Chapter 34: Origin and Evolution of Vertebrates Flashcards
(29 cards)
Chordate
- Bilateral symmetry
- Belong to Deutorosomia
- Derived traits include notochord, dorsal, hollow nerve cord, pharyngeal slits or clefts, and a muscular, post-anal tail
Notochord
- Longitudinal, flexible rod located between the digestive tube and nerve cord
- Large, fluid-filled cells encased in fairly stiff fibrous tissue
Pharyngeal Slits
- Allow water entering mouth to exit body without passing through entire digestive tract
Dorsal, Hollow Nerve Cord
- Develops from plate of ectoderm that rolls into tube located dorsal to the notochord
- Unique to chordates; signifies development of brain and spinal cord
Importance of muscular, post-anal tail
- Contains skeletal elements and muscles; helps people many aquatic species in the water
Lineages of chordates without a head?
Lancelets and tunicates
Craniates? Example?
- Chordate with a skull
- Examples include hagfish, lamprey, jawed vertebrates
Lampreys and role in chordates history
- Jawless vertebrates
- Various marine/freshwater environments
- Most are parasites
- Primitive fossils resembling lampreys were found that straddle transition to vertebrates
Amniotes
- Tetrapods that have a terrestrially adapted egg
- Derived characteristics of amniotes: anioti eg; rib cage to ventilate lungs
Tetrapod + Derived Characteristics
- Gnathostjomes + Limbs
- Have limbs with digits; head is separated from body by neck; bones of pelvic girdle are fused to backbone
Major (current) hypothesis for jaws?
Evolved from modification of skeletal rods; supported precursor jaw-form
Evidence for life to transition onto land?
- Tiktaalik–evolutionary medium between transition from water to land
- Have neck, ribs, eyes on top of head, fin skeleton, flat skull
Lateral line system
Organs that form a row along each side of the body and are sensitive to vibrations in the surrounding water
Do mammals have amniotic eggs?
Some do
Amniotic egg
- Contains four specialized membranes: amnion, chorion, yolk sac, and allantois
- Key for allowing embryo to develop on land
- Slows dehydration of egg in air
Amphibian
- “Both ways of life”
- Fertilization is external in most species
- Ectothermic
Ectothermic
Absorb external heat as main source of body heat
Amphibian
- “Both ways of life”
- Fertilization is external in most species
- Ectothermic
- Eggs lack a shell
Ectothermic
Absorb external heat as main source of body heat
Reptiles
- Scales that act as barrier
- Most lay shelled eggs on land
- Most are ectothermic
Birds
- Derived characteristics: Keratin feathers, lack of urinary bladder, females with one ovary, small gonads, loss of teeth
- Endodermic (maintain body temp. through metabolism)
Origin of Birds?
- Likely descended from theropods (carnivorous dinosaurs)
Mammals
- Amniotes that have hair and produce milk
- Larger brain
- Differentiated teeth
- Three group: Monotremes, marsupials, eutherians
Evolution of Apes
- Diverged from Old World monkeys 25-30 million years ago
