An Introduction To Zoology

AN INTRODUCTION TO
ZOOLOGY
SAMEH ABDELGHANY
Abstract
Many scientists invented the evolution of living organisms long time ago. Different
theories have been discussed. Some of them are good others not accurate. The study
of evolution had led to the study of the life cycle of organisms and the survival
strategies that organisms follow in the changing environments. It is crucial to study
mitosis and cell division processes in the animals and draw a comparison between
replication processes in different species. It shows that there are several differences
and little similarities in those species. Another an important mechanism that is
unique in animal species is the homeostatic mechanism. Another area of interest
that we need to discuss is the architectural patterns of the levels of organization of
animal. The importance of understanding these patterns in the sentience and
survival of organisms. The modern theory of evolution has several implications in
several areas. The critical evaluation of these implications can help to understand
the impact of this theory on our life. Finally, phenotype and inheritance patterns are
influenced by the environmental changes.
DOI: 10.13140/RG.2.1.2156.9680

SAMEH ABDELGHANY 1
1 AN INTRODUCTION TO ZOOLOGY
An Introduction to Zoology
Introduction
Many scientists invented the evolution of living organisms a long time ago. Different theories have
been discussed. Some of them are good others not accurate. The study of evolution had led to the
study of the life cycle of organisms and the survival strategies that organisms follow in the changing
environments. It is crucial to study mitosis and cell division processes in the animals and draw a
comparison between replication processes in different species. It shows that there are several
differences and little similarities in those species. Another important mechanism that is unique in
animal species is the homeostatic mechanism. Another area of interest that we need to discuss is the
architectural patterns of the levels of organization of animal. The importance of understanding these
patterns in the sentience and survival of organisms. The modern theory of evolution has several
implications in several areas. The critical evaluation of these implications can help to understand the
impact of this theory on our life. Finally, phenotype and inheritance patterns are influenced by
environmental changes.
Evolution Theories
Several theories of evolution related to animals. This paper discusses the most relevant approaches.
In 1801, John Baptise Lamarck (Evolution.berkeley.edu, 2016) proposed a theory of evolution. It
states that organisms change their behavior as the environment change. If organisms’ organs are
used more frequently, it will develop in their lifetime. He also stated the theory of Use and Disuse.
He argued that the giraffe, for example, had a short neck. It made the nerve fluid to flow into its neck
and stretch it. This property would inherit in its offspring. He also invented the theory of Transition
of Acquired Characteristics. I think this theory is not accurate for two reasons. Firstly, there is no
evidence in the fossil records that there were different species of a giraffe that has a short neck.
Secondly, if we considered this theory, so the offspring of the swimmer will have long legs or
stretched body. Another theory that based on the catastrophic events on the Earth, George Cuvier
(1769- 1832) (Anthro.palomar.edu, 2016) argued that the significant events such as great floods, and
the rapid formation of mountain chains have led to killing plant and animals that are lived during
these periods. I partly agreed with this idea, as the fossil records showed some of the unconformities
in the strata analysis, but again here, there is no evidence that these events had killed all animals and
plants. There is also no evidence that these events helped in the evolution of animals. Darwin's
Theory and Natural selection have been discussed as the most accurate theory that explains the
evolution of animals. Some animals can survive a specific environment by natural selection.
According to the hereditary characteristics of animals, they have different chances to survive. The
number of offsprings and the survival of the offspring determines how big the next generation will
be (G, 2014). I would maintain that I like the theory of natural selection and it is more accurate and
reasonable rather than Lamarck’s and Cuvier’s theories.
The Life Cycle of Organisms

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A life cycle can be defined as a description of stages that an individual organism passes through
between the time of born until the date of producing offspring (Olson, 2016). The life cycle of an
organism has many stages. It starts from the juvenile stage, as the organism grows and mature, then
the reproductive phase in which the organism can produce offspring. Some microorganisms have
different life cycles in order to adapt to survive. The life cycles of an organism can be simple such as
in humans as the morphological characteristics still the same in all stages. Another type of life cycle
is complex. In this life cycle, the organism can change morphology, its environment, and diet as they
transfer from a stage to another, for example, the monarch butterfly ‘Danaus plexippus.’ The stages of
the monarch butterfly life cycle are divided into four phases. The first stage is the Egg stage which is
very small, oval, rounded or cylindrical. The second stage is the larva or caterpillar. It comes after the
egg stage. The third stage is Pupa or Chrysalis. The caterpillar rapidly changes inside the chrysalis.
The metamorphism process occurs in pupa as the old body parts of caterpillar undergo a
transformation process. The fourth stage is the Adult Butterfly. I can say that this is an excellent
example of the complex life cycle. The body of the butterfly changes in every stage. However, this
strategy is only applied to a butterfly. Some organisms have the same physiology in the embryonic
stage until the mature stage.
Adaptation Strategies
Kalman, B. and Reiach, M. (2002). The life cycle of a butterfly. New York: Crabtree Pub. Co.

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Animal survival in the desert is one of the most famous adaptation strategies. In the desert, animals
adapt their behavioral and physiological mechanisms to overcome the heat and water issues. Birds,
such as the Phainopepla, can breed during the cold periods of the year. It leaves the desert and moves
to higher cooler areas. Many animals restrict their activities in the day and start their activities in the
cooler temperature of the night. Some animals retain water by occupying deep moist soil during the
daylight hours. I like this type of adaptation, as it proves that animals are intelligent, and they can
keep their body water stable. It supports the theory of Darwin of Natural Selection. In polar regions,
some animals hibernate, take shelter, or even migrate to warmer places (BBC Nature, 2016). An
excellent example of the survival strategies of animals can be found in Chameleon. It can change its
skin color to avoid predators. However, I believe it does not have any strategy to adapt to climate or
environmental changes. If the environment change, I guess it might be threatening.
Mitosis and Cell Division in Animals
Mitosis is a process to split the cell nucleus into two nuclei. It helps in the cell division processes. It
divided into several phases. Interphase is the phase that occurs before the mitosis processes. It
includes the G1 (first gap), S (Synthesis of DNA), G2 (Second Gap), and M phase (mitosis and
cytokinesis). Prophase starts at the beginning of the mitosis process. The chromosomes’ replication
takes place. It produces 12 chromatids in 6 pairs of sister chromatids. The nuclear envelope begins
to divide into small vesicles. In Prometaphase, the centrosome moves to the two poles of the cell. In
the Metaphase, the sister pairs of chromatids gather in the center of the cell align along with the
metaphase plan. In the Anaphase, the polar microtubules separate the chromatids and push the
chromosomes to each pole. Finally, in the Telophase, the two cell daughters are formed, and the cell
separate to produce two distinct nuclei. I guess the mitosis process of animals is a little similar to
those in the plant, but I can argue that it is more complicated in animals than a plant.
There are some differences and little similarities between replication processes in different species.
I will here compare between Prokaryotes and Eukaryotes as they are the two major classes of species
(Stillman, 2008).
Biggs, A. (2004). Biology: The Dynamic of Life. 3rd ed. New York: Glencoe/McGraw-Hill.

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Prokaryote Eukaryote
Location Inside the cytoplasm Inside the nucleus
Origin Two origins per DNA Molecule. Ranging from 100-
200 or more nucleotides.
Several origins formed about 150 nucleotides.
Initiation At one point carried out by protein DNA & DNB Replication occurs at several points, conducted by
many proteins.
Stages of Division Only two replication forks Many replication forks
No. of Replicons One Numerous in one replicating DNA (50,000 and
above)
Okazaki Fragments Abundant (1000-2000) nucleotides long Short (100-200) nucleotides long
Speed of replication Very fast and rapid. Slow
Termination Single termination site Several termination sites.
Direction Bi-directional Process Bi-directional Process
Primers Required Required
Strands Leading and lagging Leading and lagging

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Homeostatic Mechanism
Homeostatic is a process of stabilizing water, minerals, and other components’ levels of animal body
fluids and other thermal regulations. This mechanism is unique in the animal species; as the organism
can maintain, it is physiological and behavioral stability in different environmental conditions. There
two mechanisms that animal uses; Conforming and Regulation (Pond and Bell, 2005). Conforming is
a process that an animal adapts to their environment so their internal body composition will match
with external conditions surrounding. For example, the concentration of the marine crab body fluid
is the same in the surrounding seawater. Regulation is a mechanism that an animal regulates the
internal fluid composition that is different from external environmental conditions. For example,
vertebrates are said to be regulators. I believe that the regulation mechanism is better than
conforming. I would maintain that conforming is a cheap mechanism for survival. It needs an
enormous amount of energy for a small organism to adjust its body temperature.
Level of Organization: Architectural Patterns in Animals
There are five significant levels of Organization; Protoplasmic Level, Cellular Level, Cell-Tissue Level,
Tissue- Organ Level, and Organ-System Level (Biggs, 2004). Protoplasmic Level is found in the
unicellular and protozoa organisms. All life activities are limited within the cell boundaries. The
organelles can perform special functions. Cellular Level is that the organism is an accumulation of
cells. Those cells perform different functions. Each cell is specialized for a particular function, for
example, reproduction. Cell-Tissue Level is the accumulation of the same cells into a specific pattern
to become a tissue, for instance, Jellyfish and Cnidaria. Tissue-Organ Level is the gathering of the
tissues in an organ. Different kinds of tissues are forming the organ. Platyhelminthes are the first
organisms that have well-defined organs that have first appeared, such as eyespots. Organ-System
Level is all organs work together to perform many functions, such as the circulatory system and the
nervous system. I would like to maintain that it is a vital strategy to understand the level of
organization of organisms. I believe it will help to understand how animals’ bodywork.
The study of the architectural pattern is vital to comprehend the sentience and survival strategies of
an animal. I would like to discuss the Nervous system and how I believe that this evidence is
imperative to prove the theory of architectural patterns. The nervous tissue is responsible for
initiating and conducting electrical signals in animals’ bodies. The membrane consists of several
nerve cell – neurons; all are connected. The spinal cord is the nervous tissue that transfers the
electrical signals from the brain to the body cells and vice versa. Nervous tissue plays a critical role
in controlling the activities of the body cells. The sentience characteristics of the animal help the most
crucial role in an animal’s survival. When an electrical signal generated in one neuron, it will inhibit
other neurons from producing new electrical signals. These signals may stimulate muscle tissues to
contract or catalyze the glandular cells to release some chemical substances into the animals’ body
fluid.
In the above example, we can see that all the body’s cells, tissues and organs respond to the one
external activity or thread. The nervous system consists of neurons, which are the nerve cells. All
neurons accumulate to form nervous tissue. There are two types of nerve cells in the nervous cells;
neurons – nerve, and neuroglia. The neuron conducts the primary function of the nervous system

SAMEH ABDELGHANY 6
while neuroglia is different non-nervous cells that cover the neuron membranes and serve various
functions (Brooker, 2011). This classification is critical to understand the theory of the level of
organization. When I look at the types of nerve, I will see that there are different kinds according to
the functions and number of cell processes. According to the function, there are sensory cells-
conduct impulses toward the central nervous system (CNS), motor – send signals away from CNS,
and associate – that initiate signals within the CNS (Jurd and Jurd, 2004). According to the number of
cell processes, we can find that there are Bipolar, Unipolar, Multipolar and pyramidal cells.
All the above evidence is imperative to understand how the architectural pattern works, and
significant is this. We can do the same analysis for all different body systems, for example, the
reproductive system, circulation system, and respiratory system. Some people may argue that each
system is different and may have more complex levels. I can partially agree with this idea, but on the
other hand, it was evident that all body levels of an organization are the same in the complex animals.
Modern Evolutionary Theory
Charlies Darwin, 1859 has discovered that all known animals are related by descent from common
ancestors (Darwin, Einstein, and Smith, 1859). This theory is what Darwin stated and discovered
when he invented the Theory of Evolution. Darwin argued that evolution might happen from
generation to another due to genetic variation and natural selection. The Genetic Variation occurs
among individuals of a given species. The genetic characteristic passes from parents to offspring.
Natural Selection is a process that in each generation, offspring may survive and reproduce or die.
It is according to how they will adapt and cope with environmental changes (Brooker, 2011). I can
say that I wholeheartedly agreed with the Natural Selection theory, as it can generate new species
with a combination of several traits that may be different from those of the original species. Finche
species of larger beaks and various color are an example.
Although Darwin’s theory is a milestone in the science of evolution and biology, many people argue
that it was not accurate. I can say that his theory has made considerable implications. His approach
Jurd, R. and Jurd, R. (2004). Instant notes animal biology. New York: Bios Scientific Publishers.

SAMEH ABDELGHANY 7
has a significant impact on genetic science. By Darwin's theory, scientists recognized that the genetic
structure of populations is very complicated. I also can argue that Darwin influenced the medical
field. His approach helped to understand the history of human disease and health. It also contributes
to predicting human resistance to pathogens. Darwinian theory has religious implications. Let me
tell you a personal story. I was discussing the theory of evolution with one of my colleagues from the
science point of view. He was arguing that this theory is against his beliefs. He believes that God, who
creates life and there is no evolution. This discussion is not a one-to-one discussion. I think this
debate has been alive today. Darwin states that complex organisms like human beings evolve from
less complicated living people (Dinis, 2010). This process took place through the mechanism of
natural selection. Church and some Mosques, violently attacked Darwin’s ideas as they think that his
views are against the Role of God. The most difficult to accept was the claim of the human, and the
apes have common ancestors. This claim led some Christians in the U.S. during the 1920s to ban the
teaching of Darwin’s theory in the Government Schools (G, 2014). The U.S. Supreme Court repeal the
ban because of the constitution’s grant of religious freedom. I believe that the Darwinian Theory is a
magnificent and unique theory. We have to separate the scientific point of view from religious.
Religious books are not scientific books; they are only a guide to life. However, we cannot connect
the scientific knowledge with faithful as some people are not religious at all.
The environmental changes influence phenotype and inheritance patterns. There is much evidence
that can be considered as proof of the impact of environmental changes on living organisms. We can
find that the environment can impact the phenotype of organisms — poor diet as an example of an
environmental factor that can affect human height. For instance, if someone has inherited genes to
be tall has an improper diet, it might not reach their expected height (Monaghan, 2008). Phenotypic
plasticity or genetic change may result in a phenotypic variation. For instance, Teplisky et al. (2008)
provided evidence that climate-driven plastic decreases in the body size of red-billed gulls ‘Laris
novaehollardiae’ happened due to environmental stress. (Merilä and Hendry, 2014). The
environmental changes can affect the control of the development of the organism’s genetic structure.
When poor conditions of maternity exist, it will result in a poor quality of offspring. The change of
environment is evident in the European Map butterfly ‘Araschnia levana’. This species can have
different color forms in different environmental temperature and photoperiod. Personally, I can say
that the changes in the environment can affect the phenotype and inheritance pattern of an organism.
I would like to argue that I do not think that the poor diet may influence the human inheritance
pattern. If an individual has an inherited gene of tall, how can the poor diet affect that gene? I cannot
find any scientific evidence on this debate.
Conclusion
The theory of evolution can be divided into the pre-Darwinian period, Darwin Theory of evolution
and post-Darwinian period. The theories of the pre-Darwinian period are inaccurate and had lots of
implications. Study of the butterfly lifecycle is vital to understanding how different organisms grow
and reproduce. Studying of lifecycle gave a very deep dive on how animals develop and reproduce.
Cell division and mitosis have several steps and phases. One of those steps is DNA replication. The
replication is different in Prokaryotes than that in Eukaryotes. As we have seen, the homeostatic
mechanism exclusively exists in animals. It helps animals to adapt easily to various environments. It

SAMEH ABDELGHANY 8
is very clear that the study of Levels of organization gave a deep insight on how life evolved from
unicellular to a complex organism. It also gave an opportunity to understand how it helps in animal
survival, for example, the importance of the nervous system in animal survival. Darwin’s theory made
and still make a great debate between scientists and religious people. This debate should be fixed by
separating the religion beliefs and science. Also, the phenotype and inheritance patterns may change
by changing the environmental conditions. Many examples and strategies can prove this principle.

SAMEH ABDELGHANY 9
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