bio2 test 3 animal diversity

animal characteristics

eukaryotic, multicellular heterotrophs, no cell walls, ingestion, 2n, sexual reproduction, homeotic genes

animal diversification

1 billion years ago, rapid adaptive radiation, Cambrian explosion, complex prey-predator, atmospheric oxygen

animal bodies vary in

symmetry, presence/absence of tissues, number of embryonic tissue layers, presence/type of body cavity, embryonic development

Animal body symmetry

radial-regular arrangement of parts around central axis (sea anemone)

biltateral-mirror image right and left, dorsal and ventral, anterior and posterior, cephalization (goat)

animal bodies tissues

specialized cells, working together, ex: muscle tissue

animal bodies embryonic layers

• Most have 3 layers (endoderm, ectoderm, mesoderm) triploblastic 

• Some have 2 layers (ectoderm, endoderm) diploblastic

animal bodies body cavity (triploblastic)

• Fluid filled space between the digestive tract and outer body wall 

• Cushions internal organs 

• Fluid forms a hydrostatic skeleton 

• True coelom-body cavity completely lined with mesoderm 

• Pseudocoelom-body cavity not completely lined with mesoderm 

• Acoelom-no body cavity

animal phylogeny

5 group: Sponges 

• Radially symmetrical eumetazoans 

• Lophotrochozoans: non-molting protostomes 

• Encydosozans: molting protostomes

• Deuterstomes

Phylum Porifera: Sponges

simple, sedentary, no true tissues, filter feeders

Water enters through pores in the body wall moves through central cavity and then out through a larger opening

sponges: choanocytes

• “collar cells” create water current and capture food particles 

sponges: spicules

• sharp mineral projections: support and protection 

sponges: amoebocytes

• move through body, produce spicules, protein fibers, other cells 

Phylum cnidaria: cnidarians

• Radial symmetry, diploblastic 

• 2 basic body plans 

  • Sessile polyp=feeding, asexual reproduction 

  • Motile medusa-dispersal, sexual reproduction 

cnidarians-cnidocytes

• stinging cells; prey capture, defense 

  • Eject a barb (nematocyst) into prey 

• Sea anemone, coral, jellies 

Phlyum Plateyheminthes: Flatworms

• Bilateral, triploblastic, acoelomate 

• Marine, freshwater, damp terrestrial habitats 

• Parasitic free living 

• 3 major groups 

  • Planarians 

  • Flukes 

  • Tapeworms

flatworms: planarians

• Free living 

• Light sensitive eyecups 

• Simple nervous system 

• Branched gastrovascular cavity, single opening 

• Ex: dugesia

flatworms: flukes

• Parasitic 

• Complex life cycle with multiple hosts 

• Suckers for attachmen t

• Ex: liver fluke, clonorchis

flatworms: tapeworms

• Intestinal parasites 

• Ribbon like body made of repeated units (proglottids)

• Scolex anterior region, attaches to host 

• No mouth or gut absorb food directly across body

Phylum Nematoda: Round worms

• Bilateral, triploblastic, protosome, pseudocoelom 

• Nonliving cuticle that is shed (ecdysis) periodically 

• Complete digestive tract (mouth and anus) 

• Some are parasitic (ex: heart worms) 

• Most are freeliving and microscopic 

Phylum Mollusca: Molluscs body plan

• Muscular foot (locomotion) 

• Visceral mass (contains guts) 

  • Complete digestive system

• Mantle (covers visceral mass, may secrete shell)

• Scraping radula (feeding)

mollusks: gastropoda

• Largest group of molluscs 

• Freshwater, marine, terrestrial 

• Often protected by a single spiral shell

• Radula scrapes algae, plants 

• Ex: snails and slugs 

molluscs: bivalves

• Shells divided into 2 halves hinged together 

• Most are suspension feeders 

• Little to no cephalization 

• Ex: clams, oysters, mussels, scallops 

molluscs: cephalopods

• Most are fast, agile predators 

• Large brains, sophisticated sense organs, including complex image-focusing eyes 

• Closed circulatory system 

• Most have reduced or no shell 

• Radula modified into crushing beak 

• Ex: squid, octopus, nautilus

Phylum Annelida: Segmented worms 

• Triploblastic, bilateral, coelomate, protostomes 

• Show segmentation 

  • Subdivision of the body into repeated parts 

  • Added mobility, specialization 

• Closed circulatory system, complete digestive system 

• Terrestrial, marine, freshwater, parasitic

segmented worms: oligochaetes

• Earthworms 

• Small bristles anchor in soil 

• Eat their way through soil 

• Important in aerating soil

segmented worms: polychaete

• Largest group of anelids 

• Each segment has a pair of fleshy appendages with stiff bristles 

• All marine 

• Filter feeders, predators on sea floor 

• Ex: feather duster worms, sandworms

segmented worms: leeches

• Most are free living 

• Some are blood sucking parasites

• Secrete hirudinin-anesthetic and anticoagulant 

• Medicinal leeches used for digit reattachment

Phylum Arthropoda: Arthropods

• Bilateral, triploblastic, coelomare, protostome 

• Open circulatory system 

• Most successful group of animals

  • Segmentation 

  • Hard exoskeleton 

    • Ecdysis-molting, growth, repair 

  • Jointed appendages (esp. Mouthparts, legs) modified for many functions 

  • 4 major extant groups

arthropods: chelicerates

• Most are terrestrial, some marine or freshwater 

• Most are predators, some parasites and detritivores 

• Have chelicerae-piercing or pinching mouthparts 

• Ex: horseshoe crabs, spiders, scorpions, mites, ticks

arthropods: myrapodia

• Numerous segments, each with walking legs 

• Millipedes-herbivores; 2 pairs of legs/body segment; often with chemical defenses 

• Centipedes-carnivores; 1 pair of legs/body segment; poison fangs

arthropods: crustaceans

• Nearly all aquatic (some terrestrial) 

• Chewing mouthparts, numerous legs 

• Ex: crabs, shrimp, barnacles,  lobster 

arthropods: insects body plan

• Head-feeling and sensory appendages 

• Thorax-movement; 3 pairs of legs, 1 or 2 pairs wings (usually) 

• Most successful animals and arthropods (~75% named species are insects

insects reasons for success

• Segmentation, exoskeleton 

• Jointed appendages (feeding, movement) 

• Waterproof cuticle 

• Complex life cycle involving metamorphosis

insects metamorphosis

• Most go through complete metamorphosis 

• Egg to larva to pupa to adult 

• Larval, adult stages usually very different 

• Reduces competition between adult and larva 

• Ex: butterfly 

• Others go through simple metamorphosis 

• Eggs to several immature stages to adult 

• Less difference between adult and immature stages 

• Ex: assassin bug

Phylum Echinodermata: echinoderms

• Triploblastic, coelomate, deuterostome, radial symmetry 

• All marine ~6000 species 

• Calcium carbonate endoskeleton of ossicles 

• Spiny skin 

• Water vascular system-series of connected tubes; movement, gas exchange, prey capture, osmoregulation 

• Larvae are bilaterally symmetrical, change into pentaradial adult 

• Ex: sea star

Phylum Chordata: Chordates

• Triploblastic, deuterostome, coelomate, bilateral 

• Chordates characteristics: 

  • Dorsal, hollow nerve cord 

  • Flexible, supportive notochord 

  • Pharyngeal slits 

  • A muscular post anal tail 

chordates: Tunicates and lancelets

• are invertebrate chordates 

  • Suspension feeders 

• Tunicates 

  • Larvae have all chordae features 

  • Adults are sessile, lose notochord and tail 

• Lancelets 

  • Small, bladelike chordates buried in marine sediment 

  • Show all chordate characteristics throughout life cycle

1. Define animals, and distinguish them from other forms of life.

Animals are multicellular organisms that eat food, move, and respond to their environment, unlike plants, fungi, or bacteria.

1. Describe the general animal body plan.

The general animal body plan includes a symmetry, a body cavity, tissues and organs, and a digestive system.

1. Describe the Cambrian explosion, and list three hypotheses to explain its occurrence.

Cambrian Explosion:

• Rapid rise of many animal groups ~541 million years ago.

Three Hypotheses:

1. More oxygen → bigger animals

2. Predation → new diversity

3. Hox genes → complex bodies

1. Compare the  animal phyla discussed in this chapter according to the following traits: (a) presence of true tissues; (b) no symmetry, radial symmetry, or bilateral symmetry;
   (c) no coelom, a pseudocoelom, or a true coelom; and (d) protostomes or deuterostomes.

Phylum	True Tissues	Symmetry	Body Cavity	Development
Porifera	No	None	None	–
Cnidaria	Yes	Radial	None	–
Platyhelminthes	Yes	Bilateral	None	Protostome
Nematoda	Yes	Bilateral	Pseudocoelom	Protostome
Annelida	Yes	Bilateral	True coelom	Protostome
Mollusca	Yes	Bilateral	True coelom	Protostome
Arthropoda	Yes	Bilateral	True coelom	Protostome
Echinodermata	Yes	Radial (adult)	True coelom	Deuterostome
Chordata	Yes	Bilateral	True coelom	Deuterostome

1. Describe the characteristics of and distinguish between the following phyla: Porifera, Cnidaria, Platyhelminthes, Nematoda, Mollusca, Annelida, Arthropoda, Echinodermata, and Chordata. Note several examples of each phylum.

• Porifera: no tissues, no symmetry → sponge

• Cnidaria: radial, stinging cells → jellyfish, coral

• Platyhelminthes: bilateral, flat, no coelom → planaria, tapeworm

• Nematoda: bilateral, pseudocoelom → roundworm, hookworm

• Mollusca: bilateral, soft body, coelom → snail, octopus

• Annelida: bilateral, segmented, coelom → earthworm, leech

• Arthropoda: bilateral, exoskeleton, jointed → insect, crab

• Echinodermata: radial (adult), spiny, coelom → starfish, sea urchin

• Chordata: bilateral, notochord, coelom → fish, bird, mammal

1. Define segmentation, explain its functions, and note the animal phyla where it occurs.

• Segmentation: body in repeating units

• Functions: helps movement, specialization, limits injury

• Phyla: Annelida, Arthropoda, Chordata

1. Compare the characteristics of the four major arthropod lineages. Note examples of each.

• Chelicerates: 2 body parts, 6 pairs legs, no antennae → spiders, scorpions

• Myriapods: many segments, 1–2 pairs legs per segment → centipedes, millipedes

• Crustaceans: 2 antennae, mostly aquatic, branched legs → crabs, lobsters

• Hexapods: 3 body parts, 3 pairs legs → insects (beetles, ants)

1. Describe the common characteristics of insects.

• Body: 3 segments – head, thorax, abdomen

• Legs: 3 pairs (6 total)

• Antennae: 1 pair

• Wings: usually 2 pairs (some have 1 pair or none)

• Exoskeleton: hard outer covering

• Metamorphosis: undergo complete or incomplete metamorphosis

• Respiration: through tracheae (tubes)

1. Describe the defining characteristics of the chordates.

• Notochord: flexible rod along the back (supports body)

• Dorsal hollow nerve cord: develops into brain and spinal cord

• Pharyngeal slits: openings in throat area (for gills or other functions)

• Post-anal tail: tail extends beyond anus at some stage

• Endostyle or thyroid gland: involved in metabolism and filter feeding