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Lecture 24

BIO 201 Lecture 24: Animals Part 2

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BIO 201
John Trueand Ross Nehm

Lecture 24: Animals Part 2 Animal body plan: 5 key characters (4) External appendages (states: absent, present) (5) Nervous system (states: absent, net, central) (4) External appendages o Outgrowths of the body in animal lineages appear to have the same genetic underpinnings. o Appendages are used for: ▪ Locomotion ▪ Feeding ▪ Reproduction ▪ Defense ▪ Etc. • Examples: o Squid arm o Jellyfish tentacle o Tiger paw o Insect leg o Worm parapodia (5) Nervous system: • Some animals have no nervous system (Porifera) • Nerve nets are diffuse systems (Cnidarians) • Central nervous systems: centralized system (Bilaterians) Animal body plan: 5 key characters (1) Symmetry (states: absent, radial, bilateral) (2) Body cavity type (states: coelom absent, present) (3) Segmentation (states: absent, present) (4) External appendages (states: absent, present) (5) Nervous system (states: absent, net, central) Porifera: Sponges: No symmetry, no tissues, no coelom, no nervous system, no appendages. Animal Phylogeny: Cnidarians Cnidarian Synapomorphy: Nematocysts (Stinging Cells) Corals—type of Cnidarians • Corals grow in clear, nutrient-poor tropical waters • They have photosynthetic dinoflagellates as endosymbionts • The corals provide nutrients and a place to live; the dinoflagellates provide food to the corals (sugars produced through photosynthesis) • Reef-forming corals are typically restricted to clear surface waters with enough light to support photosynthesis Cnidarian ecology: Tropical beaches are often made by cutting down mangrove forests Life cycle of cnidarians: polyp and medusa Cnidarian sex: sperm+egg to zygote to adult to meiosis to gametes • Many Cnidarian species have a polyp phase and a medusa (“jellyfish”) phase. • Fertilization is often external, with eggs and sperm released into the water • Timing of gamete release becomes important, and can be a pre-zygotic isolating mechanism Cnidarian reproduction: sperm, egg released into water Protostome diversity Bi
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