【正文】 過程中，一是母體可以通過胎盤把一部分抗體可以傳給孩子，二就是通過母乳喂養(yǎng)，母乳里面有很多的免疫物質(zhì)，6個月以后母乳本身的抗體就降低了，再加上六個月以后活動范圍大，接觸傳染病的機(jī)會也多了，所以往往六個月以后病就多起來了．解：反射弧是生物體完成反射活動的基礎(chǔ)，a為感受器；b為傳入神經(jīng)；c為神經(jīng)中樞；d傳出神經(jīng)；e效應(yīng)器．A、若此圖表示膝跳反射的反射弧，由于膝跳反射屬于低級的反射活動，是由脊髓控制的，所以c代表脊髓的神經(jīng)中樞．故不符合題意．B、若此圖表示學(xué)生聽到鈴聲進(jìn)入教室的反射弧，這屬于高級的反射活動，是人類特有的反射活動．在聽覺的形成過程中，耳蝸能感受外界刺激，產(chǎn)生神經(jīng)沖動，所以感受器即為耳蝸，而鼓膜只起傳遞聲波振動的作用．故符合題意．C、若此圖表示人看到酸梅分泌唾液的反射弧，在視覺的形成過程中，視網(wǎng)膜上有感光細(xì)胞，能感受刺激產(chǎn)生神經(jīng)沖動，所以感受器即為視網(wǎng)膜，故不符合題意．D、若此圖表示使運(yùn)動協(xié)調(diào)和維持身體平衡的反射弧，由于小腦具有協(xié)調(diào)身體平衡，維持身體運(yùn)動的功能，所以代表小腦的神經(jīng)中樞．故不符合題意．分析：甲狀腺激素是由甲狀腺分泌的，它的主要作用是促進(jìn)新陳代謝、促進(jìn)生長發(fā)育、提高神經(jīng)系統(tǒng)的興奮性．解：破壞蝌蚪的甲狀腺，發(fā)現(xiàn)蝌蚪發(fā)育停止，不能發(fā)育成成蛙，說明蝌蚪發(fā)育成成蛙與甲狀腺有關(guān)；在飼養(yǎng)缸的水中放入甲狀腺激素，破壞甲狀腺的蝌蚪又發(fā)育為成蛙，說明甲狀腺激素能促進(jìn)蝌蚪發(fā)育成成蛙，綜合分析以上實(shí)驗結(jié)果可以得出結(jié)論：甲狀腺分泌的甲狀腺激素能促進(jìn)蝌蚪的發(fā)育．分析：呼吸肌的收縮和舒張而造成胸腔有規(guī)律的擴(kuò)大與縮小，叫呼吸運(yùn)動，包括吸氣和呼氣兩個過程；呼吸運(yùn)動的基本意義是實(shí)現(xiàn)了肺的通氣，即肺內(nèi)氣體與外界氣體進(jìn)行交換．解答：解：呼吸運(yùn)動的過程是：平靜吸氣時，膈肌與肋間肌收縮，引起胸腔前后、左右及上下徑均增大，肺隨之?dāng)U大，形成主動的吸氣運(yùn)動；當(dāng)膈肌和肋間外肌舒張時，肋骨與胸骨因本身重力及彈性而回位，結(jié)果胸廓縮小，肺也隨之回縮，形成被動的呼氣運(yùn)動．可見呼吸運(yùn)動是由呼吸肌的收縮和舒張引起的．由于在氧含量高的地方，血紅蛋白與氧結(jié)合，使得血液呈現(xiàn)鮮紅色；在氧含量低的地方，血紅蛋白與氧分離，使得血液呈現(xiàn)暗紅色．由于空氣中的氧氣含量高，所以正面的血紅蛋白與氧結(jié)合，使血液呈現(xiàn)鮮紅色；背面的血紅蛋白因為玻璃阻隔不能接觸到空氣，所以不能與氧結(jié)合，故血液呈現(xiàn)暗紅色．第三篇：八年級下冊英語重點(diǎn)短語短文Unit 1 What’s the matter? 重點(diǎn)短語lie down 躺下 have a cold 感冒have a stomachache 胃痛take one’s temperature 量體溫 have a fever發(fā)燒go to a doctor 看醫(yī)生 get off 下車to one’s surprise 使 take risks(take a risk)冒險 run out(of)用盡 off 切除get out of 離開；從care for = look after = take care of 照顧；照料decide（not）to do （不）做某事try out for 競爭報名參加put out 張貼公布a good way to do Dear Helen，Last Sunday, my classmates and I went to the want to take some father was out at that time, so I took his camera without telling , the camera went out of my bag and dropped on the ground when I wasclimbing the did not work at put it back quietly after I returned I have not told him till I face my father ,I feel should I do?Yours, David Dear David，F(xiàn)irst, I think you’d better tell your father you tell him the truth ,he will be angry with at least you will prove how honest you I think you should offer to you should not use your pocket , a camera is expensive, maybe you can’t afford you offer to do some jobs around the house, he will realize that you are truly , remember to be careful next wishes,Helen Unit5 What were you doing when the rainstorm came? 重點(diǎn)短語At the time of 在請據(jù)此寫一篇80詞左右的英文觀后感。注意：觀后感須包括所給的內(nèi)容要點(diǎn)，要求語句通順，意思連貫。持從??出萍 oneself 受傷 a bandage on ll down 摔倒 sick 感到惡心 a nosebleed 流鼻血 his knee 割傷他的膝蓋 her head back 把她的頭向后仰 problems breathing 呼吸困難 climbing 登山運(yùn)動 used to doing out(of)用完。 you think it es from a newspaper or a book? 你認(rèn)為它是來自報紙還是書呢？ think I sat in the same way for too long without 。散發(fā) up with 想出；提出 a plan 制訂計劃 some notices 做些公告牌 out 試用。散發(fā)。募捐 after 與......相像。解決 similar to 與??相似 up 建立。 volunteers at an animal hospital every Saturday ，他都在一39。 want to put off my plan to w o rk in an animal hosp ital u n til next 。總是 day/evening 整曰/夜 housework 做家務(wù) back 大聲回應(yīng) away 走開 26..share the housework 分擔(dān)家務(wù) fortable home 一個舒適的家 surprise 驚訝地 something to drink 拿點(diǎn)喝的東西 one show 觀看一個節(jié)目 out 閑逛 使某物弄濕 to do chores 做雜務(wù) sb.(to)d o /with sth?幫助某人干某事 a tent帶頂帳篷來 some snacks買些小吃 to the store去商店 invite a party邀請某人參加聚會make enough stress足夠的壓力a waste of time浪費(fèi)時間 in order to為了get good grades取得好成績 mind doing depend on依賴。 mom came over as soon as I sat down in front of the T ，我媽媽就過來了。t you forge t about it? 你為什么不忘掉它呢？ she ’ s wrong , i t 39。 guess I could, b u t I d o n ’ t w a n t to surprise 。 World Trade Center 世貿(mào)中心 down 拆除。3.— What was Jenny doing while Linda was sleeping? 琳達(dá)在睡覺的時候，珍妮正在干什么？— While Linda was sleeping, Jenny was helpingMary with her ，珍妮正在幫瑪麗做作業(yè)。 is because...This is because he can make 72 changes to his shape and size, turning himself into differentanimals and ，做出72種變 化，可以將自己變成不同的動物或東西。Unit 7 W hat’s the highest mountain in the world?一、重點(diǎn)短語 big as 與??一樣大 of the oldest countries 最古老的國家之一 free to do far as I know 據(jù)我所知 objects 人造物體 o f.........的組成部分 highest mountain 最高的山脈 the world 在世界上 other mountain 其他任何一座山 a ll the salt lakes 在所有的咸水湖中 along 跨越? ? weather 冰凍的天氣 in air 呼吸空氣 first people to do the face of difficulties 面臨危險 up doing one’ s dream 實(shí)現(xiàn)某人的夢想 forces of nature 自然界的力量 the top 到達(dá)頂峰 though 雖然。3....show(s)that...The spirit of these climbers shows us that we should never give up trying to achieve our ：我們永遠(yuǎn)都不應(yīng) 該放棄實(shí)現(xiàn)自己的夢想。/ 不，我沒有。5....came to realize how much...She came to realize how much she actually missed all of ，事實(shí)上她是多么想念他們所有的人。4）他/她什么時候開始打嗝？他/她在1922年開始打嗝。8）他10歲時就成為一名滑冰冠軍。12）你開始學(xué)英語時多大？13）我能做什么來變得出名？