Amazing World of Animals Course Notes PDF

Course Code: ZOO-100 Title of the Course: Amazing World of Animals Number of Credits: 04 (3 +1) Dr. Sandesh Gawas Ph.D Life Science-Zoology MODULE I: Origin, diversity and distribution of Animals Evolution of earth; the first living cell; Bri...

Course Code: ZOO-100 Title of the Course: Amazing World of Animals Number of Credits: 04 (3 +1) Dr. Sandesh Gawas Ph.D Life Science-Zoology MODULE I: Origin, diversity and distribution of Animals Evolution of earth; the first living cell; Brief idea of geological time line and evolution of animals; Outline classification of animal kingdom; Major habitats associated animal diversity (desert, Savanna grassland, forest, cave, oceanic); Paleozoology as a tool to demonstrate evolution.  Evolution of earth Man has been speculating on the origin of Earth for thousands of years. Numerous hypotheses 1. Nebular Hypothesis 2. Planetesimal Hypothesis 3. Tidal Hypothesis Recent Hypothesis 1. Dust-Cloud Hypothesis 2. Nova Hypothesis 3. Binary-star Hypothesis  Nebular Hypothesis Proposed by Immanuel Kant and Pierre- Simon Laplace in the 18th century. The nebular hypothesis, also known as the protoplanetary disk model, is a scientific theory that describes the formation of the solar system. It proposes that the Sun, planets, and other celestial bodies formed from a rotating cloud of gas and dust called a nebula.  Nebular Hypothesis According to the nebular hypothesis, a massive molecular cloud composed mostly of hydrogen and helium, along with trace amounts of heavier elements, began to collapse under its own gravity. As the cloud contracted, it started to spin faster and flatten into a spinning disk shape due to conservation of angular momentum. The central region of the disk, known as the protosun, became increasingly dense and hot. Eventually, nuclear fusion was ignited in the core, leading to the birth of the Sun. The remaining material in the disk consisted of gas, dust, and small solid particles known as planetesimals.  Nebular Hypothesis Over time, these planetesimals began to collide and merge through a process called accretion, gradually growing in size. Through further collisions and gravitational interactions, larger bodies called protoplanets formed. These protoplanets eventually underwent further growth and differentiation to become the planets of the solar system. In the case of Earth, it went through a process of differentiation, with denser materials sinking to the core and lighter materials accumulating in the mantle and crust. The process of differentiation also generated heat, leading to the development of a molten interior.  Nebular Hypothesis Objections 1. The planet possess 98% of the rotational energy of the solar system, whereas the sun has about 99.87% of the mass. 2. The heavy elements in the earth can originate only at temperatures far higher than those prevailing on the sun. 3. Some of the satellites revolve in a retrograde (backward) direction, and one of them revolves faster than its planet rotates.  Planetesimal Hypothesis Proposed by Thomas Chamberlin and Forest Moulton in 1895. According to this hypothesis, the Solar System's planets were thought to have formed from a collision between the Sun and another star.  Planetesimal Hypothesis Chamberlin–Moulton stated that the Solar System's planets had formed as a result of a collision between the Sun and another star. In this scenario, the gravity of the passing star shredded a series of bolts from the solar surface. Bolts ejected from the Sun's near side were thrown out to distances comparable to those of the big planets, while those ejected from the Sun's far side are ejected less forcefully to distances comparable to those of the terrestrial planets.  Planetesimal Hypothesis The planets' original cores were produced from the inner leftovers of these bolts. The outer parts expanded and cooled into a massive swarm of solid particles that strewn across a disc moving around the Sun in a plane specified by the passing star's speed. The cores gradually developed into planets by accumulating in planetesimals, with the majority of the expansion taking place in the Solar System's outer parts, where the material was more abundant. Hot gas in the smaller bolts is presumed to have condensed rapidly into liquid and then cooled to solid particles, called Planetesimals.  Planetesimal Hypothesis Objections 1. This theory failed to explain the massive passing star, which must remain in close proximity to the Sun. 2. The alignment of one star with the Sun appears to be incorrect. The stars in space are so far apart, that moving from one to the next is impossible. 3. It was not able to explain why only nine planets formed. Also, this hypothesis was not able to explain the different dimensions of planets.  Tidal Hypothesis Unconvinced that the earth has always been solid, James Jeans a Harold leffries, English astronomer and geophysicist, respectively, proposed in 1917 a gaseous two-star hypothesis. They theorized that another star closely approach the sun, producing tidal bulges, from which streamed an enormous cigarshaped filament of solar gases. This incandescent filament was put into revolution around the sun. It then broke into segments which contracted into rotating spheres, the planets. Cooling from gas to liquid one of these planets, Earth, gradually solidified to its present condition.  Origin of Life THEORIES OF ORIGIN OF LIFE The innate curiosity of mankind has always seemed to lead to questions concerning the origins of life, it has only been in recent years that definitive scientific answers have begun to appear. Part of the reason for this is that a description of the beginning of life on earth has awaited appropriate concepts regarding the nature of the primitive earth and its atmosphere, as well as methods for measuring with some accuracy the ages of very ancient rocks and sediments of the earth.  Origin of Life THEORIES OF ORIGIN OF LIFE If we ask, how the living plants and animals that we know have come to be what they are, we probably receive answers in the following theories: (a) Theory of Special Creation, (b) Theory of Spontaneous Generation, (c) Theory of Biogenesis (d) Theory of Eternity of Life, (e) Theory of Catastrophism (f) Theory of Organic Evolution, and (g) Modern Concept of Origin of life.  Origin of Life A) Theory of Special Creation This theory was proposed by Hebrew and others, and states that each organism has come into being independently by a process of Special Creation. The greatest supporter of this theory was Father Suarez. He believed that world was created by super natural power the God. The whole world originated in 6 days. On the first day materia primia including earth and heaven was created. The creation of sky was made on the second day. Plants were originated on the third day. On fourth day the sun, the moon and the stars were created. The fish and birds were originated on the fifth day. On the sixth day other animals and human beings were created. First man, Adam, was moulded by God from inanimate material and given the soul and later female-Eve was created from the 12 rib of man.  Origin of Life A) Theory of Special Creation There are three important points in the theory of special creation. They are: (a) All the different kinds of animals and plants were created at once or at short intervals. (b) All the animals and plants were created in the same form in which they exist at present. (c) Their bodies and organ have been designed to fully meet the needs of the environment. This theory is purely religious thinking and has no scientific base.  Origin of Life (B) Theory of Spontaneous Generation This theory is also known as theory of abiogenesis. According to this theory, life has originated from nonliving organic material. Anaximander and Anaxagoras believed that life appeared in small seeds (spermeia), which came to earth along with rainwater. Aristotle suggested that a number of animals originated in the way mentioned above. Worms, larvae bee or wasps, ticks, flies and many other insects develop from the morning dew or from decaying slime manure, from dry wood, hair, sweat and meat while tapeworms are born in the rotting portions of the body and excreta.  Origin of Life (B) Theory of Spontaneous Generation Mosquitoes, flies, moths, beetles, fleas, bed- bug and bees are generated in the slime of well, rivers or sea, in the humus of the fields, manure, in decaying tree or fruits etc. Crabs and molluscs were thought to come from the moist soil and decaying slime. Some higher animals and even man have similar origin though in the case of latter his first appearance is in the form of a worm. In fifteen century, It was thought that leaves falling from trees turned into fish if they fell into water, and turned into birds if they fell on land.  Origin of Life (C) Theory of Biogenesis This theory refers to the origin of life from pre-existing life by reproduction. According to this theory insects came from insects, rats from rats and horses from pre-existing horses. Franceseo Redi (1626-1698) was perhaps the first to discard the concept of spontaneous generation. He placed meat or fish in three jars. One jar was left open, one was covered with gauze, and one was covered with a muslin cloth. The meat/fish decayed in all the jars and flies were attracted to all. He showed that the white maggots in meat of 1st jar, were the larvae of flies and nothing else. He noticed that in the second case, worms did not ap pear in the meat because the netting allowed air to enter and prevented flies from landing on the meat. However, he reported the eggs wire gauge. Redi's experiment showed convincingly that other flies. Redi's hypothesis was confirmed, and a major blow was struck against the hypothesis of spontaneous generation.  Origin of Life (C) Theory of Biogenesis Lazzaro Spallanzani, an Italian scientist disproved the theory of spontaneous generation in 1765. He designed an experiment to test the hypothesis of spontaneous generation of micro- organisms. Spallanzani hypothesized that microorganisms formed not from air but from other microorganisms. He knew that microorganisms grew easily in food, such as broth made from boiled meat. Spallanzani reasoned that boiling broth in the long necked flask would kill all the microorganisms in the broth, on the inside of the glass, and in the air in the flask.  Origin of Life (C) Theory of Biogenesis For his experimental group, Spallanzani boiled clear, fresh broth until the flask filled with steam. While the broth was hot, he sealed the flasks by melting their glass necks. The broth in the sealed flasks remained clear and free of microorganisms for months. No sign of life was reported. Needham claimed that by boiling, the vital forces necessary for spontaneous generation had driven out. Then the seal was broken and broth was exposed to fresh air. On testing the broth, the presence of microbes proved the origin of life from pre- existing life.  Origin of Life (C) Theory of Biogenesis Louis Pasteur in the nineteenth century disproved the theory of spontaneous generation. He used a swan-necked flask. He boiled a solution of sugar and yeast for several hours. Then the flask was left be unsealed for the free exchange of air with the environment. The solution remained free of microbes, because, the swan- neck was shaped so to trap viable microbial particles and to allow only air to enter the flask. Broth boiled inside the experimental swan necked flasks remained clear upto a year. But when Pasteur broken off the curved necks, the broth became cloudy and contaminated with microorganisms within a day. Pasteur reasoned that the contamination was due to microorganisms in the air. With the Pasteur's experiment, the principle of biogenesis became a cornerstone of biology.  Origin of Life (D) Theory of Eternity of Life The theory was given by Richter, Helmholtz, Preyer, Arrhenius, Hoyle and Bondi. They believed in the eternity of life. According to them, life only changes its form but is never created from dead substances. It has no origin and has always existed. Preyer assumed that life must have existed even at that time, when earth was a mass of molten liquid. According to him, life comes from life and never from lifeless matter. Richter proposed a theory called Cosmozoic theory. According to this theory, life came from other planet in the form of celestial bodies and small particles carrying viable germs or spores, which upon reaching on earth accidentally, could develop and initiate d panoply of living organisms.  Origin of Life (D) Theory of Eternity of Life Helmholtz was of the opinion propounding the meteorite idea. According to him, life came in the form of germs along with meteorites falling from other planets. Arrhenius proposed a theory of Cosmic panspermia. This theory holds that spore, b of life together with particles of cosmic dust could be transformed from one heavenly body to g another under the pressure of stellar rays. The spores then evolved on earth into the riad of forms that we know today. These theories of interplanetary exchange of viable spores have been rejected, due to intense cold, extreme dryness and intense radiation of interstellar space. Even the most resistant living spores cannot withstand in the exposure to interstellar space.  Origin of Life (E) Theory of Catastrophism Cuvier (1769-1832) gave to the world another theory, the theory of catastrophism, which explains the extinction of several forms. According to this theory, there had been several ups and downs in the history of the earth and that each, at the end of its period, had been wiped out by some cataclysmic upheaval; and a fresh set of organisms created on different lines. Furthermore, it was also believed that new organisms were not created on the spot but descended in some way. However, this theory retained its position for half a century. d'Orbigney (1802-1857) believed that catastrophes were world wide and destroyed the population as a whole, and then repopulated by recreation after each. According to him catastrophe has occurred 27 times.  Origin of Life (F) Theory of Organic Evolution According to this theory, life originated slowly and gradually by the doctrine of organic evolution which teaches us that species of any kinds are not immutable but are subject to changes. The organisms present now, have arisen by natural evolution from simpler preexisting forms of life, these forms from still simple ones and so on, back to the mist of life's beginnings. This idea of evolution has been an ascending process from the lower to the higher or from simpler form to complex form. Many attempts have been made to explain this evolution and the credits of which go particularly to Charles Darwin (1809-1882), Lamarck (1744-1829). Wallace (1823-1913) and Hugo De Vries (1848-1935).