How to Know Bacterial, Plant, Animal Cell Types
Cells and Features, Differences Similarities in Biology's Kingdoms
Aug 21, 2009
About 5 to 30 million species — distinct, specific forms of life — exist. Biology, the study of life, has 3 major domains: Archaea , Bacteria, and Eukarya, and within Eukarya are fungi (Mycota), protozoa (Protista), plants (Plantae) and animals (Animalia). How does a scientist know what organism is presented or seen, and to which kingdom it belongs?
Prokaryotes and Eukaryotes, Major and Distinct Types of Cellular Organization
Robert Hooke, the Englishman, coined the term "cells" for those microscopic structures he observed in thin slices of cork. These cells resembled the small rooms in monasteries. Anton von Leeuwenhoek described many types of microscopic cells such as bacteria, protozoa and human cells. His "animalcules", or little animals, now known as microbes, were never seen before and were interesting. Pasteur described "new yeasts" or bacteria, that were distinctly different from yeasts.
All cells, whether prokaryote (primitive nucleus), or eukaryote (true nucleus) have these basic similar and different features:
- cell size: prokaryotes, 0.2 - 10.0 micrometers; eukaryotes, 2.0 -100 micrometers.
- DNA: prokaryotes, DNA with no nuclear membrane; eukaryotes DNA surrounded by a nuclear membrane. Also, each DNA coding is distinctive and characteristic for each domain, and this applies to all the different kingdoms and their species.
- cell membranes: phospholipid membranes, with different enzymes and structural proteins in different kinds of organisms.
- ribosomes: 70S (Svedberg unit, mass size) in prokaryotes, 80S in eukaryotes.
- enzymes: are common to both cell types. Enzymes with very similar functions actually may have differences in structure (amino acids); some enzymes are unique to prokaryotes and are not found in eukaryotes and vice versa.
In summary, prokaryotes and eukaryotes are distinguishable on the basis of size, nuclear structure, cell membranes, ribsomes and enzymes.
Domains and Kingdoms and Characteristics of Species
The Archaea are the oldest of the prokarotes, and the Eubacteria are more recent prokaryotes. Both are considered the earliest, primitive types of life. Eukarya are divided into: Protista (protozoa), Mycota (fungi), Plantae (plants) and Animalia (animals).
The Plantae are photosynthetic, autotrophic eukaryotes; the remaining kingdoms are non-photosynthetic, heterotrophic organisms. Remember, the presence of the green photosynthetic pigment chlorophyll is important. Some bacteria are photosynthetic and, therefore, contain chlorophyll. However, these bacteria are prokaryotes and have distinct size, cell membrane and envelope features that readily set them apart from eukaryotic plants.
Autotrophs make there own food from simple inorganic molecules. Heterotrophic organisms need organic, carbon-based compounds of carbon and hydrogen molecules to live.
The fungi, or Mycota, are a diverse group of different organisms that have characteristic cell walls of chitin or cellulose, or mixtures of both. Yeasts and mushrooms are characteristic of the fungi.
The Protista are protozoa such as common amebae, flagellates, ciliates.Some exotic disease-causing protistans are the trypanosomes of sleeping sickness and Chagas disease, and the notorious malarial Plasmodium species, transmitted by Anopheles mosquitoes.
Finally, the Animalia are a huge kingdom with much diversity. Here in Animalia are simple sponges, worms, or starfish, to more complex snakes, lizards, cattle, cats, dogs, apes and humans. Animalia is an impressive kingdom, and all species are heterotrophic eukaryotes.
Study and Learning Biology can be Logical and Memorable by Proper Scientific Inquiry
Some people get overwhelmed by the depth and breadth of the biological sciences. It is true that Biology as a discipline is very broad and deep. A good approach to the study of biology is to see the big picture and the principles and foundations via good, enjoyable biology texts.
Eukaryotic, human stem cells indicate the importance of cell research.
Resources
Alters, S and B. Alters. 2006, Biology. John Wiley & Sons Inc., Hoboken, N.J. 755 pp
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