题干

在一个发育良好的森林里,从树冠到地面可划分为乔木层、灌木层、草本层和地被层;同时枝下透光度不同的地点,植物种类组成也有区别,这表明群落具有(   )

A:物种组成和数量比例

B:对种群产生重大影响的优势种

C:垂直结构和水平结构

D:彼此之间有直接或间接的营养关系

上一题 下一题 0.0难度 选择题 更新时间:2016-07-22 05:32:05

答案(点此获取答案解析)

C

同类题5

阅读下列短文,根据短文内容填写表格。(每空限填一词)

    We have only one earth. It is the only environment for humans, animals and plants to live or grow in. However, we are polluting our earth every day. Good news is that the whole world has realized the serious problems and has taken action to fight against it.

    World No Tobacco Day (May 31)

    The first World No Tobacco Day is April 7, 1988. Since 1989, it was changed to be May 31st every year. The purpose of the World No Tobacco Day is to encourage people not to smoke.

    World Water Day (March 22, 1993)

    United Nations named 22 March as the first World Water Day in 1993. It's a day to celebrate water. It's a day to prepare for how we manage water in the future. It is celebrated around the world every year.

Earth Hour ( 2007)

    Earth Hour started for the first time on March 31, 2007 in Sydney, Australia. Since then, the last Saturday of every March was named as Earth hour day that year. On March 19, 2016, more than 350 famous buildings in 178 countries around the world turned off the lights for one hour to remind people to save electrical power.

    Actions in China to save our environment

    Smoking is not allowed in all indoor public places from 2014.This is the first time for China to care about personal health in public places.

    Ban(禁令) on free plastic bags. Since June 1, 2008, free plastic shopping bags are not allowed to provide in all supermarkets, shopping malls, and other places. It is to encourage people to use cloth bags or baskets for their shopping things.

Theme:The only environment for all the____ things has serious problems, but the whole world has done____to prevent pollution.

Actions around the world

No Tobacco Day

Started on April 7,1988,then changed to May 31st every year. Encourage people to ____ up smoking.

World ____ Day

Started on March 22nd 1993, celebrated around the world every year.

Earth Hour

Started for the____ time on March 31st 2007, turned off lights for an hour to____ electrical power.

Actions in ____

Public places

Smoking is allowed in____ public places to care about personal health.

Supermarket &

Shopping malls

Encourage people to ____ cloth bags or baskets for shopping things. You need to____if you use plastic bags provided by the supermarket.