Chapter 13 – Why Do We Fall ill

 

Chapter 13 – Why Do We Fall ill

We all do a lot of activities like exercises,eating meals, fruits, etc. in order to achieve good health. But do we know exactly what is good health? Are we actually healthy? Let us learn about the meaning of being healthy and unhealthy. We know that our body is formed of many organs and also, there are so many systems operating in the body. If one organ stops working, then other functions are also affected. This leads to uneasiness.

 

Health

It is a state of physical, mental and social well being. For being healthy, one needs to eat a balanced diet, take rest, take proper sleep, live in a hygienic place, etc . But sometimes, certain signs appear in a person that cause uneasiness. This uneasiness is called disease.

 

Disease

It is a state when the body is not functioning properly due to one or more reasons. We do not actually feel comfortable in carrying out routine tasks like there can be pain in the body or body part or we may suffer from certain problems in breathing or it can be any other uneasiness. This all comes under diseases.

Health is influenced by many factors like community and personal hygiene. As we know, we live in societies, our social environment also plays a key role like-

1.     We should keep our houses clean.

2.     Proper sewage disposal system should be maintained.

3.     No stagnant water should be there.

4.     No open drains, etc. should be there.

Similarly, personal hygiene is important like –

1.     One should take bath regularly.

2.     One should wear clean clothes.

3.     Drink clean water.

4.     Eat adequate nutritious food.

5.     One should maintain social harmony and equality.

 

Sources of diseases

We have seen that there are many factors that can cause infection or spread disease. There can be different factors responsible for uneasiness. Let us check them out .

There are different sources of diseases, out of which the main factors are as follows-

1.     Intrinsic factors

2.     Extrinsic factors

Intrinsic factors

These are those factors that are within the human body. These diseases are caused by internal factors, therefore, they are also called organic diseases.

The internal factors can be as follows-

1.     Malfunctioning of any body part

2.     Genetic disorder

3.     Hormonal imbalance

4.     Malfunctioning of immune system

Diseases can also be caused by improper secretion of hormones like Goiter, Diabetes, Cretinism, Addison’s disease, etc.

Extrinsic factors

The diseases that are caused by factors that are not present within the body.

The extrinsic factors can be the following-

1.     pathogens.

2.     Unbalanced diet.

3.     Environmental pollution.

4.     Narcotic drugs, etc.

 

Types of diseases

(a)Diseases caused by pathogens

 

 

(b)Diseases caused by inadequate diet

 

 

(c) Diseases caused by environmental pollution

 

  

Classification of diseases

(a) Depending upon the harm it can cause to the body, the diseases fall in different categories as given below-

1.     Physical diseases that affect organs

For example: bone fracture, leprosy, etc.

2.     Infectious diseases that are spread by pathogens.

For example: typhoid, AIDS, malaria, etc.

3.     Deficiency diseases that occur due to nutrient deficiency.

For example: scurvy, Marasmus, Kwashiorkor, etc.

4.     Inherited diseases that occur due to default genetic makeup.

For example: sickle cell anemia, etc.

5.     Degenerative disease that is caused due to a gradual increase in age.

For example: poor sight, poor hearing, etc.

6.     Mental disorders that occur due to certain tensions.

For example: depression, etc.

7.     Social disorder that is due to certain bad habits.

For example: drug addiction, etc.
(b) Depending upon whether the disease can spread from a sick person to a healthy person or not.

1.     Communicable diseases

2.     Non communicable diseases

Communicable diseases: Those diseases that can spread from a sick person to a healthy person by contact are called communicable diseases. They are mostly caused by external factors. They are transmitted through direct contact or through air, water, vector, etc. They are also called infectious diseases.

 

 

For example: Common cold, Cholera Tuberculosis, Pneumonia, Malaria, etc. These diseases are mainly spread through pathogens and the mode of transmission is either air, water, vector or sexual contact. As you must have seen that sometimes, if our friend is suffering from cold and we sit close to him or use his handkerchief, we also fall sick. The reason behind this is that the virus passes to us as well and we suffer from the infection. Let us see how these factors help in the transmission of diseases.

 

Mode of transmission of diseases

a) Air borne infections

The diseases that are passed by air are called air borne infections. They are transferred by droplet infection.

 

For example, if any person having cold sneezes, then he releases the droplets in air. The same air is inhaled by an infected person which passes the disease causing agents to a healthy person. For example : common cold, cough, etc.

 

b) Water borne infections

If the infected agent is spread by dirty water, then the infection is called water borne infection.

 

 

For example: if the stool of any sick person passes into a water body and that water is not purified and by any chance it mixes with drinking water. This water, when taken, causes infections. For example: cholera.

 

c) Sexually transmitted diseases

They are caused due to Sexual contact with a sick person, use of same syringes, etc. For example: Syphilis and AIDS, etc.

 

 

d) Vector borne infections

Vectors are those carriers that do not directly affect us but they transfer the disease causing agent to us.

 

 

For example: Female anopheles mosquito carry malaria pathogen plasmodium in its saliva. When this mosquito comes in contact, it mixes its saliva containing pathogens with our blood. Due to which the pathogen is transferred to us. So, in the case of malaria, vector is female mosquito and pathogen is plasmodium.

Non communicable diseases

The diseases that are not transferred from sick person to a healthy person. For example: arthritis, kidney failure, etc.

 

 

For example: if a person is suffering from kidney failure or pancreas infection and you sit close to him then the disease will not be transferred to you.

(c) Depending upon the duration for which the disease lasts in us, we have different types of diseases as given

1.     Acute disease

2.     Chronic disease

Acute diseases

They are the diseases that last only for a short span. They do not cause such long term bad effects. For example : cold, Cough, Typhoid, etc.

Chronic diseases

They are those diseases that last for a long time. They cause long term bad effects. For example: elephantiasis, diabetes, etc.

(d) Depending upon the time at which the disease is present in the body.

1.     Congenital diseases

2.     Acquired diseases

 

 

Congenital diseases

These are those diseases that are present since birth. These are caused due to a genetic defect or malfunctioning of body parts or metabolic disorder etc .They are permanent. They may pass to children. For example: sickle cell anemia, etc.

Acquired diseases

They are not present from childhood or we can say that they are acquired during lifespan. They can be communicable or noncommunicable. For example: Arthritis.

 

Symptoms and signs

 

Whenever there is occurrence of some disease- short term or long term, there are always certain signs of uneasiness that are felt or seen by us. Like, if somebody is infected by malarial parasite, then before the disease can be diagnosed, certain signs are seen like one feels excessively cold, high fever, loss of appetite, weakness, etc. These all signs appear during the incubation period when the infection is just spreading. They indicate the presence of disease.

The symptoms of each disease are particular. We often confuse symptoms with signs. So, let us see that what is the sign of a disease.

Signs

They actually are the symptoms that are not general or are particular for a particular disease. For example: in below given picture we can see that it can be headache, eye pain, rashes, nausea, etc.

  

Prevention of diseases : vaccination and immunization

 

If there can be diseases, obviously, we have treatments to prevent or cure them. There are very few diseases that do not have a cure. Let us see how we can prevent or cure them.

We can remove the disease by following either of two steps:

1.     Reduce the effects of disease

That is – we can take proper medication to destroy the infection causing agent in our body.

 

2. Remove the causes of microorganisms

That is- we can take certain measures in order to prevent the spread of microorganisms.

 

Prevention of diseases

1. General ways of prevention

For air borne infections

1.     Keep the house ventilated.

2.     Do not be in overcrowded places.

3.     Live in a clean environment ,maintain personal and community hygiene .

 

For water borne infections

Drink clean and pure water

For vector borne disorder

1.     Do not chase street dogs.

2.     Do not let water to stand near your houses.

3.     Keep food items covered.

 

2.Specific ways of prevention

If we have strong immune system, then the infecting agent or its toxin can’t affect us.

 

Immunity

Suppose if you and your one or more friends are sitting close to an infected person. After a while, you feel uneasy but your friend doesn’t. This can happen as there may be a chance that your body does not possess the power to fight infections but your friend’s body may have the power to resist or fight infections. Here comes the factor of immunity. Let us learn about it.

Immunity: It is the resistance against diseases. To raise our immunity level, vaccination is done.

Vaccination

You must have seen that when a child is born, the doctor injects him with a few medicines. This is done in order to enhance the immunity of the newly born child. As we know, the newly born child is going to encounter a new environment, so he may take time to adapt himself. Therefore, injections provide artificial immunity to him so that he can resist himself from infections.

Vaccination: It is the process of injecting either killed or weakened microorganisms in a person’s body so as to raise his immunity level.

It functions in the following manner- when vaccine is given, that is killed or weakened microorganism is injected, the body fails to recognize it and in response, secretes certain antibodies that try or kill the infection causing foreign agent. These antibodies, once made, remain in the body and protect us throughout our life from the particular antigen.

The first vaccine was prepared by Edward Jenner in 1796 against smallpox. Now- a- days, many vaccines are given to a newborn child in order to raise its immunity.

 

Why do we fall ill Class 9 Question Answers

 

1.State any two conditions essential for good health?

Ans : Balanced diet, community and personal hygiene are the two conditions essential for good health.

 

2. What are the various means by which infections are spread?

Ans : Infections are spread by air, Water, Vector and Sexual contact.

 

3. What is immunization?

Ans : Immunization is the process of making people immune to a disease by artificial methods.

 

4. What precautions will you take at school to reduce the incidence of infectious diseases?

Ans :The precautions to be taken at school to reduce the incidence of infectious diseases are – drinking clean water, availability of proper food, proper ventilation and to stay away from an infected person.

 

5. What are antibiotics?

Ans :Antibiotics are the medicines that are advised by doctor in case of microbial infections.

 

6.Why are we advised to take balanced diet when we are sick?

Ans : Nourishing food is good for health and simple food and is easy to digest. It helps in strengthening the body and increases our immunity.

 

7.In which case would the long term effects on your health be most unpleasant?

1.     If you get jaundice

2.     If you get acne

3.     If you get lice

Ans : Jaundice will be chronic as it has long term harmful effects. It can also be fatal.

 

8.Under which condition you are most likely to fall sick :

1.     When you are giving exams

2.     When you are travelling in bus or train for two days

3.     When your friend is suffering from measles.

why?

Ans : In case my friend is suffering from measles, I will be most likely to fall sick because it is an infectious and contagious disease.

 

9.Under what condition person is most likely to fall sick?

1.     When she is recovering from Malaria.

2.     When she has recovered from malaria and is taken care of someone who is suffering from chicken pox.

3.     When she is on four day fast after recovering from malaria and is taking care of a person suffering from chicken pox.

why?

Ans : When a person is on a four day fast after recovering from malaria and is sitting with a person suffering from chicken pox, he is likely to fall sick soon because of less food in the body. Organs such as liver do not recover so soon. A person will get infected with chickenpox as his immunity is not too strong.

 

10.A baby is not able to tell his caretakers that he is sick. What would help us to find out :

1.     That the baby is sick?

2.     What is the sickness?

Ans : Signs of diseases like :Baby is cranky, restlessness is seen, baby feels hot, eyes start watering, cough, loose motions, vomiting indicate that the baby is sick.

But Sickness can be known by consulting a doctor.

 

11. Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by localites to prevent diseases.

Ans : The common diseases are: loose motions, cough and cold and malarial fever.
Prevention:

1.     Reduce the effect of infectious diseases.

2.     Public cleanliness needed.

3.     Immunisation.

4.     Use of clean drinking water.

 

12.A doctor is exposed to many sick persons than others in a community. Find out how he avoids getting sick?

Ans : To reduce the incidence of infections, the following can be done:

1.     Immunisation

2.     Wear gloves and masks

3.     Take prophylactic medicines

4.     Wearing coat

5.     Washing hands with soap after examining.

 

13. What changes can we make in our habits to prevent diseases?

Ans : The following changes can be made in our habits to prevent diseases-

1.     Avoid contact with infected person

2.     Drinking clean water

3.     Consume balanced diet

4.     Community and personal cleanliness

5.     Proper disposal of waste

 

Diversity in Living Organisms

 

Diversity in Living Organisms

Introduction – Biodiversity

We see a lot of organisms around us and each organism is unique in its sense. In the world, there are 12 mega biodiverse countries. These countries are divided into 10 biogeographical regions. The variety of physical features, climatic conditions result in the occurrence of a wide variety of habitats like forests, etc. This leads to the occurrence of varied life forms. This is called biodiversity.
Biodiversity refers to the varied forms of living beings which differ from one another in external appearance, size, colour, pattern, internal structure, nutrition, etc.

 

Basic tools -Taxonomy and Binomial nomenclature

For Naming Organisms

In the old system, common vernacular names were introduced according to which the names were given to organisms like dog is called kutta in Hindi, kukar in Bangla and Naai in Tamil. As these names are differently used in all parts of the country, so, they are not understood by others. Therefore, Binomial nomenclature is used for assigning proper names.

Taxonomy

To assign names there is a biological science that deals with identification, naming  and classification of organisms and is called Taxonomy. The main function of a taxonomist is to provide scientific names to organisms.

Binomial Nomenclature

It was developed by Linnaeus and was mentioned in his book published in 1753. His system of naming is accepted worldwide and he is called the father of taxonomy.

According to it, every organism is given two proper names-

First – Is the name of genus (it is shared among closely related organisms). It is just like surname that is shared by all the members of a family.

Second name – Is the name of species to which it belongs (species – a particular kind of organism like we all are humans).

These names are set according to International code of binomial nomenclature.

Whenever the name is written-

• Genus (first with first letter capital)
• species (written after generic name and always in small letters).

Please Note – Both the names have space between them and are underlined separately.

Example:  For frog, the name is -Rana  tigrina

Classification systems

We have a lot of organisms existing around us. To study them we need an easy method so as to recall different characteristics of different forms. This can be done by classifying different life forms.

Classification: It refers to identification and grouping of similar organisms together on the basis of their form and function.

Importance of classification

1.     It makes the study of a wide variety of organisms easy.

2.     It projects the picture of all life forms at a glance.

3.     It is essential to understand the interrelationships among different groups of organisms.

4.     It forms the basis of development of other biological sciences.

Classification is done as:

• Two kingdom classification
• Five kingdom classification

Two kingdom classification

As we all know we see a variety of plants and animals around us and there are a lot of differences existing between plants and animals related to their food habits, cell structure, etc. So, scientists thought that we can classify the organisms into 2 main groups .Therefore, the classification was done as:

• Plant kingdom
• Animal kingdom

This classification was suggested by Carolus Linnaeus  in 1758.

But as more and more diverse forms were discovered, this classification took a back seat and a new system was proposed that is five kingdom classification.

Five kingdom classification

It was given by Whittaker in 1959.

According to it, the organisms are classified into 5 kingdoms:

• Monera (consists of prokaryotic bacteria and blue green algae)
• Protista (consists of unicellular eukaryotic organisms-  protozoa, fungi and algae)
• Fungi (consists of higher fungi)
• Plantae (consists of multicellular green plants and advanced algae)
• Animalia  (consists of multicellular organisms)

This classification was based on three aspects-

1.     Prokaryotic versus eukaryotic.

2.     Unicellular versus multicellular.

3.     Modes of nutrition.

 

Hierarchy in Classification

The main aim of a taxonomic study is to assign organisms an appropriate place within the systematic framework of classification.
He had to frame a proper chart to address the organisms so, he decided to make a framework and this framework was regarded as hierarchy.
According to this, groups are arranged in a definite order from higher to lower categories. Each category is called taxon.
The order of levels is as follows:

Let us define them:

1.     Kingdom: It refers to all the organisms who share a set of distinguished common characters. Example: plant kingdom and animal kingdom

2.     Phylum: It includes all organisms belonging to different classes having common characteristics.

3.     Class: It represents the organisms of a related order.

4.     Order: It is an assemblage of families resembling one another in a few characters.

5.     Family: It is represented by a group of related genera that   are more similar to each other than to the genera of other families.

6.     Genus: It is a group of species which are related and have less characters in common as compared to species.

7.     Species: It is a group of individuals with similar characters.

8.      

Basic characteristics of five kingdom

As you can see different forms with different features like a butterfly, Cow, elephant etc So, Let us learn about the different and important features of different organisms belonging to different kingdoms.

Kingdom Monera

The kingdom prokaryotes are divided into two sub kingdoms:

• Archae-bacteria.
• Eubacteria.

Archaebacteria

• Most Archaebacteria are autotrophs and only photosynthesize.
• They derive energy for metabolic activities from oxidation of chemical energy resources like ammonia, methane, etc.

They are divided into 3 groups –

• Methanogens: They make methane as a result of metabolic activities.
• Thermoacidophiles: They favour hot and acidic environment and use hydrogen sulphide as an energy source.
• Halophiles – They grow in salty environment (alkaline).

Eubacteria

• They have an outer cell wall that surrounds the plasma membrane.
• They have cytoplasm, ribosome but membranes enclosed bodies are absent like nucleus, etc.
• A circular strand of DNA is present.

The bacteria are of different shapes like:

 

1.     Bacilli (rod shaped).

2.     Cocci (spherical).

3.     Spirillium (spiral).

4.     Vibrio (comma).

The bacteria are classified as gram positive and gram-negative bacteria.

• Gram positive bacteria: Stains red with gram stain.
• Gram negative bacteria: Do not stains red.

Kingdom Protista

• It includes unicellular eukaryotic organisms.
• They have hair like appendages called cilia, flagella, etc.
• Their mode of nutrition can be autotrophic or heterotrophic.
• Example: Unicellular algae chlorella, diatoms, etc.

 

It includes phylum protozoa which has the following characteristics:

• Unicellular.
• Solitary or colonial.
• Body naked or covered by shells.
• Body shape may be irregular, spherical, oval, etc.
• Cytoplasm is divided into outer ectoplasm and inner endoplasm.
• Locomotion by pseudopodia, flagella, cilia, etc.
• Nutrition is heterotrophic.
• Asexual reproduction by fission and sexual.

It has 5 Classes

1.     Mastigiphora

• They have locomotors flagella.
• For Example: Euglena, Trypanosoma, etc.

2.     Sarcodina:

• Locomotion by Pseudopodia.
• For Example: Amoeba, etc.

3.     Sporozoa

• They lack locomotory organs and all are parasites.
• For Example: Plasmodium, etc.

4.     Ciliata

• They have cilia as locomotors orgas
• Example :Paramecium etc

5.     Suctoria

• No locomotory organs.
• For example: Ephelota, etc.

Kingdom fungi

•  
• They are simple, non – green plants that are not photosynthetic.
• They are heterotroph & eukaryotic organisms.
• Some fungi are parasites, and some are decomposers and many are saprophytes.
• They may be unicellular like yeast or filamentous like most of the other fungi. The filamentous fungus is called mycelium and it has several thread- like structures called hyphae.

• Cell wall of fungi is made up of chitin and cellulose.
• The reserve food is in the form of glycogen.

Example: Bread mould (Rhizopus), mushroom, etc.

Lichens

They are the symbiotic association of blue green algae with fungi. The algal component is called phycobiont and the fungal part is called mycobiont.

In this association, the role of fungus is to absorb water and minerals and function of algal part is to prepare food and supply to fungus.

Example: Foliose lichens, Crustose lichens, etc.

Kingdom Plantae

• It includes multicellular organisms except the primitive algae.
• They are eukaryotes.
• Cell wall consists of cellulose.
• A mature plant cell has a large vacuole for storing food in the form of starch.
• They have double membrane organelles plastids
• Some plastids have photosynthetic pigment called chloroplast.
• They are autotrophic.
• Growth is indefinite.
• Body form is irregular as it possesses branches.

Kingdom Animalia

• They are wall – less eukaryotes.
• They are heterotrophic with holozoic mode.
• Growth of animals is limited.
• They generally have a definite shape, size and symmetry.
• Some animals are mobile. The locomotion is necessary for obtaining food, etc. Movements occur through muscular system.
• They have organ level organization. Locomotory organ  is cilia. For Example: Paramecium, etc.

Plant kingdom

Classification of Kingdom plantae is based on three major factors:

1.     Plant body is differentiated or not

2.     Presence or absence of vascular tissues

3.     Ability to bear seeds and whether these are enclosed within the fruit or not.

Let us study about different divisions of Kingdom Plantae

 

Division Algae

Characteristics

1.     Most primitive and simple

2.     Body is not differentiated into roots, stems or leaves and occurs in the form of undivided thallus.

3.     They are water growing.

4.     They usually contain green photosynthetic pigment but some also possess red, brown and purple pigments.

5.     They are autotrophic.

6.     They have cell wall made up of cellulose.

7.     No vascular tissues.

8.     Asexual reproduction by spores.

9.     Sex organs are simple and there is no embryo formation.

Example: Green algae – Ulothrix  ,spirogyra ,Red Algae – Batra ,Brown Algae- Laminaria, etc.

 

Division – Bryophytes

Characteristics

1.     They are small green multi-cellular land plants.

2.     They are also called amphibians of the plant Kingdom.

3.     Their plant body is flat, green thallus in liverworts like Riccia, etc and leafy erect structures in mosses like funaria, etc. They lack root, stem, leaves and flowers.

4.     Their plant body is flat, green thallus in liverworts like Riccia, etc and leafy erect structures in mosses like funaria, etc. They lack root, stem, leaves and flowers.

5.     No true vascular system present.

6.     Rhizoids are present to absorb water and nutrients.

7.     Sex organs are multicellular.

8.     Embryo is formed.

Example: Riccia, etc. 

Division – Pteridophytes

Characteristics

1.     They are found in damp places.

2.     Their body is made up of root, stem and leaves.

3.     They have well developed vascular system.

4.     They don’t have flowers and fruits.

5.     Sex organs are multicellular.

6.     Fertilized egg develops into an embryo.

Example: Club mosses – Lycopodium, horsetails – Equisetum and ferns- Azolla, etc. 

Division – Gymnosperms

1.     They are primitive and simple seed plants.

2.     The seeds produced by them are naked and are not enclosed in fruits.

3.     They are primitive and simple seed plants.

4.     They are perennial, evergreen and woody plants.

5.     The sporophylls are aggregated to form cones (male and female cones).

6.     In them Xylem lacks vessels and Phloem lacks companion cells.

Example: Cycas, Pinus, etc.

 

Division – Angiosperms

1.     They are highly evolved and produce seeds that are enclosed within fruits.

2.     The reproductive organs are present in flowers.

3.     Embryo of these have cotyledons that is seed leaves.

4.     Endosperm has triploid cell that supplies nutrients to embryo.

5.     Embryo of these have cotyledons that is seed leaves.

6.     Endosperm has triploid cell that supplies nutrients to the embryo.

 

Depending upon the number of cotyledons, the angiosperms are divided into groups:

• Monocots
• Dicots

Monocots

1.     The seeds with one cotyledon.

2.     Their leaves have parallel venation.

3.     They have fibrous roots.

4.     Flowers are tri-merous.

5.     Vascular bundles are scattered and closed.

6.     Example: Maize, rice, etc.

 

Dicots

Characteristics

1.      

1.     They have 2 cotyledons.

2.     They have reticulate venation.

1.     They have tap root system.

2.     Flowers are penta-merous.

3.     Vascular bundles are arranged in ring.

 

Example: Pea, Sunflower, etc.

 

  

Animal kingdom

Basic Characteristics of Animals

• Except a few, most of them are motile.
• Animals are arranged from simple to highly complex animals
• Except a few, most of them are motile.
• Animals are arranged from simple to highly complex animals

Animals are divided into two Branches

• Parazoa
• Eumetazoa

Parazoa

• The animal body is made of loosely aggregated cells
• They have poor differentiation of tissues
• They have no organ and digestive cavity

Eumetazoa

• The cells are properly arranged into tissues and organs.
• Their digestive tract is mouth but with or without anus.

They are further classified on the basis of:

• Number of germ layers present in embryo
• The symmetry of the body of organism
• The mode of origin of mouth.

• The symmetry of the body of organism
• The mode of origin of mouth.

Germ Layers

They are the layers that surrounds the embryo.

The organisms with two germ layers are called Diploblastic organisms.

• The outer layer is called the ectoderm.
• The inner layer is called endoderm.
• Both the layers enclose a non-cellular jelly-like fluid called mesoglea.

The organisms with three germ layers are called triploblastic animals.

• Outer layer   – Ectoderm
• Middle layer – Mesoderm
• Inner layer         – Endoderm

 

Let us learn about the symmetry of body

 

Bilateral Symmetry

• When two sides of the body are mirror images of one another

Radial Symmetry

• It is the arrangement of usually similar parts in a regular pattern around the central axis.

On the basis of the origin of the mouth, the animals are

Protostomia

• When the mouth arises from or near blastopore of gastrula.

Deuterostomia

• When mouth arises anteriorly at some distance from blastopore.

 

Based on the presence or absence of body cavity (coelom) the organisms are:

Acoelomates

• Which do not have a body cavity because there is no space between the body wall and digestive tract.

Pseudocoelomates

• They have a cavity between the body wall and digestive tract.

Coelomates

• They have a true body cavity which originates from mesoderm and is not lined by epithelial cells.

Let us discuss different phylum of animal kingdom (from simple to complex)

 Phylum 1 Porifera

1.      

1.     They are sessile, sedentary and marine. They are non motile and are attached to solid support.

2.     They are multicellular, simple and diploblastic.

3.     They have tissue level differentiation.

4.     They are asymmetrical or with radial symmetry.

5.     They are also called as sponges and are vase – like, sac – like or branched.

6.     Body has many pores called ostia that open into the canal system which is lined with cells called choanocytes.

7.     The oral opening is called osculum.

8.     The canal system helps in circulating water throughout the body to bring food, oxygen and water.

9.     Mouth, digestive system and anus are absent.

10.                        Skeleton is made up of spicules that are made up of collagen fibres.

1.     Reproduction is both asexual and sexual.

2.     Asexual by budding and Sexual by fertilization

 

Many other examples :

 

Phylum 2 – Cnidaria or Coelenterata

1.     Aquatic, mostly marine and few are fresh water.

2.     Some live in colonies and some live solitary.

3.     They are multicellular, diploblastic, with tissue level organisation.

4.     A coelenteron is present which lacks anus but has mouth surrounded by tentacles.

5.     They have special cells called stinging cells (Nematocysts).

6.     They help in paralyzing and holding the prey.

7.     Respiratory, Circulatory and excretory systems are absent.

8.     Primitive nervous system is present.

9.     They show the phenomenon of polymorphism.

10.                        Body shows two main forms: Polyps and medusae.

11.                       

12.                        Polyp: Diploid, cylindrical and sedentary. They occur in colonies or solitary and reproduce asexually.

13.                        Medusae: Diploid, umbrella – like and free-swimming sexual phase of organism.

14.                        Asexual reproduction by budding and sexual by gamete formation.

Example: Hydra, Obelia, Aurelia, Rhizostoma , etc.

 

Phylum 3 – Ctenophora

1.     Transparent body with bilateral symmetry.

2.     Triploblastic.

3.     Marine, solitary and free-swimming.

4.     Nematocysts are absent but adhesive cells called colloblasts are present.

5.     No polymorphism

Example: Cestum, Ctenoplana, etc. 

Phylum 4 – Platyhelminthes

1.     Bilateral symmetry.

2.     Body is thin, leaf – like.

3.     Triploblastic and without body cavity.

4.     Digestive system with single opening that is mouth, no anus present.

5.     Circulatory, skeleton and respiratory systems absent.

6.     Excretory system consists of blind tubules called protonephridia whose end bears flame cells.

7.     Hermaphrodite organisms

Example: Planaria, Fasciola, Taenia solium, etc.

 

Phylum 5 – Nematoda

1.     Bilateral symmetry, triploblastic, unsegmented and pseudocoelomate.

2.     Body is Worm – like, cylindrical or flattened.

3.     Body is covered with tough, resistant cuticle, cilia is absent.

4.     Alimentary canal is straight and complete with mouth and anus.

5.     Body is covered with tough, resistant cuticle, cilia is absent.

6.     Alimentary canal is straight and complete with mouth and anus.

7.     Sexes are separate.

8.     They are parasitic.

9.     Parasitic nematodes causes different diseases like elephantiasis.

Example: Ascaris, Wuchereria bancrofti, etc. 

Phylum 6- Annelida

•  
• They are triploblatsic, bilateral, symmetrical, soft , elongated, cylindrical or flattened organisms.
• Body is metamerically segmented externally by grooves and internally by septa.
• Exoskeleton absent, the body is covered by a thin cuticle.
• Locomotory Organs: Lateral appendages, parapodia.
• Complete alimentary canal.
• True coelom with closed vascular system.
• Excretion by nephridia.
• Nervous system consist of dorsal brain and ventral nerve chord having ganglia and nerves.
• Reproduction by sexual means.

• Sexes may be hermaphrodite or separate.
• They live in a variety of habitats.

 

 Phylum 7- Arthropoda

1.      

1.     Triploblastic, bilateral symmetry and segmented animals.

2.     Body segments are grouped into

3.     two regions: Cephalothorax and abdomen

4.     or into

5.     three regions: Head, thorax and abdomen.

6.     They have complex muscular system, striated muscles for rapid actions and smooth muscles for visceral organs.

7.     Each body segment bears lateral and joint legs.

8.     Body cavity is haemocoel.

9.     Alimentary canal is complete.

10.                        Respiration through general body surface, gills or trachea.

11.                        Circulatory system is open with dorsal heart, arteries and haemocoel but no capillaries and veins present.

1.     True nephridia absent.

2.     Sexes are separate.

3.     Internal fertilization.

4.     This is the largest phylum.

Example: Prawn, Peripatus, etc.

 Phylum 8 – Mollusca

1.      

1.     Body is soft, bilateral, symmetrical with little segmentation.

2.     No appendages are found.

3.     Body is divided into head, ventral muscular foot and a hard dorsal mass. The entire body is covered with a thin skin called mantle.

4.     Haemocoel is present.

5.     Digestive tract is simple.

1.     Respiration through gills.

2.     Circulatory system is an open type.

3.     Sexes are separate.

4.     They are aquatic, mostly marine and freshwater.

Example: Chiton, Pila, Limax, etc.

 Phylum 9 – Echinodermata

1.      

1.     Simple animals, star-like.

2.     Triploblastic, coelomate, unsegmented and radially symmetrical.

3.     Body lacks head but has oral and aboral surfaces.

4.     Body wall is covered with hard calcareous plates that form endoskeleton.

5.     Locomotion by tube feet.

6.     Digestive system is complete.

1.     Excretory organs absent.

2.     Sexes are separate.

3.     Sexual and sexual reproduction is seen.

Example: Echinus, Asterias. Etc.

 

 Phylum 10 Hemichordata

1.      

1.     Body is soft, unsegmented worm-like with bilateral symmetry.

1.     Body is divided into proboscis, collar and trunk.

2.     No nephridia present.

3.     Notochord present.

Example: Balanoglossus, etc.

 

Phylum 11 Chordata and its groups

They are characterized by three important features:

1.     Dorsal, hollow, tubular nerve cord

2.     Notochord is replaced by a bone or cartilage to form the vertebral column.

3.     Paired gill slits in pharynx

Please note: notochord is a long rod-like support structure that runs along the back of an animal and separates the nervous tissue from the gut.

• Body is bilaterally symmetrical, segmented, triploblastic and with coelom.
• A post anal tail is present at some stage.
• Segmental muscles in unsegmented trunk.
• Ventral heart with dorsal and ventral blood vessels  and closed blood vascular system.
• Complete digestive system.
• Endoskeleton present.
• This is the most advanced group of animals.

Chordata is divided into two groups:

• Protochordata
• Vertebrata

Vertebrata

•  
• Animals that have vertebral column and cranium.
• They are primitive.

• They are without paired appendages.
• They are without true jaws.

Its subphylum is: Gnathostomata.

• Vertebrates with jaws and paired appendages.

The subphylum is divided into the following 6 classes.Lets study about them :

 

Class 1 Chondrichthyes

• It includes marine fishes with cartilaginous endoskeleton.
• Streamlined body is either laterally compressed and spindle-shaped or flattened and disc-shaped.
• Mouth is ventral in position.
• Skin is covered with scales.
• Tail or caudal fin is present for movement.
• Heart is 2 chambered.
• Digestive system has J – shaped stomach.
• Alimentary canal and urinogenital ducts open into common aperture called cloaca.
• Ureotelic Animals.
• Examples: Scoliodan, Torpedo, etc.

Class 2 Osteichthyes

• It includes marine and freshwater fishes with partly or wholly endoskeleton.
• It includes marine and freshwater fishes with partly or wholly endoskeleton.
• The shape of body is spindle-like.
• Skin is neither naked nor covered with scales
• Mouth is terminal in position.
• Four pairs of gills are present and are covered by operculum.
• Cloaca is absent.
• Ammonotelic organisms.
• Heart is 2 chambered.
• They are cold blooded.
• They lay eggs and fertilization is external.
• Example: Labeo, Hippocampus, Anabas, etc.

Class 3 Amphibia

• They live on land but lay eggs in water.
• They live partly in fresh water and partly on land.
• Skin is smooth, rough, moist, slimy and mostly without scales.
• Body has a distinct head, trunk but no neck.
• Mouth is large.
• Three chambered heart.
• Respiration by gills, lungs, skin, etc.
• Oviparous.
• Example: Rana, Bufo, Hyla, etc.

Class 4 Reptilia

•  
• They are cold blooded, terrestrial or aquatic vertebrates with body covered with dry waterproof skin having horny scales.

• Body has head, neck, trunk and tail.
• Limbs are tetrapodus pentadactyle type with clawed digits.
• Tympanum is small.
• Teeth are present in all reptiles.
• Respiration is through gills.
• Heart is three chambered.
• Fertilization is internal.
• Example: Green turtle, land tortoise, etc.

Class 5 Aves

• Warm blooded, tetrapodus.
• Size ranges from small sized hummingbird to large ostrich.
• Horny scales are present, but feather covers the whole body.
• Body is divided into head, neck, trunk and tail.
• Forelimbs are modified into wings for flight.
• Hind limbs bear four clawed digits.
• Narrow jaws bear horny beak, teeth are absent.
• Bones are hollow.
• They breathe through lungs.
• Four chambered heart is present.
• Cloaca is present.
• Uricotelic organism.
• Birds have highly developed vision, voice & hearing.
• Fertilization is internal and are oviparus.
• Examples: Crow, sparrow, pigeon, etc.

Class 6 Mammalia

•  
• They are warm blooded and the most evolved animals.
• Hair and subcutaneous fat form an insulating layer.
• Body is divided into head, neck, trunk and tail.
• Eyelids are movable.
• Females have milk producing glands.
• External ears present.
• Teeth are thecodont and are heterodont.
• Two pairs of pentadactyl limbs are present.
• Respiration through lungs.
• Heart is 4 chambered.
• Ureotelic organisms.

• Fertilization is internal.
• Viviparous.
• They can live in all kinds of habitats.
• Examples: Kangaroo, mole, flying fox, squirrel, human being, etc.

  

Diversity in Living Organism

 Question Answers

Q1 Why do we classify organisms?

Ans : 1. It helps in study of variety of organisms in a simple manner .

2. It reveals interrelationships between different organisms.

 

Q2 Give three examples of the range of variation that you see in life forms around you.

Ans : Different forms in which life occurs on earth:

1.     Size: Microscopic bacteria a few micrometers in size at one end of the size scale and 30 metre long blue whale and 100 metre tall redwood trees of California.

2.     Life span: Pine trees live for thousands of years while insects such as mosquitoes die within a few days.

3.     Colour: Colourless or transparent worms to brightly coloured birds and flowers.

 

Q3 Which do you think is more basic characteristic for classifying organisms?

(a) The place where they live

(b)The kind of cells they are made up of .

why?

Ans: The kind of cell is more basic characteristic for classification of organisms. The cells may be prokaryotic or Eukaryotic .The presence or absence of nucleus or membrane bound organelles would reflect on every aspect of cell design and capacity to make multicellular body.

 

Q4 What is the primary characteristic on which the first division of organism is made up of ?

Ans : Nature of cell : Prokaryotic and Eukaryotic

 

Q5 On what basis are plants and animals put into different categories?

Ans : 1. Mode of nutrition : plants prepare their own food by photosynthesis due to the presence of chlorophyll and animals acquire ready made food .

2. Plants are fixed whereas animals are motile .

3. Plants show limited growth whereas animals stop growing after attaining a proper size .

4. Plant cells have a cell wall while animal cells lack cell wall.

 

Q6. Which organisms are called primitive and how they are different from the so called advanced organisms?

Ans : Primitive organisms : they have ancient body designs  and are called lower organisms .

Advanced organisms : They acquire particular design recently therefore called higher organisms .

 

Q7 Will advanced organisms be the same as complex organisms? why?

Ans : Yes, completely in design will increase evolutionary time. Hence, older organisms are simple while younger organisms are more complex.

 

Q8 What is the criteria for classification of organism as belonging to kingdom monera or protista?

Ans : The criterion for classification of monera or protista.

Nature and number of cells : Prokaryotic belong to the kingdom monera and single celled eukaryotes belong to the kingdom protista.

 

Q9 In which kingdom will you place an organism which is single celled eukaryotoic and Photosynthetic?

Ans : Protista

 

Q10 In the hierarchy of classification, which grouping will have the smallest number of organisms with a with a maximum of characteristic in common and which will have the largest number of organisms?

Ans : (a) Species will have smallest number of organisms with maximum number of similarities in common.

(b) Kingdom will have largest number of organisms.

 

Q11 Which division among plants has simplest organisms?

Ans : Algae (Thallophyta)

 

Q12 How are Pteridophytes different from Gymnosperms?

Ans :

Pteridophytes	Gymnosperms
1. Seeds are not formed .	1. Seeds are formed .
2. Secondary growth absent	2. Secondary growth present .
3. Reproductive organs hidden	3. Well developed exposed reproductive organs prominent .
4. Example : Ferns	4. Example : Cycas etc

 

Q13. How will you differ between angiosperms and gymnosperms?

Ans :

Gymnosperms	Angiosperms
1. Seeds are naked .	1. seeds are enclosed in fruits .
2. Reproductive organs form cones .	2. Reproductive organs are flowers .
3. Ovules are not enclosed in ovaries	3. ovules are enclosed in ovaries .
4. Xylem lack vessels .	4. Xylem contain vessels .
5. Companion cell in phloem absent .	5. Companion cell in phloem present.

 

Q14. How do Porifera differ from Coelenterates?

Ans :

Porifera	Coelenterates
1. Numerous  pores are present called ostia for the entry of water and single opening called osculum  for exit of water .	1. the body bears single pore .
2. Appendages absent.	2. Tentacles as appendages present .
3. Intercellular digestion	3. Intracellular digestion
4. Spicules present	4. Stinging cells called cnidoblast present.

 

Q15 How Annelids differ from arthropods?

Ans :

Annelids	Arthropods
Exoskeleton absent	Exoskeleton Present
Appendages not joined	Appendages joint
Excretion by nephridia	Excretion by Malapighian tubules ,green glands, etc.

 

Q16 Difference between Aves and Mammals?

Ans :

Aves	Mammals
They are oviparous	They are viviparous
No mammary glands	Mammary glands present
Wings present	Wings absent
Pinna absent	Pinna present

 

Q17  Difference between Amphibians and Reptilians?

Ans :

Amphibians	Reptiles
1. skin is most slimy and moist .	Skin is dry and covered with scales .
2. Lay eggs in water	Lay eggs outside water
3.Their larvae have gills	No larvae is produced .
Example : Crocodile	Example : Snake

 

Q18 What are the advantages of classifying organisms?

Ans : It makes the study of wide variety of organisms easy.

It is responsible for description of species .

It helps in understanding the interrelation among different groups of organisms .

It recognizes the basic taxonomic units of species.

It helps in understanding the evolution of organisms .

 

Q19 How would you choose between two characteristics to be used for developing a hierarchy in classification?

Ans : Characteristic is the particular form or function. Many interrelated characteristics are used in order to classify all living forms .

(1) Nature of cell is basic characteristic of classification.

(2) Number of cells

 

Q20 Explain the basis for grouping organisms into 5 kingdoms.

Ans : Nature of cells

Number of cells

Mode of nutrition

 

Q21 What are the major division in plantae? What are the basis of this division?

Ans : Major divisions are :

 

Q22 How is the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

Ans : Criteria of dividing plants : The first level of classification depends upon whether the plant body is differentiated or not.

The next level is based upon the presence of vascular bundles or not.

Third level is based on the ability to bear seeds or not and where these seeds are present.

Criteria of division of animals :

The eukaryotic multicellular heterotrophic and lacking cell wall are placed in an animal kingdom. Further classification is on the basis of body design.

 

Q23  Explain how animals in vertebrates are classified?

Ans : Classification of vertebrates