Animals Without Backbones1

7/30/2019 Animals Without Backbones1

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What Is This Module About?

This is the first of four modules prepared for you about the animal world. Three

modules are concentrated on animals without backbones and one, the last module, is on

animals with backbones. All the modules are especially prepared to equip you with

knowledge about animals. You will be made aware of the many kinds of animals in ourworld. You will see how much they differ from one another in size, structure and

characteristics. The modules will also give you an idea on how the different groups of

animals affect us. This module will focus on sponges and cnidarians.

This module is made up of three lessons:

Lesson 1 What Is an Animal?

Lesson 2 The Pore-Bearing Animals

Lesson 3 The Cnidarians

What Will You Learn From This Module?

After studying this module, you should be able to:

identify the characteristics of animals;

explain how animals are classified;

recognize and describe porous animals;

explain how porous animals affect people;

identify and describe bag-shaped animals; and

explain how bag-shaped animals affect people.


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Lets See What You Already Know

Before studying this module, take this simple test first to find out how much you already

know about its topics.

Write the letter of the correct answer in the blank provided.

____1. Which of the following is not a common characteristic of animals?

a. ability to produce their own food

b. ability to digest food

c. ability to move from one place to another

d. ability to breathe

____2. Which among the following is the largest unit of classification?

a. kingdom

b. phylumc. class

d. order

____3. What two classifications are scientific names (in the binomial system of

classification) composed of?

a. family and genus names

b. local and international names

c. order and genus names

d. species and genus names

____4. Which among the following animals have many pores on its body?

a. tapeworm

b. ascaris

c. sponge

d. earthworm

____5. Which of the following is a characteristic of porous-bodied animals?

a. hard-bodied

b. soft-bodied

c. spinyd. rough in texture

____6. Which among the following is a bag-shaped animal?

a. sea anemone

b. sponge

c. tapeworm

d. earthworm


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____ 7. What do you call the process of grouping, naming and identifying plants

and animals?

a. conserving

b. preserving

c. classifyingd. collecting

____ 8. What are the powerful tentacles of jellyfish for?

a. capturing food

b. reproducing their young

c. excreting wastes

d. sensing their enemies

____ 9. Which of the following is the simplest form of animal?

a. squid

b. earthworm

c. sponge

d. insect

____10. Which of the following is a vertebrate?

a. sponge

b. fish

c. starfish

d. oyster

Well, how was it? Do you think you fared well? Compare your answers with those in the

Answer Key on page 27 to find out.

If all your answers are correct, very good! This shows that you already know much

about the topics in this module. You may still study the module to review what you already

know. Who knows, you might learn a few more new things as well.

If you got a low score, dont feel bad. This means that this module is for you. It will

help you understand some important concepts that you can apply in your daily life. If you

study this module carefully, you will learn the answers to all the items in the test and a lot

more! Are you ready?You may go now to the next page to begin Lesson 1.


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LESSON 1

What Is an Animal?

Animals are generally thought of as creatures that breathe, move and eat. Yet we cannot

define animals strictly on the basis of these characteristics because not all of them inhale and

exhale like humans do. Not all of them move like we do too. Not all of them have mouths and

digestive systems. But in spite of our lack of a completely satisfactory definition of animals and of

living examples that do not fit neatly into any informal definition, we can still categorize animals

roughly as those organisms that breathe, move and eat. Before we discuss animals further, try to

reflect first on the following questions:

1. What do animals have in common?

2. How do they differ from one another?

Find out the answers to these questions as you go on with your study of animals.

Lets Try This

Below are pictures of some animals. Answer the riddles on the next page by choosing what

animal each riddle is referring to from the given pictures. Write your answers in the blanks

provided.

Snake Jellyfish Earthworm

Whale

Butterfly Starfish

Ascaris

Tapeworm

Ostrich

Frog

Crab


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1. My skin is soft and sticky. I can live both on land and in water. I lay eggs in the

water. What am I? __________

2. I am a reptile, I am long and can coil. I am a predator. I attack and eat chicks,

frogs, birds and other animals. What am I? __________

3. I have tentacles and can swim. I sting my prey with my poison. Many animals are

afraid of me. What am I? __________

4. I am round. My home is your intestine. We share the food that you eat. What am I?

__________

5. I am flat, segmented and very long. My home is your intestine. We eat the same

food together. What am I? __________

6. My home is the sea. I look like a star. My skin is spiny. What am I? __________

7. I have ten legs and a flat shell or carapace. I am your favorite food. I am reddish

when cooked. What am I? __________

8 I have colorful wings. I can fly in the sky. My best friends are flowers. I siphon

their nectars. What am I? __________

9. My home is wet soil. My body is segmented. My best friends are farmers. What

am I? __________

10. I live in the sea. I love to swim. I am the biggest of them all. I am a mammal like

you. What am I? __________

11. I am a bird but cannot fly. My body is too heavy to carry. I lay big eggs. What am I?

__________

Compare your answers with those in theAnswer Key on page 27. How well did you

do? Did you get all the answers right?

Lets Learn

You are now about to begin studying the most diverse kingdom of all living things, the

animal kingdom. Some animals have forms that are amusing. Others resemble creatures from

a nightmare or a horror movie. Some animals are so small that they can live inside our

bodies. Others are many meters long and live very deep under the sea. Animals can be black,

white, multicolored or almost transparent. They swim, walk, crawl, burrow or fly around

us. Although animals are different in many ways, all of them share the following basiccharacteristics:

1. Animals cannot make their own food. They depend on other living organisms for

food.

2. Animals digest their food. They cannot use proteins, fats and carbohydrates

directly.

3. Many animals move from place to place. By moving around, they can find food,

escape their enemies, find better places to live in and find mates.

4. Animals have many cells. Their different cells carry out functions such as

digestion and reproduction.5. Animal cells are eukaryotic. Their cells have nuclei surrounded by a membrane

and various organelles.


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But before we start our journey to the animal world, take a look first at the illustration

below and see how the different groups of animals are related.

The figure above shows us how the two main groups of animals developed from the

most basic types of living organismsthe protists. From this, we can see too which animals

are classified as arthropods and which are chordates.

Arthropods are members of the phylumArthropoda which contains 80% of all known

animal species. They all have exoskeletons, jointed legs and segmented bodies. Examples of

these include:

1. cnidarians radially symmetrical organisms that have two distinct cell layers

and no distinct head;

2. flatworms characterized by very flat, thin bodies having no spaces between the

layers of tissue inside their bodies;3. roundworms characterized by a one-way digestive tract and a body cavity;

4. mollusks includes such varied organisms as oysters, snails and squids;

5. annelids segmented worms that have coelums; earthworms;

6. arachnids a major class of chelicerates that includes spiders, scorpions, mites and

ticks;

7. crustaceans mandibulates with great degrees of specialization in various body

segments;

8. millipedes diplopods; literally, millipede means thousand feet, even though

in reality, few millipedes have more than a few hundred feet;

The evolutionary tree of the animal world

Centipedes

Millipedes

Fishes

Amphibians

Reptiles

Birds

Mammals

Insects

Roundworms

Mollusks

Annelids

Arachnids

Crustaceans

Flatworms

Cnidarians

LanceletsTunicates

Echinoderms

Sponges

Protist ancestors

Arthropods Chordates


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9. centipedes chilopods; literally, centipede means hundred feet; may have

between 15 and 150 pairs of legs and are usually only a few centimeters long; and

10. insects typical arthropods which have exoskeletons, jointed legs and

segmented bodies but have three major body sections, the anterior head, the

middle thorax and the posterior abdomen.

Chordates, on the other hand, are organisms with notochords, dorsal nerve chords and

gill slits. Examples of these include:

1. sponges have specialized cell types that are not so interdependent that they

would die if separated from the organisms as a whole;

2. echinoderms marine organisms having tube feet and endoskeletons that have

spiny projections extending through the epidermis;

3. tunicates have all the characteristics of chordates but lack backbones;

4. lancelets organisms that normally bury all but their heads into the sand;

5. fishes free-swimming organisms;

6. amphibians cold-blooded vertebrates belonging to the classAmphibia; they

hatch as fishlike eggs and transform into adults that can live on land;

7. reptiles snakes, lizards, turtles, alligators, etc. which reproduce on land by

laying eggs;

8. mammals most of these develop their young internally and after giving birth

nurse them on milk; a few though hatch from eggs; have hair or fur at some time

during their lives; and

9. birds have feathers and bodies adapted for flight; reproduce by laying eggs.

Lets Review

Match the items in Column A with their descriptions in Column B. Write only the letters

of the correct answers in the blanks provided.

Column A Column B

a. a major class of chelicerates that includes

spiders, scorpions, mites and ticks

b. cold-blooded vertebrates belonging to the class

Amphibia

c. radially symmetrical organisms that have two

distinct cell layers and no distinct head

d. have specialized cell types that are not so

interdependent that they would die if separated

from the organisms as a whole

e. most of these develop their young internally and

after giving birth nurse them on milk



___1. cnidarians

___2. arachnids

___3. sponges

___4. amphibians

___5. mammals


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Lets Learn

Scientists have identified and named over one million species of animals. Some

estimate that there are five to ten million more to identify and name. Have you ever

wondered how and why animals are grouped?Animals are classified based on:

Let us first discuss how animals are classified on the basis of similarities of body

parts. Look at the illustration below.

How are these animals classified?

You can probably think of a number of ways into which the organisms above could be

grouped. Try to use structural similarities as a basis for grouping. In other words, examine the

organisms general appearance and arrangement of body parts and try to put similar organisms

together.

Notice that the animals in the middle frame are grouped according to number of legs.

Those in Frame A have three pairs of legs each, while those in Frame B have four. Notice

that each group is further divided into smaller groups. Under Frame A, the organisms with

wings were grouped (Frame A1) as well as those which do not (Frame A2 ). Under FrameB, the organisms that have two main body parts were grouped (Frame B

1) and those which

A B

A1

A2

B1

B2

Structure

Chemicalmakeup

Animal classificationFoodneeds

Behavior


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have only one main body part were also put together (Frame B2). With each sorting, you can

see that the organisms in the group become more and more alike.For better understanding,

look at the concept map below:

Lets Try This

Answer the following questions briefly.

1. What four factors do biologists study when classifying animals?

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

d. _____________________________________________________________

2. What was the basis for the classification system shown in the previous activity?

_________________________________________________________________

_________________________________________________________________

Compare your answers with those in theAnswer Key on page 27. How well did youdo? Did you get the answers right?

Group of animals

Animals with three

pairs of legs

Animals with wings Animals without

wings

Ani

b


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Lets Learn

The animal kingdom is divided into nine major phyla and more or less 21 minor phyla.

In this module, we will only concentrate on the nine major phyla.

The nine major phyla of the animal kingdom are: Porifera, Coelenterata,Platyhelminthes, Aschelminthes, Molluska, Annelida, Arthropoda, Echinodermata and

Chordata. All these animals have the characteristics that we mentioned at the beginning of the

lesson. So how does a scientist begin to classify a new animal he/she encounters?

The first step is to determine if the animal has a backbone or not. Animals with

backbones are called vertebrates. Some examples of vertebrates are fishes, humans, whales

and snakes. About 95% of animals are invertebrates or animals that do not have backbones.

Sponges, jellyfish, worms, insects and clams are examples of these. The next thing that a

scientist will look at is the arrangement of the animals body parts or the animals

symmetry. Some animals have body parts arranged around a central point. These animals

are said to have radial symmetry. Sea anemones and starfish are examples of these. Most

animals though have bilateral symmetry or their body parts are arranged in the same way on

either side of their bodies. Bilateral animals can be divided into right and left halves by

drawing an imaginary line down the length of their bodies. Animals that do not have definite

shapes are called asymmetrical animals.

Lets Try This

Apply what you just learned by classifying the animals below based on structural

similarities. Use the concept map on the next page for this.

Snake Butterfly Fish Spider


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do?

Lets Learn

In Carolus Linnaeus time, there were only two kingdomsthe plant kingdom and the animal

kingdom. The system worked well until further advances were made in classifying organisms. Biologists

now use a five-kingdom system. In fact, a six-kingdom system is now being proposed. The five-

kingdom system we now use includes the kingdoms Protista, Monera, Fungi, Plantaeand

Animalia. A kingdom is the largest group of classification. It is subdivided into several phyla

(phylum, singular). Each phylumis divided into classes,which are further divided into orders.

Orders are divided into families and families into genera.Each genus (genera, singular) is

divided into species. The species is the basic unit of classification.

Lets Try This

Make a concept map of the various classifications of living things below from the

biggest to the smallest group.

Compare your concept map with the one in theAnswer Key on page 28. How well did

you do?

snake, butterfly, fish, spider

Animals with

backbones

1. __________

2. __________

Anima

3.

4.

Animal with

gills

5. __________

Animal without

gills

6. __________

Animal with

legs

7. ________


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Lets Learn

What would happen if we didnt use names? For example, what if somebody asks you

about something or someone and instead of using its or his/her name, he/she gives acomplete description just so youd understand what or who he/she is talking about? That

would be too much work, dont you think? Names give us a quick and easy way of

identifying things or people.

This is precisely the reason why over 200 years ago, a Swedish naturalist, Carolus

Linnaeus, organized a simple naming system for animals that we still use today. He gave each

animal species a scientific name. Each scientific name is composed of two words, the genus

and species names. This system is called the binomial system of naming organisms. The names

are in Latin. An example of this is the scientific name for the domestic cat, Felis domesticus.

The genus name is Felis and the species name is domesticus. Using scientific names for

animals ensures that there can be no confusion. Anyone who sees the words Felis domesticuswill know that what is being referred to is a cat.

Lets Review


1. Who was the proponent of the binomial system of classification? What is the binomial

system of classification?_________________________________________________________________

_________________________________________________________________

2. What is the purpose of naming organisms?

_________________________________________________________________

_________________________________________________________________


do? Did you get the answers right?


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Lets See What You Have Learned

Enumerate the following:

1. Three basic characteristics of animals:

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

2. Animals can be classified according to:

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

d. _____________________________________________________________

3. Three kinds of arthropods:

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

4. Three kinds of chordates:

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

5. Levels of classification:

a. _____________________________________________________________

b. _____________________________________________________________

c. _____________________________________________________________

d. _____________________________________________________________

e. _____________________________________________________________

f. _____________________________________________________________

g. _____________________________________________________________

Compare your answers with those in theAnswer Key on pages 28 and 29. How well

did you do? Did you get a perfect score? If you did, then you learned a lot from this lesson. If

you didnt, dont worry. Just review the parts of the lesson you didnt understand very well

before going to Lesson 2.


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Lets Remember

Animals are organisms that eat, breathe, move and digest food.

There are more or less 1.5 million species of animals that have been identified

and many more are being discovered.

Animals can be grouped based on similarity in structure, chemical makeup,

behavior and food needs.

There are seven units or levels of classification with the kingdom as the largest

unit and the species as the most basic unit.

Originally, there were only two kingdoms established by Linnaeus. However, due

to further advances in science, the number was increased to five. Now, we are

using a five-kingdom system. However, a sixth kingdom is already being

proposed. There are nine major phyla in the animal kingdom. The simplest of these include

the pore-bearing animals, while the most complex is composed of the mammals.

Carolus Linnaeus introduced the binomial system of classification. In this system,

he uses two levels of classification in naming each organism the genusand

species names.

The scientific names given to organisms are in Latin.


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LESSON 2

The Pore-Bearing Animals

Have you ever visited large aquariums or gone snorkeling with your friends? If so, Im

sure you have already seen some of the animals that we will discuss in this lesson. Here we

will take up the simplest group of animals, the sponges or the pore-bearing animals.

Sponges are among the most ancient of all the animals that are alive today. The first sponge

ever reported to exist dates back to around 580 million years ago. Sponges belong to the

phylum Porifera which literally means pore bearers. Sponges have tiny openings all over

their bodies.

Of the million or more existing animal species, 95% have no backbones and are

classified as invertebrates. They have a wide variety of shapes and sizes, from

microscopic ones to a giant squid measuring up to 55 ft. long. It is said that such squids are

big enough to fight with whales that try to prey upon them. Many of these invertebrates live

in the ocean. Others live in freshwater, on land, in the soil and even on the bodies of other

animals.

Lets Try This

If you live near the sea, it will be convenient for you to perform this activity. It will

acquaint you with the sponges. Be sure to take the necessary precautionary measures. Stroll

along the beach and look for organisms similar to the one below. Do not touch them. Just

observe them. If you want to touch them wear gloves because some of them may be itchy due

to sponginand spicules.

If you dont live near the sea, you may just look at display specimens in a museum.

Sponges


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Lets Learn

Years ago, scientists thought sponges were plants. Why? Simply because they dont

move from one place to another like other animals. They remain steady in one place or stay

attached to a substrate. There are around 3000 species of sponges. The most common of

these are the bath sponges. They are considered the simplest multicellular animals. They

have tiny holes or pores in their bodies. They are usually found in the sea. They have two

layers of cells, an outer layer and an inner layer. They take in food by engulfing them.

They usually feed on particles suspended in water like plankton and some bacteria. They

have wide openings known as oscula (osculum, singular)or openings where food passthrough. They digest their food in gastrovascular cavities much like our stomachs. They do

not have anuses and so the food they fail to digest pass through oscula too.

Some groups of sponges grow on the bodies of other animals like corals and on the

shells of mollusks. In shellfish farms, sponges are unwanted since they can grow luxuriantly

on the shells of mollusks and badly affect them.

Proper care should be taken in handling sponges since their bodies contain thousands of

spicules or needle-like structures which can cause irritation to ones skin. These spicules are

composed of siliceous or glasslike materials and calcium carbonate. The Venus flower

basket is an example of a beautiful sponge with siliceous spicules.

The most common sponges in the sea

Poterion

Callyspongia

Leucosolenia

Euplectella

Venus flowerbasket


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Aside from spicules, sponges bodies are also composed of collagen and fibrils of

collagen collectively known as spongin. This gives support to the sponge and prevents it

from collapsing. They are ideal scrubbing materials. They have only a few enemies. Their

unique skeletal framework and often noxious odor or taste protect them from most potential

predators who find them unattractive and unpalatable.

Lets Try This


1. How do sponges take in food?

_________________________________________________________________

_________________________________________________________________

2. Why are sponges a problem in tahong and other shellfish industries?

_________________________________________________________________

_________________________________________________________________

3. What makes sponges ideal for scrubbing?

_________________________________________________________________

_________________________________________________________________



Lets Learn

Do you know how sponges can affect our lives? Read on to find out.

Not all sponges are beneficial to humans. Some may grow on shellfish like oysters

and mussels preventing them from getting their food. This may even result in their

death. Therefore, sponges can indirectly affect humans by harming the oyster

industry.

Most sponges are beneficial to humans because of the presence of unique skeletal

structures making them ideal for scrubbing and cleaning dirty materials in the kitchen.

The family of sponges, popularly called boring sponges, are important in

cleaning up the ocean floor.

Since the time of the Greeks and Romans, humans have been using dried and

cleaned bodies of sponges in bathing. Most of the sponges you see in supermarkets

today are artificial but natural bath sponges are still available.

Now, scientists are trying to discover other uses of sponges especially in

manufacturing chemicals.


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Lets Think About This

Based on what you have just learned, are sponges more beneficial or harmful to

humans? Why?

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Have your Instructional Manager check your work. Ask him/her for some feedback on

your answers.


Match the terms in Column A with their definitions/descriptions in Column B. Write the

letters of the correct answers only in the blanks provided.

Column A Column B

a. Literally means pore bearers

b. A flexible protein fiber that makes up the

skeletons of some sponges

c. A mouthlike aperture in a sponge

d. Important kind of sponge because they

clean up the ocean floor

e. Aquatic, usually marine, invertebrate

multicellular animals that consist of a

large cluster of cells attached to a solid

object such as a rock and which usually

live in colonies

f. Animals that do not possess backbones

g. Needlelike projections that form the firm

part of sponges

h. A deep-sea sponge with a skeleton made

of glassy spicules


do? Did you get a perfect score? If you did, then you learned a lot from this lesson and are

ready to move on to the next one. If not, dont worry. Just review the parts of this lesson that

you didnt understand very well before going to Lesson 3.

______ 1. Sponges

______ 2. Porifera

______ 3. Invertebrates

______ 4. Spongin

______ 5. Spicules

______ 6. Osculum

______ 7. Venus flowerbasket

______ 8. Boring sponges


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Lets Remember

Sponges are the simplest kinds of animals. They have no organs, only tissues.

There are around 3000 living species of sponges.

Bath sponges are the most common kind of sponge.

The osculum serves as the mouth of a sponge. This is a large opening on top of a

sponge.

Sponges produce skeletons in the form of spongin and spicules.

Sponges vary in shape and color. They are one of the most colorful animals in the

sea.

In ancient times, the principal use of sponges was for bathing. Now, they are being

tested for medical/chemical uses.


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LESSON 3

The Cnidarians

If you live close to the sea, you will find not only sponges but cnidarians as well. In

some books, they are popularly referred to as coelenterates or bag-shaped animals.

Cnidarians include many animals with brilliant colors and unusual shapes. Delicate jellyfish

float in ocean currents. Brightly-colored sea anemones cling to rocks, looking more like

underwater flowers than animals. These beautiful and fascinating animals are found all over

the world but most species live only in the sea. Our seas abound with them, in fact, we have

beautiful sea anemones and jellyfish. This lesson will talk about the different cnidarians. We

will talk about their different kinds as well as how they affect our lives.

Lets Try This

If you live close to the sea, look for and examine these invertebrates. Take the

necessary precautions though. Be very careful not to provoke or intimidate them. They might

hurt you. Do this activity during low tide. Do not forget to equip yourself with a glass-bottom

box, a trowel and a pair of forceps or gloves.

Use the glass-bottom box to locate these animals. Do you see the beautifully colored

sea anemones? They are stationary but with very movable tentacles. If you disturb their

surroundings, they tend to react and hide their tentacles. Do not touch them for they might hurt

your hand with stinging cells. Other cnidarians are stationary like the corals. How many

types of corals do you see? Try to look for other cnidarians. See if jellyfish are available. If

you see one, do not go very close to it. It might sting you. Just observe its body movements.

Notice that unlike the sea anemones, jellyfish are very mobile. They move from one place to

another.

If you do not live close to the sea, just study the illustrations of cnidarians below. Note

their similarities and differences. One similarity that is very noticeable is the presence of

tentacles or arms. In corals, however, such tentacles are not visible because their polyps arevery small.

Sea anemone Jellyfish Coral


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Lets Learn

There are more than 9000 different species ofcnidarians,the Latin term for stinging

cells. Most species are marine while few are terrestrial. The most common freshwater

species of cnidarians is the hydra. This is only around 5 mm long. Some cnidarians are bag-shaped like the sea anemones. Their bodies are hollow with one opening at the top, the

mouth or osculum. Inside their bodies are gastrovascular cavities where extracellular

digestion of food takes place. They have circular tentacles that can shoot out stingers or

nematocysts that can poison and paralyze other organisms.

Their tentacles can capture their prey which are then broken down as food with the help

of digestive substances. This method of capturing food is best demonstrated by sea anemones

and corals.

Have you ever seen coral decorations? Did you know that these are only secretionsor

skeletonsformed by the animals that formerly occupied it.

Lets Read

Do you want to find out how the coral decorations mentioned earlier are made? Read

on then.

Preparing Corals for Display

1. Collect fresh corals from the sea.2. Soak them in plastic containers with ordinary tap water for around two

days. This process will kill the animals or polyps living in them.

3. On the third day, change the water and clean the corals using a brush.

4. Soak them in water with some bleaching agents. This will make your corals

whitish in color.

5. Rinse and air-dry your specimens.

6. Now they are ready for display.

7. Some people mix dye with the water to make the corals more colorful.

Collecting corals was banned years ago to preserve our natural resources. However,

for educational purposes, a few can still be collected.


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Lets Learn

The most harmful species of jellyfish is Chironex flickerii. This is a jellyfish found in

the tropical seas of Australia. This species can kill a person it stings in 3 to 20 minutes after

the attack.

Remember when a total blackout occurred in Luzon because of the uncontrolled growth of

jellyfish. They damaged the power plant near their habitat. The heat the plant emitted must

have triggered their increase in number. Jellyfish flourish during the summer when seawater is

warm. The illustration below presents the life cycle of a jellyfish.

Let us define some of the terms in the illustration above.

1. ovary the female reproductive organ

2. medusa a bell-shaped, free-swimming body form found in cnidarians

3. testis a male gonad that produces sperm

4. sperm male reproductive cells made in the testes (testis, singular)

5. egg the female reproductive cell or gamete

6. blastula a small, fluid-filled ball of cells that is an early stage in the

development of an embryo

7. planula a ciliated larval type found in cnidarians

8. obelia colony an example of a cnidarian

After learning about the important terms that have to do with the life cycle of the

jellyfish, let us now look at how jellyfish go about their lives.

Hydranth PerisarcCoenosarc

Ovary MedusaTestis

SpermEgg

Blastula

Free-swimmingplanula

Hydrorhiza

Obelia colony

Gonangium

Gonotheca

Hydrotheca

Hypostome

Mouth

Tentacles

Blastostyle

Gonopore

Medusabuds

The life cycle of a jellyfish


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Jellyfish exist in one of two body forms. One form is known as a polyp, the other body

form is the medusa. Their life cycle alternates between these two stages. Medusae (medusa,

singular) reproduce sexually. In most medusae, sexes are separate with females producing

eggs and males producing sperm. After fertilization, the zygote develops into a blastula

which elongates to form a planula. The planula eventually attaches itself to the bottom of the

ocean floor where it grows into a polyp. The polyp reproduces asexually by formingmedusae which develop one on top of another. When the medusae form egg and sperm, the

cycle is complete.

Lets Learn

Did you know that cnidarians have various economic uses.

They are important in island formation and building reefs. The reefs serve as

shields for islands against strong waves and serve as nurseries for the millions

of fishes in the ocean.

Red and black corals can be made into precious jewelry.

Coral reefs are also valuable tourist attractions.

Some cnidarians are used in medical research. Corals are now being studied to

provide us with anti-cancer drugs.

Lets Review

From the previous activity you will see that cnidarians have many economic uses. How then

can you in your own way preserve them? List down some measures you can take in the space

provided below.

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

Have your Instructional Manager check your list. Ask him/her for some feedback.


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Match the terms in Column A with their definitions/descriptions in Column B. Write the

letters of the correct answers only in the blanks provided.

Column A Column B

a. A freshwater polyp with a tubelike

body and tentacles round the mouth,

remarkable for its ability to multiply

b. A kind of cnidarian

c. A small, fluid-filled ball of cells that

is an early stage in the development of

an embryo

d. Radially symmetrical organisms thathave two distinct cell layers and no

distinct head

e. Where extracellular digestion of food

takes place

f. A bell-shaped, free-swimming body

form found in cnidarians

g. A ciliated larval type found in

cnidarians

Compare your answers with those in theAnswer Key on page 29. How well did youdo? Did you get a perfect score? If you did, then you learned a lot from this lesson. If you

didnt, dont worry. Just review the parts of the lesson you didnt understand very well

before going to the next part of the module.

______ 1. Cnidarians

______ 2. Hydra when cut or divided

______ 3. Gastrovascular cavities

______ 4. Obelia colony

______ 5. Medusa

______ 6. Blastula

______ 7. Planula


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Lets Remember

Cnidarians are soft- bodied animals with tentacles used for stinging their enemies.

There are more or less 9000 different species of cnidarians. They are mostly

marine but with a few terrestrial exceptions.

Some cnidarians are stationary while others are mobile. Cnidarians show a

variety of shapes and colors. They are simple, mostly bag-shaped animals. They

have tentacles to capture their prey with.

Polyps secrete substances that form the exoskeletons of corals.

Some species of jellyfish like Chironex flickerii are deadly. They can kill their

victims in 30 seconds.

Some cnidarians are now being studied for medical purposes.

Well, this is the end of the module! Congratulations for finishing it. Did you like it? Didyou learn anything useful from it? A summary of its main points is given below to help you

remember them better.

Lets Sum Up

This module tells us that:

Animals are organisms that eat, breathe, move and digest food.

There are more or less 1.5 million species of animals that have been identified

and many more are being discovered.

Animals can be group based on similarity in structure, chemical makeup, behavior

and food needs.

There are seven units or levels of classification with the kingdom as the largest

unit and the species as the most basic unit.

Originally, there were only two kingdoms established by Linnaeus. However, due

to further advances in science, the number was increased to five. Now, we areusing a five-kingdom system although adding a sixth kingdom is already being

proposed.

There are nine major phyla in the animal kingdom. The simplest of these include

the pore-bearing animals while the most complex is composed of the mammals.

Carolus Linnaeus introduced the binomial system of classification. In this system,

he uses two levels of classification in naming each organismthe genus and

species names.

The scientific names given to organisms are in Latin.

Sponges are the simplest kinds of animals. They have no organs, only tissues. There are around 3000 living species of organisms.


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Bath sponges are the most common kind of sponges.

The osculum serves as the mouth of a sponge. This is a large opening on top of a

sponge.

Sponges produce skeletons in the form of spongin and spicules.

Sponges vary in shape and color. They are one of the most colorful animals in the

sea.

In ancient times, the principal use of sponges was for bathing. Now, they are being

tested for medical/chemical uses.

Cnidarians are soft-bodied animals with tentacles used for stinging their enemies.

There are more or less 9000 different species of cnidarians. They are mostly

marine but with a few terrestrial exceptions.

Some cnidarians are stationary while others are mobile.

Cnidarians show a variety of shapes and colors. They are simple, mostly bag-

shaped animals. They have tentacles to capture their prey with. Polyps secrete substances that form the exoskeletons of corals.

Some species of jellyfish like Chironex flickerii are deadly. They can kill their

victims in 30 seconds.

Some cnidarians are now being studied for medical purposes.

What Have You Learned?


1. Give three common characteristics that distinguish animals from other living

organisms.

a. _____________________________________________________________

_____________________________________________________________

b. _____________________________________________________________

_____________________________________________________________

c. _____________________________________________________________

_____________________________________________________________

2. Define what a sponge is.

________________________________________________________________________________________________________________________

________________________________________________________________________________________________________________________

3. Define what a cnidarian is.

_______________________________________________________________________________________________________________________

________________________________________________________________________________________________________________________

Compare your answers with those in theAnswer Key on pages 29 and 30. How well

did you do? Did you get a perfect score? If you did, thats very good. You may then move onto the next module. If you didnt, dont worry. Just review the parts of this module you didnt

understand very well before studying another module.


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Answer Key

A. Lets See What You Already Know (pages 23)

1. (a) Animals cannot produce their own food.

2. (a) The kingdom is the largest unit of classification.

3. (s) The binomial classification system makes use of the species and genus names.

4. (c) A sponge is also known as a pore-bearing animal.

5. (b) Pore bearers are soft-bodied.

6. (a) A sea anemone is a bag-shaped animal.

7. (c) This process is known as classifying.

8. (a) They use tentacles to capture food.

9. (c) The sponge is the simplest form of animal.

10. (b) A fish is a vertebrate.

B. Lesson 1

Lets Try This (pages 45)

1. frog

2. snake

3. jellyfish

4. ascaris

5. tapeworm

6. starfish

7. crab

8. butterfly

9. earthworm

10. whale

11. ostrich

Lets Review (page 7)

1. (c)

2. (a)

3. (d)

4. (b)

5. (e)

Lets Try This (page 9)

1. Biologists classify animals based on four factors, namely, structure, chemical

makeup, behavior and food needs.

2. The basis of classification in the previous activity is similarity in structure.


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Lets Try This (pages 1011)

1. snake

2. fish

3. butterfly

4. spider5. fish

6. snake

7. butterfly

8. spider


Kingdom

Phylum

Class

Order

Family

Genus

Species

Lets Review (page 12)

1. Carolus Linnaeus

2. To avoid confusion and facilitate communication

Lets See What You Have Learned (page 13)

1. a. Animals cannot make their own food.

b. Animals digest their food.

c. Many animals move from place to place to find food, escape their enemies,

find better places to live in and find mates.

(There may be other answers to this, just refer to page 5.)

2. a. structure

b. food needs

c. behavior

d. chemical makeup

3. a. centipedes

b. millipedes

c. crustaceans

(There may be other answers to this, just refer to the illustration on page 6.)


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4. a. birds

b. reptiles

c. mammals

(There may be other answers to this, just refer to the illustration on page 6.)

5. a. kingdomb. phylum

c. class

d. order

e. family

f. genus

g. species

C. Lesson 2


1. Through the osculum

2. They prevent shellfish from getting food causing them to die

3. The presence of spongin and spicules

Lets See What You Have Learned (page 18)

1. (e)

2. (a)

3. (f)

4. (b)5. (g)

6. (c)

7. (h)

8. (d)

D. Lesson 3

Lets See What You Have Learned(page 24)

1. (d)

2. (a)

3. (e)

4. (b)

5. (f)

6. (c)

7. (g)

E. What Have You Leaned? (page 26)

1. a. Animals cannot make their own food.

b. Animals digest their food.

c. Many animals move from place to place to find food, escape their

enemies, find better places to live in and find mates.

(There may be other answers to this, just refer to page 5.)


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2. A sponge is any of several hundred different species of aquatic, usually

marine, invertebrate multicellular animals that consist of a large cluster of

cells attached to a solid object such as a rock and which usually live in

colonies.

3. A cnidarian is a radially symmetrical organism that has two distinct celllayers and no distinct head.

Glossary

Bilateral symmetry Having identical parts of the body when an imaginary line divides

an objects body vertically.

Calcium carbonate Usually insoluble, whitish and coarse composition of species.

Collagen A tough, fibrous protein found in some sponges that make them ideal for

scrubbing.

Classification The process of grouping living things.

Gastrovascular cavity The cavity in coelenterates that functions both in digestion and

circulation and has a single opening serving as both mouth and anus.

Invertebrate An animal without a backbone.

Medusa The jellyfish or free-swimming stage in the life cycle of cnidarians.

Nematocyst A stinging structure on the tentacle of a cnidarian that is used to paralyze

and kill its prey.

Osculum The mouth or the excurrent opening in a sponge.

Polyp Sessile, flower-like cnidarian.

Phylum The second largest unit of classification used for living things.

Radial symmetry Arrangement of the body parts of an organism in such a way that

they repeat around an imaginary line drawn through the center of the organisms body.

Sessile Immobile.

Siliceous Glasslike materials composed of silica.

Species The basic unit of classification.

Spicule One of the minute, siliceous skeletal bodies found in sponges and corals.

Spongin Fibrous, collagenous materials making up the skeletal network of sponges.

Vertebral column Backbone which encloses and protects the nerve cord.


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References

Balzer, L.Introduction to Biology. Glenview, Illinois: Scott, Foresman and Co., 1986.

Campbell, N.Biology. Fourth ed. U.S.A.: Benjamin Cummings, Inc., 1996.

Hickman, C. and L. Roberts.Animal Diversity. Chicago, U.S.A.: Wm. C. Brown

Publishers, Inc., 1995.

Hopson, J. and N. Wessels.Essentials of Biology. U.S.A.: McGraw-Hill Publishing,

Inc., 1990.

Miller, K. and J. Levine.Biology. New Jersey: Prentice Hall, 1991.

Ortleb, Daniel E. and D. Biggs.Life Science. U.S.A.: McGraw-Hill Publishing, Inc.,

1994.Wong, H. and M. Dolmatz.Biology: Key Ideas. New York, U.S.A.: Globe Book

Company, Inc., 1986.

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