UNIT 4 DAY 3 - NOSE, EYES & EARS

Question 1

sense of smell - anatomical

Answer 1

• body’s responses to floating molecules

Question 2

sense of smell - molecular

Answer 2

• lock and key mechanism
• odour molecule (key) binds to receptor on nerve cell (lock), different receptors respond to different molecule (chord analogy)

Question 3

How SARS-CoV-2 virus destroys brain cells

Answer 3

• infects brain by binding to nasal receptors and infecting olfactory nerves

Question 4

What did Buck and Axel discover about genes for smelling?

Answer 4

• 3% of our entire genome is devoted to genes for detecting different odours –> each gene make a receptor for an odour molecule

Question 5

Buck and Axel water-to-land transition

Answer 5

• 2 types of smelling genes, lampreys have receptors that combine both genes –> the primitive fish arose before smelling genes split
• number of odour genes increased overtime
• dolphins and whales have mammalian air specialised genes, all are present but none are functional

Question 6

Buck and Axel - duplication

Answer 6

• duplication allowed for odour genes for formation of more receptors
  –> but mutations have made many nonfunctional –> not necessarily a problem - dolphin nasal pathway turned blowholes, perhaps in exchange for increased sight

Question 7

How do eyes function in the same way as cameras

Answer 7

• camera-like eye, common to every creature with a skull, evolved from simple, light-detecting patches

Question 8

opsin

Answer 8

• protein that combines with vitamin A to form a molecule that captures light
• when a molecule splits, initiates chain reaction –> leads to neuron sending an impulse to our brain

Question 9

how do opsins provide evidence that all eye animals are related

Answer 9

• every animal uses same kind of light-capturing molecule
• twisted path of opsin similar to molecular behaviour in molecules

Question 10

How have old world monkeys evolved more acute colour vision than other mammals?

Answer 10

• colour-vision began when 1 gene in other mammals duplicated and the copies specialised overtime –> monkeys benefitted as could distinguish between different fruit and leaves

Question 11

polycheate worms

Answer 11

• evidence for animal interrelatedness, BOTH kinds of photoreceptors (ones similar to vertebrates and invertebrates) found

Question 12

why does the eyeless gene (Pax-6) control eye development throughout animals

Answer 12

• could put it anywhere and it would grow an eye
• Pax-6 controls development

Question 13

parts of the ear

Answer 13

• outer ear –> visible, newly evolved
• middle ear –> contains little ear bones
• inner ear –> consists of sensory cells, fluid, tissues

Question 14

middle ear bones

Answer 14

• malleus and incus (first arch / trigmenial)
• stapes (second / facial nerve)

Question 15

semicircular canals

Answer 15

• 3 fluid-filled canals in the inner ear responsible for sense of balance

Question 16

cochlea

Answer 16

• a coiled, bony, fluid-filled tube in inner ear through sound waves which triggers nerve impulses –> contains movement sensing hair cells

Question 17

how do sensory cells (hair cells) allow us to sense balance and acceleration?

Answer 17

• inner ear, filled with gel that can move
• when gel moves, hairs on end of cells that bend and sends an electrical impulse to the brain
• coordinates eye movement through eyes giving information for stability and position
• alcohol interferes and gives you the spins –> ear gel, causes it to move around, causes eye twitches in response to spinning sensation, liver removes alcohol from blood stream but goes to inner ear

Question 18

neuromast

Answer 18

• organs similar to tetrapod inner ear in gel movement, triggers nerve impulses, arise from same tissue during development
• organs can be repurposed from one function to another –> evolutionary innovation

Question 19

how have mammal ears improved

Answer 19

• now can detect higher frequencies of sound and tell head positions

Question 20

amphioxus and hair cells

Answer 20

• amphioxus possesses hair cells, lack ears or neuromast organs

Question 21

Pax-2 gene

Answer 21

• active in ear region, appears to start a chain reaction of gene activity, leads to development of inner ear

Question 22

jellyfish and pax genes

Answer 22

• jellyfish don’t have pax-2 or pax-6
• genes that forms eye is mosaic that has a structure of pax-2 and pax-6 –> major genes that control our eyes and ears correspond to single genes in more primitive creatures

Question 23

ectopic

Answer 23

abnormal position or place

Question 24

Halder et al (1995)

Answer 24

• cause ectopic eye structures can develop in parts of flys head
  –> several thousand genes in development, eyeless controls set of regulatory genes and develops nervous system
• expands in Spemann –> observing and identifying genes that are necessary to cause ectopic eyes
• similar because antennapedia controls formation of legs in insects but when mutated causes multiple legs to be formed
• ectopic eye mutation - causes formation in wrong place
• mammals and insects share master control gene for eye creation indicated that genetic control mechanisms of development are more universal than thought

Question 25

mammalian species functional odour receptors

Answer 25

dogs (many), humans (fewer), dolphins (none)

Question 26

structures with hair cells

Answer 26

- canals of ears, snail-shaped cochlea neuromast organs on sides of a shark