Lab 2 - Animal Phylogeny (BIOL 1030)

caudal

tail region of an animal

posterior

tail or hind end of an animal

anterior

front or head end of an animal

cephalic

head region, specifically

ventral

underside of an animal

dorsal

back or uppermost of an animal

distal

structure farthest away from a point of reference

e.g. the wrist is distal to the shoulder

proximal

structure nearest to a point of reference

e.g. elbow is proximal to the shoulder

oral

mouth region

what clade to all animals belong to? (animals are monophyletic)

Metazoa

• synonymous with the kingdom Animalia

how many phyla are within the metazoa clade

around 35

Sponges ( 10 phyla)

Porifera

Corals, anemones, jellies (10 phyla)

Cnidaria

Seat stars, sea cucumbers, sea urchins, etc (10 phyla)

Echinodermata

Fish, amphibians, reptiles (including birds), mammals, etc. (10 phyla)

Chordata

Flat worms (10 phyla)

Platyhelminthes

Segmented worms (10 phyla)

Annelida

Chitons, slugs, snails, clams, etc. squid and octopi (10 phyla)

Mollusca

Lampshells (10 phyla)

Brachiopoda

Round worms (10 phyla)

Nematoda

Spiders, etc.., centipedes, etc.., crustaceans, insects.. (10 phyla)

Arthropoda

animal clades

smaller than the Metazoa but bigger than phyla

animal life cycle stage 1

cleavage

• series of rapid cell cycle with short to no G1 or G2 phases

• cell number increased, but the size of the embryo does not change, the cells just get smaller

• results in solid balls of cells

morula

solid balls of cells from the cleavage stage that eventually hollow outs out to become a blastula

how many ways can cleavage occur

2 ways

blastula

hallow ball formed at the end of cleavage that is typically one cell “layer” thick

animal life cycle stage 2

gastrulation

• one-layered embryo folds in on itself to produce a multiple layered embryo - the gastrula

  *note that cell division never stops*

• gastrula has the beginnings of the digestive tract, the archenteron which starts with one opening, the blastopore (second opening to this developing gut will form in most animals)

define tissue

all animals have layers of cells, working together to perform a specific function

• however not all animals have true tissues

true tissues

separated from each other by a thin protein layers

• higher level of communication between cells/organ systems

what divides the Eumetazoa clade into two smaller clades

body symmetry

body symmetry

describes how an organism can be “cut” in half to produce two equal and opposite halves - essentially mirror images

plane of symmetry

imaginary line in body symmetry

asymmetry

no body pattern

• these animals could not be cut in “half”

• e.g. Parazoas

radial symmetry

numerous ways to cut them in half

bilateral symmetry

one single plane of symmetry

• most animals today

cephalization

collection of sensory organs at the anterior end speeds up reaction time and allows for more complex and coordinated behaviors

• undoubtedly advantageous

clade that has two distinct body plans

radiata

two body plans of radiata clade

1. polyp: sessile

2. medusa: free moving

two major patterns in the embryos of animals with true tissues

• two tissues layers

• three tissue layers

what do all eumetazoans have

• ectoderm - an outer layer

• endoderm - inner layer

diploblastic

animals that only have the two ectoderm and endoderm layers

mesoderm

a third layer in the 8 phyla that have true tissues

triploblastic

animals with all three layers

archenteron

primitive gut that forms during gastrulation

blastopore

single opening of the archenteron (primitive gut)

• blastopore opening persists throughout development as an opening to the animal’s digestive tract

• opening it forms the basis of the subdivision of the clade Bilateria

in what type of animals intestinal tracts for adults can have two opening one of which is formed in to blastopore

triploblastic animals

• blastopore of these animals may become either the mouth or the anus

protostomes

animals whose blastopore becomes the mouth (mouth first, and anus may or may not form second)

• e.g. a lobster

deuterostomes

blastopore becomes the anus

• mouth always forms from the second opening to the gut

• translates to “second mouth”

• e.g. a frog

what 2 phyla does the Deuterostomia clade include

Echinodermata and Chordata

4 traits unique to chordates

1. dorsal nerve chord (hollow)

2. bilateral symmetry & triploblastic

3. closed circulatory systems (pharyngeal slits)

4. notochord, post-anal tail, central nervous system

3 clades that chordate divide into

1. Cephalochordata

2. Urochordata

3. Vertebrata

Cephalachordata

• have all 4 chordate characteristics but are the basal taxon of chordates

• notochord - (main skeletal feature, extends from anterior to posterior tip, large)

• dorsal hollow nerve cord - dorsal to the notochord, the “nervous system” - no true brain

• mouth & pharynx - anterior end of the W.M. , specialized for collecting food

• pharyngeal gill slits - creates a water current (assists with suspension feeding) - so water can pass over these slits but not enter the gut tract

• post-anal tail (found in W.M) - caudal end (will not see post anal tail in the C.S)

Urochordates

• more closely related to vertebrates than cephalochordates

• key chordate features most prominently in larval stages

• gill slits (larval) - in large head like barrel shaped portion of body where post anal tail extends

• notochord & dorsal hollow nerve cord - within long tail

• within the head: rudimentary bran and sensory organs - where food is gathered

• in adult stages = no notochord or dorsal hollow nerve cord, but a simple nerve ganglion

3 major clades within the Bilateria

1. Deutrosomia

2. Lophotrochozoa

3. Ecdysozoa

   *these clades were established on molecular homologies*

   members of each clade grow

Bilateria clade that grows continuously

Lopjotrochozoa

Bilateria clade that grows by spurts in a stepwise pattern

Ecdysozoa

Bilateria clade that’s covered by hardened covering or cuticle that prevents continual growth

Ecdysozoans ( nematodes and arthropods)

• must moult and grow rapidly before creating a new cuticle