Unit 3: Animal Diversity Study Guide

Animal Diversity

• Common characteristics of animals:
  • Can move and capture prey
  • Multicellular
  • No cell walls
  • Heterotrophic
  • Eukaryotes
• Animals are thought to have evolved from flagellated protists, with choanoflagellates being the closest living relatives
• The Cambrian explosion marks a period of rapid animal diversification

Animal Body Plan

• Radial symmetry vs. bilateral symmetry
  • Most animals evolved to have bilateral symmetry, which allows for faster movement and formation of a head with sensory organs and central nervous system

Embryo Development

• Animal zygotes undergo cleavage, a succession of cell divisions without growth between divisions
• Cleavage leads to the formation of a blastula, often in the form of a hollow ball of cells

Animal Tissues

• Only a few groups of animals have no tissue (e.g., sponges)
• Most animals have germ layers that give rise to tissues and organs
  • Diploblastic: ectoderm and endoderm
  • Triploblastic: ectoderm, endoderm, and mesoderm
• Body cavity: coelom (a cavity surrounded by tissues derived from mesoderm), hemocoel (filled with hemolymph), or no cavity at all (e.g., flatworms)

Protostome vs. Deuterostome Development

• In protostome development, the blastopore becomes the mouth
• In deuterostome development, the blastopore becomes the anus
  • Examples: echinoderms and chordates

Chordata and Invertebrates

• Chordata is the only phylum of animals that includes vertebrates
• Most other animals are invertebrates
• Invertebrates: animals without a backbone
  • Examples: Porifera (sponges), Cnidarians, Lophotrochozoans, Flatworms (Platyhelminthes), Molluscs, Annelids, Ecdysozoans, Nematodes, Arthropoda

Vertebrate Animals

• Common characteristics of chordates:
  • Bilateral
  • Deuterostome development
  • Mostly vertebrates with two groups of invertebrates
• Four characteristics of chordate embryos:
  • Notochord
  • Dorsal nerve cord
  • Pharyngeal pouches (slits)
  • Post-anal tail
• Vertebrate examples:
  • Lancelets and tunicates (invertebrate chordates)
  • Hagfishes and lampreys (lacking jaws)
  • Sharks and rays (oil in the liver to maintain buoyancy)
  • Ray-finned and lobe-fin fish (swim bladder for buoyancy)
  • Amphibians (need water and land for living, metamorphosis, frogs and salamanders)
  • Reptiles (scales, shelled and amniotic eggs, ectothermic)
  • Birds (endothermic, direct descendants of dinosaurs)
  • Mammals (mammary glands, hair, endothermy)

Animal Form and Function

• Tissues:
  • Groups of cells with similar appearance and function
  • Four types: epithelial, connective, muscle, and nervous tissue
• Epithelial tissue:
  • Covers the outside of the body and lines organs and cavities
• Connective tissue:
  • Holds tissues and organs together
  • Examples: tendons, ligaments, bone, adipose tissue, blood
• Muscle tissue:
  • Responsible for movement and contraction
  • Three types: skeletal, smooth, and cardiac
• Nervous tissue:
  • Functions in receipt, processing, and transmission of information
  • Two types: neurons (nerve cells) and glial cells (support cells)

Animal Nutrition

• Variation in diet:
  • Herbivores
  • Carnivores
  • Omnivores
• Food processing:
  • Ingestion
  • Digestion
  • Absorption
  • Elimination
• Digestive system:
  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
• Energy storage:
  • Liver and muscle cells (glycogen)
  • Excess energy stored in fat

Circulation and Respiration

• Open and closed circulatory systems:
  • Insects, arthropods, and some molluscs: open circulatory systems with hemolymph
  • Annelids, cephalopods, and vertebrates: closed circulatory systems
• Human cardiovascular system:
  • Heart
  • Blood vessels
  • Arteries
  • Veins
  • Capillaries
• Blood circulation:
  • Right ventricle pumps blood to lungs
  • Oxygen-rich blood returns to left atrium
  • Blood flows into left ventricle and is pumped out to body
• Gas exchange:
  • Occurs in capillary beds
  • Oxygen-poor blood from body is channeled into vena cava and reaches right atrium

Immune System

• Examples of pathogens:
  • Viruses
  • Bacteria
  • Fungi
• Innate immunity:
  • Non-specific
  • Active immediately upon infection
  • Barrier defenses (skin, mucus, body fluids)
  • Cellular defense (neutrophils, macrophages, dendritic cells, eosinophils, natural killer cells)
  • Inflammation
  • Interferons
• Adaptive immunity:
  • Activated after innate response
  • Develops more slowly
  • Enhanced by previous exposure to pathogen
  • T cells and B cells
• Primary vs. secondary immune response:
  • Immunization: protection provided by second immune response
  • Vaccines are used for immunization

Osmoregulation

• Osmoregulation:
  • Controls solute concentrations and balances water gain and loss
• Animal's nitrogenous waste:
  • Consumption of proteins and nucleic acids causes nitrogenous waste
  • Animals need to remove nitrogenous waste products by excretion
  • Examples: ammonia, urea, uric acid
• Key functions of most excretory systems:
  • Filtration
  • Reabsorption
  • Secretion
  • Excretion
• Excretory systems:
  • Malpighian tubules (used by insects and other terrestrial arthropods)
  • Kidney (the excretory organs of vertebrates and some other chordates)

Hormones

• Hormone:
  • A secreted molecule that circulates through the body and stimulates specific cells
• Communication and control in animals:
  • Endocrine system: chemical signaling by hormones
  • Nervous system: a network of specialized cells (neurons) that transmit signals along dedicated pathways
• Feedback regulation:
  • Negative feedback: reduces the initial stimulus
  • Positive feedback: reinforces a stimulus to produce an even greater response
• Hormone examples:
  • Oxytocin
  • Testosterone
  • Estrogen
  • Progesterone
  • Growth hormone
  • Thyroid hormone