Lectures 2, 3, 4 V

What is the big division of vertebrate?

Amniotes and non-amniotes

What are the groups of non-amniotes

1. Fishes: Cyclostomata—Jawless fishes (hagfish and lampreys)

2. Fishes: Chondrichthyes—sharks, rays, ratfishes

3. Bony fishes—ray-finned actinopterygii, lobe-finned sarcopterygii

4. Lissamphibia

What are the groups of amniotes?

• Lepidosauria—lizards, snakes

• Testudines—turtles

• Crocodilia—crocodiles, alligators

• Aves

• Mammalia

What is the largest group of non-amniotes?

Bony Fishes, ray-finned actinopterygii and lobe-finned sarcopterygii

Clade?

Monophyletic group, most recent common ancestor and all of its descendants

What is a paraphyletic group

Monophyletic group that excludes some of its descendants

What is a polyphyletic group

Group consisting of members from two or more non-overlapping monophyletic groups

What is an apomorphy?

A derived character that is different from the ancestral condition

Synapomorphy

A derived character that is shared like arm bones in vertebrates

Autapomorphy

Derived condition in only one lineage (e.g., arm buds in snakes")

What is a plesiomorphy?

A character trait that is shared with the ancestor

What is a symplesiomorphy?

the same ancestral trait shared by two or more groups

What is a homoplasy

Similarities in traits due to function (similar body sizes of fish) convergent evolution

What is a homology

A similarity due to ancestry,

Explain the order of the geological time sscale

Pre-cambrian, cambrian, Ordovician, silurian, Devonian, Carboniferous, permian, triassic, jurassic, cretaceous, paleogene, neogene, quaternary

What was the precambrian

Period of time before cambrian explosion that contains the Ediacaran period where fauna existed

What is the Burgess shale?

A fossil site in the Canadian Rockies BC showing fauna after the cambrian explosion

What did Burgess shale fauna look like 510 mya?

Slow animals, 60% deposit feeds, 30% sedentary filter feeders and 10% scavengers or predators. Low oxygen levels caused small body sizes

What are the classic chordate characteristics

1. Notochord

2. Neural tube

3. Postanal tail

4. Endostyle

5. Pharyngeal slits

What are the classic vertebrate traits

1. Cranium

2. Tripartite brain

3. Muscular pharynx

4. Vertebrae

What do vetulicolians show us?

that our classic chordate characteristics may not always uniquely define chordata as some characteristics may have originated before the chordate lineage. Pharyngeal slits appear to be an ancestral deuterstome characteristic meaning that the trait does not mean it is necessarily a chordate. A trait can be a classic chordate characteristic without being derived.

What were the Vetulicolians

Tadpole like animals that lived in China during the Cambrian. We are unaware if they are chordates or not. They have a mixture of deuterostome and possible chordate features that help scientists investigate early chordate evolution and which traits are classic chordate characteristics

What was the earliest known chordate? Where was it found?

Pikaia, found in the Burgess Shale fossil site in the BC canadian rockies

Name at least 2 classic characters of Phylum Chordata. Using an example, debate whether these characters should be used to define this clade

Two classic characters of Phylum Chordata are the notochord and pharyngeal slits. However, these characters may not be sufficient by themselves to define the clade because some may have originated before the chordate lineage. For example, vetulicolians are interpreted as early stem chordates and possess pharyngeal/gill slits, suggesting that this characteristic may have been present very early in chordate evolution or inherited from an even earlier deuterostome ancestor. Therefore, the presence of a single classic chordate characteristic does not necessarily establish that a fossil is a chordate; multiple characteristics and their position on the evolutionary tree should be considered.

What are the living non-vertebrate chordates?

Cephalochordates and urochordates

What is the basic body plan of vertebrate?

Bilaterally symmetrical and segmented animals with cellular skin. Complete digestion, circulation, and respiration. There are nervous and sensory systems as well as waste removal.

What are the basic things that makes a vertebrate a vertebrate?

1. Cranium—dermal bone neural crest around brain

2. Head, sense organs and tripartite brain

3. Complex endocrine organs (e.g., pituitary gland)

4. Muscular gut tube

5. Multichambered heart

6. Mineralized tissues (e.g., bone, teeth)

7. Gills derived from endoderm

How did early vertebrates evolve compared to nonvertebrate chordates?

They became more active and predaceous, developing larger body sizes than nonvertebrates

What are the three germ layers?

1. Ectoderm—layer that forms outer surface as well as neural crest

2. Mesoderm—middle layer that forms stuff like notochord and bone tissue

3. Endoderm—inner layer that forms things like digestive tube and pharynx

What is a eucoelomate?

an animal with a true body cavity lined with tissue derived from the mesoderm. Most triploblasts are eucoelomates.

What do true body cavities allow for?

Protection and differentiation of specialized internal organs

What cavity contains the heart

The pericardial cavity

What cavity contains the viscera? (internal organs like liver, pancreas, gall bladder)

The peritoneal cavity

What cavity contains the lungs

The pleural cavity

What is the neural crest?

A collection of multipotent stem cells next to the neural tube that is unique to vertebrates. They migrate in the developing embryo in the head and trunk. It is referred to as the fourth germ layer and it forms neurulation

What do neural crest cells do?

Give rise to a diverse range of structures including cranial skeleton, nerves, and some glands

What are the parts of the tripartite brain?

1. Forebrain: olfactory system

2. Midbrain: ocular system

3. Hindbrain: balance, hearing, taste, touch and respiration

What are true tissues?

Tissues derived from germ layers that also excrete an extracellular matrix that keeps the cells together

What are the vertebrate tissues?

1. Epithelial—lines surfaces in body

2. Muscle tissue

3. Nervous tissue

4. Connective tissue

What is mineralized tissues?

Tissues consisting of collagen and mineral with a matrix in alternating directions. They make up structural materials like enamel and spongy bone and dentine

What are the two types of skeletons vertebrates have

1. Dermal or exoskeleton—dermal bone, teeth, scales

2. Endoskeleton—cartilage, endochondral bone

What is dermal bone

Bone formed in the dermis of the skin through intramembranous ossification. It is formed directly in connective tissue derived from mesoderm. First seen in jawless fishes

Teeth and denticles of vertebrate

Derived from external armour

• Enamel—crystalized calcium phosphate making it brittle and hard

• Dentine—keeps fractures under control as it is softer than enamel but harder than bone

• Bone at base with living tissue

What is endochondral bone?

Bone formed through the replacing cartilage model. Only found in bony fishes and tetrapods but alows for formation of long bones as well as growth and repair

What does adult bone look like?

Dermal and endochondral is indistinguishable and it is often highly remodeled with osteons, and haversian canal systems

What features are needed for motion?

• Bone (lever)

• Cartilage (cusion and lube)

• Tendons/ligaments (transmit force to skeleton)

• Muscles (generate power)

How does muscle contraction work

Muscles are striated so filaments slide past each other making shortening limited. Strength is proportional to the cross-sectional area of the muscle