Animal Development and Architecture

Plasmogamy vs karyogamy

• Plasmogamy- the cytoplasm of two parent mycelia fuse together without the fusion of nuclei, as occurs in higher terrestrial fungi. After plasmogamy occurs, the secondary mycelium forms. The secondary mycelium consists of dikaryotic cells, one nucleus from each of the parent mycelia.

• Karyogamy- In fungi that lack sexual cycles, it is an important source of genetic variation through the formation of somatic diploids.

Core concept

Animals are multicellular, heterotrophic eukaryotes. In contrast to the autotrophic nutrition of plants and algae, animals must take into their bodies preformed organic molecules; they cannot construct them from inorganic chemicals. Most animals do this by ingestion---eating other organisms or organic material that is decomposing.

Animal cells lack the cell walls that provide strong support in the bodies of plants and fungi. The multicellular bodies of animals are held together by structural proteins, the most abundant being collagen.

Most animals reproduce sexually, with the diploid stage usually dominating the life cycle. In most species, a small flagellated sperm fertilizes a larger, non-motile egg to form a diploid zygote.

Keywords

Vertebrate invertebrate symmetryirregular symmetry radial symmetry

bilateral symmetrypenta radial symmetry anterior posteriordorsal ventral multicellularCleavage blastula gastrulationGastrula metamorphosis cephalization

Recall: Development and growth

• Specialization is due to multicellularity• An animal is a product of a diploid zygote• Reconstruction is due to– Cleavage (mitosis)

• Morula (32 cells)– Blastulation

• 128 cells• blastocoel

– Gastrulation • Formation of endoderm, mesoderm, ectoderm• Followed by organogenesis

Animal Development

• Product of aggregation of identical cells– Colonial protists

• Formation of hollow unspecialized cells• Specialization to reproductive and somatic cells• Cellular infolding and gastrulation-like process

The development of animals proved a strong indication of our origin from colonial protistan ancestors.

 

Portuguese Man-of-War

Animal Architecture

Animal symmetry is of three types: irregular (asymmetry), radial and bilateral. Irregular symmetry is the most primitive type of symmetry followed by radial, and the most advanced type which is the bilateral symmetry. 

Symmetry

Animal multicellularity, cephalization, and trends in size play an important role in the animal evolution. Why?