Chapter 24 Study guide
1. What is the difference between asymmetry, radial symmetry, and bilateral symmetry?
symmetry- describes the similarity or balance among body structures or
organisms.
Asymmetry – has no tissue and has asymmetry. Ex. Is a sponge.
radial - can be divided along any plane, through the axis, into roughly equal halves.
Ex. Jelly fish.
bilateral - can be divided into mirror image halves only along one plane through the
central axis. Example would be a bird.
2. What is dorsal and ventral? And give me an example of each.
Dorsal – also called the backside of every bilateral symmetry animal.
Ventral – also called the underside or belly of every bilateral symmetry animal.
3. How can you tell the difference between coelom, pseudocoelom, and acoelomates?
Coelom – has tissue formed from mesoderm and lines and encloses the organs in the coelom.
Pseudocoelom – is a fluid filled body cavity that develops b/t the mesoderm and the
enedoderm rather than developing entirely within the mesoderm as in coelomates.
Acoelomates – have solid bodies without a fluid filled body cavity b/t the gut and body wall.
4. Continuing from above, Can they all be in an animal at the same time?
No, an animal can only have one type of body plan. Coelom and pseudocoelom are very close
b/c they both have fluid filled cavities but coelom is formed from mesoderm. Pseudocoelom
is formed b/t mesoderm and enedoderm. Acoelomates is fluid filled but its formed b/t gut
and body wall.
5. Why are coeloms important to animals?
It enables animals to develop specialized organ systems, grow large, and move easily.
6. What is cephalization?
Animals with bilateral symmetry that have anterior and posterior ends. The tendency to
concentrate nervous tissue and sensory organs at the anterior end of the animal.
7. What is considered the “head end” _Anterior___ of a bilateral symmetry animal and what is the
“tail end” __Posterior____ of a bilateral symmetry animal.
8. What is it called when animals produce both eggs and sperm in the same animal body?
Hermaphrodites
9. What is it called when fertilization occurs when the sperm penetrates the egg to from a
fertilized egg cell? Zygote
10. What is the difference between internal and external fertilization?
Internal – occurs when the sperm and egg combine inside the body
External – occurs when egg and sperm combine outside the body.
11. What is the difference between endoskeleton and exoskeleton?
Endoskeleton – internal skeletons that grow with the animal
Exoskeleton – are hard or tough outer coverings that provide a framework of support.
12. What is the difference vertebrate and invertebrate?
Vertebrate – animals with endoskeletons and a backbone.
Invertebrate – animals without a backbone that make up b/t 95% to 99% of animal species.
13. Which one happens first blastula or gastrula? How do they happen?
Blastula happens first. The embryo continues to undergo mitosis and cell divison, forming a
solid ball of cells. These cells continue to divide, forming a fluid filled ball of cells call blastula.
The blastula continues to undergo cell division. Some cells move inward to form a gastrula, a
two cell layer sac with an opening at one end.
14. Do sponges have tissues?
No, they are asymmetry with means no tissue.
15. How does a sponge get its food? What’s it called?
Gets its food by filtering small particles from water which is called filter feeder.
16. What are choanoflagellates?
are a group of free-living unicellular and colonial flagellate eukaryotes.
17. Why are they important in this chapter?
Might have been the earliest true animals. As animals evolved from this multicellular
ancestor, they developed adaptations in structures that enable them to function in numerous
habitats.