Deuterosomes Flashcards
2 phyla of deuterosomes
1) Echinodermata
2) Chordata
General features of deuterostomes (4)
1) Bilateral symmetry
2) Coeom
3) Radial cleavage
4) Blastopore
Examples of Echinodermata
Starfish, sand dollars, sea urchins, sea lillies, sea cucumbers and brittle stars
Do echinoderms or chordata share a common ancestor with humans?
Echinodermata
Echinodermata exoskeleton is made out of (1)
CaCO3 (Calcium carbonate)
Types of sexual reproduction in echinodermata
Contain sexual and asexual reproduction capabilities
Sexual: Reproduction
Asexual: shed leg to form new individual
Holothioidea
Sea cucumbers
Important food in certain cultures
3 sub-phylums of Chordata
1) Vertebrata
2) Cephalochordata
3) Urochordata
Urochordata
Sea squirts
Four common features of Chordates
1) Notochord
2) Pharyngeal slits
3) Dorsal, hollow nerve cord
4) Muscular, post-anal tail
Where does the notochord develop from?
Mesoderm
Placement of the notochord
Dorsal to the coelom
Beneath (but parallel to) the CNS
Notochord features
Core of cells & fluid surrounded by fibrous sheath
Allows for locomotion through lateral undulation (tail movement like sperm)
Who contains notochord and when?
Present in bony fish and terrestrial vertebrates
- present during embryonic development
- replaced by ventral column
- persists as nucleus pulposes in intervertebral disk
Who and when contain Pharyngeal slits?
Terrestrial vertebrates (present in embryo, lost during embryogenesis)
Aquatic vertebrates (gills develop adjacent to pharyngeal slits; allow for water flow across gills)
Location of the dorsal, hollow nerve cord
Lies above (superficial) to the gut
What is the dorsal hollow nerve cord made out of?
fluid-filled neurocoel
Muscular post-anal tail
- posterior elongation of the body beyond the anus
- consists of segmental musculature and the notochord
Cephalochordata
Subphylum of Chordata resemble earliest chordates fossils in cambrian era Temperate and Tropical seas Anatomically simple Living: Brachiostoma - amphioxus
Branchiostoma
Subphylum of chordata Possess all 4 chordate features in adult Blade like body shape - Filter feed - ciliated pharynx - mucous nets across slits
Systems in Cephalochordata
Digestive system
Circulatory system
“Brain” is not differentiated - cluster of cells
How is the Chordate brain similar to human brain? (3)
Similar gene expression in human embryos compared to chordate
1) BF1
2) Otx
3) Hox3
Urochordata
Subphylum of Chordata
All species are marine
Tunicates
Ex) Sea Squirts
Which Chordate subphylum evolved alongside vertebrates and have a common ancestor?
Urochordates
What are the three divisions of the CNS in chordates?
1) Sensory vesicle
2) Visceral ganglion
3) Nerve cord
Sensory Vesicle
Part of chordate CNS
Contains (2)
1) Ocellus
2) Otolith
Ocellus
Photoreceptive organ
Otolith
Gravity-sensitive structure
Visceral ganglion (2)
Part of Chordate CNS
1) Sends nerve tracts to musculature
2) Receives sensory nerves from tail
Nerve Cord
Part of Chordate CNS
- Ciliated ependymal cells around neurocoel
- move CSF through nerve chord
- Same type of cells that humans have
Ependymal cells
CNS cells which function to move cerebral spinal fluid (CSF) through nerve chord
4 structures found in Chordate Larvae
1) Central Nervous system
2) Neural Crest Cells
3) Rudimentary Heart
4) Blood
Craniata
- Chordates with heads (craniums) for movement and feeding
What is the unique feature of Chordate Larvae
Presence of the neural crest
- population of cells that give rise to many structures (teeth, bone, neurons, etc.)
Hagfish
Craniate, part of chordata Cartilaginous skull - not bony skull No jaw or vertebrae Notochord in adult All Marine Feed on detritus Produce mucus for defence
Lampreys
Vertebrate, derived from craniates
Cartilaginous skeleton
Lack jaws, have rasping tongue/teeth
Primitive vertebrae ENCLOSE vertebrae
What was the most significant step towards selective feeding?
Development of jaws in Gnathostomes
2 classes of Gnathostomes
1) Chondrichthyes (cartilagenous fish)
2) Osteichthyes (bony fish)
Chondrichthyes
Cartilaginous skeleton Sharks and rays cartilaginous skeleton replaces notochord Internal Fertilization Contain Placoid Scales Lack swim bladder
Placoid scales (3)
1) Dentine and enamel
2) Surface denticles (“small teeth”)
3) Develop in dermis (project through epidermis)
What destinguishes between males and females in Chondrichthyes
Males: Claspers
Females: Cloaca
What allows Chondrichthyes eggs develop in harsh water environment
Oviparous: Tough, leathery egg cases
How long is the dogfish (chondrichthyes) gestation period?
2 years
Osteichthyes
Class Vertebrata Bony fish Predominantly bone scales (do not penetrate epidermis) Swim Bladder External fertilization
2 subclasses of Osteichthyes
1) Actinopterygii - ray finned fish (trout)
2) Sarcopterygii - lobe-finned fish (lungfish)
Actinopterygii (2)
Ray-finned fish
muscles that control fins are within the body
1) Palaeonisciformes
2) Sturgeons (largest freshwater fish)
Sarcopterygii
Lobe-finned fish
Fleshy fins composed of soft muscles
HUMANS derived from fleshy-finned fish
subclass of Sarcopterygii (1)
Coelacanth
- Vertebrate tiny
- Notochord well developed
- Swim Bladder
