Animal Cell, Tissue and Organ

Animal Cell

Animal cells are eukaryotic cells, or cells with a membrane-bound nucleus. Unlike prokaryotic cells, DNA in animal cells is housed within the nucleus. In addition to having a nucleus, animal cells also contain other membrane-bound organelles, or tiny cellular structures, that carry out specific functions necessary for normal cellular operation. Organelles have a wide range of responsibilities that include everything from producing hormones and enzymes to providing energy for animal cells. There are different types of cell in organism for different purposes of body function.

Functions of the Animal Cell

The functions of animal cell are as follow, carried out by the different cell organelles.

Nucleus :- The nucleus is referred to as the heart of the cell. The nucleus houses the genetic material of the organism which is the DNA. DNA replication and RNA synthesis occurs in the nucleus. It regulates the activities of the other cell organelles thus a very important cell organelle. The cell nucleus is bound by a definite membrane called the nuclear membrane that separates the nucleus from the cytoplasm.

Endoplasmic Reticulum :- The endoplasmic reticulum is a network for transportation of certain critical substances in and out of the nucleus.The endoplasic reticulum is seen like a network of interconnecting pathways to enable the transport of molecules. There are two kinds of ER namely Rough ER and Smooth ER. Rough ER has ribosome molecules attached to its surface while the smooth ER does not have ribosome molecules attached to its surface.

Mitochondria :- The mitochondria is also referred to as the power house of the cell. It is a double membraned organelle that helps in energy production for the cell.The energy is generated in the form of ATP. Mitochondria also has its own genetic material called the mitochondrial DNA which is circular. The energy is generated from the glucose we take in by a process called the cellular respiration.

Lysososmes :- Lysososmes are referred to as suicide bags of the cell. They are involved in clearing the unwanted and waste materials from the cell. The lysososmes contain hydrolytic enzymes that are destructive. they kill the toxic materials of the cell time to time.They engulf materials like damaged organelles, virus, bacteria and food particles.

Golgi Apparatus :- The Golgi apparatus is involved with processing and packaging of the molecules synthesized by the cell mainly the proteins ready for secretion. The ER transports the proteins in their crude form to the golgi appratus. The golgi apparatus packages the proteins developing them into primary, secondary and tertiary proteins respectively.

Vacuole :- The vacuole is a large empty storage organelle. They store excess water or food. It is present in many numbers withing the cell floating in the cytoplasm.

Ribosomes :- The Ribosome is involved in protein synthesis.It consists of two sub units.Protein synthesis primarily occurs in the ribosomes. The ribosomes may be found freely floating in the cytoplasm or may be found attached to the ER.

Tissue

According to Biology, Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of similar cells from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.The study of tissue is known as histology or, in connection with disease, histopathology. The classical tools for studying tissues are the paraffin block in which tissue is embedded and then sectioned, the histological stain, and the optical microscope. In the last couple of decades, developments in electron microscopy, immunofluorescence, and the use of frozen tissue sections have enhanced the detail that can be observed in tissues. With these tools, the classical appearances of tissues can be examined in health and disease, enabling considerable refinement of clinical diagnosis and prognosis.

Types of Animal Tissue:-

Animal Tissue

• Connective tissue

• Muscle tissue

• Nervous tissue

• Epithelial tissue

Organ

In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. There are different types organ in animal constructing a complete body. Such as Liver, Heart, Lungs etc. Organs may found in only developed animal.

Classified study of zoology

All members belong to the animal kingdom are multicellular, eukaryotic, heterotrophic organisms. Zoology, the study of animals, has many subdivisions based on specific areas of interest and study.And the name of study for the classified group of animal are as below:

Invertebrate zoolgy is the study of multicellular animals without backbones.

• Entomology -is the  study of insects
• Myrmecology -is the  study of ants
• Apiology - is the study of honey bees
• Arachnology - is the study of spiders and their relatives
• Malacology - is the study of mollusks
• Conchology -  is the study of mollusk shells

Vertebrate zoology is the study of animals with backbones.

• Ichthyolgy - is the study of fish
• Herpeteology - is the study of amphibians and reptiles
• Ornithology - is the study of birds
• Mammalogy -is the study of mammals
• Cetology - is the study of marine mammals
• Primatology - is the study of primates

 
Morphology is the study of the shape, form, and structure of animals and their body parts.

Comparative anatomy is the study of the similarity and differences in the anatomy of different groups of animals.

• Structures are homologous if they have arisen from the same ancestral structure, but perform either similar or different functions in modern animals. Examples are the wings of birds, the human arm, and the forelimb of whales.
   
• Analogous structures have developed from different ancestral structures, but perform similar functions. Examples are the wings of birds and the wings of insects.

Layers of cells that originate in the developing embryo and become specific structures in the animal are known as germ layers.

• Ectoderm - the outer layer which forms the body covering.
• Mesoderm - the middle layer which forms the organs inside the body.
• Endoderm - the inner layer which forms the lining inside the body cavity.

There are four body types defined by the presence or absence of a coelom, or body cavity. The body types below are arranged from least complex to most complex:

1. Acoelomate, with only two germ layers, ectoderm and endoderm. (Hydra)
2. Acoelomate, with three germ layers, ectoderm, mesoderm, and endoderm. (Flatworms)
    
3. Pseudocoelomate, with a "cavity" forming between the mesoderm and the endoderm. (Roundworms)
    
4. Coelomate, with a true body cavity forming within the mesoderm. (Segmented worms, Freshwater muscles, all Arthropods, and all Chordates)

 Taxonomy is the science of naming and classifying organisms on the basis of their evolutionary relationships. Visible traits are most often used for this classification.

Although the binomial system requires that each species be assigned a unique, two-word (Latin) name, there must be a hierarchical system for arranging organisms in a logical and retrievable fashion. Such a system now recognizes at least seven taxonomic ranks (taxa) to which each organism must be assigned.

1. kingdom
2. phylum
3. class
4. order
5. family
6. genus
7. species

In addition to the basic seven categories above, many other taxonomic ranks exist (Subphyla, Superclasses, Subspecies, etc.).

For example, the Linnaean Classification of Human Being  is:

Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Mammalia
Subclass:	Theria
Infraclass:	Eutheria
Order:	Primates
Suborder:	Anthropoidea
Superfamily:	Hominoidea
Family:	Hominidae
Genus:	Homo
Species:	sapiens

Classification of animal kingdom

 Generally animal kingdom is divided into two main group. They are invertebrates and vertebrates.

 Invertebrates :- The animal without backbone or vertebral column are known as invertebrates. Such as insects, earthworm, protozoa, etc.
It is further divided into 9 phylum.They are listed below:

1. Protozoa
2. Porifera 
3. Cnidaria 
   
4. Platyhelminthes
5. Nemathelminthes
6. Annelida
7. Arthropoda
8. Mollusca
9. Echinodermata

Vertebrates :- The animal with backbone or vertebral column are known as vertebrates.Such as Human, birds, fish, snakes etc. It is further divided into five class. They are listed as below:

1. Aves
2. Amphibia
3. Mammalia
4. Pisces
5. Reptile 

 

Introduction of zoology

Zoology,  is the branch of biology that relates to the animal kingdom, including the structure, embryology,  

evolution, classification, habits, and distribution of all animals, both living and extinct. The term is derived from Ancient Greek word zoon = animal +logos= knowledge and being zoology. 

 Although the study of animal life is ancient, its scientific incarnation is relatively modern. This mirrors the transition from natural history to biology at the start of the nineteenth century. Since Hunter and Cuvier, comparative anatomical study has been associated with morphography shapins the modern areas of zoological investigation: anatomy, physiology, histology, embryology, teratology and ethology. Modern zoology first arose in German and British universities. In Britain, Thomas Henry Huxley was a prominent figure. His ideas were centered on the morphology of animals. Many consider him the greatest comparative anatomist of the latter half of the nineteenth century. Similar to Hunter, his courses were composed of lectures and laboratory practical classes in contrast to the previous format of lectures only. This system became widely spread.

According to Darwin, ancient history of Zoology

Charles Darwin

The history of zoology traces the study of the animal kingdom from ancient to modern times. Although the concept of zoology as a single coherent field arose much later, the zoological sciences emerged from natural history reaching back to the works of Aristotle and Galen in the ancient Greco-Roman world. This ancient work was further developed in the Middle Ages by Muslim physicians and scholars such as Albertus Magnus. During the Renaissance and early modern period, zoological thought was revolutionized in Europe by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Vesalius and William Harvey, who used experimentation and careful observation in physiology, and naturalists such as Carl Linnaeus and Buffon who began to classify the diversity of life and the fossil record, as well as the development and behavior of organisms. Microscopy revealed the previously unknown world of microorganisms, laying the groundwork for cell theory. The growing importance of natural theology, partly a response to the rise of mechanical philosophy, encouraged the growth of natural history (although it entrenched the argument from design).

Over the 18th and 19th centuries, zoology became an increasingly professional scientific discipline. Explorer-naturalists such as Alexander Von Humboldt investigated the interaction between organisms and their environment, and the ways this relationship depends on geography, laying the foundations for bio geography, ecology and ethology. Naturalists began to reject essentialism and consider the importance of extinction and the mutability of species. Cell theory provided a new perspective on the fundamental basis of life.