plants and animals classification

8/9/2019 Plants and Animals Classification

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Vocabulary

cellchloroplastcytoplasmgenusinvertebratesnucleusspeciesvertebrates

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by Laura Johnson



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The Building Blocksof Living Things

Think about the building blocks you played withwhen you were younger. You started with just one block.If you put a few blocks together, you could build ahouse. If you put many blocks together, you could buildsomething complicated, like a castle with towers. Allliving things—plants and animals—are made of cells.

A cell is the smallest unit of a living thing. You canthink of cells as building blocks. Some living thingsare made of just one block, or cell. Most plants and

animals are made by putting thousands, millions,or even billions of cells together.

Cells can have many jobs. Some cells help aliving thing to be healthy. Other cells help

it to adapt to its environment.Microscopes make objects appear

larger than they really are. By lookingat cells under a microscope,

scientists can see insidethem and learn howthey work.

blood cell

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The Parts of a CellCells have different parts, and each part has a

specic job to do. The nucleus is like the “brain” ofthe cell. The instructions for the cell’s job are storedin the nucleus.

The cell membrane is a thin covering all aroundthe cell. It has two jobs. It separates the cell fromthings around it. It also acts as a guard that decideswhat can come into and go out of the cell.

Cytoplasm holds everything a cell needs to carry

out its life processes. It is a material similar to jelly thatlls the cell. The nucleus oats in the cytoplasm.Plant cells have the same parts as animal cells—

plus some extras. The cell wall is outside of the cellmembrane. The walls of all the cells help hold up aplant. Chloroplasts are the parts of a cell that trapenergy from sunlight so a plant can make its own food.

cell wall

plant cellanimal cellmembrane

cytoplasm

chloroplasts

nucleusnucleus



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From Cells to OrganismsCells have different shapes, depending on the kinds

of jobs they do. For example, nerve cells are very thin.They act like wires that send messages through thebody. Nerve cells can be as long as your arm oras short as the period at the end of this sentence.

Cells that look alike and have the same shape dothe same job. These cells combine to build tissue.For example, nerve tissue is made of nerve cells.

Tissues of the same type combine to form organs.For example, the brain is an organ that is made ofnerve tissue.

nerve cell nerve tissue

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Organs that work together form anorgan system. Two organs—the brainand the spinal cord—build the centralnervous system in your body.An organism is the completeliving thing that is made whenall the parts are combined.

An organism is made ofmany cells. Unlike anorganism, a virus is a verytiny particle with similaritiesto both living and nonliving

things. It uses plant andanimal cells to make moreviruses.

brain

central nervous system



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Sorting Living ThingsInto Groups

There are more than a million organisms. Whokeeps track of them all? Biologists! In order to identify,compare, and study all these organisms, biologists use a

classication system. Using this system, they place everykind of organism into a group. All the organisms in agroup have common characteristics.

Biologists would ask questions like these to help themdecide if a shark and a dolphin belong in the same group.

Do sharks and dolphins have one cell or many cells?They have many cells. That is a common characteristic,so they belong in the same group.

Where do sharks and dolphins live? They live in theocean. That is another common characteristic, so theystill belong in the same group.

How do sharks and dolphins get oxygen? Sharks getoxygen from the water. Dolphins get oxygen from theair. That is a different characteristic, so they belong indifferent groups.

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Kingdoms—The Largest GroupKingdoms are the largest groups in the

classication system. Many scientists divideorganisms into six kingdoms. The kingdom thatan organism belongs to depends mostly on howmany cells it has, what cell parts it has, where itlives, and how it gets its food.

Kingdom Number of Cells Cell Parts Habitat Food Source

Ancient one cell no separate land or water make theirBacteria nucleus own food

True Bacteria one cell no separate land or water some kinds getnucleus food; some make

their own food

Protists usually one cell have a nucleus water and damp many get food; and other cell places on land some make

parts their own

Fungi usually many cells have a nucleus land get food

and other cellparts

Plants many cells have a nucleus land and water make theirand cell wall own food

Animals many cells have tissues, land and water get food organs, systems

The Six Kingdoms of Living Things



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Dividing the KingdomsSorting living things into six kingdoms is only the

beginning! Next, scientists divide the members of eachkingdom into smaller and smaller groups. They useorganisms’ features to decide which organisms are ineach group. After kingdoms, the groups are divisions,classes, orders, and families. The last two groups aregenus and species. Scientists use these last groups toname animals. A genus is a group of animals that aresimilar in many ways. For example, a dog and a wolf aremembers of the same genus. Their genus is Canis . Thegenus group is divided one more time into groups ofspecies. A species is a group of animals whose members

can reproduce. The species name often describes wherethe animal lives or what color it is.

The rst part of an animal’s scienticname is the genus. The second part is thespecies. So, although you might nameyour pet dog Max, hisscientic name wouldbe Canis familiaris.

FAMILYGENUSSPECIES

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KINGDOMDIVISIONCLASSORDER

How Living Things Are ClassiedAt the right of the chart is the kingdom, thelargest group to which your family dog belongs.The groups get smaller and smaller, and moreand more specic, until the nal twogroups, which form the animal’s

scientic name.



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How ScientistsClassify Plants

To sort plants into groups, scientists look at two maincharacteristics. One is the way that a plant transportswater and nutrients. The other is how a plant reproduces.

Moving Water and FoodSome plants, called vascular plants, have parts that

look like tubes. Water and nutrients from the soilmove up and down these tubes to the roots, stems, and

leaves. Vascular plants are all around you. You may havestepped on some this morning, if you walked on grass.If you had celery with your lunch, you ate one! Thetissue that makes up the tubes supports a plant’s stemsand leaves. Because of this, vascular plants can grow tobe very tall.

moss

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ReproductionThe second way that scientists

classify plants is by how they

reproduce, or make new plants.One group reproduces by makingseeds. A seed is a structure witha protective covering. Inside theseed is a young plant. In plants withowers, the seeds are in the owers.

Conifers are plants that make seedsbut do not have owers. In conifers,the seeds are in the cones.

Some plants have no seeds at all. Theyuse spores to reproduce. A spore is a singlecell surrounded by a cell wall. It can growinto a new plant if it falls on a place whereit can get the water and food it needs. Fernsand mosses have spores.

Plants without these tubes are callednonvascular plants. These plants pass waterand nutrients through cell walls, from onecell to the next. This process is very slow, sononvascular plants usually grow close to theground. That way, water and nutrients donot have to travel so far. Some nonvascularplants are mosses, lichen, and algae.

seed



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How ScientistsClassify Animals

The animal kingdom is divided into two maingroups. One group is vertebrates, or animals witha backbone. The other group is invertebrates, oranimals without a backbone.

VertebratesScientists have divided vertebrates into ve smaller

groups. This chart shows the characteristics that are

true for most of the vertebrates in each group.

Vertebrate Covering Breathing Birth

mammals hair or fur lungs live birth

birds feathers lungs hatch from eggs

reptiles scales lungs live birth or hatch from eggs

amphibians wet skin lungs or gills hatch from eggs

sh scales gills most hatch from eggs

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ReptilesLet’s take a closer look at one group of vertebrates—

reptiles. Reptiles include lizards, snakes, turtles,crocodiles, and alligators. These animals live in the waterand on land. As you can see from the chart, reptilesbreathe air with their lungs. Many people are verysurprised when they touch a reptile for the rst time.They expect them to be wet and slimy, but they havedry skin covered with scales.

People often confuse crocodiles and alligatorsbecause the bodies of these reptiles are similar in manyways. An easy way to tell them apart is to look at their

mouths. You can see a crocodile’s teeth when its mouthis shut, but you cannot see an alligator’steeth in that position.

alligator

crocodile



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The Life Cycle of a ReptileSea turtles spend most of their time underwater,

where they swim, sleep, and eat. Like all reptiles,they have to come to the surface to breathe airwith their lungs. If they are swimming, theyneed to come up for air about every ve or tenminutes. However, if they are asleep, they can stayunderwater for hours. Male sea turtles rarely comeon land, but female sea turtles come on land aboutsix times each nesting year to lay their eggs.

A female seaturtle lays hereggs on land.

Baby turtles hatch from theeggs between forty-ve andseventy days later, and theymake their way to water.

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Scientists are not sure how oldfemale sea turtles are when theynest for the rst time. But they doknow that they swim back to thesame area where they were hatchedas babies—even if that place ismiles and miles away.

The turtles grow tobe adults who willreproduce.



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Animals WithoutA Backbone

Animals without a backbone are calledinvertebrates. You might be surprised to learn thatmost animals in the world are invertebrates.

Arthropods are the largest group of invertebrates.This group includes ticks, spiders, bees, shrimp,scorpions, and centipedes. At rst, these animals seem

very different because some swim, some y, and somecrawl. However, they have two common characteristicsthat cause scientists to group them together. Therst characteristic is that all arthropods have legs

and a body that are divided into sections. Thesecond is that all arthropods are covered with

a lightweight, hard skin that protects them.This hard skin is called an exoskeleton.

centipede

bee

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The second largest group of invertebrates aremollusks. This group includes scallops, oysters, squid,and snails. Mollusks have soft bodies. Some have ahard shell and some don’t. Most mollusks live in water,but some live on land in damp places. Most mollusksare only a few inches long,but a few kinds are huge!Giant clams, for example,can grow to more than fourfeet long and weigh more thanve hundred pounds!

scallop

squid



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The Life CycleOf a Mollusk

When octopuses are ready to mate, themale fertilizes the female’s eggs. The femaleattaches the fertilized eggs to a rock or placesthem in a hole. Over the course of several days,a female may lay more than 100,000 eggs! Ifthe female has laid her eggs in a hole, she willoften seal up the hole to protect the eggsand ensure that they are not harmed.

Females guard the eggs constantly.Depending on temperature, the eggshatch anytime between four weeksand seven months later. A shorttime after the baby octopusesemerge from their eggs, thefemale octopus dies.

When the baby octopusesemerge from their eggs, theyoat to the top of the water.They stay there until theygrow larger and can returnto the bottom of theirwater habitat.

eggs

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baby octopus

adultoctopus



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Animal AdaptationsAdaptations are physical features or behaviors

passed on from parents. Adaptations help animals getfood, protect themselves, move, and reproduce. Animalswith the best adaptations have a better chance at gettingthe resources they need, so they have a better chanceof reproducing.

Adaptations ThatHelp and Protect

Many animals have physical adaptations that help

them move. Did you know that birds have hollow bonesto make them lighter? Did you know that sh have bagsof air in them that help them oat? Or that amingoeshave long necks so they can submerge their heads inwater and nd food in the muddy bottom? What aboutsnails? They have a at foot that oozes a sticky liquid.They move by sliding along paths of their own slime.

Shapes and colors can provide protection by makinganimals nearly invisible. When the long, thin razorsh holds itself straight up and down in the water,

it looks like a piece of oating grass.Features such as claws, tusks, andhorns protect some animals.

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Chemicals are another kind of adaptation. Somechemicals give animals a nasty smell or taste so otheranimals won’t eat them. Others poison their victims.An octopus can use its sharp teeth to drill a hole in aclamshell. It then injects poison through the hole. Afterthe clam is poisoned, its shell can be opened easily.

sharpteeth



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Animal InstinctsInstincts are behaviors that are inherited from

parents. These natural behaviors tell young animals howto move, how to hide, and how to catch food. They willremember these things all their life. Remember the babyturtles that nd their way to the sea? That is an instinct.

Migration and HibernationMigration is an instinct. Many animals migrate

to nd food as seasons change. Arctic terns leave theArctic Ocean in the fall, when the ocean begins to freezeand sh are scarce. They y to Antarctica, where share plentiful. In the spring, when the ice in the ArcticOcean begins to melt, the terns y home to nest.

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Another natural behavior thatdoes not need to be learned ishibernation. Some kinds of mammals,reptiles, and amphibians hibernate, orbecome inactive, when the weather isvery cold and food is hard to nd.

Chipmunks, for example, eat alot in the fall. The food is stored asbody fat that gives them energy duringwinter, when they hibernate. Theydon’t sleep straight through the winterbut wake for short periods to movearound and snack on saved food.

hibernating frog

Animals LearnNot all animal behaviors are

instincts. Many animals learnbehavior from their parents. Motherbears teach their cubs to sh. Andwolves have a way of teaching theiryoung to avoid traps!

All living things, from thesmallest cell to the largest organism,can be classied. Knowing theclassication of living things givesus information about what they aremade of and how they adapt.



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Glossary

cell the smallest unit of a living thing

chloroplast the part of a plant cell that trapsenergy from sunlight so the plantcan make its own food

cytoplasm the substance in a cell that containswhat the cell needs to carry out itslife processes

genus a group of closely related animals

invertebrates animals without a backbone

nucleus the control center of a cell

species a group of animals whose memberscan mate

vertebrates animals with a backbone

1. Describe how organisms are built from cells.

2. What are the ve groups of vertebrates?

3. What are adaptations? Give an exampleof one.

4. Plants can be vascular ornonvascular. Describe on your own paperhow they differ. Include details from thebook to support your answer.

5. Compare and Contrast Think aboutcrocodiles and alligators. How are theysimilar? How are they different?

What did you learn?

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