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 3)试读：
版权信息书名：跟美国学生同步学科学(彩色英文版 Grade 3)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：9787201120232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 · —01Amazing FlowersMost of the plants on Earth have flowers. They are beautiful to look at and smell, but they are also important to the plant because they make seeds. Plants need seeds to reproduce, or make new plants.
The sizes, colours, and smells of flowers are all different. Scientists call these differences adaptations.
Flowers make seeds when pollen travels from the male part of a flower to the female part. Insects help carry pollen from one flower to another. When an insect lands on a flower, pollen sticks to the insect. Then, when the insect visits another flower, some of the pollen falls off its body and pollinates that flower. Bees are very good at pollinating flowers.Word List
reproduce: to make new plants or babies
adaptation: a change in a living thing that helps it live in its environment
pollen: a kind of yellow dust made by the male part of a flower
pollinate: to bring pollen from one flower to another flowerYou Practice
I. Answer the following questions.
1) Why are flowers important to plants?
2) What are adaptations?
3) Where does pollen travel?
4) How do insects help pollinate flowers?
5) What kind of insect is good at pollinating flowers?
II. What's the word? Using the clues, write the correct words from the reading.
1) to make babies: r _ _ _ _ _ _ _ _
2) this part of a plant is very pretty: f _ _ _ _ _
3) this is a kind of yellow dust made by the male part of the flower:p _ _ _ _ _
4) bees are a kind of this animal: i _ _ _ _ _
5) this means to live, not die: s _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Only a few kinds of plants have flowers.
____ 2) Flowers look beautiful, but are not important.
____ 3) Pollen is made by the male part of the flower.
____ 4) Pollen is sticky.
____ 5) Flowers can be many different sizes and colours.02Cactus in the Desert
It is very difficult for living things to survive in the desert because most deserts are dry and hot. There may not be any rain for months. And when it does rain, the hot, dry weather makes the water quickly evaporate. Without clouds there is not much shade from the Sun. A desert plant like cactus, must adapt to the harsh desert conditions in order to stay alive and grow.
The needles on a cactus are called spines and are actually a kind of leaf. These spines help the cactus survive in the desert. There are different kinds of cactus spines. Some of the spines help the cactus collect rain. They direct water to the cactus' s roots.
Other kinds of spines grow thickly over the cactus. They protect it from the Sun and help stop the cactus from drying out. Water doesn' t evaporate as fast if the Sun is not shining directly on the cactus' s skin.
Still other kinds of spines protect the cactus from animals looking for a juicy meal. The spines break off easily and stick in an animal' s mouth if it tries to eat the cactus.
Some spines even help the cactus reproduce. For example, the jumping cholla breaks apart when an animal brushes against it. These spines stick to the animal. When the cactus piece finally drops off, it grows roots and becomes another plant.Word List
evaporate: turn from liquid to gas
spine: a stiff, sharp needle of a cactus
harsh: strong, difficultYou Practice
I. Answer the following questions.
1) Why are there not many plants or animals in the desert?
2) How does a cactus adapt to life in the desert?
3) What do different kinds of spines on a cactus do?
4) What happens if an animal tries to eat a cactus?
5) How does the jumping cholla help the cactus reproduce?
II. Opposites—Find words in the reading that are the opposite of these words.
1) die: s _ _ _ a _ _ _ _
2) nice, pleasant: h _ _ _ _
3) dry: j _ _ _ _
4) thinly: t _ _ _ _ _ _
5) the same: d _ _ _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) All spines on the cactus help it reproduce.
____ 2) Water evaporates very quickly in the desert.
____ 3) Deserts don' t get a lot of rain.
____ 4) Some spines protect the cactus against animals.
____ 5) Spines are actually a kind of leaf.03The Migration of Birds
As the seasons change, some animals migrate, or move from one place to another. Birds are very good at migrating because they can fly! Some birds travel only a few hundred kilometres, while others travel many thousands of kilometres. The Arctic tern travels the longest distance. It leaves its nesting place in the Arctic and migrates to Antarctica. That' s a trip of over 16000 kilometres!
The main reason birds leave their habitats and migrate is to go where food will be when the season changes. When fall comes to the north, the days get shorter and the flowers and insects disappear. Birds feed on nectar, berries, seeds, and insects, so they need a new supply of food. They head south where it is warmer and the days are longer. Some birds live in wet habitats like rivers and lakes. These bodies of water dry up at certain times of year. When this happens, these birds migrate.
Birds don' t stay in the south all the time because the north is a better place for them to reproduce and raise their young. There are also fewer predators in the north. Birds return in the spring because plants start growing again. There are also more daylight hours in the summer months, which means there is more time to fi nd food.Word List
migrate: travel from one place to another when the seasons change
predator: an animal that hunts other animals for foodYou Practice
I. Answer the following questions.
1) Why are birds better than other animals at migrating?
2) What is the main reason that birds migrate?
3) Which bird travels the furthest to migrate?
4) Why do birds return to the north in the spring?
5) What kinds of food do birds mostly eat?
II. What' s the word? Using the clues, write the correct words from the reading.
1) a kind of bird: A _ _ _ _ _ t _ _ _
2) a kind of fruit: b _ _ _ _ _ _
3) the bottom of the world: A _ _ _ _ _ _ _ _ _
4) a body of water: r _ _ _ _
5) to have babies: r _ _ _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) All birds migrate to Antarctica.
____ 2) The north has more daylight hours than the south in summer.
____ 3) Birds are the only animals that migrate.
____ 4) Birds sometimes migrate because their habitat becomes too wet.
____ 5) The Arctic does not have much food for birds in winter.04Fruits and Vegetables
Most people know that carrots are vegetables and grapes are fruit. However, did you know that tomatoes are also a kind of fruit? Green beans and squash are also fruit! They are all called fruits because they contain seeds. If a plant contains seeds, scientists call it a fruit.
Fruit comes from the flowers of a plant and grows after a flower is pollinated and forms seeds. The fruit grows around the seeds and continues to grow after the flower dies. Because fruit tastes good, birds and other animals carry fruit away to eat. This helps seeds move to new places where they can become new plants.
Vegetables can be leaves, stems, or roots. Each part of the plant has a special job to help the plant grow. People and animals eat these plant parts so they can grow, too!Word List
fruit: the part of a flowering plant that includes the seeds
vegetable: a plant part that can be eaten and has no seeds
seeds: the parts of a plant that can grow into a new plant
root: the plant part in the soil that absorbs water from the ground
stem: the part of the plant that connects and roots and the leavesYou Practice
I. Fruit or vegetable? Write F for fruit or V for vegetable.
apple _______
celery _______
carrot _______
cucumber _______
spinach _______
II. Answer the following questions.
1) How do we know that green beans are a fruit?
2) When does fruit grow?
3) What parts of a plant can be vegetables?
4) How do seeds move to new places?
5) Why do birds and other animals like fruit?
III. Fill in the blanks—Complete the following sentences with words from the reading.
1) Flowers make seeds after they are ____________.
2) You will fi nd ____________ inside fruit.
3) After a flower dies, the ____________ continues growing.
4) If a plant contains seeds, it is a ____________.
5) Vegetables do not contain ____________.05Review(Lessons 1-4)
I. Fill in the blanks—Complete the following sentences with words from Lessons 1-4.
1) The s_ _ _ _ _ on cactus are very sharp.
2) Male flowers make p_ _ _ _ _. 3) Some birds m_ _ _ _ _ _thousands of kilometres.
4) We know apples are fruit because they have s_ _ _ _.
5) A wolf is an example of a p_ _ _ _ _ _ _.
II. Answer the following questions.
1) What are three examples of vegetables?
__________, __________, and __________.
2) What are three example of fruit?
____________, ____________, and __________.
3) What is a place where water evaporates very quickly?
4) What is a place that has harsh conditions?
5) How do spines help a cactus survive?
III. Read the following sentences. Write Yes or No for each one.
____ 1) Insects help pollinate flowers.
____ 2) Cucumber is a fruit.
____ 3) Roots are under the ground.
____ 4) A stem is the long part of the plant.
____ 5) Green beans are a kind of predator.06How Plants Get Water
All living things need water in order to grow and survive. The water that plants need usually comes from rain falling on the ground and soaking into the soil. A plant' s roots are able to get water, but the leaves and stems need water, too. So, since water can' t move on its own, the different plant parts must work together to move the water.
Roots absorb water from the ground, but not all plants have the same kind of roots. Some plants have tap roots that grow deep into the ground. Tap roots are good for finding water buried deep below the surface. Plants that live in dry areas with hard dirt often have tap roots. Other plants have diffuse roots. These roots spread out far and are good for making sure a plant is strongly supported. Plants that grow in mud or sand often have diffuse roots.
Water that is absorbed by a plant' s roots must get to all the cells in the plant. The stem helps with this job. A plant' s stem has two parts. The outside of the stem is made from tough fibers to protect it. The inside of the tube is made of long tubes. These tubes move the nutrients upward from the roots.Word List
absorb: to soak up
diffuse root: a kind of shallow root that spreads out far
tap root: a kind of root that is long and extends deep into the ground
nutrients: substances found in soil that help a living thing stay healthyYou Practice
I. Answer the following questions.
1) What do all living things need?
2) Where do plants usually get their water from?
3) How are tap roots and diffuse roots different?
4) What is the main job of the stem?
5) Where do diffuse roots usually grow?
II. Opposites—Find words in the reading that mean the opposite of these words.
1) shallow: d _ _ _
2) weakly: s _ _ _ _ _ _ _
3) inside: o _ _ _ _ _ _
4) week: t _ _ _ _
5) downward: u _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Diffuse roots are deeper than tap roots.
____ 2) A plant' s leaves and stems need water.
____ 3) A plant' s stem has three parts.
____ 4) The stems of some plants can be eaten.
____ 5) Plants cannot grow in mud or sand.07Dandelions
In spring, yellow-headed dandelions seem to pop up everywhere — beside roads, in the cracks of sidewalks, and on grass. Where do these dandelions come from? We know that new plants grow from seeds, but how do the dandelion seeds get to all those different places?
If you have ever blown on a dandelion after the flower has turned white and fluffy, you can tell how the wind helps dandelions distribute their seeds.
Every dandelion seed is attached to a fine white hair called a parachute. The parachute catches the wind and carries the seed through the air. In this way, seeds can travel to new places where they can grow. However, a dandelion seed won' t grow until it fi nds the right conditions. It needs soil, sunlight, and water.
All seeds are covered by a seed coat, which protects the living part of the seed, called the seed germ, until it is time to grow. Seed coats protect the seeds in many ways. For example, they are light and help seeds float on water. They are also hard, which protects the seed from being damaged. Some seed coats also keep seeds from becoming too dry.Word List
distribute: to scatter
conditions: things that are needed before something can happen
parachute: the part of a dandelion that makes the seed float in the air
seed coat: the outer part of a seed that is hard and protects the rest of the seed
seed germ: the part of a seed that grows into a new plantYou Practice
I. Dandelion facts—Fill in the spaces with the correct answers about dandelions.
1) what dandelions need to grow: s _ _ _, s _ _ _ _ _ _ _, w _ _ _ _
2) the colours of dandelions: y _ _ _ _ _, w _ _ _ _
3) places dandelions grow: b _ _ _ _ _ r _ _ _ _, g _ _ _ _
II. Answer the following questions.
1) How do dandelions get to so many different places?
2) What are the fi ne, white hairs of dandelions called?
3) What is the living part of the seed called?
4) How do seed coats protect seeds?
5) Do you think dandelions would grow closer together or farther apart in places that have a lot of wind? Why?
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Dandelion seeds can travel very long distances.
____ 2) Seed coats are very heavy.
____ 3) Animals help distribute dandelion seeds.
____ 4) Dandelion seeds are yellow.
____ 5) Dandelions can grow in any conditions.08Fossils
A fossil is the remains or traces of a plant or animal that lived long ago. Fossils form when living things die and get buried quickly, before their bones, shells, or other hard parts decay. This usually happens when an animal or plant falls into water and is quickly covered by sediment. Floods, volcanic eruptions, or sandstorms can also bury plants and animals quickly. However, it often takes millions of years for the buried remains to become fossils.
Living things are buried by sediment when they die. Water, which contains minerals, seeps into the remains. After a long time, more layers of sediment pile up and the weight causes the sediment to harden into rock. Hardened minerals create fossils.
Most fossils are formed when minerals replace the hard parts of a plant or animal, such as wood or bones. This called a cast.
Sometimes a plant or animal decays completely after being buried in sediment. It leaves only its shape in the rock. This kind of fossil is called a mold.
Another kind of fossil is a trace fossil. This isn' t from the remains of a plant or animal. It is from signs of animal activity. Animal footprints or nests are examples of trace fossils. They help scientists learn about how the animals behaved or moved.Word List
decay: to rot or break down
fossil: the remains or traces of an animal or plant from long ago
sediment: soil or sand that settles to the bottom of a river, lake, or ocean
cast: a fossil made when minerals take the place of hard plant or animal parts
minerals: things found in nature that are not animal or plant
mold: a fossil made when an animal or plant rots away, leaving its shape in the rock
trace fossil: a fossil of an animal' s footprints or other signs of activityYou Practice
I. Answer the following questions.
1) What is a fossil?
2) How do plants or animals get buried quickly?
3) What is a mold?
4) What is a trace fossil?
5) What can trace fossils tell scientists?
II. What' s the word? Using the clues, write the correct words from the reading.
1) this is found at the bottom of lakes: s _ _ _ _ _ _ _
2) these happen when there is too much rain: f _ _ _ _ _
3) these are homes for birds: n _ _ _ _
4) this is a shape in rock: m _ _ _
5) these are many things on top of each other: l _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.____ 1) It takes a long time for fossils to form.
____ 2) A trace fossil could be made by a bird.
____ 3) Sand and soil are two kinds of sediment.
____ 4) Minerals replace the hard parts of an animal.
____ 5) It takes about ten years for a plant to turn into a fossil.09Where to Find Fossils
Rock that is made from sediment is called sedimentary rock. As layers of sediment build up over millions of years, the top layers press down on the bottom layers. The pressure turns the layers into rock. Sandstone, limestone, and shale are all types of sedimentary rock.
There are a lot of fossils in sedimentary rock because the remains of plants and animals become trapped in layers of sediment. As new layers of sediment are added, these layers protect and preserve the covered remains.
Fossils are found in all parts of the world. They are easy to find because most of the rock we see is sedimentary rock. We find fossils when we dig up the rock or when the rock erodes and reveals buried layers.
Scientists who study fossils are called paleontologists. When these scientists find a fossil they want to study, they use special tools to remove the layers of sedimentary rock from around the fossil. They must be very careful because fossils can be damaged easily.
Paleontologists have to know a lot about rocks in order to find fossils. They also study rocks to find out what the weather was like millions of years ago. Sometimes paleontologists fi nd ripples from waves and holes from raindrops made millions of years ago!Word List
preserve: protect from damage and keep in a certain condition
sedimentary rock: a kind of rock formed from layers of sediment
erodes: wears away
paleontologist: a scientist who studies fossilsYou Practice
I. Answer the following questions.
1) How is sedimentary rock made?
2) What are some different kinds of sedimentary rock?
3) Where are fossils found?
4) What is the name for scientists who study fossils?
5) Why do you think it is important to study fossils?
II. What' s the word? Using the clues, write the correct words from the story.
1) a kind of sedimentary rock: l _ _ _ _ _ _ _ _
2) to save something: p _ _ _ _ _ _ _
3) these are made by water: w _ _ _ _
4) under rocks or soil: b _ _ _ _ _
5) water that falls from the sky: r _ _ _ _ _ _ _ _
III. Read these sentences carefully. Write Yes or No for each one.
____ 1) Fossils are usually found in sedimentary rock.
____ 2) Fossils can be damaged easily.
____ 3) Fossils are only found in a few places in the world.
____ 4) Sedimentary rock is the kind of rock we usually see.
____ 5) Fossils can tell us things about the weather long ago.10Review(Lessons 6-9)
I. Fill in the blanks—Complete the following sentences with words from lessons 6-9.
1) A s _ _ _ c _ _ _ protects a seed from being damaged.
2) A t _ _ r _ _ _ goes deep into the ground below a plant.
3) Sediment p _ _ _ _ _ _ _ _ plants and animals after they die.
4) Animals help d _ _ _ _ _ _ _ _ _ seeds.
5) A t _ _ _ _ f _ _ _ _ _ shows footprints from millions of years ago.
II. Answer the following questions.
1) Would you like to be a paleontologist? Why or why not?
2) What conditions do most plants need to grow?
3) Where is a good place to find sediment?
4) What does seed germ turn into?
5) What are two good ways to distribute dandelion seeds?
III. Word groups—Complete the following word groups with words from lessons 6-9.
1) Parts of a plant: s _ _ _, r _ _ _ _, l _ _ _ _ _
2) Remains of an animal or plant: f _ _ _ _ _, m _ _ _, c _ _ _
3) They study fossils: s _ _ _ _ _ _ _ _, p _ _ _ _ _ _ _ _ _ _ _ _ _
4) They help plants reproduce: a _ _ _ _ _ _, p _ _ _ _ _ _ _ _ _,
5) They help keep plants and animals healthy: m _ _ _ _ _ _ _, n _ _ _ _ _ _ _ _11How Old Are Fossils?
Nobody knows exactly how old the Earth is because people weren' t around then. Scientists think life on Earth began about 4 billion years ago. The fossil record has helped scientists come to this answer. By studying fossils in different layers of rock, scientists can understand what Earth was like a very long time ago.
Scientists divide Earth' s past into blocks of time. Each block of time is millions of years long and during each period certain kinds of plants and animals lived. Not all plants and animals became fossils, but enough did that scientists are able to tell what lived during what period.
When a scientist finds a new or unfamiliar fossil, he or she looks at a marker fossil for clues about the age of the unfamiliar fossil. For example, trilobites are marker fossils. Trilobites are extinct, but between 520 and 250 million years ago, they were so common that there are more fossils of trilobites than any other creature. This is why they serve as “markers”of the time period they are from. If a scientist finds a new kind of fossil in the same rock as a trilobite fossil, the scientist can figure out when this plant or animal lived.
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