bio chapter 27 in class

closest relatives of animals

opisthokonta - supergroup including

• fungi

• choanoflagellates

• animals

metezoa (animals) distinguished by…

multicellularity

animal characteristics

• eukaryotic

• multicellular

• heterotrophic

• mobile

• no cell walls

• most reproduce sexually

key transitions in animal evolution

• tissues

• symmetry

• body cavity

• patterns of development

• segmentation

porifa (parazoa)

• about 7000 marine species and 150 freshwater speciez

• closest to choanoflagellates

• tissues, symmetry

• larve and adults: free swimming vs sessile

parazoa species

sponges

sponge feeding and anatomy

• water moved by flagellated choanocytes

• Large or small body cavity and chambers

• choanocytes/collar cells - flagella move water through the collar.

• endocytosis and intracellular digestion

• amoebocytes - a motile, amoeba-like cell found in the bodies of various invertebrates, including sponges, mollusks, echinoderms, and horseshoe crabs.

• passing through a screen

choanocytes/collar cells

a specialized flagellated cell found lining the internal chambers of sponges

amoebocytes

a motile, amoeba-like cell found in the bodies of various invertebrates, including sponges, mollusks, echinoderms, and horseshoe crabs.

colonial

group of identical or similar individual organisms that love closely together in a connected, cooperative, association

eumetazoa distinguished by 2 evolutionary innovations

1. true tissues

2. symmetry

radially symmetrical animals

• cnidarians

• ctenophores

both are

• no cephalization

• dipoblastic - an embryonic condition where an organism develops from two primary germ layers (the ectoderm and the endoderm)

• endoderm - gut lining

• ectoderm - outer covering

dipoblastic

an embryonic condition where an organism develops from two primary germ layers (the ectoderm and the endoderm)

ctenophora are the…

comb jellies

cnidarians

• jellyfish, corals, hydrozoans, sea anemones

• have two body forms

  • medusa - mobile, usually mouth down

  • polyp body form - sessile, usually mouth up

    • corals

    • sea anemones

    • hydrozoans - polyp or medusa, many are colonial

cnidarians 2 body forms

• medusa - mobile, usually mouth down

• polyp body form - sessile, usually mouth up

cnidarian feeding

• extracellular digestion - a biological process in which organisms break down complex food particles or organic matter into smaller, absorbable molecules outside their cells

• release enzymes to digest pray in gastrovascular cavity, absorb nutrients

extracellular digestion

a biological process in which organisms break down complex food particles or organic matter into smaller, absorbable molecules outside their cells

stony corals

• most important reef builders

• deposit calcium carbonate cups for each plyp; some other corals use different materials

bilaterians are…

tripoblastic

bilaterians

• blastopore

• archenteron

• blastula (to grastula)

• endoderm - digestive tract

• mesoderm - skeleton and muscles

• ectoderm - body covering and nervous system

acoelomates

lacks a coelom

coelom

fluid-filled cavity between the body wall and the digestive tract

pseudocoelomates

fluid filled cavity in invertebrate animals that isn’t completely lined by the mesoderm

most animals have a

coelomate

• cushioning and flexibility for organs

• hydrostatic skeleton in softbodied animals

• in vertebrates, the fluid is gas

hydrostatic skeleton

a flexible skeletal structure supported by fluid-filled internal cavities and hydrostatic pressure rather than rigid bones or hard shells

deuterostomes

• blastopore forms anus

• radial cleavage

• indeterinate early development

• coelomates

protostomes

• blastopore forms mouth

• mostly spiral cleavage

• determinate early growth

• coelomates, pseudocoelomates, acoelomates

lophotrochozoans phylums

• platyhelminthes

• mollusca

• annelids

lophotrochozoans have 1 of 2 characteristics

1. lophophore - specialized ring or horseshoe-shaped aquatic feeding organ made up of a crown of hollow, ciliated tentacles surroundiing the mouth

   1. bryoza - tiny, nearly aall are colonial

   2. brachiopoda - resemble bivalves (which are mollusks)

2. trochophore - a small, free-swimming planktonic marine larvae

   1. mollusca

   2. annelida

lophophore

specialized ring or horseshoe-shaped aquatic feeding organ made up of a crown of hollow, ciliated tentacles surroundiing the mouth

1. bryoza - tiny, nearly aall are colonial

2. brachiopoda - resemble bivalves (which are mollusks)

trochophore

small, free-swimming planktonic marine larvae

1. mollusca

2. annelida

mollusks

• 2nd most diverse phylum (after arthropods)

• some have trochophores

• most common classes

  • gastropods - snails and slugs

  • cephalopods - squid, nautilus, octopus

  • bivalves - clams, oysters, mussels, scallops.

gastropods (mollusks)

snails and slugs

cephalopods (mollusks)

squid, nautilus, octopus

bivalves(mollusks)

clams, oysters, mussels, scallops.

mollusk body plan

• mantle - may secrete shell

• foot (in cephalopods, divided into arms or tentacles)

• very small coelom

• “visceral mass”

• aquatic mollusks have gills - 2 functions

  • gas exchange

  • salt and water balance

• most have a radula

• radula - key feeding organ, a tongue-like chitinous ribbon covered in rows of microscopic teeth

2 functions of gills in aquatic mollusks

• gas exchange

• salt and water balance

radula

key feeding organ, a tongue-like chitinous ribbon covered in rows of microscopic teeth

mollusk reproduction

• most use external fertilization or sperm are taken into female from water. gastropods are internal

• zebra mussels and quagga mussels are invasive in North America

annelids

• body built of repeated units (excretory organs, ganglion, locomotion)

• may not be monophyletic

• many annelids are marine, and have a trochophore. some are terrestrial with no trochophore

  • head with cerebral ganglion - cephalization

  • ventral nerve chord

  • closed circulatory system and gasses diffuse through surfaces

  • coelom - hydrostatic skeleton

  • examples - leeches, earthworms

ecdysozoans

• molt

• molting = ecdysis

• stepwise growth

• includes arthropods and nematodes

phylum nematoda

• roundworms

• highly diverse and abundant

• unsegmented, molt, sexual life cycle

• free living heterotrophs, parasitic, some cause disease

• 30% of children in US have pinworms

arthropod morphology

• segmentation

  • head

  • maybe tagmata - head,thoprax, abdomen, cephalothorax

• exoskeleton

  • chitin and protein

  • muscle, dessication

  • ecdysis

• jointed appendages

chelicerata (arthropods)

mouthparts are chelicerae (pincers or fangs)

crustacea (arthropods)

mouthparts a mandibles; appendages are biramous (two branched) the head has two pairs of antennae

hexapoda (arthropods)

mouthparts are mandivles, the body consists of three regions: a head with one pair of antennae, a thorax, and an abdomen; appendages are uniramous

myriapoda (arthropods)

mouthparts are mandibles, the body consists of a head with one pair of antennae, and numerous segments, each bearing paired uniramous appendages

most arthropods are…

hexapoda

class chelicerata

• spiders, ticks, mites, scorpions, daddy long legs, horseshow crabs, sea spiders

• about 35k species

• chelicerae and then pedipalps are the most forward. function in feeding

• body divided into 2 tagmata

  • ANTERIOR - 6 pairs of appendages (chelicerae, pedipalps, and 4 pairs of walking legs

  • posterior - (opisthosoma) contains reproductive organs

class crustacea

• crabs, shrimps, lobsters, barnacles, crayfish, pill bugs, sand fleas, barnacles

• 3 tagmata, often cephalothorax

• 2 pairs of antennae, 3 pairs of chewing appendages, lots of legs, usually biramous

• gas exchange through gills or across cuticle

• nauplius stage - several larvel stages

class hexapoda

• insects

• most abundant and diverse animals; more than ½ of all named animal species

• 6 jointed legs, sometimes wings

• about 10^18 insects living at one time

class myriapoda

• centipedes (subclass chilopoda)

  • one pair of appendages per segment

  • carnivorous with poison fangs

• millipedes (subclass diplopoda)

  • 2 pairs per segment

  • herbivorous and stinky

deuterostome phylums

• echinoderms

• chordates

phylum echinodermata

• sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers

• endoskeleton made of calcium carbonate ossicles (plates)

• marine, symmetry?

• have a water vascular system for movement and other functions

  • madreporite —→ stone canal —→ ring canal ——> radial canal

• tube feet

phylum chordata

• nearest relatives

• fishes, amphibians, reptiles, birds, mammals

• 4 key chordate features

  • hollow dorsal nerve chord

  • notochord - cartilage, may be replaced be certebral column

  • pharyngeal slits - opening from pharynx to outside. originally for fiulter feeding

  • postanal tail

• all may be present for only part of the life cycle