Animal Diversity lecture 17 - vertebrates

Question 1

Features of chordates

Answer 1

1) Notochord
2) Dorsal, hollow nerve cord
3) Pharyngeal (gill) slits
4) Post-anal tail
5) Endostyle

Question 2

Notochord

Answer 2

• flexible rod providing support ‘
• Most vertebrates lose this during development
• Jawless vertebrates retain it as they have a minor vertebral column

Question 3

Dorsal, hollow nerve cord

Answer 3

• forms the nervous system , much more well developed in vertebrate chordates than invertebrate chordates.

Question 4

Pharyngeal (gill) slits

Answer 4

• if used in verterbrates they are used for respiration

e. g. fish and some larval amphibians

Question 5

Endostyle

Answer 5

• Structure that produces mucus and helps with filter feeding
• Homologous to thyroid gland of vertebrates , both retain iodine (either from surrounding water or blood) to make thyroxine

Question 6

How do vertebrates and invertebrate chordates differ

Answer 6

1) Vertebrae- provides support for the animal

-usually replaces notochord
-discs are remnants of
notochord
-vertebrae can be made of cartilage or bone.

2) cranium - protects the brain ( can be bony, cartilaginous or fibrous)
- highly modified in mammals

Question 7

what are Vertebrates Embryological differences from invertebrate chordates

Answer 7

1) Duplication of Hox gene complex (homeobox) in evolution of vertebrates
2) Amphioxus + tunicates gave 1 hox gene cluster , ancestral jawless vertebrates have 2
3) Further duplications associated with evolution of other features e.g. jaw

• Overall higher level of complexity in vertebrates

Question 8

Homeobox genes

Answer 8

a large family of similar genes that direct the formation of many body structures during early embryonic development. A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development morphogenesis in animals, fungi, and plants.

Question 9

How does the neural crest develop

Answer 9

- Neural plate gives rise to 
 the nervous system 
- At either end of neural 
 plate is neural crest tissues, 
 they end up sandwiched 
 between the epidermis and 
 neural tube 
- Newly created Neural crest cells (from tissues) can migrate to diff parts of the body and become diff cell types

Question 10

What is the importance and function of the neural crest

Answer 10

1) responsible for new structures, especially in head
2) can be regarded as another germ layer -> quadroblastic
3) Gives rise to e.g. adrenal glands + pigment cells in the skin
4) unique vertebrae feature (makes them easily identifiable)

Question 11

Placodes

Answer 11

• formed by thickening of the ectoderm (in head)
• complex sense organs
• give rise to structures such as hair follicles, feathers and teeth.

Question 12

Features of vertebrae brains

Answer 12

• Very large
• Has 3 parts: forebrain, midbrain, hindbrain
• Brain of amphiouxus not divided but has similar genes (except front of forebrain)

Question 13

How do vertebrates and invertebrate chordates differ in terms of body size and activity

Answer 13

1) Vertebrates have increased body size and increased activity
2) require proper organ systems as they cant rely on ciliary action or diffusion
3) higher metabollic rate that non-vert chordates
4) can sustain periods of anaerobic respiration

Question 14

Vertebrate adaptions for a more active lifestyle

Answer 14

1) unique mineral hydroxyapatite (calc+phos) only found in vertebrates.
2) more resistant to lactic acid after anaerobic respiration
3) Mineralised tissues - Collagen fibres, proteinaceous tissue matrix and hydroxyapatite
4) very hard + resistant substances, but also lightweight

Question 15

What are the five types of tissue that can become mineralised

Answer 15

1) Mineralised cartilage
2) Bone
3) Enamel + dentine
4) Enamloid
5) Cementum

Question 16

Mineralised cartilage

Answer 16

-forms main mineralised internal skeletal tissue (sharks)

Question 17

Bone

Answer 17

• Internal skeleton of bony fish and tetrapods + highly vascularised (good blood supply)
• Dermal (grows in skin) + endochondral (grows within body)
• 70% mineralised

Question 18

Enamel + dentine

Answer 18

-Associated with teeth (96%) -or exoskeleton (90%)

Question 19

Enamloid

Answer 19

• Similair to enamel but has different origin

- teeth, dermal scales of cartilaginous fishes (96%)

Question 20

Cementum

Answer 20

Fastens teeth in sockets (45%)

Question 21

How have mineralised tissues evolved in vertebrates

Answer 21

1) Lampreys -unmineralized endoskeleton
2) Ostracoderms (armoured fish) - origin of mineralized skeleton
3) Bony fish - mineralized endoskeleton
4) Tetrapods - reduction of exoskeleton in the trunk , retained dermal mineralised tissue in head region + internal skeleton.

Question 22

Why did mineralised tissues evolve

Answer 22

1) Defensive structure
2) Protected electroreceptors
3) regulation of phosphorous/ mineral storage

Question 23

What were the earliest vertebrates

Answer 23

Conodonts 500 MYA

Question 24

What was the environment of early vertebrate evolution

Answer 24

• Orginated in marine environment

Evidence:
1) Paleontological - earliest fossils in marine sediments

2) Comparative physiology - invert chordates ( + other deutrostomes) marine + body fluids isotonic to mw
3) Primitive vertebrate (hagfish) marine and isotonic to mw

mw = marine water