Practical #3 - Chordates

Question 1

What are the 4 key caracteristics of Phylum Chordata?

Answer 1

• Notochord
  
  • cartilage-like connective tissue underneath dorsal surface
• Pharyngeal gill slits
• Nerve cord
  
  • dorsal - leads to brain
• Post-anal tail

Question 2

What are other similar characteristics of the Chordates?

Answer 2

• Extracellular digestion
  
  • Complete digestion tracts
• Possess well-defined respiratory, circulatory, and excretory systems
  
  • closed circulatory system
• Highly developed nervous system
• Most are dioecious
  
  • ​fertilization is external or internal depending on the group

Question 3

What are the key characteristics of Subphylum Urochordata? (The sea squirts)

Answer 3

• Integumentary (skeletal)
  
  • ​Also called the “tunicates” because of hard polysaccharid outer covering - tunic
• Excretory
  
  • ​ammonia diffuses across body
• Digestive
  
  • ​Complete digestive system: Mouth –> Anus
• Nervous
  
  • ​reduced in adults. Have a couple ganglia
• Ciruclatory/Respiratory
  
  • ​Have a heart and open circulatory system
• Muscular
  
  • ​Adults are sessile, lose notochord. circular and longitudinal muscles
• Habitat
  
  • ​filter feeders, shallow marine
• Reproductive System
  
  • ​monoecious
  • Some can undergo budding

Question 4

What are the key characteristics of Subphylum Cephalochordata? (Lancelets)

Also called the Amphioxus

Answer 4

• Posses Oral hood with finger like cirri that act as food sensors and strainers
• Muscular System and Locomotion
  
  • ​Myomeres -segments muscles andDorsal finandCaudal fin move the lancelet
• Integumentary/Skeletal
  
  • ​Notochord is present in adults - gives structure to head and muscles
  • Has epidermis and dermis skin
• Nervous
  
  • ​Nerve cord is dorsal to notochord. No distinct cephalization
  • Has an eyespot - detects shit
• Digestive
  
  • ​Need to look at page 20-6/20-7 for info
• Respiratory
  
  • ​gas exchange across skin epithelium
• Circulatory
  
  • ​Closed circulatory system
• Excretory
  
  • ​They use protonephridia
• Reproduction - dioecious

Question 5

What are the general vertebate characteristics?

Answer 5

• Vertebae are made of bone (or cartilage)
• possess a living endoskeleton that grows with the animal
• Integument that has inner dermis and outer epidermis
• Have kidneys with nephrons
• Have hearts, RBCs, hemoglobin, and closed circulatory systems

Question 6

What does the term ‘Agnathans’ mean? And which vertebrates does it refer to?

Answer 6

• Agnathans - are the jawless vertebrate animals
• Lampreys and Hagfish fall under this category

Question 7

What are the general hagfish Characteristics?

(Class Myxini)

Answer 7

• Marine, predatory/scavenging
• Rasping tongue w/ teeth (made of keratin)
• Skeleton composed of cartilage
• Lack jaws and vertebrae
  
  • retain notochord as support structure
• Slime glands on naked skin
  
  • creates protective slime
• No paired appendages
• Single nostril
• One pair of semicircular canals
• no scales
• Pore-like gill slits
• Multiple hearts
• Iso-osmotic with seawater (osmoconformers)
• Oviparous
  
  • no larval stage, young hagfish hatch from eggs

Question 8

What are the general Characteristics of Lampreys?

(Class Cephalaspidomorphi)

Answer 8

• Ammocoete Larvae - shows all four hallmarks of a chordate. Long life as larvae - 5-7 years
• Persistent Notochord - becomes partially enclosed by cartilage…skeleton is made of cartilage
• Lack jaws and paired appendages
• Pore-like gill slits
• Circular mouth with keratinized teeth/ with rasping tongue
• well developed eyes and advanced brain
• Body fluids osmotically and ionically regulated
• 7 pairs of cills and closed circulatory system
  
  • ​heart has 2 chambers

Question 9

What are general Gnathostome characteristics?

Answer 9

• Jaws and teeth are present
• All have paired limbs
• Have three pairs of semicircular canals
• brain is well developed
• Have advanced sensory organs
  
  • eyes, ears, etc

Question 10

What 2 groups make up the ‘Jawed Fishes?’

Answer 10

• Chondrichthyes
• Osteichthyes
• Use gills for respiration
• Close circulatory system
  
  • heart with 2 chambers

Question 11

What are the characteristics for Class Chondrichthyes?

Answer 11

• Includes - sharks, skates, rays (all marine)
• Possess a cartilaginous endoskeleton
• Placoid sclaes - spiny touch to their skin
• The sharks tail provides propulsion and the fins are stabilizers - also called heterocercal
• Do not have swim bladder
• Continuously swim in order to remain in water column and to breather
• Dioecious - internal fertilization
• Blood is iso-osmotic to seawater - excrete urea

Question 12

What are the three major types of reproduction in jawed fishes?

Answer 12

• Oviparous
  
  • a few sharks lay eggs that hatch externally
• Ovoviviparous
  
  • Most sharks lay eggs that hatch in the femal. They egg yolk and glands provide nourishment
• Viviparous
  
  • a few sharks bear live youn. No eggs. Young are nourished similary to placental animals

Question 13

What are the three classes of Osteichthyes? Which fish comprise these classes?

Answer 13

• Class Actinopterygii
  
  • ​Ray-finned
  • Largest in terms of species (perches, sunfish, catfish)
• Class Sarcopterygii
  
  • ​Lobe-finned
• Class Dipnoi
  
  • ​Lung Fish

Question 14

What are the characteristics of all bony fishes?

Answer 14

• Skeleton is made of bone
• Found in both marine and freshwater
• Possess air-filled swim bladder - conserves energy
• Four-Five paired gills - covered by the operculum
• Tails and Flexible Fins
• Contain a dermis and epidermis - scales are embedded into the dermis
• Osmoregulators - ammonia is secreted by kidneys and nephridia
• two-chambered heart and a closed circulatory system
• External Fertilization - oviparous
• well-developed brain, spinal cord, and complex set of sensory organs
  
  • Lateral line oran - can detect small changes in water movement
• Carnivorous

Question 15

What are the three amniote classes?

Answer 15

• Class Reptilia
• Class Aves
• Class Mammalia

Question 16

What are the general characteristics of Class Amphibia

Answer 16

• Contains frogs, toads, salamanders
• 4 limbs - with webbed toes
• MUST return to water to lay eggs (which lack a shell)
• Show metamorphosis
  
  • Eggs –>larvae –>metamorphose–> adults
  • Dioecious, external fertilization
• Adults still have to stay moist on land
  
  • skin is a major respiratory organ
• three-chambered heat with a closed circulatory system
  
  • ​2 loops - like humans
• Elimiate urea - water is replaced by taking it up through the skin
• Generally carnivores with a complete digestive tract
  
  • ​ lack teeth
• lateral line organs - similar to fish
• Larvae must live in water - tadpoles
• Posses eyes, external nostrils brings in air to internal nostrils
• Tympanum membrane behind each eye detects sound (no ear)

Question 17

What is probably the main reason reptiles were able to evolve from amphibians?

Answer 17

• The amniotic egg
  
  • ​shelled to prevent desiccation
  • Possesses a series of extraembryonic membranes that help the embryo develop totally inside a terrestrial egg
  • Membranes - cushion the embryo, keep it moist, help it espire, and store food and wastes within the egg

Question 18

Describe the 4 different Extraembryonic Membranes

Answer 18

• Chorion - outermost membrane
  
  • involved in gas exchange with the outside
  • Cuts down water loss
  • (Helps to produce placenta in placental animals)
• Allantois - place to store wastes
  
  • Allows for water conservation and invovled in gas exchange
• Yolk Sac - surround the yolk
  
  • Yolk and Albumin provide nutrients
• Amnion - fourth and innermost membrane
  
  • immediately surrounds the embryo and the amniotic fluid
  • bathes embryo in embryonic fluid
  • Prevent dehydration and cushions embryo

Question 19

What characteristics do all Amniotes share?

Answer 19

• Four extraembryonic Membranes
• 3/4-chambered hearts with closed criculatory systems
• Eliminate urea and uric acid
• Tough leathery skin
• Claws
• Have strong jaw muscles to crush or grip prey
  
  • evolved from pharyngeal slit arches
• Internal fertilization
• Efficient circulatory systems
• Rib cage - diaphragm….positive pressure breathing

Question 20

What are the general characteristics of Class Reptilia?

Answer 20

• 4 limbs with digits (absent in snakes and some lizards)
• Amniotic Egg - covered witha. calcareous or leathery shell
• Oviparous - but they use internal fertilization and are dioecious
• Scales made of keratin
  
  • ​arise from the epidermis
  • Integument = Epidermis and dermis
  • Cant perform ecdysis
  • Chromatophores - in dermis that contain melanin or other pigments
• Lungs for gas exchange
• Three-chambered heart
  
  • double circulatory systme
  • RBCs are nucleated
• Ectotherms
• Kidneys - expel uric acid
  
  • ​Salt Glands - to excrete excess salt
• Complete digestive tract, carnivores
• No outers ears, but they have tympanum - ear drum membrane that can be covered by thin layer of skin
  
  • middle ear and inner ear

Question 21

What are general characteristics of Class Aves?

Answer 21

• Modified scales - feather
  
  • ​​Possesses epidermis and dermis
  • Also have beaks
• oviparous - eggs with calcareous shell
• Dioecious
• Birds can fly….duh
• 4-chambered heart, efficient respiratory with diaphragm
• Endotherm - can regulate their own body temperature
• RBCs are nucleated
• SIngle bone in middle ear
• Jaws are made of bone - beaks - no teeth
• Excrete uric acid
• Uterus opens to the cloaca - no bladder
• Well developed brain with cerebrum
• Sexual Selection

Question 22

What are the 3 main reasons for flight in birds?

Answer 22

• Feathers
• Strong breast muscles
• lighter bones

Question 23

What are the general characteristics of Class Mammalia

Answer 23

• Have leathery skin with modified scales as hair
• Sabaceious glands and sweat glands are on the skin
• Mammary glands - produce milk to nourish young
• teeth are highly modifed - heterdonts = more than one type of tooth morphology (incisors, canines, and molars for example)
• 3 inner ear bones and auditory ossicles
• Secondary palate - separates the oral cavity from the nasal cavity = breath and hold things in their mouth
• Efficient respiratory system with diaphragm
• Endotherms
• 4-chambered heart - double circulation
• Non-nucleated, biconcave RBCs
• Dioecious with internal fertilization
• Urea as metabolic waste
  
  • urine is held in bladder
• Omnivores
• highly specialized and advanced brains
  
  • largest cerebrum
  • memory and learning