Final Vertebrates

What are the four defining characteristics of chordates?

Notochord, dorsal hollow nerve cord, pharyngeal slits, muscular post-anal tail

In most chordates, what do pharyngeal slits function for? But what do tetrapod pharyngeal pouches develop into instead?

Gas exchange and suspension-feeding in most chordates; in tetrapods they develop into structures of the ear, head, and neck

Those genes that build lancelet brains (BF1, Otx, Hox 3) - what's the big deal about them?

The same genes build our brain - showing evolutionary conservation of brain development genes

What exactly ARE Hox genes and what do they do?

Hox genes regulate development and form in clusters; they orchestrate construction of body parts

Explain the "mechanical clock" DNA spool thing - how long for each new gene and how long for complete unwinding? What do those times correspond to?

New gene comes out of spool every 90 minutes = new layer of embryo; Two days for complete unwinding = all layers of embryo

arose through hox gene duplication, giving them sets of hox genes.

Vertebrates arose through hox gene duplication, giving them 2 sets of hox genes

What is the neural crest and what's it involved in forming?

Group of embryonic cells forming near dorsal margins of closing neural tube; involved in forming skeletal system and complex nervous system

What key features do vertebrates have that help them capture food and evade predators?

Skeletal system and complex nervous system

Describe hagfish and lampreys - what families, key characteristics, and lifestyle?

Hagfish (Myxini): marine scavengers, huge slime-producing, jawless. Lampreys (Petromyzontida): jawless, oldest living vertebrates, external parasites

What's the hypothesis about how mineralization spread through early vertebrates (starting with what, then what, then what)?

Mineralization initiated in teeth, then to armor, then to endoskeleton

MIDTERM ALERT: How many Hox gene clusters do gnathostomes have? (and how would you identify family/phyla by cluster number?)

Gnathostomes have 4 Hox clusters. Invertebrates: 1 cluster; Cyclostomes (jawless vertebrates): 2 clusters; Gnathostomes: 4 clusters

How did jaws evolve and what advantages did they provide?

Jaws evolved by modification of skeletal rods; advantages include active predation and diverse feeding

What other features did gnathostomes develop? (think sensory - forebrain and that system…)

Enhanced forebrain, enhanced smell, lateral line system

What's special about Chondrichthyes' skeleton - what's it made of and is this ancestral or derived? What immune system thing did they develop?

Skeleton made of flexible cartilage (derived, not ancestral); developed learned/adaptive immune system

Name the three classes of Osteichthyes (bony fish).

Actinopterygii (ray-finned fishes), Actinistia (lobe-finned fishes/coelacanths), Dipnoi (lungfishes)

What's the crazy story with coelacanths?

Thought to be extinct 65 million years ago, but rediscovered in 1938

Describe lungfishes - where do they live, what's their special organ, and what can some do during dry season?

Three living genera in southern hemisphere (one on each continent); live in ponds and swamps; have lungs; can burrow into mud and aestivate (summer dormancy)

What's that self-recognition thing in tunicates about?

Self-recognition: only fuse together when they share an allele for fusion (histocompatibility complex gene)

What happened during the Silurian/Devonian period with jawed fish?

Jawed fish underwent explosive diversification

Tunicates are weird - describe their larva vs. adult forms.

Adults look more like sponges than chordates. The larva is a tiny, tadpole-like swimmer with a notochord, dorsal nerve cord, and tail

Where would we find transitional species during the aquatic-terrestrial transition? (be specific about habitat and climate)

Shallow estuary, tidal flat environments

Tell me about Tiktaalik - when was it found, how old is it, and what key transitional features did it have?

Found in 2006, 375 million years ago; had flat skull, eyes on top, ear notches, and a neck

What's the deal with tetrapod digits and the pelvic girdle? How do they help with movement on land?

Tetrapod digits transmit muscle force to ground; pelvic girdle has bones fused to vertebrae so force from hind legs is transferred to rest of body

How is the tetrapod neck different from fish, and why does that matter?

Tetrapod neck can rotate, separated from body by one or more vertebrae (fish lack this mobility)

Why were amphibians so successful early on? (think about climate, food, competition)

Amphibians lacked competition, benefited from moist climate and abundant food

Describe the frog metamorphosis - what do tadpoles have and what happens during metamorphosis?

Tadpoles have gills, lateral line, swim by tail; during metamorphosis: develops legs, lateral line disappears, gills replaced by lungs

What are the two big limitations amphibians still have that keep them tied to water?

Amphibians need water for reproduction and their eggs lack shells

_ egg enables all terrestrial life cycle. What do the extraembryonic membranes do?

Amniotic egg enables all terrestrial life cycle; extraembryonic membranes provide gas exchange, waste storage, and transfer stored nutrients to embryo

List the key adaptations reptiles have for living in drier habitats (think skin, fertilization, temperature regulation).

Lungs, scales with keratin, waterproof skin, internal fertilization

How do reptiles actually breathe? (Common misconception to avoid!)

Reptiles breathe through lungs, NOT through skin like some amphibians

What did we discover about dinosaur body temperatures for the first time, and what was surprising?

Dinosaur temperatures were as warm as modern mammals (surprising because reptiles are typically ectothermic)

What are the three periods called the "Age of Reptiles"?

Triassic, Jurassic, Cretaceous

What's the deal with that T. rex medullary bone and what does it store?

T. rex medullary bone stores calcium (used for egg production, indicating it was female)

Based on collagen protein sequences, what's T. rex's closest living relative?

Ostrich

Birds are actually _ reptiles. What's the first known bird fossil, when was it found, and from what period?

Birds are feathered reptiles; Archaeopteryx is the first bird fossil, from the Mesozoic period