Biology Chapter 32: Animal Diversity Study Guide

Animal Diversity

• Animals share common characteristics: ability to move, 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 marked a period of rapid animal diversification
• Animal body plans can be classified as radial or bilateral symmetry, with bilateral symmetry being more common and allowing for faster movement and the formation of a head with sensory organs and a central nervous system

Embryo Development

• Animal zygotes undergo cleavage, a series 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
• Protostome vs. deuterostome development:
  • In protostomes, the blastopore becomes the mouth
  • In deuterostomes, the blastopore becomes the anus

Invertebrate Animals

• Invertebrates are animals without a backbone
• Porifera (sponges):
  • Simplest animals
  • Filter feeders
  • No tissue
• Cnidarians:
  • True tissues
  • Gastrovascular cavity
  • Polyps and medusa life forms
  • Nematocysts
  • Radial symmetry
• Lophotrochozoans:
  • Have a lophophore for feeding or a trochophore larval stage
• Flatworms (platyhelminthes):
  • Flat body form for large surface area
  • Examples: planarians, tapeworms
• Molluscs:
  • Muscular foot
  • Visceral mass
  • Mantle
  • Major groups: Gastropoda, Bivalvia, Cephalopoda
• Annelids:
  • Segmented worms
  • Have a coelom
  • Examples: leeches, earthworms
• Ecdysozoans:
  • Cuticle
  • Molting
• Nematodes:
  • Have a hemocoel
  • Examples: roundworms
• Arthropods:
  • Segmented body
  • Exoskeleton
  • Jointed appendages
  • Open circulatory system with heart and hemolymph
  • Examples: Pancrustaceans (including insects), Chelicerates, Myriapods

Chordates

• Common characteristics: 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
• Invertebrate chordates: lancelets, tunicates
• Vertebrate chordates:
  • Hagfishes and lampreys: lack 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 (high metabolic rate)

Animal Body Organization

• Tissues:
  • Groups of cells with similar appearance and function
  • Four types: epithelial, connective, muscle, and nervous
• Epithelial tissue:
  • Covers the outside of the body and lines organs and cavities within the body
• Connective tissue:
  • Holds many tissues and organs together in place
  • Examples: tendons, ligaments, bone, adipose tissue, blood
• Muscle tissue:
  • Skeletal muscle: responsible for voluntary movement
  • Smooth muscle: responsible for involuntary body activities
  • Cardiac muscle: responsible for contraction of the heart

Animal Form and Function

• Homeostasis:
  • Automatic tendency to maintain a constant and optimal internal environment
  • Positive and negative feedback
• Endotherm vs. ectotherm:
  • Pros and cons of each
• Hypothalamus: physiological thermostat

Animal Nutrition

• Variation in diet: herbivores, carnivores, omnivores
• Food processing:
  • Ingestion
  • Digestion
  • Absorption
  • Elimination
• Most complex animals have a digestive tube with two openings (alimentary canal)
• Advantages of having a complete digestive system:
  • Specialized regions with diverse functions
• Digestive system in humans:
  • Oral cavity: salivary glands, amylase
  • Pharynx: junction of the esophagus and trachea
  • Esophagus: connects to the stomach, food is pushed by peristalsis
  • Stomach: gastric juice, chyme, breaks down proteins
  • Small intestine: most enzymatic hydrolysis of macromolecules occurs here
  • Large intestine: absorbs water and salts, includes colon, cecum, and rectum

Circulation and Respiration

• Open and closed circulatory systems:
  • Insects, other 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 flow:
    • Right ventricle pumps blood to the lungs
    • Oxygen-rich blood returns from the lungs to the left atrium
    • Blood flows into the left ventricle and is pumped out to the body
• Gas exchange in capillary beds occurs
• Blood pressure: a force exerted in all directions, including against the walls of blood vessels
• Blood and its components:
  • Plasma: liquid matrix
  • Platelets: fragments of cells involved in clotting
  • Red blood cells (erythrocytes): transport oxygen
  • White blood cells (leukocytes): defense
• Cardiovascular disease:
  • Hypertension (high blood pressure)
  • Atherosclerosis
  • Heart attack
  • Stroke

Immune System

• Examples of pathogens: agents that cause disease, such as 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: histamine triggers blood vessels to dilate and become more permeable
  • Interferons: provide innate defense by inhibiting the replication of viruses
• Adaptive immunity:
  • Activated after the innate response
  • Develops more slowly
  • Enhanced by previous exposure to the pathogen
  • T cells (mature in thymus)
  • B cells (mature in bone marrow)
  • Primary vs. secondary immune response
• Immunization: the protection provided by a 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
  • Ammonia: very toxic
  • Urea: less toxic and higher solubility in water
  • Uric acid: relatively non-toxic and not soluble in water, energetically expensive to produce than urea
• Key functions of most excretory systems:
  • Filtration: filtering of body fluids
  • Reabsorption: recovering valuable solutes
  • Secretion: adding nonessential solutes and wastes to the filtrate
  • Excretion: processed filtrate containing nitrogenous wastes is released from the body
• Malpighian tubules: used by insects and other terrestrial arthropods to remove nitrogenous wastes from hemolymph
• Kidney: the excretory organs of vertebrates and some other chordates, function in excretion and osmoregulation
• Nephrons: the functional units of the vertebrate kidney
• Nephrons consist of a long tubule and a ball of capillaries called the glomerulus
• ADH: antidiuretic hormone, released from the posterior pituitary and activates membrane receptors on collecting duct cells, causing an increase in water recapture (reduces urine volume)

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
• Pheromones: some animal species communicate with pheromones, chemicals that are released into the environment
• Types of hormones:
  • Polypeptides
  • Steroids
  • Amines
• Feedback regulation:
  • Negative feedback: the response reduces the initial stimulus (more common)
  • Positive feedback:

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 (closest living relatives: choanoflagellates)
• Cambrian explosion: marks a period of rapid animal diversification
• Animal body plan: radial symmetry vs. bilateral symmetry (most animals evolved to have bilateral symmetry, allowing for faster movement, formation of a head with sensory organs and central nervous system)

Embryo Development

• Animal zygotes undergo cleavage, a succession of cell division 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 have no tissue (e.g., sponges)
• Most animals have germ layers that give rise to the 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 some animals have no cavity at all (e.g., flatworms)

Invertebrate Animals

• Invertebrates: animals without a backbone
• Phyla of invertebrates:
  • Porifera (sponges): simplest animals, filter feeders, no tissue
  • Cnidarians: true tissues, gastrovascular cavity, polyps and medusa life forms, nematocysts, radial symmetry
  • Lophotrochozoans: have a lophophore for feeding or a trochophore larval stage
  • Flatworms (platyhelminthes): flat body form for large surface area (e.g., planarians, tapeworms)
  • Molluscs: muscular foot, visceral mass, mantle (major groups: Gastropoda, Bivalvia, Cephalopoda)
  • Annelids: segmented worms, have a coelom (e.g., leeches, earthworms)
  • Ecdysozoans: cuticle, molting
  • Nematodes: have hemocoel (e.g., roundworms)
  • Arthropods: segmented body, exoskeleton, jointed appendages, open circulatory system with heart and hemolymph (example groups: Pancrustaceans including insects, Chelicerates, Myriapods)

Chordates

• 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
• Invertebrate chordates: lancelets, tunicates
• Vertebrate chordates: hagfishes, lampreys, sharks, fish, amphibians, reptiles, birds, mammals

Animal Form and Function

• Tissues: groups of cells with a similar appearance and function
• Four types of tissues:
  • Epithelial tissue: covers the outside of the body and lines the organs and cavities within the body
  • Connective tissue: holds many tissues and organs together in place (e.g., tendons, ligaments, bone, adipose tissue, blood)
  • Muscle tissue: responsible for movement
  • Nervous tissue: functions in the receipt, processing, and transmission of information

Animal Nutrition

• Variation in diet: herbivores, carnivores, omnivores
• Food processing: ingestion, digestion, absorption, and elimination
• Most complex animals have a digestive tube with two openings (alimentary canal)
• Advantages of having a complete digestive system: specialized regions with diverse functions

Circulation and Respiration

• Open and closed circulatory system
• Types of circulatory systems: open (insects, other arthropods, and some molluscs), closed (annelids, cephalopods, and vertebrates)
• Human cardiovascular system: heart, blood vessels, arteries, veins, capillaries
• Respiratory system: gas exchange, oxygen-rich blood, oxygen-poor blood, circulation of blood

Immune System

• Examples of pathogens: viruses, bacteria, fungi
• Innate immunity: non-specific, active immediately upon infection
• Adaptive immunity: activated after the innate response, develops more slowly, enhanced by previous exposure to the pathogen

Osmoregulation

• Osmoregulation: controls solute concentrations and balances water gain and loss
• Animal's nitrogenous waste: ammonia, urea, uric acid
• Key functions of most excretory systems: filtration, reabsorption, secretion, excretion

Hormones

• Hormone: a secreted molecule that circulates through the body and stimulates specific cells
• Communication and control in animals: endocrine system, nervous system, pheromones
• Types of hormones: polypeptides, steroids, amines
• Feedback regulation: negative feedback, positive feedback