- Plasmogamy involves the fusion of cytoplasm between two parent fungi without nuclear fusion, forming a secondary mycelium with one nucleus from each parent. Karyogamy involves nuclear fusion and produces genetic variation through somatic diploids.
- Animal cells lack cell walls and have structural proteins like collagen to hold their multicellular bodies together. Most animals reproduce sexually through fertilization and have a diploid stage dominating their life cycle.
- Animal development proceeds through cleavage, formation of a blastula and gastrula, and then organogenesis from the three germ layers. Their multicellular origin can be traced to colonial protistan ancestors.
2. 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 .
3. 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.
4. 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.
5. 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.
7. 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
8. 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.
10. 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.