W10: Invertebrate Physiology (Physiology Of Sight: Insect Vision) [Dr. Blair] Flashcards

1
Q

Cambrian explosion attributes? (3)

A
  • ~530-540Mya.
  • Modern day Phyla emergence.
  • Arthropods: Trilobites (extinct) were one of the first animals to have complex, compound vision.
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2
Q

Types of eyes that insects have? (2)

A
  • Simple eyes (ocelli).
  • Compound eyes.
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3
Q

Ocelli attributes? (5)

A
  • Simple eyes.
  • Found on the heads of insects.
  • Positioned in a triangular arrangement between the compound eyes (often 3 ocelli).
  • Help in light detection, stabilisation & orientation.
  • Narrow field of view.
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4
Q

Compound eyes attributes? (4)

A
  • Composed of many ommatidia, each with its own lens.
  • Produce a mosaic image of the environment.
  • Wide/Panoramic field of view.
  • For movement detection, image formation & colour vision.
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5
Q

Ommatidia attributes? (2)

A
  • Functional parts for vision forming the facet.
  • Function independently to each other in apposition eyes.
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6
Q

Some insects have a Pseudopupil. What’s a Pseudopupil?

A

= a false pupil that is an optical illusion seen in the compound eyes of some insects like the praying mantis.

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7
Q

Components of ommatidia? (3)

A
  • Lens.
  • Rhabdom.
  • Photoreceptors.
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8
Q

Lens?

A

= consists of the cornea & cone.

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9
Q

Cornea?

A

= outer structure that initially focuses light.

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10
Q

Cone?

A

= structure in the lens that directs lights to the photoreceptors.

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11
Q

Rhabdom?

A

= structure in the ommatidia where light absorption & channeling occurs.

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12
Q

Photoreceptor?

A

= structure with retinula cells that contain pigments to detect light & convert it to electrical signals.

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13
Q

Insect Imaging (Compound eyes): Apposition eyes attributes? (3)

A
  • Type of compound eye that is optimised for bright light environments.
  • Each ommatidium works independently to provide sharp & detailed vision.
  • Highly effective for diurnal insects that are active during the day.
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14
Q

Insect vision attributes? (7)

A
  • Insects have photoreceptor cells in ommatidium (act as different wavelengths of light).
  • High/Low resolution depends on the type of insect & number of ommatidium (act like pixels).
  • Types of colour vision (2) come down to pigments (rhodopsins).
  • Perceive a range of colours & UV light.
  • More ommatidium = high resolution.
  • Larger eye = more light.
  • Trade-offs.
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15
Q

Trade-off when it comes to vision: If an insect wants to increase its resolution, it needs to increase its ommatidia, but it will need a bigger eye, so what then?

A

Visual adaptations.

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16
Q

Visual adaptation attributes? (2)

A
  • Species dependent.
  • Environmental pressures.
17
Q

Eg of visual adaptations?

A

Hairs in the eyes of bees that protect their eyes when foraging in pollen.

18
Q

Why do flowers have UV light?

A

To provide nectar guides for pollinators.

19
Q

Who sees the best?

A

Diurnal fliers, particularly dragonflies.

20
Q

Why do dragonflies have the greatest/exceptional vision? (2)

A
  • High resolution (30 000 ommatidia).
  • Divided eyes: dorsal & ventral.
21
Q

Dorsal eyes of Dragonflies?

A

= detect prey/predators against the bright sky.

22
Q

Ventral eyes of Dragonflies?

A

= detect prey/other objects against the ground or water.

23
Q

Types of colour vision in insects? (2)

A
  • Dichromatic colour vision.
  • Trichromatic colour vision.
24
Q

Dichromatic colour vision attributes? (3)

A
  • Most insects like stink bugs.
  • 2 colour pigments.
  • Unable to discriminate all colours.
25
Q

Trichromatic colour vision attributes? (3)

A
  • Some insects like bees & butterflies.
  • 3 colour pigments.
  • “True colour’.
26
Q

Sexual dimorphism in flies?

A

Male flies make their field of view as wide as possible through their “love spot’ to search/detect female mates (aids in reproductive success).

27
Q

Who sees the least?

A

Nocturnal insects, especially moths.

28
Q

Why do nocturnal insects/moths see the least? (4)

A
  • Low resolution.
  • High sensitivity to light.
  • Increased size of ommatidia, but fewer.
  • Triangular cornea to further capture & trap light.
29
Q

Why do nocturnal insects increase the size of their ommatidia but have fewer of them?

A

It helps with more light capture to be able to see at night.

30
Q

Advancing vision: Diurnal insects?

A

Apposition eye.

31
Q

Advancing vision: Nocturnal insects?

A

Superposition eyes.

32
Q

Superposition eyes attributes? (2)

A
  • Nocturnal or crepuscular (active at dawn/dusk) insects.
  • Light from multiple ommatidia converge to enable vision in low light conditions.
33
Q

Dung beetles attributes? (4)

A
  • Low resolution.
  • High sensitivity to light.
  • Navigate using celestial cues stars.
  • 1st insects to know how to use starlight for navigation.
34
Q

Why are insects attracted to light?

A

It’s because of a phenomenon called positive phototaxis, where insects instinctively move toward light sources, but several reasons exist.

35
Q

How do lights in cities affect phototaxis?

A

Lights in cities negatively influence an insect’s ability to navigate due to air pollution, which blocks light & stars.

36
Q

Super summary? (3)

A
  • Vision origins (cambrian explosion, modern day arthropod diversity & vision).
  • The compound eye (ommatidia, seeing in colour, visual trade-off).
  • Vision (environment, visual adaptations, diurnal vs nocturnal).