INTRODUCTION TO ZOOLOGY NSELEC 2 WEEK 1 PREPARED BY: CHRIST JOHN S. SABERON COLLEGE OF ARTS SCIENCE AND ENGINEERING BESTLINK COLLEGE OF THE PHILIPPINES HISTORY OF ZOOLOGY Zoology is the branch of biology concerned with the study of animals and animal kingdom. It is also known as animal biology. The study of zoology includes the interaction of animal kingdom in their ecosystems such as classification, habits, structure, embryology, distribution, evolution, and extinct species. An ancient Greek philosopher, Aristotle, was a first-person to broadly classify the living things in the 4th century BC. Firstly he divided living things into animals and plants and then continued with his further classifications. Aristotle divided animals into two classes: one with red-blood and another without such as insects and crustaceans. Then, he further classified creatures into those who were able to walk, flow and swim. The classification by Aristotle was followed until the 16th century, during the Age of Enlightenment, scientists finally began to research closely. Now, zoology has become much more complex, where the living things are divided into five kingdoms, in which animal kingdom themselves divided into several smaller categories of Phylum, Class, Order, Family, Genus and, finally, Species. These developments were synthesized in Charles Darwin’s theory of evolution by natural selection. In the year 1859, Charles Robert Darwin presented the theory of organic evolution along with its observational evidence. MAJOR BRANCHES OF ZOOLOGY • Anthrozoology- Study of past, present and future interactions between animals and human beings • Archaeozoology or Zooarchaeology- Study of dead animals • Arachnology- Branch of biology that deals with the study of spiders, scorpions or other arachnids • Carnicology- Study of Crustaceans • CetologyStudy of marine mammals (Dolphins, Whales, Porpoises) • Embryology- Study of egg fertilization, embryos and fetuses • Entomology- Study of insects • Ethology- Study of the behavior of animals to interpret their effects on evolution • Herpetology- Study of reptiles and amphibians • Histology- Study of anatomy of cells and tissues of animals • Ichthyology- Study of Fishes • Mammalogy/ Mastology- Study of Mammals • Malacology- Study of animal forms with shells (Snails, Octopus, Slugs) • Morphology- Study of form and specific structures of animal organisms • Ornithology- This branch of zoology concerns the study of birds. • Primatology- Study of primates (apes, gorillas, monkeys, prosimians) • Taxonomy- This field studies, groups and formulates nomenclature rules of animals on the basis of common characteristics. • Zoography(Descriptive Zoology)- Study of animals and their respective habitats • Zootomy Study of animal anatomy EVOLUTION Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. 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 John Baptise Lamarck (1801) It states that organisms change their behavior as the environment change. If organisms’ organs are used more frequently, it will develop in their lifetime. • Theory of Use and Disuse- explains that the parts of an organism that the organism uses most will undergo hypertrophy and will become more developed. • Theory of Transition of Acquired CharacteristicsThe inheritance of such a characteristic means its reappearance in one or more individuals in the next or in succeeding generations. EVOLUTION THEORIES Darwin’s theory of evolution following fundamental ideas. entails the • Species (populations of interbreeding organisms) change over time and space. • All organisms share common ancestors with other organisms. Over time, populations may divide into different species, which share a common ancestral population. • Evolutionary change is gradual and slow in Darwin’s view. Extinct predecessors of modern whales. Small changes over time adapted the now extinct land mammal Pakicetus to life in water. Over time these changes made it more whalelike. Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. This variation means that some individuals have traits better suited to the environment than others. PROKARYOTIC CELL DIVISION Prokaryotic cell division is the process responsible for the production of daughter cells from a parent, prokaryotic cell. And, this process is known as binary fission, which proceeds through three steps. They are DNA replication, chromosome segregation, and separation into daughter cells. EUKARYOTIC CELL DIVISION Eukaryotic cell division is the process responsible for the production of daughter cells in eukaryotes. Generally, eukaryotic cells contain multiple chromosomes packed inside the nucleus. Therefore, DNA replication of eukaryotes occurs during the growth phase of their cell cycle. Also, this occurs inside the nucleus. Moreover, the two stages of eukaryotic cell division are the nuclear division and cytokinesis. ANIMAL HOMEOSTATIC MECHANISM The term ‘homeostasis’ was coined by American physiologist Walter Cannon, and is linked to Bernard’s notion of the physiological stability of the internal environment. In 1932, Cannon defined homeostasis as the series of physiological processes that are involved in the regulation and maintenance of the state of an organism in the face of any disturbance. The homeostatic processes involve a series of internal sensors (sensory receptors) that can detect any kind of deviation from an optimal physiological state, and, at the same time, to initiate the appropriate actions to correct these alterations. This optimal state can be maintained. Homeostasis includes both physiological and ethological mechanisms: sweating, panting (physiological thermoregulation), occultation, fur (ethological responses to cold), etc. In short, homeostatic mechanisms are essential for animals, as they regulate and maintain the organism in optimum conditions, even when they face adversity THE IMPORTANCE OF MAINTAINING A CONSTANT INTERNAL ENVIRONMENT The cells that form the organs and tissues of animals are immersed in a liquid medium, a fluid compartment that Claude Bernard, father of modern physiology, called ‘internal environment’. The internal environment refers, mainly, to extracellular fluid (ECF), a section that separates blood from cells, which is, in turn, composed by interstitial fluid, plasma liquid and lymph, fluids that are crucial in the performance of physiological functions. METHODS OF HOMEOSTATIC REGULATION Reactive Homeostasis Reactive homeostasis is a direct response to the changes that take place in the internal environment (a variation in pH, for example); that is, it occurs when an internal parameter of the organism is subject to a variation that must be corrected. An example of reactive homeostasis is the moment when an animal drinks as a response to a dehydration caused by excessive panting or heavy sweating. METHODS OF HOMEOSTATIC REGULATION Predictive Homeostasis The internal oscillating mechanisms act as true chronometers, which can prepare a physiological response to external environmental changes in advance. This early preparation is known as ‘predictive homeostasis’ , a term proposed by Martin Moore-Ede. Predictive homeostasis is a response to changes in the external environment. It’s anticipatory, meaning that it allows to predict the appearance of an environmental stimulus, and to anticipate a proper response to any disturbance.
