Biology lecture 4/15/15Intro to animals1. Animal general features2. Animal classification- Morphology, anatomy, and embryological developmentAnimals are members of the super group unikontaChoanoflagellates: Nearest non-animal taxon- Coloral protists; similar to animal ancestors- They form “multicellular” bodies- Cells adhere with proteins homologous to animalsAnimal characteristics- All are multicellular (“Metazoa”)- Heterotrophic: to feed by ingestion- Dipontic: life cycle of an animal- The only haploid phase of the life cycle is the sperm and egg- all other states of the life cycle are diploid- Has distinctive embryonic development: zygote → blastula → gastrulaEarliest animal fossils- ~ 35 million years ago, late Proterozoic (Vendian period): “Edicaran fauna”Ediacaran fauna: - Animals that exhibited radical/bilateral symmetry- They are similar to jelly fish and wormsMost Edicaran animals appear to have become extinct ~540 million years agoAnother burst of animal evolution occurred shortly thereafter “Cambrian Explosion” (542-525 million years ago)Animal classification- Currently about 35 animal phyla are recognized- Phylogenetic relation are controversialAnimal classification relies on:- Morphology- Anatomy- Development (embryological)- Molecular (DNA sequence data)Morphology body symmetryRadical symmetry and bilateral symmetry: The two groups of morphology body symmetryRadical symmetry: symmetrical around a central axis and has no distinctive front of rear endsBilateral symmetry: left and right sides, dorsal, ventral, posterior, and anteriorAnatomy- Embryonic germ tissues- Body cavitiesTissue: a group of cells that are specialized for a particular functionGerm Tissues: relatively unspecialized tissues at gastrulation; give rise to more specialized
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