2 How do plants reproduce? When a plant grows, it goes through a series of stages. The stages that aliving thing goes through are called aLIFE CYCLE.Most food that we eat comesfrom plants.As consumers of plants we need tounderstand the life cycle of plants.
3 Most plants grow from seeds. First, a seed is placed in soil, so it can sprout.Next, the plant grows until itreaches maturity. A mature plant maygrow flowers or cones.Then, these structures make more seeds.The cycle continues.
6 There are about 274,000 different kinds of plants on Earth. Almost 90% of them reproduceby making seeds.Most seed-producing plants makeseeds in the flowers.
7 Only about 760 plants make seeds in structures calledcones.
8 In plants with cones, sperm are made in male cones and eggs are made in female cones.
9 Most cone-bearing plants are trees. Pines, spruces, and cycads are all cone-bearing plants.
10 reproductive structures. They produce reproduction sex cells. Flowers and cones arereproductive structures.They produce reproduction sex cells.Reproduction sex cells are used duringsexual reproduction.Male reproductive cells are called sperm.Female reproductive cells are eggs.
11 The male organ in the flower is called the stamen. It consists of a thinstalk topped by a saclike anther.The anther produces pollen.
12 FERTILIZATION Fertilization is the process of a sperm and an egg cell joining together.A fertilized egg grows into a newplant inside a seed.
13 In plants with flowers, sperm are contained in grains of pollen produced in the anthers.
14 Eggs are made in a structure called a pistil. Most flowers have both anthers and a pistil.
17 Everything the new plant needs in contained within the seed’s coat. Even a drop of water.Plant cell
18 Petals are the outer parts of the flower Petals are the outer parts of the flower. They are usually bright colors to attract insects.The male organ is the stamen. It is a thin stalk topped by a saclike anther, which produces the pollen.
19 In order for an egg to be fertilized, pollen has to move from the male POLLEN POWERIn order for an egg to be fertilized,pollen has to move from the maleparts to the female parts.
20 Plants reproduce through pollination. POLLINATION is the process of pollenmoving from a male plant part to afemale plant part.There are several ways this can happen.POLLEN
21 Sometimes wind can blow the pollen from one plant to another.
22 Other plants are pollinated by pollinators. Bees, birds, and butterflies, and otheranimals can be pollinators.A butterfly goes from flower toflower drinking nectar.The pollen on the stamensrubs off on the butterfly.As the butterfly visits flowerafter flower, pollen drops off and falls on the pistil.If this happens the flower will be pollinated.
23 Many water plants,such as rushes,are pollinated bywater. Flowing watercarries the pollenfrom one plantto the next.
24 Wind and water pollinate the other 25%. Animals pollinate 75% ofseed-making plants.Wind and water pollinate the other 25%.Use this information to create a circle graph.
25 The base of the pistil of some flowers grows into a big fruit that Animals pollinate 75%of seed-making plants.The base of the pistil of someflowers grows into a big fruit thatcontains the flower’s seeds.When an animals eats the fruit, theseeds pass through the animal’s bodybefore being deposited elsewhere.
27 Other animals will find and bury seeds. Think of squirrels.Squirrels bury acornsso they will have foodin winter. They dig upand eat most of theacorns, but they willforget a few. Thesewill grow into new oak trees.
28 Seeds such as burs travel when they stick to an animals body.
36 Quick Check cone cycle fertilization flower germination maturity pollen pollination seed1. What process happens when a sperm joins with an egg? _________2. What stage has a plant reached when it can reproduce? __________3. What process happens when a small root and plant begins to grow out of a seed? ___________________________________________4. What are the structures that contain a plant’s male sex cells? _____5. What structure do pine and spruce trees use to reproduce? _______6. What forms after a plant egg is fertilized? _______________________7. What process happens when pollen falls on a flower’s pistil? ______8. All of the stages a plant goes through is called its life ____________.9. What structure do rose bushes and apple trees use to reproduce?____________
39 Set up a formal experiment about seeds. What is your QUESTION? SCIENTIFIC PROCESSSet up a formal experiment about seeds.What is your QUESTION?What is your HYPOTHESIS?What MATERIALS will you use?What PROCEDURE will you follow?Will you DRAW pictures?Will you make CHARTS or GRAPHS?Will you SUMMARIZE your data?
41 Like plants, animals have a life cycle. Animals are born and then they growto become an adult. When animals areadults they have young of their own.The circle of life continues on and onforever…
42 When a bird reaches adulthood, it mates with another bird. After mating, a female bird lays eggs.Birds hatch from eggs.After the eggs hatch, the parentsfeed the young birds.Over time, the birds grow andbecome independent.Soon they can live on their own.And the cycle continues….
43 Most animals reproduce sexually. During sexual reproduction, sperm from a male joins an egg from a female.The fertilized egg can then developinto a new animal.This fertilized eggwith grow into atiny mouse.
44 In some animals, such as many kinds of fish, the eggs are fertilized outsideof the female’s body.In other animals, like birds, theeggs are fertilized inside the female’sbody.After the eggs are fertilized, the femalebird lays the eggs.Birds will protect the eggs until theyhave hatched.
45 After the young are born, they begin to grow and change. Over time, newborns develop into youths.Youths continue to develop until theygrow into adults.
46 Adult animals mate with one another to produce offspring. An animal’s life cycle ends whenthe animal dies.But that animal’s offspring will haveoffspring and the life cycle repeatsagain and again.
47 and spiders hatch from eggs. Like birds, manyother animals hatchout of eggs.Most fish, reptiles,and spiders hatch from eggs.
48 What happens afteran animal is born?Some animals, suchas turtles, areon their own assoon as theyhatch from theireggs.Their parents donot help them.
49 Other animals, likepenguins, give theiryoung a great dealof care.They keep their youngwarm and feduntil the young growstrong enoughto care for themselves.
50 Animals such as deer, bear, and rabbits take care of their young by feeding them milk.These animals may stay with theirparents for months or even years.Animals that feedtheir babies milkare called mammals.
51 Tigers give birth to live young. Young cats drink their mother’s milk.
52 When a kangaroo isborn, it is aboutthe size of a dime.They crawl from thebirth canal to theirmother’s pouch.The milk glandsare inside the pouch.
53 Raccoons usuallygive birth to3 to 5 youngat one time.Raccoons onlyhave one littereach year.
54 WHAT ABOUT US? Just like other animals, humans go through stages of development.After a human egg is fertilized,it grows inside the mother.
55 After nine months, the baby is born. When babies are born they drink their mother’s milk.
56 Newborn babies have no teeth, and they are not able to walk. It is up to the adult to care for them.
57 Babies grow intotoddlers.Toddlers learn to walk.They also start tolearn how to speak.Humans get theirfirst set of teethwhen they are
58 As a child develops, the first set of teeth, or baby teeth, are replaced bypermanent teeth.The child is growingand developing manyphysical and mentalskills during thistime.
59 During the teenage years, boys and girls start looking more like the adults they will become.
60 During adulthood, people reach maturity. Often, adults marry and have childrenof their own.
61 As an adult ages, they lose some of their physical abilities. The body changes in other ways, too.The hair turns greyor it may fall out.Or they may needglasses.
62 COMPLETE METAMORPHOSIS A young frog, or tadpole,has a long tail and no legs.As it grows, its tail becomesshorter, and it begins togrow legs. An adult frog hasno tail, but it has legs.These changes are known asMETAMORPHOSIS.
63 Butterflies go through complete METAMORPHOSIS. An adult butterfly lays an egg.The egg hatches into a larva.The larva of a butterfly is calleda caterpillar.The caterpillar grows into a pupa.Inside a chrysalis the pupa becomesan adult butterfly.
65 In many animals, the young look similar to the adults. But in other animals, the young look very different.In complete metamorphosis, an animalgoes through four differentstages in its life cycle.
66 The egg hatches into larva The larvae looks like a worm The larvae develops into a pupaThe pupa is enclosed in a cocoonWhile in the cocoon thepupa develops into the adult.The adult splits its cocoon and flies out.
70 Some insects, suchas dragonfliesand termites, gothrough a differentseries of changes.In incompletemetamorphosis,an animal only goesthrough threedifferent stages ofthe life cycle.
71 First, the animal hatches from the egg as a nymph. Nymphs look like tinyadults, but they don’t have wings.As a nymph grows larger, it molts.Molting happens when an insect shedsits hard out skeleton, or exoskeleton.After several moltings, the insect, whichnow has wings, reaches its adult stage.
72 QUICK CHECK 1. Most animals grow from a fertilized _______ cell. 2. Some animals, give birth to live young and care forthe young by feeding them _______________.3. After human babies are born, they develop into______ and eventually grow into ______ and then adults.4. Animals that have a larva stage and a pupa stage undergo _________ metamorphosis.5. Animals that have a nymph stage undergo_________ metamorphosis.
73 Some animals are endangered. Scientists study the life cycles of WHY DO WE CARE?Some animals are endangered.Scientists study the life cycles ofendangered animals to try to savethem and help them increasetheir numbers.Sea turtles are endangered.
74 Sea turtles have been hurt by hunting, pollution and beach erosion. To help sea turtles, people havelearned about their life cycle.They have used what they learnedto protect the sea turtles and helpthem survive and flourish.
78 Have you ever noticed how children often look like their parents? This happens because of a processknown as heredity.The passing of traits from parentsto their offspring is calledHEREDITY.
79 Look at the girl’s traits. The eyes are The hair is___________ ___________The ear lobes The chin isare _________ __________The tongue can___________
80 When you look in the mirror the you that looks back is a reflection of your parents’ traits.A trait is a feature of an individual,such as brown eyes.You inherit your eye color from your parents.You inherit your skin color and yourhair color and even freckles fromyour parents.
86 Genes are found inside cells. When sex cells unite, the new cell has genes from both the spermand the egg.This chicken’s feather color is inherited.
87 Half of your genes came from your mother. The other half came from your father. Because of this, youhave a mixture of traits from bothyour parents.
88 Remember that a sperm is the male sex cell. It contains genes from the father.An egg is a female sex cell.It has genes from the mother.When the two cells join, the resultingcell has genes from both parents.
89 Scientists have learned a lot about how genes control traits. Today, GENETIC ENGINEERINGScientists have learned a lot abouthow genes control traits. Today,scientists can take genes from oneliving thing and put them in another.They can change colors of vegetables.
90 This is called genetic engineering. Scientist use genetic engineering to change a living thing’s traits.For example, they can make a potatoplant poisonous to caterpillars.Scientists can also make goat milkwith medicine in it. This technology isvery new. Because of this, nobodyknows what the effects will be.
91 What do you think are three possible benefits of genetic engineering What do you think are three possible benefits of genetic engineering? What are some possible problems?BENEFITSPROBLEMS
92 Genes + Environment = YOU! Your genes alone do not control all of your traits. The environment youlive in affects your traits, too!Skin color can be changed by theenvironment. Staying in the sun canmake your skin darker. Too much sunis dangerous. Always wear sunblock.
93 These hydrangea flowers are pink. But if you want blue flowers all you need to do is change the acidity ofthe soil. You can change the acidityof the soil by adding nails to the soil.
94 Some traits are caused when your genes and environment interact. Your height is controlled by your genes.But it is also controlled by the kindsof foods you eat.If you do not eat nutritious food,you will not grow as tall as youcould on a healthy diet.
95 What other traits could be affected by the environment?
96 Plants grow toward the light. No matter where you put a plant, it will Other living things have traits caused by a mix of genes and the environment.Plants grow toward the light.No matter where you put a plant, it willalways growtoward the light.
97 The environment can change living things in other ways, too. A tadpole is a frog larva that swimsin the water. If the pond the tadpolesare living in begins to dry up, thetadpoles will undergo metamorphosisat a faster rate.They will become adult frogs fasterthan tadpoles in deep ponds.
99 The sex of alligators is affected by temperature. If an alligator egg develops at 30 degrees Celcius orless, it will be a female.If it develops at 34 degrees Celciusor more, it will be a male.
100 LEARNING LESSONS You know how to do many things. You were not born knowingEverything you need to know.You LEARNED them.
101 You know how to tie your shoes, how to read an analog clock and a digital clock. You know how toread a book and add numbers together.You know lots and lots aboutlots of things.But you weren’t born knowing howto do all of these things.
102 The ability to learn hlps an animal survive. This is called Think of how learning keeps you safe. You know to stop and look both ways before crossing the street.The ability to learn hlps an animal survive. This is calledLEARNED BEHAVIOR.Learned behavior is something ananimal learns from experience or bywatching other animals.
103 This chimpanzee is using a tool to get ants to eat. It probably learned to dothis by watching other chimpanzees.
104 Playing baseball is a learned behavior. You have to learn the rules of thegame. You also have to learn howto hit the ball with a bat.Playing baseball is a learned behavior.You have to learn the rules of thegame. You also have to learn howto hit the ball with a bat.
105 Many animals are able to learn things. Have you ever seen baby ducks following their mother?When the ducks first hatch, they learnto recognize their mother. After this,everywhere the mother goes, thebabies follow. This is called imprintingand it keeps the ducklings safe.
106 Can you think of other learned behaviors? If you have a pet, think of all thethings you have taught your pet to do.
107 Think about behaviors of working animals, such as horses and rescue dogs.
108 INSIGHT INTO INSTINCTS But not all behaviors are learned.Animals are born knowing howto do some things.Behaviors animals are born withare calledINSTINCTS.
109 Human babies have an instinct to cry Humans also have an instinct to when they are hungry.Humans also have an instinct tospeak a language.
110 But the instinct to speak is influenced by your environment. You must learn to speak a particularlanguage, such as English, Spanish,or Chinese. In this way, manybehaviors are a mix of learningand instincts.
111 Earthworms have an instinct to burrow in the ground. Calves are born with the instinct to nurse by drinking milk from their mother.
112 Other behaviors may be instinct alone Other behaviors may be instinct alone. Very soon after a baby horse is born, it is able to stand up. Within a few hours, he can walk and run. The horse does not need to learn these behaviors. It is pure instinct.
113 Spiders have an instinct to spin webs. Geese have an instinct to migratesouth in the winter.
114 RACEHORSE RUNNING ON RACETRACK Look at the behaviors below. Which are learned and which are instinctive?BEHAVIORLEARN/INSTINCTPARROT SAYING, “HELLO”RACEHORSE RUNNING ON RACETRACKBEE BUILDING A HIVEHIBERNATING SQUIRRELFISH SWIMMING
115 Living things inherit most of their traits REVIEWLiving things inherit most of their traitsfrom their parents. Inherited traits arecontrolled by genes. Traits can also becontrolled by the environment.In animals, traits include behaviors.Instincts are behaviors that an animal isborn knowing how to do. Many animalsare also able to learn behaviors. They learnthrough experience or by watching others.
116 gene heredity instinct instinctive offspring traits learned behavior Check What You Knowgene heredity instinct instinctiveoffspring traits learned behaviorPassing characteristics from parents to their young is know as ___An example of ___________ __________ is a child learning to read.A chemical instruction for a trait is known as a ________________.Green eyes and red hair are examples of _____________________.A bird chirping is an example of an __________________________.A living thing’s children are also known as its _________________.Mice, squirrels, and many other animals become inactive during the winter. This is a type of ________________________ behavior.
117 Check What You Know Explain how living things inherit traits. List 3 examples of physical traits affected by the environment.Draw and label a picture showing a learned behavior and draw and label a picture showing an instinctive behavior.