作者：(加) 韦恩·艾弗里特
出版社：天津人民出版社
格式: AZW3, DOCX, EPUB, MOBI, PDF, TXT
跟美国学生同步学科学(彩色英文版 Grade 4)试读：
版权信息书名：跟美国学生同步学科学(彩色英文版 Grade 4)作者：(加) 韦恩·艾弗里特排版：KingStar出版社：天津人民出版社出版时间：2017-08-01ISBN：9787201120249本书由北京东方神鸟图书发行有限公司授权北京当当科文电子商务有限公司制作与发行。— · 版权所有 侵权必究 · —01Beaver DamsBeavers are brown, furry mammals that live in lakes and rivers. In order to survive in this habitat, beavers build dams. They do this by using their large front teeth to cut down trees and then pile up wood to block the flow of water. Doing this causes deep ponds to form behind the dam. This gives beavers a place to hide as they can dive into the deep water. It also provides a place for beavers to live and store their food.
Beavers live in lodges that they build in the middle of ponds that are created by their dams. These lodges are made of mud, sticks, and logs. The entrance to these lodges is underwater. The inside of a beaver lodge is small compared to the outside because beavers need thick walls to protect them from other animals.
Trees are very important to beavers. They not only provide wood for shelter, but they also provide food. The diet of the beaver includes bark, leaves, and roots.
Beavers cause changes to the environment that can be both positive and negative. Ponds that are built by beavers provide new wetland habitats for fish, frogs, and water birds. These wetlands also slow soil erosion and keep more water in the ground. This allows plants to grow.
On the other hand, however, beavers also destroy trees that are the homes of birds and other animals. Beaver dams also slow down the flow of water in streams. This causes silt to build up. Dams can also flood the land behind them.Word List
lodge: a dome-shaped home that beavers build from mud, sticks, and logs
shelter: a kind of home, protection from cold, wind, etc.
silt: small particles of soil deposited by water
wetland: a habitat where shallow water covers most of the groundYou Practice
I. Fill in the blanks—Complete the following sentences with words from the reading.
1) Beavers use their _______________________ to cut down trees.
2) Beavers live in ______________________.
3) Beavers eat __________, ____________, and _____________.
4) The walls of a beaver lodge are very ______________.
5) Wood provides _______________ and _____________ for beavers.
II. Complete the chart about positive and negative effects of beaver dams.
III. Read these sentences carefully. Write Yes or No for each one.
____1) Beavers eat some parts of a tree.
____2) Beavers enter their lodge from underwater.
____3) Beaver lodges can be bad for other animals.
____4) A deep pond can provide safety for beavers.
____5) Beaver dams allow the water in streams to flow faster.02The Green Anaconda
The adult green anaconda is one of the world' s largest and heaviest snakes. Adult anacondas average about 6 metres in length, but some can grow as long as 9 metres and weigh as much as 250 kilograms! Females grow much larger than males. They are mostly olive green with black or brown spots on their bodies.
Green anacondas eat anything they can catch and overpower such as rats, fish, birds, deer, warthogs, other snakes, and even crocodiles! They kill their prey by constricting their bodies around it and squeezing until the victim dies. Anacondas can open their jaws very wide, and the prey is swallowed whole, usually head first. After eating a large meal, anacondas become very inactive and may not eat again for weeks!
The green anaconda is found in slow-moving rivers and swamps of northern and central South America. They are also sometimes found on riverbanks and grasslands near water.
Females give birth to as many as 30 live, baby anacondas after being pregnant for about 6 months. Neither the male, nor the female takes care of the baby anacondas.
There are still many anacondas in the wild, but some of their habitat is being destroyed by humans.Word List
constricting: wrapping around
swallowed whole: eaten in one biteYou Practice
I. Answer the following questions.
1) What do green anacondas look like?
2) What are some things that green anacondas eat?
3) Where can green anacondas be found?
4) How do green anacondas kill their prey?
5) How many baby anacondas are usually born at one time?
II. What' s the word? Write the correct words from the reading.
1) to be stronger than: o _ _ _ _ _ _ _ _
2) not moving a lot: i _ _ _ _ _ _ _
3) wet areas: s _ _ _ _ _
4) going to have babies: p _ _ _ _ _ _ _
5) a kind of rodent: r _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Male green anacondas are larger than female anacondas.
____ 2) Green anacondas can eat large animals.
____ 3) Green anacondas live in South America.
____ 4) Male green anacondas take care of baby anacondas.
____ 5) There are not many green anacondas remaining in the wild.03Animals in Winter
In most places in the world, winter brings shorter days and colder weather. At this time of year, there is usually less food available for animals. However, they deal with this shortage in various ways. Some animals hoard food so that they have it in the winter. Squirrels and some kinds of birds like blue jays and woodpeckers, store nuts and seeds in trees and other hiding places. Beavers store tree branches underwater near their lodges. And honeybees make enough honey to last the hive through the winter.
To get ready for winter, many animals eat more than they actually need during the warm months. This extra food is stored in their bodies in the form of fat in their bodies. The animals' bodies absorb fat to provide energy in winter.
Beavers store body fat in their tails. Bumblebees drink lots of nectar to fatten up their bodies and fi ll their honey stomachs. Bears eat enough in summer and fall to survive without eating all winter, when they are in a deep sleep.
One way animals adapt to winter is by becoming dormant. These animals may look like they are sleeping, but they are actually conserving energy by staying still. Chipmunks, for example, are dormant during the winter and are active only once in a while to eat food stored in their dens.
Animals such as bats and snakes shut down so completely in winter that their body temperature drops and their breathing and heart rate slows. This is called hibernation. Bears do something similar to hibernating, but their body temperature doesn' t drop as much. However, bears are able to go months without eating.Word List
hoard: to gather things and store them or hide them for later
dormant: inactive in order to save energy
hibernation: a special kind of inactivity where the body processes slow down enormouslyYou Practice
I. Answer the following questions.
1) Why do many animals hoard food during the warm months?
2) How do bees prepare for winter?
3) What are some animals that become dormant in winter?
4) Why is it a good idea for many animals to hibernate in winter?
5) Do bears hibernate? Explain.
II. What' s the word? Using the clues, write the correct words from the reading.
1) arms of trees: b _ _ _ _ _ _ _
2) saving: c _ _ _ _ _ _ _ _ _
3) a small animal: c _ _ _ _ _ _ _
4) not active: d _ _ _ _ _ _
5) homes for some animals: d _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) All animals hibernate.
____ 2) Bears eat a lot of food in winter.
____ 3) Beavers cannot store fat.
____ 4) Birds sometimes hoard sunflower seeds.
____ 5) Becoming dormant is a good way of adapting to winter.04Venus
Venus is sometimes called Earth' s sister planet because of its similar size. At night it is easily viewed with the naked eye and is sometimes called “the evening star” or “the morning star”. However, Venus is covered by thick, poisonous clouds that obscure the surface. These thick clouds cause an extreme insulating effect that radiates the heat back to the surface. The surface temperature is often over 800 degrees Fahrenheit!
The surface of Venus is rocky and dusty and dotted with mountains, canyons, and some volcanoes. Some of the mountains are enormous-higher than the highest mountains on Earth! In contrast to the high mountains, however, 65 percent of Venus is covered by smooth plains.
Venus is about 95 percent as big as Earth and about 80 percent its weight. It is the second closest planet to the Sun at about 108 million kilometres away. It has no moons.Word List
obscure: not able to see
insulating: keeping heat inYou Practice
I. Answer the following questions.
1) Why is Venus sometimes called Earth' s sister planet?
2) What is the surface of Venus like?
3) How close to the Sun is Venus?
4) How many moons does Venus have?
5) Would you like to live on Venus? Why or why not?
II. What' s the word? Using the clues, write the correct words from the reading.
1) the top layer: s _ _ _ _ _ _
2) not clear: d _ _ _ _
3) having many: d _ _ _ _ _
4) very different: c _ _ _ _ _ _ _
5) very big: e _ _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Venus is larger than Earth.
____ 2) Venus is very cold.
____ 3) Venus is closer to the Sun than Earth.
____ 4) Venus has higher mountains than Earth.
____ 5) Venus cannot be seen in the sky.05Review(Lessons 1-4)
I. Fill in the blanks—Complete the following sentences with the correct words from Lessons 1-4.
1) Clouds have an i _ _ _ _ _ _ _ _ _ effect. They keep heat in.
2) It is important for some animals to h _ _ _ _ food.
3) Some snakes kill their prey by c _ _ _ _ _ _ _ _ _ _ _.
4) Animals that are d _ _ _ _ _ _ in winter are trying to save energy.
5) A l _ _ _ _ is a kind of home that is made by beavers.
II. Answer the following questions.
1) What are some different kinds of shelters for animals?
2) Why can' t people live on Venus?
3) What are some different ways that animals adapt to winter?
4) What kind of animals live in wetlands?
5) What are some animals that live in dens?
III. Opposites—Find the opposites to these words in the readings.
1) active: d _ _ _ _ _ _
2) rough: s _ _ _ _ _
3) narrow: w _ _ _
4) shallow: d _ _ _
5) used: s _ _ _ _ _06Bison
The American bison is the largest mammal found in North America. Bison are often called buffalo and have short, white horns on their head. Males can measure 5 metres long and weigh up to 1100 kilograms.
The American bison normally eats over 12 kilograms of grass per day. They can be found on open plains and woodlands. They are very migratory and travel long distances in search of food. Bison don' t have many enemies except people, wolf packs, and grizzly bears.
Bison are highly social animals. The females travel in groups of sixty or more, while the males travel in smaller groups or by themselves. After baby bison are born, they stay with their mothers for about three years. The male bison do not help raise the offspring.
There were once an estimated 70 million bison in North America, roaming the plains from Canada to Mexico. However, because of too much hunting, that number was reduced to 355 by 1883. Today, several wild herds can again be found on the plains, but their numbers will never be as high as they once were.Word List
migratory: moving around a lot
offspring: babies
roaming: traveling around
herds: large groups of animalsYou Practice
I. Answer the following questions.
1) What do bison look like?
2) What do bison eat?
3) What enemies do bison have?
4) Why do you think the number of bison will never be as high as before?
5) Who takes care of baby bison?
II. What' s the word? Choose the correct words from the reading.
1) communicate with each other: s _ _ _ _ _
2) flat areas: p _ _ _ _ _
3) another name for bison: b _ _ _ _ _ _
4) to help young animals grow up: r _ _ _ _
5) groups of wolves and some other animals: p _ _ _ _
III. Read theses sentences carefully. Write Yes or No for each one.
____ 1) Male bison are larger than female bison.
____ 2) Bison eat mostly meat.
____ 3) Today there are about 70 million bison.
____ 4) Bison move around a lot.
____ 5) Female and male bison usually travel together.07Our Solar System
Our solar system is made of the Sun and all objects bound by gravity. The Sun is a massive yellow dwarf star that contains 99.86 percent of the mass of the entire solar system. Our solar system is part of the Milky Way galaxy, which covers about 100,000 light years and contains about 200 billion stars.
Four terrestrial or “inner” planets orbit the Sun. These are Mercury, Venus, Earth, and Mars. Four outer planets (called “gas giants”) also orbit the Sun. These planets are Jupiter, Saturn, Uranus, and Neptune. The area between the inner and outer planets is a big open area called the“asteroid belt”, which lies between Mars and Jupiter. Objects in this area are bound by the gravity of Jupiter. Beyond Neptune is the Kuiper Belt. This is a huge area of dwarf planets and icy bodies bound by the gravity of Neptune. Pluto, which used to be considered the ninth planet, is one of the dwarf planets of the Kuiper Belt. Beyond the Kuiper Belt is a region called the Oort Cloud. This area is filled with billions or trillions of icy comets. The solar system also includes comets, the moons of the planets, and other objects.Word List
massive: very large
dwarf: very small
comet: an object made of rock, ice, and dustYou Practice
I. Answer the following questions.
1) What is the solar system made of?
2) How large is the solar system?
3) What are the inner planets?
4) What are the outer planets?
5) Where is Pluto located?
II. What is it? Read the description and tell what it is.
1) a massive yellow dwarf star: ______________________________
2) the area between Mars and Jupiter: _________________________
3) the area beyond Neptune: ________________________________
4) the area beyond the Kuiper Belt: ___________________________
5) a terrestrial planet: ______________________________________
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) The Sun is the largest object in the solar system.
____ 2) Pluto is one of the outer planets.
____ 3) The inner planets are closest to the Sun.
____ 4) Objects in the asteroid belt are bound by the gravity of Neptune.
____ 5) The Milky Way is larger than our solar system.08The African Penguin
The African penguin has a black cap, face, nape, back, and tail. The wings and feet are also black. It has white underparts and a white throat separated by a black stripe across the breast.
African penguins stand about 70 centimetres tall. Males are larger than females. They eat various types of small fish. Between the months of February and August, they are usually nesting. Females typically lay two eggs after an incubation period of about 40 days. The male and female take turns incubating the eggs. These shifts last for between 1 and 3 days. After the chicks hatch, the parents continue to protect them and keep them warm for another 40 days. The young African penguins jump into the sea when they are about 3 months old.
Over the past few decades, the population of African penguins has decreased. Part of the reason for this decrease is egg hunting. Also, in 2000, over 19000 African penguins were covered in oil because of an oil spill in Capetown, South Africa. Today, there are about 56000 breeding pairs of African penguins. However, this number is only about 10 percent of its former levels.Word List
cap: top of the head
incubation: the time it takes to hatch eggs
decreased: become fewer in numberYou Practice
I. Complete the chart about African penguins.
1) Appearance: ___________________________
2) Size: _________________________________
3) Food: ________________________________
4) Breeding: _____________________________
5) Population: ____________________________
II. What' s the word? Using the clues, write the correct words from the reading.
1) the front, chest: b _ _ _ _ _
2) come out of an egg: h _ _ _ _
3) a kind of disaster: o _ _ s _ _ _ _
4) neck: t _ _ _ _ _
5) how many: p _ _ _ _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) The number of African penguins is increasing.
____ 2) Only the female penguin takes care of the babies.
____ 3) The female penguin usually lays three eggs.
____ 4) African penguins jump into the sea right after they are born.
____ 5) Oil spills have killed some African penguins.09The Komodo Dragon
The komodo dragon is the world' s largest living lizard. It is found only on a few different islands in Indonesia. This prehistoric lizard can be a long as 3 metres, and weigh as much as 160 kilograms. They are gray and have very powerful arms and legs. Their yellow, forked tongue is used for smelling. Although their hearing is poor, they have excellent vision and can smell carrion that is more than 3 kilometres away!
The komodo dragon is a strict carnivore and feeds on deer, monkeys, pigs, birds, and other medium-sized mammals. They usually swallow their prey whole, sometimes after ramming it against a tree to make it more compact. Because they eat such large meals, they only need to eat once or twice a month. Prey is either killed very quickly, or very slowly. After biting an animal, this animal dies over a period of days from contact with the komodo dragon' s toxic saliva. Research suggests that komodo dragons have even dug up human remains and eaten them.
Female komodo dragons lay their eggs in September. Usually about 20 eggs are laid at one time. Young dragons have many enemies, including adult komodo dragons.
The komodo dragon population is threatened because of its small population, narrow distribution, habitat loss, and illegal poaching.Word List
prehistoric: from a very long time ago
carnivore: meat eater
ramming: hitting very hard
saliva: liquid in the mouth of an animal
poaching: the illegal killing of animalsYou Practice
I. Answer the following questions.
1) What does the komodo dragon look like?
2) What does the komodo dragon eat?
3) Why is the komodo dragon a threatened species?
4) Where can komodo dragons be found?
5) How big can komodo dragons get?
II. What' s the word? Using the clues, write the correct words from the reading.
1) smaller: c _ _ _ _ _ _
2) touching: c _ _ _ _ _ _
3) dead body: r _ _ _ _ _ _
4) ability to see: v _ _ _ _ _
5) poisonous: t _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Komodo dragons are found on islands all over Asia.
____ 2) Komodo dragons can hear very well.
____ 3) Komodo dragons eat mostly vegetables.
____ 4) Komodo dragons may eat dead people.
____ 5) There are not many komodo dragons in the world.10Review(Lessons 6-9)
I. Fill in the blanks—Complete the following sentences with words from lessons 6-9.
1) P _ _ _ _ _ _ _ animals is a very bad thing to do!
2) The number of some animals is d _ _ _ _ _ _ _ _ _ because of hunting.
3) Things that are m _ _ _ _ _ _ are very large.
4) M _ _ _ _ _ _ _ _ animals travel around a lot.
5) Some lizards have poisonous s _ _ _ _ _.
II. Answer the following questions.
1) What kind of animals are prehistoric?
2) What is a dwarf planet?
3) What are some kinds of migratory animals?
4) What are comets made of?
5) What kind of animals have caps?
III. What' s the word? Using the clues, write the correct words from the readings.
1) a kind of bird that can' t fly: p _ _ _ _ _ _
2) a large planet: S _ _ _ _ _
3) the largest North American mammal: b _ _ _ _
4) very poisonous: t _ _ _ _
5) babies, young, : o _ _ _ _ _ _ _ _11The Jaguar
The jaguar has yellowish-brown fur and spots all over its body. Their size depends on their location, but they are the largest cats in the western hemisphere. They can weigh anywhere from 35 to 70 kilograms. The jaguars found in the dense jungle of the Amazon are usually smaller than the ones found in open areas.
Jaguars are extremely powerful carnivores. They may be active at all times of day or night, and eat animals as large as cows and horses to deer and smaller animals like armadillos, rodents, reptiles, and fish. Jaguars have very powerful jaws and often kill their prey with a single bite to the back of the skull. They are also excellent swimmers and climbers and live a very solitary life.
Female jaguars give birth to 1 to 4 cubs after 3 to 3 and a half months. The young jaguars stay with their mothers for about 2 years.
Jaguars live in wet forests and jungles from central Mexico throughout most of South America.Word List
dense: very thick, hard to get through
solitary: alone, not living with others
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