Animals Lec 27-29: Mollusca, Gastropods, Echinoderms, & Chordates

Question 1

Which clades and groups are the phylum Mollusca part of?

Answer 1

Lophotrochozoa and Protostome clade - crest and wheel animals

Question 2

What are lophophores? Trochophores?

Answer 2

Lophophore - feeding structure, ciliated crown of tentacles around mouth
Trochophore - larval development stage. Marine, freshwater and terrestrial.

Question 3

waht are shared features of molluscs?

Answer 3

Coelomate (non-segmented) - complete guts

3 Body regions -
Head
Ciliated or muscular foot
Visceral body region

Mantle - extension of dorsal body wall that covers visceral mass to form flaps

Radula - horny, ribbon structure in mouths of all molluscs (except bivalves)

Mucus - protects skin, anti-predator, and food capture

Question 4

Explain the mollusc body plan and how it relates to the Heart, Radula, Nervous system, and metanephridium:

Answer 4

Heart - dorsal heart pumps circulatory fluid (haemolymph) through arteries into sinus (body space). Organs of mollusc are continually bathes in haemolymph (not in cephalopods)

Radula - mouth region in many species containing a rasp-like feeding organ. Belt of backward curved teeth repeatedly thrust outwards and retract into mouth the scrape and scoop food.

Nervous system - ring of nerves around esophagus where nerve cords extend to foot

Metanephridium - excretory organs, removes metabolic waste from haemolymph.

Question 5

How do Gastropoda move?

Answer 5

crawling, and holding (body plan twisted). Mantle usually fully hidden in shell but the smaller the shell, the more mantle shows

Question 6

How do Bivalvia move?

Answer 6

digging, burrowing, and crawling. Bright colors of mantle protect it from bright sunlight

Question 7

How do cephalopoda move? and how do they achieve camouflage?

Answer 7

Cephalopoda - arms and tentacles help swim.
Mantle is all that is visible behind the head - used as jet propulsion
Outer body wall and fins are all mantle

Chromatophores in Cephalopod Mantle:
Change color, texture, and shape. - used for camouflage, defence, and communication

Question 8

What are the shared features of the Echinoderms?

Answer 8

Deutrostome cleavage in bilateral larva

Pentamerous radial symmetry in adults (oral and aboral surfaces)

Water Vascular System (WVS) - fluid filled coelomic tubes ending in feet.

Madreporite connects WVS to outside

Endoskeleton embedded in body wall (dermis)

Excretion via tiedmanns body

Nerve ring with radial nerves
Enormous regeneration capability

Question 9

summarise the characteristics of Mollusca: development, digestion, body cavities, gas excahgne, circulation, osmoregualtion, excretion, and mucus

Answer 9

Mollusca:

Protostomous
Coelomate
Complete gut
Gills
Open (closed for cephalopods)
Yes, they can osmoregualte
Nephridia (kidny)

If aquatic = urine is ammonia
If terrestrial = urine is uric acid

Protects skin, anti-predator, and food capture

Question 10

summarise the characteristics of echinoderms including; development, body cavity, digestion, gas exchange, circulation, osmoregulation, excretion, and mucus

Answer 10

Echinoderms
Deuterostome
Coelomate
Complete gut
Papula
Open circulatory system
No
No excretory organ

Protects skin, anti-predator, and food capture

Question 11

Major Characteristics of Chordata

Answer 11

1. Bilateral symmetry, segmented bodies, and 3 germ layers, well developed coelom
2. Notochord (skeletal rod) - cartilaginous rod, axial skeleton in chordate embryos
3. Single, dorsal, tubular nerve cord
4. Pharyngeal gill slits
5. Post anal tail
6. Segmented muscles and cartilaginous exoskeleton
7. Ventral heart
8. Completed digestive system

Question 12

Chondrichthyes Characteristics

Answer 12

Cartilaginous skeleton
Lack of swim bladder
Lipid storage in liver
Unique hematopoietic organs

Question 13

Actinopterygii Characteristics:

Answer 13

bony and rigid skeleton, not cartilage.
Many spines and ribs, complex skull of several layers.
Has a swim bladder.
Lateral lines, scales, and gills.

Question 14

Briefly explain chordate phylogeny, and how agnathans and gnathostomes are rlated:

Answer 14

Chordate Phylogeny - deuterostomia, bilateria. Closely related to echinoderms nad hemichordates

Agnathans and Gnathostomes are common ancestors of chordates from cephalochordata with function of notochord.
Directly after vertebral column adaptations

Question 15

Waht is ectothermy?

Answer 15

Ectothermy - an organism’s body temperature is determined by heat exchange with surroundings. Cannot produce or retain enough metabolic heat to elevate body temperature above ambient temp. Uses behavioural mechanisms instead

Question 16

What is endothermy?

Answer 16

Endothermy - organism able to use its own metabolism as a major source of heat to maintain a greater bdoy temperature than surroundings. Allows independence from the environment and enhances physiological functions.

Question 17

Explain the body plans of cyclostomes

Answer 17

Cyclostomes - median fins, 2 chambered hearts, simple digestive system, has sensory organs and external fertilization.

Question 18

give an example of a cylcostome and one of its main processes of protection:

Answer 18

Hagfish - slime helps protect against predation. Slime is produced from any harm done to the surface of the fish, causing a very thick slime to form that, when in contact with water, very quickly congeals. This makes predators unable to bite down and eat hagfish

Question 19

Critical innovations from superclass Gnathostomata:

Answer 19

1. Jaws and mineralised skeletons - started as dental elements in head, then teeth, denticles, and skull. Finally skeleton of derived vertebrates
2. Paired fins
3. Scales and teeth
4. Lateral lines - sensory system receives vibrations in water through skin pores. Canal tube under skill transmits vibrations to travel to neuromast and nerve fibers.

Question 20

Waht is single circulation?

Answer 20

Single circulation - have a closed circulatory system with a hearth, veins, and arteries that only moves in one direction.

Question 21

Explain a shark’s circulatory system steps:

Answer 21

Shark Circulation = sinus venosus → pericardium → atrium → ventricle → conus arteriosus → truncus arteriosus → pericardium → venal aorta

Question 22

Waht is the conus arteriosus? and what does it do?

Answer 22

Conus Arteriosus - muscular sac with valves that direct blood flow from heart. Acts as a pump into arterial arches leading to gills

Regulates blood pressure, and elastic reservoir function helps reduce pressure fluctuations

Question 23

waht makes up shark skin? And explain shark teeth:

Answer 23

made of pulp cavity, dentine, enamel, epidermis, and dermis, with placoid scales making up complex bony structures of teeth.

Shark teeth are homologous to dermal denticles (placoids) that are continually replaced through old teeth being shed, new teeth coming in, and developing teeth in the back

Question 24

explain amphibial and reptile placement in chordate phylogeny, and give a good intermediate species:

Answer 24

From last common ancestor of cordate, Amphibians evolved 7 branches, Reptilia is 8 branches having evolved from Amphibians

Tiktaalik - important transitional species in the “fishbian” sequence from lungfish to amphibian evolution. Shows the intermediate evolved species between lobe-fish and early tetrapods

Reptiles have 2 lines - Diapsids (archosaurs and lepidosaurs) and Synapsids

Question 25

Compare the Fish characteristics and tetrapod characteristics of Tiktaalik species

Answer 25

Fish characteristics - scales, evidence of fins, gills, and lungs Tetrapod Characteristics - neck, ribs, fin skeleton, and wrist and radius, elbow, humerus. Flat skull, and eyes on top of skull.

Question 26

what are 10 amphibian key characteristics?

Answer 26

Bony skeleton (# vertebrae vary), some ribs typically fused to vertebrae or just absent Variety of body forms - Salamander has distinct body regions (tail, trunk, head). Frogs are compressed, no head. Usually 4 limbs, no fingernails Smooth moist skin with many glands over that skin and cutaneous respiration with gas exchange Large mouth with small teeth Gills, lungs, skin breathing 3 chamber heart and double circulation Separate sexes, mix of internal and external fertilization Ectothermic Live on land and water

Question 27

What are 8 reptilian key characteristics?

Answer 27

Ectothermic, and undergo behavioural thermoregulation Body with keratinized epidermal scales Paired limbs with typically 5 toes Have scales/bony ossified skeletons Lay eggs - amniotic filled eggs with shell to prevent water loss Lungs, NOT gills 3 chambered heart Internal fertilization, separate sexes

Question 28

explain the life cycle of amphibians, why they require water, and how it relates to metamorphosis:

Answer 28

Require water for reproduction, eggs to stay moist, and development of young from water to land Metamorphosis - eggs hats to swimming larva (have fish characteristics and are herbivorous) → thyroxine surge triggers metamorphosis (reabsorption of tail and growth of legs) → adult frogs

Question 29

What are the 7 key characteristics of Reptilian eggs

Answer 29

Embryo Chorion - gas exchange Amnion/Amniotic cavity - protection from desiccation, filled with amniotic fluid Albumen - shock absorption and nutrients Allantois - waste disposal Shell - protection Yolk sac/Yolk - nutrient supply

Question 30

What do reptiles have regarding their breathing and scales?

Answer 30

Reptiles have rib breathing (increased breathing efficiency), keratinised scales, and abandoned skill breathing (both for water conservation)

Question 31

Explain the Reptilian Order of Crocodylia (do NOT give information about circulatory system yet)

Answer 31

From Mesozoid period Tails revert to swimming organs Sarcosuchus - ancestral species that lived with dinosaurs Breathing - have similar structures to humans (trachea, larynx, oral cavity) but also have external naris, nasopharynx, and internal naris Have thoracic pump - inhalation expands intercostals and liver to pump to pelvic girdle. When exhalation occurs, everything deflates again.

Question 32

Explain Crocodylia Circulatory system:

Answer 32

Circulatory system of Crocodiles: have the first completely divided heart Similar circulation as humans - blood is pumped from left and is deoxygenated, comes back through the right atrium and pumped to lungs and oxygenated again. Crocodiles have 2 major artery branches; the right and left systemic arches. The right systemic arch originates in the left ventricles and receives oxygenated blood from the heart. Left systemic arch originates from the right ventricle, and is still supplying oxygenated blood by shunting blood from the left ventricle via a hole called the foramen of Panizza. The pressure between the circuits differs with pulmonary being greater, this keeps the hole closed.

Question 33

Explain the reptilian order of squamata and their key characteristics (do NOT explain their circualtory system yet)

Answer 33

Developed from lizards, but lost legs Trachea allows breathing while feeding Have unique sensory organs with pit organs that detect infra-red via temperatures simulation of ion channels Jacobson’s organ connected to nerves and brain and uses tongue to sense Kinetic skull - jaws not fused to allow dynamic range of movements and to help with eating Role of venom - hunting and defense, helps immobilise and digest prey Waste as Uric Acid

Question 34

Role of Venom: (steps and purposes)

Answer 34

snakes can control the level of administered venom or just have dry bites. Operate by blocking acetylcholine receptors for neurotransmitters Activate lipases to break down lipids making cell membranes break down and affect neural transmission Used for hunting and defense helps immobilise and digest prey, useful if no appendages Causes tissue necrosis - predigestion Some have a bite and release strategy. Venom allows prey to be identified

Question 35

Explain squamata's circulatory system:

Answer 35

Circulatory system of Snakes: Has pulmonary and systemic circuit - right systemic aorta pumps between left and right atriums to then connect back up with left systemic aorta to transport blood into capillaries. Has an incomplete septum separating the left and right sides of the heart.

Question 36

Explain the key characteristics of sphenodontia (tuatara/lizards):

Answer 36

Tuatara have 2 bony arches at back of skull, teeth fused to jaw, no external ear hole or penis, and well developed parietal organ Lizards have 1 bony arch at back of skull, teeth are attached to inner jaw surface and replaced throughout life, have both external ear holes and penis, and a simple parietal organ Lizard breathing - have simple sacs with gas exchange through mix of skin and lungs. Breathing with dry skin (intercostals). Have nostrils, trachea, lungs, and ribs. Lungs have little cutaneous exchange to save water. Lungs greatly compartmentalized to increase SA Waste as Uric acid

Question 37

Explain the reptilian order of testudines (turtles) - do NOT explain their circulatory system yet

Answer 37

ancient, successful, aquatic and terrestrial, and have plastron (underside of shell) Breathing - ventilation through carapace that interferes with intercostals, and have cloacal breathing through bursa in cloaca that absorbs oxygen from water and releases CO2 through cloaca Waste - as urea

Question 38

explain Testudines circulatory system

Answer 38

Circulation - have pulmocutaneous circuit and systemic circuit with lungs, capillaries, atriums, and ventricles. Pulmocutaneous is from right atrium with O-poor blood to lungs with O-rich blood Systemic is left atrium with O-rich blood to capillaries of circuit to O-poor blood back up into right atrium to go to the pulmocutaneous circuit.

Question 39

waht are lepidosaurs

Answer 39

Lepidosaurs - one surviving lineage is tuatara whose ancestors lived well into the Cretaceous period. Others are australian thorny devil lizard, saltwater crocodiles, carpet pythons, and squatemates (small animals mainly lizards).

Question 40

explain the origin of reptiles:

Answer 40

all early reptiles were diapsids (known for a pair of holes on sides of skull behind the eye sockets with muscles passing through to control jaw movements. Diapsids composed of lepidosaurs (lizards and snakes, produced mainly marine reptiles, all of them are extinct) and archosaurs (turtles, crocodiles, and dinosaurs) Dinosaurs - very diverse, made of two lineages; the Ornithischians (herbivores with physical predator protection), and saurischians (long-necked giants and bipedal carnivores called theropods).

Question 41

what are archosaurs?

Answer 41

Archosaurs - Turtles, crocodilians, and birds: Turtle - no holes behind eye sockets via evolution, archosaurs, boxlike shell of upper and lower shields fused to vertebrae, clavicles, and ribs that provides protection that evolved in stages. Crocodilians - Triassic period, used to be quadrupeds but species adapted to be larger. Breath air through upturned nostrils Birds - adaptations facilitate flight (lack univary bladder, females only have one side of reproductive organs which are generally small and only increase in size during breeding season, and they’re toothless).

Question 42

explain the origin of birds:

Answer 42

Theropod ancestors evolved 160 mya, Archaeopteryx is the earliest known bird. Cretaceous period show gradual loss of certain ancestral dinosaur features (e.g. teeth and clawed forelimbs)

Question 43

explain neornithes:

Answer 43

Neornithes - clade including 28 orders of living birds found before Cretaceous-Paleogene boundary 66 mya. Ratites - order of bird including ostrich, rhea, kiwi, and emu - flightless. Absent sternal keel, and small pectoral muscles. Penguins - order of lightless birds, but have powerful pectorals to flap underwater.

Question 44

explain bird beaks and feet structure importance:

Answer 44

Specialised beak shapes match diets - hummingbird to access long flower tubes, parrots can crack nuts, flamingos have strainers in their beak for filtering. Foot structure - different uses for perching, grasping food, defence, swimming, walking, and courtship.