lab 10

what are animals

• Multicellular eukaryotes

• Heterotrophs (ingest food)

• Body plans differ by: symmetry, embryonic layers, body cavity, and embryonic development patterns

• Species within a phylum can still vary widely and inhabit different environments

types of body symmetry

1) asymmetry: sponge

2) radial: sea anemone

3) bilateral: lizard

Germ layers formed during embryonic development

• Ectoderm: skin and nervous system

• Mesoderm: muscles, skeleton, kidneys, reproductive organs

• Endoderm: lining of the gut and related organs

animal body plans/ tissue layers/ cavities

• acoelomate: no colem, only digestive cavity

• pseudocelomate: “sort of” body cavity, is between mesoderm and endoderm, also digestive cavity

• eucoelomate: true body cavity: also digestive cavity

gametes formed in animals

• Formed in gonads (testes or ovaries) via meiosis

• Fertilization (sperm + egg) produces a diploid zygote

• Fertilization membrane prevents multiple sperm from entering the egg

Internal vs External Fertilization

• Internal: Sperm meets egg inside the body; fewer eggs; higher investment. (woman)

• External: Eggs and sperm released into air/water; more eggs; lower investment per egg (fish)

protostomes and deuterostomes

• Protostomes: mouth develops first

• Deuterostomes: anus develops first

• Sponges and cnidarians show primitive features

Porifera

• also known as sponges

• no distinct body plan

• lack tissues = no true organs

• sessile (imobile) and are filter feeders

poriferia anatomy

• Ostium: pores where water enters

• Osculum: large opening where water exits

• Collar cells (choanocytes): use flagella to draw water

• Spicules: structural support, deter predators

cnidaria

• Jellyfish, Coral, Anemones

• Radial symmetry

• Diploblastic (2 layers: ectoderm & endoderm)

• Muscle and nerve tissue → movement

• Tentacles with cnidocytes (stinging cells) to capture prey

cnidarian body plan

• polyp: sessile, tentacles up, attached to surface

• Medusa: free-swimming, bell-shaped

• Some anemones can "swim" to escape predators

what are protostomes

• Bilateral symmetry

• Cephalization (head region with brain, eyes)

• Triploblastic (3 germ layers)

• Organ systems: muscular, nervous, digestive, reproductive

• Two major groups: Lophotrochozoa and Ecdysozoa

Platyhelminthes

• flatworms

• 3 groups: planarians, flukes, tapeworms

• Acoelomate (no true body cavity)

• Organ systems lie in mesoderm

• Incomplete digestive system (gastrovascular cavity)

• Tapeworms: no digestive system, absorb nutrients from host

tapeworm adaptations for parasitism

• Scolex: head with suckers and hooks

• Proglottids: reproductive segments

• Live in host intestines, absorb nutrients directly

annelida

• 3 groups: earthworms, leeches, polychaetes

• Eucoelomate (true body cavity)

• Coelom = hydrostatic skeleton

• Metameric segmentation: repeating segments with duplicate organs

• Complete, one-way digestive tract (mouth → anus)

Mollusca

• 4 main groups: chitons, gastropods, bivalves, cephalopods

• Eucoelomate

• Complete digestive tract

• Radula (scraping mouthpart, not in bivalves)

• Muscular foot (movement), mantle (covers organs, may secrete shell)