Lecture 12 Deuterosomes Flashcards
Describe several features of birds that are adaptive for flight.
- Lightweight skeleton
- Bones are thin + hollow.
- Air sacs (see next slide)
- Flight requires a lot of energy!
- Tubes lead from lungs to elastic air sacs – improves air flow and oxygen uptake.
- Reduction of organs
- Females only have 1 ovary.
- No urinary bladder
Describe the major characteristics of phylum Echinodermata.
They are all radially symmetric!
–> Why are they “bilaterians”?!
• Evolved from an ancestor that was bilateral.
• Evolved pentaradial symmetry as part of adult body plan
• Larvae are bilateral.
Pentaradial symmetry (in most) have tube feet Endoskeleton composed of hard calcareous plates
Describe the structure and function of the water vascular system in echinoderms.
Water-vascular system.
• Fluid filled tubes and chambers.
• Sea water flows in and out via an opening = madreporite.
• Cilia line the interior of the tubes and chambers, assist in moving fluid around.
Functions in locomotion and feeding
Distinguish between classes Asteroidea, Echinoidea, and Holothuroidea.
Echinoidea
• No arms, but they still have 5 rows of tube feet.
• Sea urchins: globe-shaped bodies and long spines.
• Sand dollars: flattened and shorter spines.
• Feeding:
• Sea urchins: herbivores - graze on kelp and algae using a unique jaw-like feeding
structure located in their mouths.
• Sand dollars: use their podia to collect food particles in sand or other soft substrates.
Holothuroidea • Sea cucumbers. • No spines. • Soft, elongated body - endoskeleton is reduced. Doesn’t look much like an echinoderm, BUT: • 5 rows of tube feet. • Some feet located around the mouth are modified as tentacles. • Feeding • Deposit feeders
Asteroidea
• Sea stars
• 5 or more long arms that radiate out from a central region = central disc.
• Surface is covered in small (or large!) spines and skeletal bumps.
• Help protect organism from predators
• Feeding:
• Predators or scavengers
• Use tube feet to grasp prey – usually clams and oysters.
• Evert their stomach through their mouth and into the narrow opening between the bivalve’s shells.
• Digestive system secretes juices that begin
to digest the mollusc within its own shell.
• The stomach is then brought back into the sea star’s body where digestion is completed.
Describe the 4 derived traits that define the phylum Chordata.
- Notochord
• A stiff, but flexible rod that runs the length of the body.
• Provides skeletal support and a flexible structure against which muscles can work during swimming. - Dorsal hollow nerve cord
• A bundle of nerves that runs the length of the body.
• Most other animal phyla have solid nerve cords that are typically ventral. - Pharyngeal slits
• The digestive tract of chordates is complete.
• The portion just posterior to the mouth = the pharynx.
• In all chordate embryos, series of pouches separated by grooves forms along the sides of the pharynx.
• In most chordates, these grooves develop into slits that open to the outside.
• Allows water to enter mouth and leave the body without passing through entire digestive tract.
• In non-craniate chordates – function in
suspension feeding.
• In craniate chordates – modified into gill slits for gas exchange. - Muscular tail
• Extends past the anus.
• Evolved for locomotion.
Explain why some organisms that do not exhibit the 4 chordate characteristics as adults are still considered chordates.
All chordatas exhibited all four of these characteristics at SOME point in their life cycle or have evidence that it once was present
Describe the key characteristics of lancelets, tunicates, and hagfishes (i.e . the
invertebrate chordates).
The LANCLETS closely resemble the idealised chordata, with an obvious notocord, dorsal hollow nerve chord, pharyngeal slits, and post anal tail. As larvae, they are free swimming and filter feed on plankton suspended in the water. As adults they bury themselves in sand and filter feed by drawing water through their paryngeal gill slits.
TUNICATES resemble other chordates in their larval stage where all four chordate characteristics can be seen. AS adults they are sessile and use their paryngeal gill slits for suspension feeding. Adult tunicates are characterized by their two siphones. One siphon draws water into the organism, from which food is collected in a mucous net, and the other expels the filtered water. This can be done quite rapidly, giving the tunicates their more common name of “sea Squirts”
The Hagfish are the fist of the chordates to possess a neural crest and a skull and so they belong to the group of chordates known as craniates. The skull is made of cartilage, but there are no jaws and there is no backbone, so a hagfish is still technically an invertebrate ( and not a fish ) Most hagfishes live on the bottom of the ocean, here they live on deposit feeders, scavenging worms and sick or dead fish
Describe the distinguishing feature(s) of subphylum Vertebrata.
Vertebral column: a column of cartilaginous or bony structures called vertebrae.
• May simply be small prongs of cartilage arranged dorsally along the notochord; however, in the majority of vertebrates, replaces the notochord during development.
Vertebrates also have large brains
divided into 3 regions:
• Forebrain, Midbrain, Hindbrain
Describe the major steps (i.e. key events or innovations) in the evolution of
vertebrates, including the significance of each innovation (i.e . the advantage
each structure provided or what it allowed for).
- -Jaws- significantly increases the diversity of food choice
- -Mineralised and jointed skeleton- more flexibility, protection and support
- -Lungs- Allows for life on land
- -Limbs- allow locomotion on land
- -Amniotic egg- the amniotic egg allows reproduction without water
Indicate the origin of each of the vertebrate innovations on a phylogenetic tree.
notes
Distinguish among the various lineages of the phylum Chordata, providing examples of each.
1) Petromyzontida- lampreys
Round, jawless mouth with rows of
horny spines + rasping tongue.
2) Chondrichthyes- sharks, rays and relatives
Some of the biggest and most successful vertebrate predators in the oceans.
3)Actinopterygii- tuna clown fish, sea hourse
Fins supported by long bony rods arrange in a ray pattern.& Protrusible jaw
4)Actinistia+ dipnoi- lung fish, coelacanths
Pectoral and pelvic fins consist of a rod shaped bone surrounded by thick layer of muscle
5)Myxini- hag fish Jawless, finless, eel-like craniates that lack vertebrae, and that have
a skull made of cartilage.
6) Cephalochordata- lanclets
7) Urochordata- tunicates
8) Amphibia- frogs, salamanders
9) Retilia- alligators
10) Mammalia- bears
Describe the way of life and unique characteristics of the lamprey, and explain the impact that lampreys have had on the Great Lakes fisheries and why.
Round, jawless mouth with rows of horny spines + rasping tongue.Most are parasitic
• Clamp onto other fish with their round, jawless mouth.
• Rasp a hole in the fishes’ side with their tongue; suck blood, tissues, and fluid.
Sea lampreys are native to the Atlantic ocean,
but were accidentally introduced into the Great
Lakes via shipping canals in the early 20th
century.
• Any guess as to what has happened and why?
• Devastating impact on the Great Lakes
fishery.
• Because sea lampreys did not evolve with the Great Lakes fish species, their aggressive,
predaceous behavior gave them a strong advantage
Describe the trends in mineralized structures in early vertebrates.
Vertebrate skeleton initially evolved as an unmineralized cartilaginous structure.
• The earliest known mineralized structures in vertebrates are the dental elements of conodonts (extinct).
• Later in fossil record:
• Armored vertebrates (“Ostracoderms”)
• Vertebrates, without jaws, that had external
plates of mineralized bone.
—> Bone first evolved as an exoskeleton!
• More derived vertebrates have a mineralized
endoskeleton.
List the shared derived features that characterize gnathostomes.
vertebrates that have jaws.
• Include jawed fish + tetrapods.
All gnathostomes are vertebrates, but not all
vertebrates are gnathostomes.
Describe the major characteristics of Chondrichthyes.
Relatively flexible endoskeletons composed predominantly of cartilage
rather than bone.
• In most species, parts of the skeleton are impregnated by calcium.
• Jaws.
• Paired fins.
• Placoid scales.
• No swim bladder.
