L01 - Lizards

Question 1

How many body cavities do lizards have?

Answer 1

• only have 1 body cavity
• known as celomic cavity
• do not have diaphragm

Question 2

What is lizards structure like?

Answer 2

• very mobile
• have a flexible backbone
• long tail for counterbalance

Question 3

Describe the structure of their backbone and vertebrae?

Answer 3

• backbone is divided into pre-sacral, sacral and caudal region
• all vertebrae except cervical ones have paired ribs

Question 4

What is the structure of their skull?

Answer 4

• more rigid than a snake skull
• have quad ratebone which has no firm attachment, allows forward and backward movement and gives advantage when biting prey
• skull articulates with cervical vertebrae with a single occipital condyle

Question 5

What is their dentition?

Answer 5

• lizards have 4 rows of teeth, 1 to each jaw
• there are no fangs

Question 6

What is the structure of their teeth?

Answer 6

• teeth are peg like in shape and are continually replaced
• some have hallow teeth allowing venom to ooze through them

Question 7

What is their axial skeleton?

Answer 7

• coccygeal vertebrae have ventral haemal arches
• tail has fracture plans and no bone

Question 8

What is autotomy?

Answer 8

• this is the spontaneous dropping of the tail
• occurs in lizards except chameleons and monitors
• coccygeal vertebrae are not replaced

Question 9

What is the pectoral girdle made up of?

Answer 9

• scapula
• coracoid
• clavicle

Question 10

What is the forelimb made up of?

Answer 10

• humerus
• radius
• ulna
• carpal bones
• phalanges/digits

Question 11

What is the pelvic girdle made up of?

Answer 11

• ilium
• ischium
• pubis

Question 12

What is the hindlimb made up of?

Answer 12

• femur
• tibia fibula
• tarsal bones
• phalanges/digits

Question 13

What limb adaptions have occurred in geckos?

Answer 13

• their foot has a sub digital adhesive lamellae, this allows them to cling to walls

Question 14

What limb adaptions have occurred in burrowing lizards?

Answer 14

• they have lost their limbs, but still have pectoral and pelvic girdle

Question 15

What limb adaptions have occurred in lizards?

Answer 15

• they can hold their forelegs off the ground and run on their hind limbs in a bipedal motion

Question 16

What is metabolic bones disease, and what causes it?

Answer 16

• a lack of vitamin D in the diet
• causes weakness and brittle bones
• normally caused by a lack of UV light or calcium deficiency in the diet

Question 17

What are the uses of the respiratory system?

Answer 17

• breathing
• threat and display
• buoyancy
• escaping predators
• vocalisation

Question 18

What type of nares do they have?

Answer 18

• paired nostrils

Question 19

What is the structure of the trachea?

Answer 19

• protected by ruminant larynx
• incomplete c shaped rings of cartilage
• trachea bifurcates into 2 main bronchi, supplying both lungs
• no epiglottis
• often no vocal cords

Question 20

What are the lungs often used for?

Answer 20

• defence mechanism
• 2 lungs

Question 21

Describe the process of inspiration?

Answer 21

• contraction of intercostal muscles plus elastic tissue

Question 22

Describe the process of expiration?

Answer 22

• contraction of intercostal and abdominal muscles plus the elastic recoil of the lung tissue

Question 23

3 key features of their digestive tract?

Answer 23

• simple in insectivores and omnivores
• swallowing of stones to aid in digestion is normal in lizards
• geckos use tails as storage device for fats, their emergency supply

Question 24

Describe the structure of their tongue and taste buds?

Answer 24

• most have a large fleshy tongue
• tongue is generally mobile and protrusible
• very poorly developed taste buds

Question 25

Describe the structure of their stomach?

Answer 25

• located on left side of their abdomen
• simple, elongated and sac like
• contains glands that secrete hydrochloric acid, pepsin and mucus

Question 26

Describe the structure of their small intestine?

Answer 26

• well developed in carnivorous and insectivorous species
• intestinal tract of herbivores is shorter
• some contain caecum
• caecum present at junction between large and small intestine

Question 27

Describe the structure of their large intestine?

Answer 27

• well developed in herbivorous species
• sacculated, so is divided into chambers by leaf like membrane
• increased surface area allows colonisation by bacterial microbes which help digest plant matter

Question 28

Describe the structure of the cloaca?

Answer 28

• large intestines empty into the cloaca
• this has 3 chambers
• coprodeum, urodeum and proctodeum
• all waste is excreted via the vent

Question 29

Describe the roles of the chambers of the cloaca?

Answer 29

Coprodeum - receives faeces

Urodeum - contains urinary and reproductive tracts

Proctodeum - collecting area for digestive and excretory wastes

Question 30

Describe the structure of the heart, and its role?

Answer 30

• paired atria and single ventricle that acts as 2
• channels deoxygenated blood to the pulmonary arteries
• oxygenated blood to the aortas

Question 31

What 2 cardiovascular systems do lizards have?

Answer 31

• hepatoportal venous supply
• renal portal system

Question 32

Describe the structure of the urogenital system?

Answer 32

• position of the kidneys is variable
• most have a thinned wall bladder
• some do nor have bladders and the urine is stored in the distal colon
• short ureter drains into the urodeum, urine flows into the coprodeum

Question 33

How does colour change occur in lizards?

Answer 33

• they have pigmented cells in the dermis
• connected to neural networks
• dispersion by hormonal or nervous signals enables change of colour according to mood or external stimuli

Question 34

Describe the structure of lizards hearing system?

Answer 34

• eardrum (tympanic membrane) is visible
• covered by thick skin or in some lizards scaly skin
• middle ear is present too

Question 35

Describe the structure of their sight system?

Answer 35

• varies from poor to good
• eyelids are usually present
• parietal eye (third eye)

Question 36

Describe the structure of the parietal eye?

Answer 36

• associated with pineal gland
• well developed, and has lens and retina

Question 37

What does the parietal eye do?

Answer 37

• regulates circadian rhythms
• is light sensitive
• for hormone production and thermoregulation

Question 38

What organ do lizards have for smell?

Answer 38

• Jacobsen’s organ

Question 39

How can gender be determined in lizards?

Answer 39

• males are often brighter coloured and ornamented (horn)
• male geckos and iguanas have femoral pores
• males have a bulge where hemipenes are located, a wider base tail
• can sometimes use a probe

Question 40

Frilled lizards defence mechanism?

Answer 40

• extends neck frills to warn off predators or intruding males

Question 41

Flying lizards defence mechanism?

Answer 41

• facing off another male, bobbing head and showing dewlap

Question 42

Regal horned lizard defence mechanism?

Answer 42

• squirts blood form their eyes in defence

Question 43

Chuckwallas and other lizards defence mechanism?

Answer 43

• overinflate the lungs in attempt to look bigger