Animal History and Classification PDF

Module 3 Animal History and Classification Ris Menoel R. Modina, MSc Assistant Professor IV Department of Biological Sciences College of Arts and Sciences Visayas State University 1  Module Overview This module includes lessons about the history of anima...

Module 3 Animal History and Classification Ris Menoel R. Modina, MSc Assistant Professor IV Department of Biological Sciences College of Arts and Sciences Visayas State University 1  Module Overview This module includes lessons about the history of animals based on fossil evidence, followed by animal taxonomy and the criteria used by biologists/zoologists in classifying animals. 2  Classification of Animals Lesson 3.1 History of Animals Lesson 3.2 Animal Taxonomy Lesson 3.3 Criteria for Animal Classification 3  Lesson 3.1: History of Animals Lesson Summary In this lesson, you will learn about the historical account of animals. You will also be introduced to some fossil evidence of animal existence in specific periods. 4  Learning Outcomes At the end of this lesson, you are expected to be able to: 1. Differentiate extinct from extant species 2. Describe what the common ancestor of all animals is like 3. Identify major eras of animal history as recorded in fossils 4. Briefly discuss the recent views on animal phylogeny using morphological and molecular data 5 The Earth’s history is Geologic divided into four Timescale major units of time known as eons. An eon is divided into eras. Each era consists of subdivisions called periods. Each period can be further split into epochs.  ▪ Each layer has a characteristic composition and set of fossils that reflect events during its deposition. Sedimentary rock layers exposed by erosion in the Arizona’s Grand Canyon  History of animals spans more than half billion years ▪ diversity of animals: ▪ extant (living) species ▪ extinct species (~99% of all animals) ▪ estimates based on molecular clocks suggests that ancestors of animals diverged from the ancestors of fungi ~1 BYA ▪ common ancestor of living animals lived ~800-675 MYA  The Common Ancestor ▪ A combination of morphological and molecular evidence indicates that choanoflagellates are among the closest living relatives of animals. What is this common ancestor like? Choanoflagellates and Choanocytes ▪ Choanoflagellates - heterotrophic microeukaryotes that use an apical flagellum to swim and to generate water flow, thus trapping bacterial prey on an actin-filled microvillar collar. ▪ Ex. Proterospongia – unicellular and colonial  Neoproterozoic Era (1 billion – 542 million years ago) ▪ molecular data ▪ Ediacaran fossils. Fossils dating to 565-550 MYA indicates an earlier include animals (a) with simple, radial forms and origin of animals (b) with many body segments. ▪ but the first generally accepted macroscopic fossil date from 565 to 550 MYA ▪ Ediacaran fossils. The name comes from the ▪ Ediacaran biota → soft- Ediacara Hills of Australia, bodied multicellular where these animals were first discovered. eukaryotes  Paleozoic Era (542 - 251 MYA) ▪ This artist’s reconstruction depicts a diverse array of organisms found in fossils from the Burgess Shale site in British Columbia, Canada. ▪ The animals include: ▪ Pikaia (eel-like chordate at top left), ▪ Marella (arthropod swimming at left), ▪ Anomalocaris (large animal with anterior grasping limbs and a circular mouth), and ▪ Hallucigenia (animals with toothpick- like spikes on the seafloor). A Cambrian Seascape  Mesozoic Era (251 - 65.5 MYA) ▪ animals from previous era spread into new habitats ▪ first coral reef formed Cenozoic Era (65.5 MYA - present) Mass extinction of dinosaurs History of animals spans more than half billion years  The Phylogenetic Relationship of Kingdom Animalia From Hickman et al. (2008)  Animal Phylogeny based on morphological and developmental based mainly on molecular evidence comparisons  Ecdysozoa ▪ The clade name Ecdysozoa refers to a characteristic shared by nematodes, arthropods, and some of the other ecdysozoan phyla. ▪ These animals secrete external skeletons (exoskeletons); the stiff covering of a cicada or cricket is an example. This molting cicada is in the process of emerging from its old exoskeleton. The animal will now ▪ As the animal grows, it molts, secrete a new, larger exoskeleton. squirming out of its old exoskeleton and secreting a larger one.  Ecdysozoa The process of shedding the old exoskeleton is called ecdysis.  Lophotrochozoa ▪ The name Lophotrochozoa refers to two different features: ▪ development of a structure called a lophophore - a crown of ciliated tentacles that function in feeding ▪ Ex. Ectoprocts ▪ other individuals go through a distinctive Morphological characteristics of lophotrochozoans. developmental stage called the trochophore larva — hence the name lophotrochozoan ▪ Ex. molluscs and annelids Key Steps in Animal Evolution