IB 104 — Lec 19: Animal Diversity, Porifera & Cnideria

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10 Terms

1
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What are the 3 main characteristics that distinguish animals from other organisms?

  • Nutritional mode — animals eat living or non-living organisms (heterotrophs)

  • Cellular structure — multicellular eukaryotes, tissues that develop from embryonic layers

  • Reproduction & development — most reproduce sexually, diploid stage is dominant in lifecycle.


2
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What are the main stages of early embryonic development?

Zygote → Cleavage (cell division) → Blastula (hollow ball of cells) → Gastrulation → Gastrula (with blastopore/digestive cavity at one end)

3
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What is the difference between radial & bilateral symmetry?

  • Radial: body parts arranged around a central axis

  • Bilateral: body can be divided into two mirror-image halves along one plane.


4
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What is the difference between diploblastic & triploblastic animals?

  • Diploblastic: 2 germ layers (ecto & endoderm)

  • Triploblastic: 3 germ layers (ecto, meso, & endoderm)


5
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What are the 3 types of body cavities in triploblastic bilateral animals?

  • Coelom — surrounded by mesoderm only

  • Hemocoel — surrounded by meso & endoderm

  • Or no body cavity (acoelomate)


6
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What is the difference between protostomes & deuterostomes?

  • Protostomes:

    • Spiral & determinate cleavage

    • Solid masses of mesoderm split & form coelom

    • Mouth develops from blastopore

  • Deuterostomes:

    • Redial & indeterminate cleavage

    • Mesoderm buds from wall to form coelom

    • Anus develops from blastopore


7
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What are the main characteristics of sponges (Porifera)?

Sessile, filter feeders that lack true tissues (not eumetazoa).

8
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How do choanocytes help sponges feed?

Use flagella to create water currents & trap food particles with their collars.

9
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What are the main characteristics of cnidarians, & what are their 2 body forms?

Radially symmetrical, diploblastic animals with stinging cells (cnidocytes).

  • 2 forms: polyp (sessile) & medusa (free swimming)

    • Corals & jellies


10
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What are the 3 characteristics of corals, & what threatens coral reefs?

  • Characteristics:

    • Can be solitary (one polyp) or colonial (many polyps)

    • Symbioses with algae (xooxanthellae)

    • Calcium carbonate exoskeletons

  • Threats:

    • Pollution

    • Overharvesting

    • Ocean acidification

    • Ocean warming/bleaching (climate change)