Chp 34 Origin and Evolution of Vertebrates Flashcards by India Davis

What are vertebrates?

Animals that have a backbone (vertebrae)

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When did vertebrates colonize land?

365 MYA around the Cambrian period

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What animals did vertebrates give rise to?

amphibians
reptiles (including birds)
mammals

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How many vertebrate species are there?

More than 57,000 species

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What group comprise of all vertebrates and two invertebrates?

Chordates

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What are chordates (phylum Chordata)?

Bilaterian animals that belong to the clade of animals known as Deuterostomia

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What two groups of invertebrates are apart of Chordates?

Urochordates
Cephalochordates

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What are the 4 key characteristics of chordates?

Have a notochord
dorsal, hollow nerve cord
Pharyngeal slits or clefts
Muscular, post-anal tail

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What is special about chordates characteristics

Only some species show these characteristics during embryonic development

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What is the notochord?

Longitudinal, flexible rod between the digestive tube and nerve cord

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What does the notochord provide?

Provides skeletal support throughout the length of a chordate

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What is the dorsal, hollow nerve cord?

Developed from a plate of ectoderm that rolls into a tube dorsal to the notochord

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What does the nerve cord develop into?

Developes into the central nervoue system: brain and spinal cord

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What are pharyngeal slits/clefts?

Grooves in the pharynx that develops into slits that open to the outside of the body

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What are the functions of the pharyngeal slits? (3)

Suspension-feeding structures in many invertebrate chordates
Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods)
Develop into parts of the ear, head, and neck in tetrapods

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What is the muscular, post-anal tail?

A tail posterior to the anus in chordates.

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What are lancelets?

Invertebrates that are marine suspension feeders that retain characteristics of the chordate body plan as adults

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What phylum are lancelets in?

Cephalochordata; named for their bladelike shape

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What are tunicates?

Invertebrates that most resemble chordates during their larval stage (only last a few minutes)

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What phylum are tunicates apart of?

Urochordata

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Are tunicates more closely related to other chordates compared to lancelets?

Yes

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What is special about turnicates?

Highly derived, and has fewer Hox genes than other vertebrates

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What is significant about the Hox gene in early chordate evolution?

Same Hox genes that organize the vertebrate brain are expressed in the lancelet’s simple nerve cord tip

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What does the sequencing of tunicate genome indicates?

Genes associated with the heart and thyroid are common to all chordates
Genes associated with transmission of nerve impulses are unique to vertebrates

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How are vertebrates and chordates related?

- Vertebrates are chordates that are related

What does the skeletal system and complex nervous system allow for vertebrates to do?

- Capture food - Evade predators

How many Hox genes does vertebrates have compared to lancelets and tunicates?

Vertebrates: Have 2 or more sets of Hox genes Lancelets & Tunicates: Have one cluster of Hox genes

What are the following derived characteristics of Vertebrates? (3)

- Vertebrae enclosing a spinal cord - An elaborate skull - Fin rays, in the aquatic forms

What are the only two lineages of jawless vertebrates that are here today?

- Hagfishes - Lampreys *Members of these groups also lacked a backbone*

What does fossil evidence of the earliest vertebrates show?

- Lacked a jaw

What is the clade of living jawless vertebrates (hagfishes and lampreys)?

Cyclostomes

What is the clade of vertebrates with jaws?

Gnathostomes

What are hagfishes? (3)

Jawless vertebrates that have a cartilaginous skull, reduced vertebrae, and a flexible rod of cartilage derived from the notochord

What are some characteristics of hagfishes? (6)

- small brain - small eyes - small ears - tooth like formations - Are marine - Bottom dwelling scavengers

What are lampreys (Petromyzontida)?

Parasites that feed by clamping their mouth onto a live fish

What are some characteristics of lampreys? (2)

- Inhabit various maine and freshwater habitats - Have cartilaginous segments that surrounds the notochord and arching partly over the nerve cord

What are the most primitive fossil from Cambrian explosion that shows transition to craniates?

Haikouella fossil that has well-formed brain, eyes, and muscular segments, but no skull or ear organs

What are conodonts?

- Earliest vertebrates in the fossil record, dating from 500 to 200 million years ago

What did conodonts have?

- Had mineralized skeletal elements in their mouth and pharynx

Where did mineralization of bone and teeth appear?

Appear with the vertebrate mouthparts

What did gnathostomes consists of? (6)

- sharks and relatives - ray finned fishes - lobe finned fishes - amphibians - reptiles (including birds) - mammals

What are gnathostomes named for?

Named for their jaws, hinged structures that, especially with help of teeth, are used to grip food items firmly and slice them

What are placoderms?

- Earliest gnathostomes in the fossil record that are an extinct lineage of armored vertebrates *appeared 440 MYA*

What are acanthodians?

Group of jawed vertebrates that radiated during the Silurian and Devonian periods

What 3 lineages of jawed vertebrates can we find today?

- chondrichthyans - ray finned fishes - lobe fins

What is the chondrichthyans (chondrichthyes) skeleton composed of?

Skeleton is composed of primarily cartilage

What is the largest and most diverse group of chondrichthyans? (3)

- Sharks - Rays - Skates

What are the 3 different ways shark eggs can develop?

- Oviparous - Ovoviviparous - Viviparous

What is oviparous?

Eggs hatch outside the mother's body

What is ovoviviparous?

- Embryo develops within the uterus and is nourished by the egg yolk

What is viviparous?

Embryo develops within the uterus and is nourished thru a yolk sac placenta from mother's blood

What is cloaca?

Location of where reproductive tract, excretory system, and digestive tract empties into

What percentage of sharks are threatened by overfishing?

95%

What are some characteristics of sharks? (5)

- Have a streamlined body/swift swimmers - Has short digestive tracts with a ridge called spiral valve - Have acute senses - Has the ability to detect electrical fields from nearby animals - Most are carnivores but can be filter feeders

What do osteichthyans include?

Includes bony fishes and tetrapods

What are fishes?

Aquatic osteichthyans that are vertebrates

What do nearly all living osteichthyans have?

All have a bony endoskeleton

What is the operculum?

A layer that protects gills when water goes over them

What are actinopterygii?

Ray-finned fishes that include nearly all familiar aquatic osteichthyans

What are the characteristics of lobe fins (Sarcopterygii)?

- Have a muscular pelvic and pectoral fins that they use to swim and "walk" underwater across the substrate

What are the 3 lineages of lobe-finned fishes that survived?

- Coelacanths - Lungfishes - Tetrapods

What are tetrapods?

- A group that adapted to life on land

What is one of the most significant events in vertebrate history?

- When fins of some lobe fins evolved into limbs and feet of tetrapods

How are tetrapods and gnathostomes related?

Tetrapods are gnathostomes that have limbs

What are the 5 adaptations of tetrapods?

- Four limbs, and feet with digits - A neck, which allows separate movement of the head - Fusion of the pelvic girdle to the backbone - The absence of gills (except some aquatic species) - Ears for detecting airborne sounds

What did the Tikktaalik have? (4)

- Fins, gills, lungs, and scales - Ribs to breathe air and support its body - A neck and shoulders - Fins with the bone pattern of a tetrapod limb

What is a Tiktaalik?

An animal named a fishapod because it had both fish and tetrapod characteristics

What are the three clades in Amphibians (class Amphibia)?

- Urodela (salamanders) - Anura (frogs) - Apoda (caecilians)

How many species make up Amphibians?

6,150 species

What are salamanders (urodeles)?

Amphibians with tails *some are aquatic but most live on land

What is paedomorphosis?

Retention of juvenile features in sexually mature organisms, is common in aquatic species

What are frogs?

Amphibians that lack tails and have powerful hind legs for locomotion on land

What are toads?

Frogs with leathery skin

What are caecilians?

Amphibians that are legless, nearly blind, and resemble earthworms

What is the secondary adaptation of caecilians?

- absence of legs

Chp 34 Origin and Evolution of Vertebrates Flashcards

(75 cards)