BIOL 152 1st Edition Lecture 12Outline of Last Lecture - Animal Diversity Outline of Current Lecture The First AnimalsAnimals most likely derived from a colonial, flagellated protists, like today’s choanoflagellates Multicellular organisms have different specialized cells Unicellular organisms have group of cells that work toward a similar goal – colonial – these ancestors lived 1.2 billion years ago – 800 million years ago Choanocytes – are collar cells that absorb food, similar colonial structuresPrecambrian animalsThe Ediacaran fossils document embryos and small, soft-bodied animalsSponges were the first fossil record cnidarians that began to appear latter during this period Geologic Time ScaleThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.The Cambrian ExplosionOccurred 542 million years agoAt the beginning of the Paleozoic was the time period when most animal phyla and all major body plans appearedPaleozoic:- fishes dominated the marine environment- insects and plants colonized land- amphibians appeared, then reptiles appeared on landCauses of Cambrian explosion?- predator prey relationship - increase in oxygen- hox gene complex aroseMesozoic:- coral reefs formed and provided new niches- reptiles dominated the seas and land- small nocturnal mammals appeared- birds began to appear during this timeCenozoic:Fig 26-10Land plantsAnimalsPaleozoicMeso-zoicCeno-zoicOrigin of solarsystem andEarth4123MulticellulareukaryotesSingle-celledeukaryotesProkaryotes- was followed after mass extinction- during this time period major radiation of flowering plants and insects appeared- large, mammalian herbivores, and carnivores appearedAnimal Characteristics1. Heterotrophs – have to consume food 2. Multicellular3. No cell walls4. Specialized cells only found in animals; muscle and nerve5. Most reproduce sexually 6. Diploid form dominated the life cycle7. Regulatory genes (hox genes)Early developmental patternsMost animals reproduce sexually The zygote proceeds through several stages of mitotic divisions: - Cleavage- Blastula- GastrulaCurrent Lecture- Animal
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