Cordates & Vertebrates (+Embryology)

Protochordate

all marine animals

hemichordata

acorn worms

cephalochordates

amphioxus

urochordates

tunicates (sea squirts)

What are the main chordate characterisitics?

1. notochord

2. dorsal hollow nerve cord

3. pharyngeal slits

4. endostyle

5. post-anal tail

What are two secondary characteristics of chordates?

bilateral symmetry and a closed circulatory system

Describe the notochord.

• an elastic, fluid filled structure

• provides support to the body

• facilitates movement as a point for muscles to pull on during contraction

• arises from the embryonic mesoderm

Describe pharyngeal slits.

• present in all chordates - not always functional

• posterior to the mouth

• a digestive tract chamber

• supports gill structures

• facilitates feeding mechanism

Describe the endostyle.

• organ in pharynx

• ciliated to accumulate food particles and move them to the GIT in lower vertebrates

• an embryonic structure - in higher vertebrates it becomes the thyroid

  • secretes iodine-binding proteins

What is ontogeny?

the study of embryonic development

developmental history of an organism from fertilization

Define fertilization

fusion of male (sperm) and femal (ovum) gametes to make a zygote

Describe the development of germ cell layers

they differentiate and approximate together

zygote

2-celled product of fertilization

morula

a clumping of cells that has developed from the zygote

blastulla

a grouping of cells distinct because of its outer layer and inner cavity

Define gastrulation

formation of gut

Define neurulation

formation of neural tube

Define organogenesis

formation of organs

Define tissue

a group of cells that perform a function

Define organ

a group of tissues that perform a function

What three layers are present in all organisms and why?

ectoderm, mesoderm, endoderm

all life happens from these layers

What does the ectoderm typically form?

forms the exoskeleton

• adrenal medula

• central and peripheral nervous system

• skin

• appendages

What does the mesoderm typically form?

develop into organs

• kidneys and ureters

• reproductive system

• bone and cartilage

• muscles

• vasculature

• lymphatics

• spleen

• adrenal cortex

What does the endoderm typically form?

forms the inner lining of organs

• GI tract

• liver

• endrocrine system

• respiratory tract

• bladder

• urethra

What are the main tissue types of the body?

1. epithelium - covers surfaces, lines tubes, glands

2. connective tissue - bone and cartiliage

3. muscle

4. nervous

What are the types of epithelium?

1. squamous - flat and irregular

2. cuboidal - cube shaped

3. columnar - tall, specialized, and long to enhance surface area

4. transitional- between squamous and cuboidal

Where might you find squamous epithelium?

the skin

Where might you find columnar epithelium?

the duodenum

Where might you find cuboidal epithelium?

in various ducts

Where might you find transitional epithelium?

in the urinary bladder

What type of tissue are glands?

specialized eptihelium

What are exocrine glands?

Glands that secrete their product into a duct.

ex. pancreas, sweat, salivary

What are endocrine glands?

Glands that secrete their product directly into blood.

ex. pancreas, pituitary, adrenal

Define phylogeny

Course of evolutionary change within related groups or organisms

What features do vertebrates have?

1. all chordate features (at some point in their life cycle)

2. vetebral column

3. cranium

What is the significance of the vertebral column?

It gradually replaced the notochord as the main support mechanisms into the centrum and in the vertebral body.

Describe the development of the cranium in vertebrates?

• The cranium is a bone/cartilage case protecting the brain

• allowed for enlargement of the neural tube controlling sensory organs (=anterior brain)

• development of sensory organs (eyes, ears, nose, etc.)

• derived form neural crest cells and epidermal placodes

What are agnathans?

• jawless vertebrate (ex. agnathan fish)

• they have a muscular pharyngeal pump

• they are craniates - chordates with a head containing a brain, eyes, and sensory organs

• many are extinct, but living examples include the hagfish and the lamprey

What are gnathostomes?

vertebrates with jaws

Describe the development of the gnathostomes.

• evolution away from suspension/filter feeding

• new food sources if the fish can “inhale” and grasp it

• led to active predation - removed prey size limitations

gnath = jaw

What two types of gnathostomes did we mostly examine?

chondrichthyes (cartilaginous fish like sharks)

teleostomi

Describe Placoderms

• a group of early gnathostomes

• “plate” and “skin”

• bony armor on external body

• large predators

• no living ancestors

What is a placode?

An embryonic structure that gives rise to other structures (hair follicles, feathers, teeth, sensory organs)

Describe chondrichthyes.

Gnathostomes with cartilagenous skeletons

chondro = cartilage

2 modern groups: elasmobranch (sharks and rays), holocephalans (chimaera/rat-tail)

What are the two modern groups of chondrichthyes?

elasmobranch - sharks and rays

holocephalans - chimaera (rat-tail)

Describe the actinopterygil of the Teleostomi.

• gnathostomes

• ray-finned fish

• most bony fishes - 25k species

  • half of all vertebrates

• muscles control fins located in body way

Adaptations

1. swim bladder

2. bony operculum

3. endoskeleton ossification

4. bony scales cover skin

5. otoliths

What does otolith mean?

bony ears, used to describe actinoptegii

Describe the sarcoterygians of the telestomi.

• small group

• gives rise to tetrapods (lungfish)

• fleshy-finned fish

• internal bony structures supporting appendages

Groups

• dipnoi (lungfish) - living

• actinistia (ceolocanths)

• rhipidistians (extinct, closet to tetrapods)

• terrestrial vertebrates

What are Lissamphibia?

• modern amphibians

• under tetrapoda of the teleostomi

What are amniotes?

• all terrestrial vertebrates except Amphibia

• have embryos envelopes in extra-embryonic membranes

• Amnion = innermost embryonic/fetal membrane of reptile, bird, mammals

Birds outnumber all types of vertebrates except ….?

fishes

What are characterisitcs of mammalian evolution?

• hair

• mammary glands

What are Monotremes?

• egg laying mammals

• aka prototheria

What are Metatheria?

• marsupials

What are Eutheria?

• mammals with placentas

• ex. humans, dolphins, seals, elephants, etc.