UNIT 2: KINGDOM ANIMALIA 1 (27) Flashcards
General features of kingdom animalia:
1) Multicellular
2) Heterotrophs
3) No cell walls
4) The ability to move
5) All symmetries
6) All habitats
7) Ability for sexual reproduction, diplontic life cycle (diploid multicellular condition)
8) Specific embryonic development that leads to germ layers and tissue types
General features of kingdom animalia (2):
- Part of Opisthokonta
- Sister group with choanoflagellates: share similar DNA, modern sponges have cells very similar to modern choanoflagellates
Five key transitions can be noted in animal evolution:
1) Tissue development
2) Symmetry
3) Body cavity formation
4) Segmentation
5) Embryo development differentiation
Parazoa
- Para = next to
- Zoo = animal
- Lack defined tissues and organs
- Have the ability to dedifferentiate and re-differentiate their cells
Eumetazoa
- Eu = true
- Meta = late
- Zoo = animal
- Have distance and well-defined tissues
- Have irreversible differentiation for most cell types
- Diploblast vs. Triploblast
Diploblast
- Di = two
- Blast = to spout
- Two cell layers
Ectoderm
- Ecto = outside
- Non-cellular middle
- Endoderm
Evolution of symmetry
- Parazoa have no symmetry and Eumetazoa does have symmetry
Radial symmetry
- Symmetry around a central axis (EX: starfish or a tulip flower)
- Body parts arranged around central axis
- Can be bisected into two equal halves in any 2-D plane
Bilateral Symmetry
- When the body plan of an animal can be divided along a line that separates the animal’s body into right and left halves that are nearly identical of each other
- Bi = two
- Lateral = side
- Only one mirror image
- Other directional bisections
- Directional movement
- Leads to cephalization
Cephalization
- The development of sense organs near the front, also known as the head (an organism with a well-developed head is known as highly cephalized)
- Cephalo = head
Evolution of the a body cavity:
- Eumetazoa may produce coelom (the body cavity in metazoans)
- =cavity, sounds like ‘seal’
- Space in between tissues, surrounded by mesoderm
Acoelomate
- No coelom
- A = without
Pseudocoelomate
- Coelom between mesoderm and endoderm
- Pseudo = false
Eucoelomate
- Coelom lined on both sides with mesoderm
- Eu = true
Evolution of segmentation
- Segmentations caused by Hox genes
- Provides three advantages:
1) Redundant systems and tissues
2) Improved locomotion
3) Regional specialization