Deuterostomes Overview

Deuterostomes

• Echinoderms - radial symmetry in adults, calcium carbonate endoskeletons, water vascular system for movement and feeding, can regenerate body parts
• Hemichordates - worm-like, possess a proboscis, collar, and trunk, have a dorsal nerve cord and pharyngeal slits, marine filter feeders
• Chordates - possess notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail, all have a head, most have a skull and vertebral column
• Xenoturbellans - lack distinct body cavities, appear more similar to flatworms

Key Terms

• Notochord - flexible rod that supports the body
• Dorsal hollow nerve cord - hollow tube that runs along the back of the body
• Pharyngeal slits - openings in the throat that are used for filter feeding or gas exchange
• Post-anal tail - a tail that extends beyond the anus
• Endoskeleton - internal skeleton

Adaptations to Habitats

• Echinoderms - calcium carbonate endoskeleton provides protection and support – allowing them to move and graze on the seafloor
  • Starfish - tube feet with suction cups to grab prey and move along surfaces
  • Sea urchins - spines for protection and for moving along rough surfaces
• Hemichordates - filter feeders with pharyngeal slits that allow them to draw water and food into their mouths
• Chordates - notochord provides structural support allowing for swimming and burrowing
  • Tunicates - sessile filter feeders with specialized siphons
  • Vertebrates - strong endoskeletons, efficient nervous systems, and diverse adaptations for movement, breathing, and feeding
• Xenoturbellans - live in marine sediments and are adapted to these environments

Cell Organization

• Cells are organized into tissues
• Tissues are organized into organs
  • Epithelial Tissue - covers body surfaces and lines cavities
    • Protective - skin, lining of the digestive tract
    • Secretory - glands that release hormones, enzymes, etc
    • Absorptive - lining of the small intestine
  • Connective Tissue - supports, binds together, and protects other tissues
    • Loose Connective Tissue - found beneath skin, around organs, and in blood
    • Dense Connective Tissue - found in tendons and ligaments
    • Specialized Connective Tissue - includes cartilage, bone, lymph, and blood
  • Muscle Tissue - allows movement
    • Skeletal Muscle - attached to bones and allows for voluntary movement
    • Smooth Muscle - found in the walls of internal organs
    • Cardiac Muscle - found in the heart
  • Nervous Tissue - receives and transmits information
    • Neurons - specialized cells that conduct electrical impulses
    • Glia - supporting cells that provide nutrition and insulation to neurons

Metabolism & Environment

• Metabolism - all of the chemical reactions that occur within an organism
• Anabolism - building up of complex molecules from simpler ones, requires energy
• Catabolism - breaking down of complex molecules into simpler ones, releases energy
• Temperature Affects Metabolism - enzymes are sensitive to temperature
  • Cold Environment - metabolic rate slows down
  • Hot Environment - metabolic rate increases
• Food Affects Metabolism - food provides the energy needed for metabolism
• Sunlight Affects Metabolism - plants use sunlight for photosynthesis, which provides energy for all other organisms

Feedback Loops

• Positive Feedback Loops - amplifies a change, tends to be less common, can lead to instability
  • Example - oxytocin release during labor
• Negative Feedback Loops - dampens a change, more common, helps maintain homeostasis
  • Example - blood glucose regulation (insulin and glucagon)

Body Size & Shape

• Surface Area to Volume ratio - smaller organisms have a higher surface area to volume ratio than larger organisms
• Heat Loss - smaller organisms lose heat more quickly than larger organisms
• Metabolic Rate - smaller organisms have a higher metabolic rate than larger organisms

Feeding Mechanisms

1. • Suspension Feeding - filter feeding, using structures like cilia or baleen
   • ex. whales, barnacles
2. • Deposit Feeding - eating sediment, extracting nutrients
   • ex. earthworms, polychaetes
3. • Herbivory - eating plants
   • ex. cattle, rabbits
4. • Carnivory - eating other animals
   • ex. lions, hawks
5. • Parasitism - living inside or on another organism and feeding off of it
   • ex. tapeworms, ticks

Form & Nutrient Gain

1. • Form affects nutrient gain
   • Mouth - adapted to type of food
   • Digestive System - length and structure depend on the type of food
   • Surface Area - increased surface area in intestines for maximal absorption
   • Specialized Organs - for digestion, storage, and elimination of waste
2. • Herbivores
   • Long digestive system to break down cellulose
   • Specialized stomachs (ruminants) or intestines for digestion of plant matter

Ventilation

1. • Inhalation - air enters lungs
   • Diaphragm - muscle contracts, pulling air into the lungs
2. • Gas Exchange - oxygen diffuses from the lungs into the blood, carbon dioxide diffuses from the blood into the lungs
   • Alveoli - tiny air sacs in the lungs where gas exchange occurs
3. • Exhalation - air leaves the lungs
   • Diaphragm - muscle relaxes, pushing air out of the lungs
4. • Circulation - blood carries oxygen to the body's cells and carbon dioxide back to the lungs
   • Heart - pumps blood throughout the body

Digestion

• Digestion - the breakdown of food into molecules that can be absorbed by the body
• Mechanical Digestion - physical breakdown of food
  • Chewing - teeth break down food
  • Churning - muscles in the stomach and intestines mix and break down food
• Chemical Digestion - chemical breakdown of food by enzymes
  • Enzymes - proteins that catalyze chemical reactions

Alimentary Canal

• Mouth - chews food
• Esophagus - transports food to the stomach
• Stomach - churns food and mixes it with gastric juices
• Small Intestine - absorbs nutrients
• Large Intestine - absorbs water and forms feces
• Rectum - stores feces
• Anus - expels feces
• Accessory Organs - pancreas, liver, gallbladder

Ruminant Digestion

• Ruminants - herbivores with four-chambered stomachs
  • Rumen - largest chamber, contains bacteria that break down cellulose
  • Reticulum - traps larger particles of food for further breakdown
  • Omasum - absorbs water and some nutrients
  • Abomasum - true stomach, secretes digestive enzymes

Gastrovascular Cavities

• Cnidarians - have a gastrovascular cavity, a single opening for both eating and excretion

• Flatworms - also have a gastrovascular cavity

• Open Circulatory Systems - blood is not always contained within blood vessels, blood flows freely through cavities and organs

  • Example - mollusks and arthropods

• Closed Circulatory Systems - blood is always contained within blood vessels, allows for efficient transport of oxygen and nutrients

  • Example - annelids, vertebrates

Arteries & Veins

1. • Arteries - carry oxygenated blood away from the heart
   • Thick walls - to withstand the pressure of blood flowing away from the heart
2. • Veins - carry deoxygenated blood back to the heart
   • Thinner walls - than arteries
3. • Capillaries - tiny blood vessels where gas exchange occurs between blood and tissues
   • One cell thick - allows for efficient diffusion
4. • Venules - small veins
   • Carry blood back to heart - collect blood from capillaries