Fill in all the gaps, then press "Check" to check your answers.
For each of the following passages, try to find the main idea. Read the topic sentences of each paragraph and paraphrase them. Then, try to state the main idea. Be on the lookout for direction markers!

Main Idea Passage A

1. Plants reproduce by seeding. The seed of the plant contains all the necessary genetic information to create a new plant, and more important, it is designed to start growing only when the surrounding conditions are perfect. For example, the seed of a plant growing in a temperate area will "wait" until the cold winter passes before growing. When spring arrives, the seed responds to environmental triggers such as water intake, rising air temperature, humidity levels, and amount of sunlight. Some seeds are programmed in such a way that they will not grow until they've passed through a period of cold weather.

2. A germinating seed will first display tiny leaves, called cotyledons. Plants are either monocotyledons, producing just a single leaf, or dicotyledons, producing two leaves. These tiny leaves quickly grow into a mature leaf system, which then begins gathering energy for the young plant. Plants gather the light of the sun and transform it into energy in a process called photosynthesis. This process allows the plant to produce glucose, which the plant then uses to both further its growth and to produce cellulose and starch, two compounds essential to a plant. Cellulose is a strong, fibrous material that gives shape and structure to the cell walls. Starch is stored in the cells and used for energy.

3. Beneath the surface, the plant's root system grows and provides not only an anchor for the plant but a constant supply of food as well. Some plants possess what is called a taproot system, in which there is one main root. Others have a more dispersed root system, which lacks a main root. In either case, the roots of the plant are covered with microscopic hairs, which spread into the surrounding soil. These hairs greatly increase the surface area of the root system and allow the plant to absorb water and essential nutrients from the soil.

4. Water drawn in through the roots undergoes a process called transpiration. During this process, minerals are carried up to the leaves of the plant, while oxygen and water vapor escape through tiny pores, called stomata, on the surface of the leaves. Interestingly, the movement of water through the plant is also responsible for keeping the plant upright; a plant that lacks water will wilt and may die. Too much water may also harm the plant by saturating the soil and preventing the roots from absorbing oxygen.

5. Once a plant reaches full maturity, its energy is devoted to reproduction. The plant forms flowers and fruits, the structures essential to reproduction. The flowers of a plant are typically hermaphrodites, meaning that they contain both male and female reproductive organs. Thus, many plants are able to fertilize themselves. The flowers of some plants are unisexual, being all male or all female. These plants require another plant for fertilization. Some plants are polygamous, meaning they have both hermaphrodite and unisexual flowers. Fruits are created from the ovaries of flowering plants. The main purpose of the fruit is to protect the seed, but many fruits aid in the seed's dispersal as well. For example, a soft, fleshy fruit attracts animals, which eat the fruit and thus spread the seeds. Or a pod or capsule will split open and scatter its seeds. Some of the seeds distributed in this manner will take hold in favorable soil, and the entire process begins anew.

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Main idea (provide the missing words) - A reproduces with a , which grows from a tiny into a mature capable of making its own .

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Дата последнего изменения этой страницы 13.08.2017

Дата последнего изменения этой страницы 13.08.2017