WHAT IS ZOOLOGY? with examples and classification methods

Zoology is derived form two Greek words. Gr zoon + logos, to study. The study of animals is called Zoology.

There is a great variety of animals and complex processes occurring within them. So it is one of the broadest fields in all of sciences. There are over 2 millions of animal species. There are over 20,000 described species of bony fishes and over 300,000 described species of beetles. Therefore, zoologists usually specialize in one or more of the branch of zoology. They may study particular functional, structural, or ecological aspects or more animal groups Or they may choose to specialize in a particular group of animals.

Example of studies in Zoology

The study of fishes is called Ichthyology. The scientist who studies fishes is called ichthyologists. He works to understand the structure, function, ecology, and evolution of fishes. These studies have ,evealed a great diversity of fishes. One large group of fishes’is cichlids It is found in Africa (1.000 species), Central and South ‘America (300 species). India (3 species) and North America (1 species). Members of this group have a great variety of color patterns habitats, and body forms.

Feeding habits: Ichthyologists have described a wide variety of feeding habits in cichlids. These fish include

(a)    Algae scrapers like Eretmodus. It cut algae with chisel-like teeth

(b)    Insect pickers. like Tanganicodus

(c)    Scale eaters. like Perissodus

All cichlids have two pairs of jaws. The mouth jaws are used for scraping or grinding of food and the throat jaws are used for crushing or macerating food before swallowing.

Reproduction: Many cichlids brood their young in their mouth. A female takes eggs into her mouth. She then inhales spent released by the male. Feert’lization and development take place within the female s mouth. Even after fte eggs hatch, young are taken back into me mouth of the female if danger comes. Hundreds of variations in color pattern body form, and behavior are nrpcpnt in this family of fishes.

It shows the remarkable diversity present in one relatively small branch of the animal kingdom. Zoologists are working around the world to understand and preserve the enormous diversity.

Examples of specialization in zoology

  1. Anatomy: The study of the structure of entire organisms and their parts is called anatomy.
  2. Cytology: The study of the structure and function of cells is called cytology.
  3. Ecology: The study of the .intcraction of organisms with their environment is called ecology.
  4. Embryology: The study of the development an animal from the fertilized egg to birth or hatching is called embryology.
  5. Genetics: The study of the mechanisms of transmission of traits from parents to offspring is called genetics.
  6. ..Histology: The study of tissues is called histology.
  7. Molecular biology: The study of sub-cellular details of animal structure and function is called molecular biology.
  8. Parasitology: The study of animals that live in or on other organisms at the expense of the host is called parasitology.
  9. Physiology: The study of the function of organisms and their parts is called physiology.

10.Systematics: The study of the classification and the evolutionary Interrelationships among animal groups is called Systematics.

Examples of specialization in zoology by Taxonomic categories

  1. Entomology: The study insect is called entomology.
  2. Herpetology: The study of amphibians and reptiles is called herpetology.
  3. Ichthyology: The study of fishes is called Ichthyology.
  4. Mammalogy: The study of mammals is called mammalogy.
  5. Ornithology: The study of birds is called ornithology.
  6. Protozoology: The study of protozoa is called protozoology.

Classification of animals

This classification system was given by Robert Whittaker In this system animals are placed in two kingdoms:

Protoctista: The protozoans are placed in the kingdom Protoctista (Protista)

•- Animalia: All other animal are placed in the kingdom Animalia. These animals are multicellular, diploid. eukaryotic and ingestive heterotrophs. They develop from two dissimilar haploid gametes. The large gamete is called egg and the small gamete is called sperm.

(1)       Sub-kingdom Parazoa ( phylum porifera)

Parazoa lack tissue organ organization. They have indeterminate shape. So they are asymmetrical,

(2)       Sub-kingdom Eumetazoa

‘These animals have tissue organ and organ system organizations. All animals of other multicellular phyla are included in this group. This sub-kingdom I divided into two groups on the basis of their symmetry:

1 Radiate

he animals with i3l symmetry are included in this group. They have simple organization. The phylum Cnidarian (coelenterate) belongs to this group.


hey have bilateral symmetry. Most of the phyla (29 phyla) belong to this group. hese animals are divided into three groups on the basis of coelom or body.

Acoelomata: These animals are without body cavity. e.g. Phylum. Platyhelminths.

ii)        Pseudocoelomata: These animals have false coelom. The false coelom is called .pseudocoel, e.g. Phylum Nematoda.

iii)    Coelomata: These animals have true coelom. e.g. Phylum Chordata


zoology is a natural science. The word science is derived from a Latin verb eaning to know. The knowledge of science is based on observations and experiments. Thus science is a way of knowing. There are different steps of cientific method. The scientific method is based on the hypothetical-deductive method.


The first part of this method is hypothesis. Hypothesis a tentative (untested) answer to some question or it is an explanation on trial. A hypothesis can be made by two methods:

a) Deductive reasoning: It moves from general to specific. In this case results

are drawn from certain general rules.



(b) Inductive reasoning: It moves from specific to general. In this case, general law or rules are formed on the basis of specific observation.


Ali and lmran are two identical twins. They sleep every day in their 1:00 chemistry class. They want to know why this happen with them Following hypothesis can be made:

  • May be eating a big lunch just before going to chemistry class everyday makes them sleepy.
  • May be the classroom is too warm.
  • May be Ali and Imran are lazy because they sit in the back of their chemistry class.
  • May be their chemistry professor is boring.
  • May be it is the timing of sleeping.

This example shows following five important points about hypotheses:

  1. Hypothesis is a possible cause of a phenomenon. A hypothesis is a tentative (untested) explanation for what we have observed.
  2. Hypothesis shows past experience with similar results. Although we should consider any hypothesis that is a possible explanation of observation. But we should test first those hypotheses which are more reasonable.
  3. Multiple (many) hypotheses should be proposed whenever possible. Proposing alternative explanations is good in science.
  4. Hypotheses should be testable via the hypothetical-deductive method. Ali sleep in chemistry class because the devil makes him do it. This hypothesis is not testable. Therefore, it cannot be tested by the scientific process.
  5. Hypotheses can be proved wrong. But it cannot be proved with absolute certainty. Any already proved hypothesis can be proved wrong by repeated experiments. Therefore, we can never prove that this hypothesis is the true explanation. Similarly some false hypotheses may make accurate predictions.
  6. Deduction: Hypothetical-deductive method

hypothesis is formed form deductive or inductive method. Then deduction is made from hypothesis. Deduction is a logical consequence of hypothesis. ‘or example:

hypothesis 1: If all organisms are made of cells.

hypothesis 2: Humans are organisms.

)eduction: Then humans are composed of cells

1 the scientific process deduction usually takes the form of predictions about the esults of experiments We should expect these results from a particular hypothesis (premise).

  1. Experiment

Ve test the hypothesis by performing the experiments. We see form experiments rhether or not the predicted results occur. For example:

hypothesis 1: If the twins sleep because they eat lunch before their 1:00 class. xperiment: Ali postpones lunch until class ends at 2:00. But lmran still eat it at :00 class.

predicted Result: Then Ali should be less sleepy than Imran in chemistry class.

hypothesis 2: If the twins get sleepy in their 1:00 class because they sit in the )ck of the room,

experiment: Ali moves to the front of the class,

predicted Result: Then Ali should be more alert than Imran during the 1:00 3SS.

Dw, suppose the result of the first experiment is that Ali is still as sleepy as Iran in their 1:00 class. The twins try the second experiment. Now Ali dozes in a front row of class instead of the back row. The twins continue to test and iect various hypotheses.

T e twins started to wake up early in the morning. However, the twins find that th y are more alert than usual in their 1:00 class. But within a few days, patterns ar back to normal. Again Ali and Imran are sleepy during their 1:00 class again.) T e twins conclude that they are just naturally sleepy this time of day and decide nit to take 1:00 classes in future semesters.

C introlled experiment

In a controlled experiment, the subjects are divided into two groups, an

e  perimental group and a control group. The two groups are treated exactly alike

e  cept for the one variable. This variable provides basis for comparison.

S me experiments are easier to control than others. But setting up the best pssible controls is a key element of good experimental.

4. Development of theory

A hypothesis is tested by repeated experiments..lf this hypothesis is not p oved wrong then if becomes a theory. It is also common for scientists to c eck the conclusions of others by repeated observations and experiments.

T ere can be cooperation and competition between the scientists. Scientists s are information through publications, seminars, meetings, and personal  communication. They also subject one another work to careful examination.

The advancement in science is the development of new ideas. This idea. coIlectively explains a number of observations. The most exciting ideas in serice are those that explain the greatest variety of phenomena. People like N ewton, Darwin, and Einstein synthesized ideas. Theirs ideas have great

e  planatory power. Such ideas were much broader than the hypotheses. These it-as are possible cause for one set of observations. These set observations are k own as theory. The theories are comprehensive. These theories are accepted if they are supported by a large number of evidence. “Natural selection” has 13 come a theory because it has broad application in many situations.. And the

eory of natural selection is widely accepted because it has been proved by so

any observations and experiments.

Scientific laws

generalized theory with many broad scope of application is called scientific laws. It is difficult to bring a theory to a status of law. That is why there a e a few laws in natural sciences like zoology. These are Mendel’s law of heritance and Hardy Weinberg law.Adopted form Campbell)

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