Hox genes cause segmentation development
2 advantage of Hox genes
Highly segmented animals, usually have nearly complete set of organs in theirs each segment of body. This result to less damage in their body, since other segment duplicate the damage segment functions
Locomotion is more efficient, since partitions isolate the segment can contract and expand autonomously.
32.3. The Classification of Animals
Animals divided into 35-40 phylum
32.3.1 Tissue symmetry separate the Parazoa and Eumetazoa
Kingdom Animalia (Metazoa) is divided into 2:
Parazoa
Animals that lack tissue and symmetry
Ex. Porifera (Sponges)
Eumetazoa (true animal)
Animals that have definite shape and symmetry and have organs
All bilateria animals are triploblasty
Can be protostomes or deuterostomes (depends on blastopore development)
Only Cnidaria (sponges) and Ctenophora are diploblasty
32.4 The roots of the Animal Tree of Life
32.4.1 Metazoans appear to have evolved from colonial protists
Evidence:
Multicellular
Colonial flagellated hypothesis
32.4.2 Molecular analysis may explain the Cambrian explosion
Result of Cambrian explosion
Emergence of new body plans
Evolution of predation
Developing in body part because of Hox genes
Ex, leg, thorax, antennae
32.3.2 Animal Phyla with the Most Species
Phylum
Example
Habitat
Key char.
Symmetry
Tissue Layer
Coelome
Protostomes
Deuterostomes
Segmentation
Porifera
(sponges)
All type of Sponges
Marine
- Have pores
- Cavities lined with food filtering flagellated cells (choanocytes)
Asymmetry
N/A
Acoelomate
N/A
N/A
N/A
Cnidaria
(cnidarians)
- Jelly fish
- Hydra
- Corals
- Sea anemones
- Sea fans
Fresh water
-Mouth open to simple digestive sac and surrounded by (nematocysts)
Radial
Diploblasty
Acoelomate
N/A
N/A
N/A
Ctenophora
(sea walnuts)
-Comb jelly
-Sea Wallnut
Marine
- Ciliated
- Gelatinous
- Transparent