We are vertebrates. What phylum do we belong to?
chordata
what phylum would be considered the closest relative to phylum Chordata? _________________ Why?
Echinodermata
Both are deuterostomes, sharing developmental characteristics like radial cleavage and the formation of the anus from the blastopore.
Notochord
A flexible rod providing structural support; it’s replaced by the vertebral column in vertebrates.
Dorsal, Hollow Nerve Cord
Forms from the ectoderm, developing into the central nervous system.
Pharyngeal Slits
In aquatic chordates, they function for filter-feeding or respiration; in tetrapods, they form structures like ear canals.
Post-Anal Tail
Extends beyond the digestive tract and is essential for locomotion in many species.
For us, as vertebrates, what remains of the notochord? Take note of the fact that a notochord is not a spinal cord
In humans, remnants of the notochord persist as the intervertebral discs between vertebrae.
Chordates are the first group to show a dorsal nerve cord. Which embryonic layer forms the nerve cord?
The ectoderm forms the dorsal, hollow nerve cord.
Pharyngeal gill slits are one of the chordate characteristics you noted in question 3. What do the gill slits become in tetrapods?
These develop into various structures, such as parts of the ear, jaw, and throat in tetrapods.
Lancelets are the _________________ group to all other living
chordates. Why are
lancelets considered chordates?
are the basal group
Explain the phylogenetic status of tunicates.
Tunicates are chordates and the closest invertebrate relatives to vertebrates.
What happens to most of the chordate characteristics as tunicates change from larvae to adults?
Tunicates exhibit all chordate traits in the larval stage but lose most, retaining only the pharyngeal slits as adults.
What is structurally unique about lampreys and hagfishes compared to other vertebrates?
Unlike other vertebrates, they lack jaws and paired fins, which are primitive vertebrate features.
Explain how lampreys feed and what impact this has had on the fishing
industry in the
Great Lakes.
Lampreys are parasitic, attaching to fish to feed on blood. This has severely impacted fish populations in ecosystems like the Great Lakes
List the three derived characters of
gnathostomes and cite the
importance of each.
- Jaws: Allow more versatile feeding strategies.
- Paired Fins or Limbs: Improve control and maneuverability in water.
- Enhanced Senses: Important for hunting and detecting predators.
What animals are in the clade Chondrichthyes?
Includes sharks, rays, and chimeras
What does the name Chondrichthyes mean? What material makes up the
skeleton of a
member of this clade?
"Cartilaginous fish"; their skeletons are primarily cartilage, not bone.
Why do sharks have to swim continuously?
Sharks must swim to push water over their gills for respiration due to the lack of a swim bladder.
What is a cloaca? What three body systems empty into a cloaca?
A common exit point for the digestive, urinary, and reproductive systems in some vertebrates, including reptiles and birds.
The “fishes” with a bone skeleton are aquatic Osteichthyes. How do they breathe?
Bony fishes breathe through gills covered by an operculum, allowing them to pump water over the gills while stationary.
What is the function of a swim bladder?
Helps bony fish maintain buoyancy in water
Why was the discovery of a coelacanth such a surprise to both scientists and the general public?
Coelacanths were thought extinct for millions of years, so their discovery provided unique insights into lobe-finned fish and the transition to tetrapods.
One of the most significant events in vertebrate history was the evolution of tetrapods. What does tetrapod mean?
Tetrapods are four-limbed vertebrates, including amphibians, reptiles, birds, and mammals
How do the bones of Tiktaalik compare to the bones in your arm?
Tiktaalik’s fin bones resemble early tetrapod limbs, showing the gradual shift from fin to limb
How do the skeletal features of Tiktaalik illustrate Darwin’s concept
of descent with
modification?
Tiktaalik illustrates incremental evolutionary changes adapting fish for life on land.
What is the most significant derived character of tetrapods?
Limbs with digits, allowing life on land
Urodela (salamanders)Amphibian Clade
Possess tails as adults.
Anura (frogs)Amphibian Clade
Lack tails as adults.
Apoda (caecilians)Amphibian Clade
Legless, adapted for a burrowing lifestyle.
What does the name Amphibia mean?
Amphibians, meaning "double life," typically have an aquatic larval stage and a terrestrial adult stage.
Most frogs have a life cycle with an aquatic larval stage, the
tadpole. How do tadpoles
breathe? What do they eat?
Larvae (tadpoles) breathe through gills and are herbivorous. Adults develop lungs and limbs, adapting to terrestrial life.
Fertilization in most amphibians is _____________. The eggs lack a
shell, and mortality is
very high
External; eggs lack a protective shell, making them vulnerable.
What two factors tie many amphibians to moist, high humidity environments?
Amphibians’ permeable skin and need for aquatic breeding sites link them to moist habitats
What factors have led to the worldwide decline in amphibian populations?
Causes include habitat destruction, pollution, climate change, and disease
What is the major derived character of the amniote clade?
How has it enabled reptiles (and a few mammals) to occupy a wider
range of terrestrial
habitats than amphibians?
The amniotic egg, with specialized membranes, protects the embryo and reduces dependency on water
Enables reptiles and mammals to reproduce on land, avoiding desiccation.
he four extraembryonic membranes seen in an
amniotic egg and
explain the role of each one
Amniotic Membranes:
- Amnion: Cushions the embryo.
- Chorion: Gas exchange.
- Allantois: Waste storage.
- Yolk Sac: Provides nutrients.
What animals are in the reptile clade?
Includes turtles, lizards, snakes, crocodilians, and birds.
Make a list of three characteristics of most reptiles.
- Scales: Prevent water loss.
- Ectothermy: Conserves energy.
- Internal Fertilization: Protects developing embryos
hich members of the reptile clade are ectothermic? Which are endothermic?
- Most reptiles are ectothermic, while birds are endothermic.
If you have a pet dog or cat it requires feeding every day, but a
snake is only fed once a
week. Explain why this is so.
Ectothermic reptiles, like snakes, have lower metabolic rates than endothermic mammals, requiring less frequent feeding
Turtles
Hard shells for protection.
Lizards
Variety in habitat and diet.
Snakes
Limbless and specialized in hunting.
Crocodilians
Powerful jaws and semi-aquatic lifestyle.
Birds
Adaptations for flight.
Adaptations for Flight:
- Feathers: Lightweight and strong.
- Hollow Bones: Reduce weight.
- Efficient Respiratory System: Maximizes oxygen intake.
- High Metabolism: Supports energy demands.
What evolutionary advantages are offered by flight?
Facilitates migration, escape from predators, and access to diverse habitats.
Discuss the statement that birds are the only living dinosaurs.
refers to the fact that birds evolved from small theropod dinosaurs, specifically within a group called maniraptorans. This means that birds are technically a subgroup of dinosaurs, sharing unique characteristics like feathers, a wishbone, and hollow bones with their theropod ancestors.
Make a list of the characteristics of mammals that have made them a
successful clade. Put
an asterisk (*) next to the traits that are
shared derived characters of mammals
<ul> <li><strong>Mammary Glands</strong>: Nourish young (<em>shared derived character</em>).</li> <li><strong>Hair</strong>: Insulates and protects (<em>shared derived character</em>).</li> <li><strong>Endothermy</strong>: Supports high activity levels.</li> <li><strong>Differentiated Teeth</strong>: Adapted to varied diets.</li> </ul> <br>
There are three groups of mammals. Contrast the groups based on how
they bear young and
give an example of each group
<ul> <li><strong>Monotremes</strong>: Egg-laying mammals (e.g., platypus).</li> <li><strong>Marsupials</strong>: Young develop in pouches (e.g., kangaroos).</li> <li><strong>Eutherians</strong>: Placental mammals with in-utero development</li> </ul> <br>
why the marsupials in the left column so
closely resemble the
eutherians on the right.
Marsupials and eutherians show convergent evolution, with similar body forms evolving due to comparable ecological roles.