Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

31. Invertebrates

Porifera and Cnideria

General Biology

31. Invertebrates

Porifera and Cnideria

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Multiple Choice

Which of the following best describes a key difference between the first cnidarians and sponges (phylum Porifera)?

Sponges have radial symmetry, while cnidarians have no symmetry.

Sponges have a nervous system, whereas cnidarians do not.

Cnidarians possess true tissues and specialized stinging cells (cnidocytes), while sponges lack true tissues and specialized cells for prey capture.

Cnidarians are exclusively sessile, while sponges are motile as adults.

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Verified step by step guidance

Step 1: Begin by understanding the key characteristics of sponges (phylum Porifera). Sponges are simple organisms that lack true tissues and organs. They rely on specialized cells, such as choanocytes, for feeding and water circulation, but they do not possess specialized stinging cells.

Step 2: Next, examine the characteristics of cnidarians. Cnidarians are more complex than sponges and possess true tissues, including an organized nervous system and muscle tissues. They also have specialized stinging cells called cnidocytes, which are used for prey capture and defense.

Step 3: Compare the symmetry of sponges and cnidarians. Sponges generally lack symmetry or may exhibit asymmetry, while cnidarians typically have radial symmetry, which allows them to interact with their environment from all sides.

Step 4: Analyze the mobility of sponges and cnidarians. Sponges are sessile as adults, meaning they are fixed in one place, while cnidarians can exhibit both sessile and motile forms depending on their life stage (e.g., polyp and medusa forms).

Step 5: Based on the provided options, identify the correct answer by focusing on the presence of true tissues and specialized stinging cells (cnidocytes) in cnidarians, which distinguishes them from sponges that lack these features.