with four legs. |
| D．A heron i a kind of dragonflies. |
| A．It makes a living by eating ducks. |
| B．It makes a living by eating frogs. |
| C．It makes a living by eating fish. |
| D．It makes a living by eating dragonflies. |
| A．Two parts. | B．Three parts. | C．Four parts. | D．Many parts. |
| A．The ducks and the heron are birds They are living parts. |
| B．The cattails are plants. They are nonliving parts. |
| C．The dragonflies are insects. They are living parts. |
| D．Air, water and sunlight are nonliving parts. |
同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
