bio chapter 27 - animal diversity

all animals are…

consumers, monophyletic

almost all animals are…

tissue having, definite shape, bilateral symmetry

differentiation is irreversible except in…

sponges

when do cells become specialized?

embryonic development

sponge cells

• can change function (differentiate)

  • prevents them from forming clearly defined tissues (organs)

evolution of specialized tissue…

fosters evolutionary diversification

triploblastic (most animals)

have 3 layers, ectoderm, mesoderm, and endoderm

what the 3 layers become

• outer ectoderm - rise to outer covering and NS

• mesoderm - skeleton and muscles

• inner endoderm - digestive system

outer ectoderm

rise to outer covering and NS

mesoderm

skeleton and muscles

inner endoderm

digestive system

protosome

can be divided into

• lophotrochozoa

• ecdysozoa

mouth develops from blastopore (in some both mouth and anus form)

deuterosome

anus develops from blastopore

• echinoderms and chordates

protosomes are divided into…

• lophotrochozoans

  • named for their larvel and feeding structures

• ecdysozoans

  • named for their trait of periodic molting that accompanies growth

lophotrochozoans

named for their larvel and feeding structures

ecdysozoans

named for their trait of periodic molting that accompanies growth

king animalia (two branches)

• parazoa (near animals)

  • lack definite symmetry with no tissues (sponges and phylum Porifa)

• eumetazoa (true animals)

  • definite shape and symmetry. all have tissue and most have organ systems.

• both descended from a common ancastor whos closest living relative is the choanoflagellates

• some recent studies place Porifa within Eumetazoa (specialized tissue may have evolved twice, or alternatively, specialized tissue may have evolved once and then been lost in sponges)

parazoa (near animals)

lack definite symmetry with no tissues (sponges and phylum Porifa)

eumetazoa (true animals)

definite shape and symmetry. all have tissue and most have organ systems.

Porifa

• lack symmetry and specialized tissue

• sponges are the simplist animals

• although some cells are highly specialized, still no tissue

• do possess cell recognition

• cell recognition - cells can recognize and identify other cells, even after being separated.

• sponges have genes for some molecules that help cells stick together. however, they don’t form the same specialized connections that cells in true tissues do.

• some recent studies place Porifa within Eumetazoa (specialized tissue may have evolved twice, or alternatively, specialized tissue may have evolved once and then been lost in sponges)

cell recognition

cells can recognize and identify other cells, even after being separated.

cnidarians possess…

both symmetry and true tissue

• radial symmetry - body organized around a central axis

  • offers an advantage of interacting with all sides of environment

radial symmetry

body organized around a central axis

• offers an advantage of interacting with all sides of environment

flatworms and rotifers are…

very simple bilaterians

bilaterians

major clade of animals characterized by bilateral symmetry

divided into 2 clades

• protosomes and deuterostomes

• acoel flatworms

Phylum platyhelminthes

unsegmented, acoelmate worms. have dorsoventrally flattened body

• 56,000 species

• ciliated, soft-bodied, broad and flat

• solid, other than the incomplete digestive cavity

• simplest bilaterals but have complex structures, like their reproductive apparatus, and the most complex life cycle

• incomplete digestive trast

• dorsoventrally flattened bodies

• have some of the most complex life cycles

mollusks are…

a large and diverse group

mollusk has 3 distinct parts

1. head-foot - muscular, adapted for several functions

2. visceral mass - central section with organs

3. mantle - heavy fold of tissue wrapped around the visceral mass like a cape, with the respiratory organs (gills or lungs) positioned on its inner surface, like the lining of a coat

• 7 or 8 recognized classes of mollusks

• mollusks are among the first animals to develop and excretory system

  • tubular structures called nephrida (type of kidney) gathers waste from the coelom to discharge into the mantle cavity

3 most common clades of mollusks

• gastropods (snails and slugs)

  • all terrestrial mollusks

• bivalves (clams, oysters, scallops, and mussels)

• cephalopods (octopuses, squids, nautiluses)

clade of mollusk that includes all terrestrial mollusks

gastropods (snails and slugs)

clade of mollusk with clams

bivalves (clams, oysters, scallops, and mussels)

clade of mollusks with squids

cephalopods (octopuses, squids, nautiluses)

how many recognized classes of mollusks are there?

7-8

bivalves (mollusks)

secrete a two-part shell with a hinge, they filter feed by drawing water into their cell

cephalopods (mollusks)

have a large brain and modified mantle cavity that creates a jet propulsion system

mollusk excretory system

tubular structures called nephrida (type of kidney) gathers waste from the coelom to discharge into the mantle cavity

Nephrida (mollusks)

a paired, tube shaped invertebrate excretory organ

the annelid body is composed of…

ringlike segments

annelid body plan

• tube within a tube

  • digestive tract is suspended within the coelom (which is a tube)

  • coelom - tube running from mouth to anus (Earthworms, mollusks, vertebrates, annelids)

• body segments are visible as a source of ring'-like structures running the length of the body

• in each cylindrical segment, the excretory and locomotor organs are repeated.

  • in marine annilids, each also has a set of reproductive organs

• the body fluid within the coelom of each segment creates a hydrostatic skeleton that gives the segments rigidity, like an inflated balloon

• because each segment is separate, each is able to expand and contract independently, allowing the worm to move in complex ways

• internally, the segments are divided from one another by partitions called septa

• despite septa separating the segments, materials and biological signals do pass through

• a closed circulatory system carried blood the length of the animal, anteriorly in the dorsal vessel and posteriorly in the ventral one.

• ventral nerve cord connects the ganglia in each segment with another and with the brain

  • there neural connections allow the worm to function as a unified, coordinated organism.

• coelomates

coelom

tube running from mouth to anus (Earthworms, mollusks, vertebrates, annelids)

septa

internal walls or partitions that divide a body cavity into separate compartments

how to annelids move?

by contracting their segments

two phyla of mostly marine animals (lophoporates)

1. bryoza

2. brachiopoda

• characterized by by a lophophore

• lophophore - circular or U-shaped ridge around the mouth bearing one or two rows of ciliated tentacles into which the coelom extends

  • surface for gas exchange

  • cilia of lophophore guides the organic detritus and plankton on which the animal feeds to the mouth

lophophore

circular or U-shaped ridge around the mouth bearing one or two rows of ciliated tentacles into which the coelom extends

nematodes consist of…

many different kinds of round worm

nematodes

bilaterally symmetrical, unsegmented worms

• covered by a flexible, thick cuticle, which they shed by molting

• their muscles are a layer beneath the epidermis and extend along the length of a worm, rather than encircling it’s body.

• pseudocoelomate

arthropods

Characterized by chitinous exoskeleton and jointed appendages

• most successful of all animals

• 1M+ species, 2/3 of all species on Earth

• 200m insects per human

• few marine insects

arthropods body

exhibit a segmented body with a rigid exoskeleton and jointed appendages.

• open circulatory system with a longitudinal muscular heart near the dorsal surface

tagmata

specialized body segments.

• head, thorax, abdomen (arthropods)

tagmatization

fusion of segments

4 classes of arthropods

• 1. Hexapoda (Insects and Relatives)

• 2. Chelicerata (Arachnids and Relatives)

• 3. Crustacea (Crustaceans)

• 4. Myriapoda (Myriapods)

chelicerae

the paired, preoral mouthparts belonging to the subphylem/class Chelicerata

chelcerata tagmata

1. Anterior prosoma (bears all appendages)

2. Posterior opisthoma (reproductive organs)

exclusively marine tagmata

horseshoe crabs, sea spiders

chelcerae characteristics

• 4 pairs of walking legs

• most are carnivorous, but mites are moslty herbivorous

• most cannot consume solid food

  • instead suck up liquids with the muscular pharynx, including solid food liquified by digestive enzymes injected by the chelcerae

crustacea examples

crabs, shrimp, lobsters

crustacea tagmata

• cephalon

• thorax

• abdomen

(cephalon and thorax together is the cephalothorax)

cephalothorax

cephalon and thorax

crustacea characteristics

• most have two pairs of antennae, 3 pairs of appendages for chewing, and varying number of legs

biramous

divided into two parts

nauplius

earliest free-swimming larvel stage of most crustaceans (monophyletic)

complete metamorphis (crustacea some)

• wormlike larvel stage

• resting stage (pupa or chrysalis)

• final molt into adult form

some crustacea undergo metamorphis, some just go through a series of molts

some crustacea undergo metamorphis, some just go through a series of molts

Class myriapoda

centipedes and millipedes

• The bodies of centipedes (subclass chilopoda) and millopedes (subclass diplopoda) consist of a segmental head region

deuterostomes are composed of…

• echinoderms

• chordates

echinoderms (deuterostomes)

• deuterostome development and exoskeleton

• endoskeleton composed of hard, calcium carbonate plates that lie just beneath the delicate skin

the endoskeleton

• ossicles - delicate epidermis that stretches over an endoskeleton

  • individual skeeltal elements are loosly joined - asteroids (sea stars)

  • ossicles form a rigid shell (test) - echinoids (sea urchins and sand dollars)

• ossicles are sometimes equipped with pores

  • through these pores extend tube feet, part of the water vascular system that is a unique feature of this phylum

ossicles

delicate epidermis that stretches over an endoskeleton

the water vascular system

• radially organized

  • from the ring canal, which encircles an animals esophagus, a radial canal extends into each branch of the body

• water enters the system through the madreporite (a sieve-like plate) which is usually the animal’s surface

  • then flowers to the ring canal through a stone canal

  • then each radial canal extends through short side branches into the hollow tube feet

    • in some echinoderms, the tube feet has a sucker at the end.

four features of chordates

1. a single, hollow nerve cord runs beneath the dorsal surface. in vertebrates, the dorsal nerve cord differentiates into the brain and spinal cord

2. a flexible rod, the notochord, forms on the dorsal side of the archenteron in the early embryo and is present at some developmental stage in all chordates

   1. notochord is rightt below nerve chord

   2. notochord may persist in some chordates, in others it is replaced duing embryonic development by the vertebral column that forms around the nerve chord

3. pharyngal slits connect the pharync (muscular tube that links the mouth cavity and esophagus) with external environemtn

   1. in terrestrial vertebrates, the slits don’t connect to the ouside and are called pouches

   2. pouches are present in the embryos of all vertebrates

      1. they become slits and open to outside in animals with gills

      2. means all vertebrate embryos have aquatic origins

4. have a postanal tail that extends beyond the anus. nearly all other animals have a terminal anus

first clade that branches off

choanoflagellates (protists) - (ONLY ONE THAT ISNT METEZOA) (no coelom)

second clade that branches off

porifera (parazoa) (NOT eumetezoa) (metezoa) (no coelom)

3rd - 5th clades branching off

ctenophora, placozoa, cnidaria (no coelom)

mollusk characteristics

body covered by a mantle, often with shells

chordata characteristics

• presence of a notochord

bilaterally symmetrical animals divided into

• protostomes

• deuterostomes

in contrast to the Parazoa, all eumetezoans have tissues and some kind of symmetry

in contrast to the Parazoa, all eumetezoans have tissues and some kind of symmetry

bilateria 2 major clades

• acoel flatworms

• protostomes and deuterostomes

spiral cleavage

a pattern of cell division during early embryonic development where cells divide at an angle to the axis of the embryo, creating a spiral arrangement

water-vascular system in echinoderms

water enters through the

1. water vascular system

2. through the madreporite

3. stone canal (reinforced by calcium carbonate)

4. ring canal

5. radial canals

chelicerates

• mostly carnivorous

• 4 pairs of walking legs

echinoderms

organisms with spiny skin that exhibit pentradial symmetry as adults, and have an endoskeleton made of calcium carbonate plates

features of chordates

• a single, hollow nerve chord

• pharyngial slits (pouches)

• notochord

• postanal tail

ossicles in asteroids, echinoids, and sea cucumbers

• asteroids - individual skeletal elements are loosely joined to one another

• echinoids - ossicles abut one another tightly, forming a rigid shell

• sea cucumbers - ossicles are widely scattered, so the body wall is flexible

open circulatory system

a circulatory arrangement where fluid is pumped by a heart into an open body cavity and bathes the internal organs directly, rather than staying enclosed within a continuous network of blood vessels

closed circulatory system

is a network where blood stays inside a continuous circuit of blood vessels and never directly mixes with body tissues

coelom

the main fluid-filled body cavity in most triploblastic animals (animals with three primary germ layers) that is completely lined with tissue derived from the middle embryonic layer, the mesoderm

pseudocoelom

a fluid-filled body cavity that lies between the endoderm (gut) and the mesoderm (muscle/body wall) in certain invertebrates, meaning it is not completely lined by mesoderm

coelom vs pseudocoelom

a true coelom is completely lined with mesoderm, while a pseudocoelom is only partially lined with mesoderm.

arthropoda classes

• insecta - insects, ants, butterflies (6 legs)

• arachnida - spiders, scorpions, ticks (8 legs)

• crustacea - lobsters, crabs, shrimp (usually 10+)

• chilopoda - centipedes (1 pair per body segment)

• diplopoda - millipedes (2 pairs per body segment

coelacanths

lobe-finned fishes

chordata orders

• squamata - lizards and snakes (class reptilia)

• caecilians - (class amphibia)

• caudates - salamanders and newts (class amphibia)

• anurans - frogs and toads (class amphibia)

squamata (order)

lizards and snakes (class reptillia) (phylum chordata)

caecilians (order)

legless amphibians (class amphibia) (phylum chordata)

caudates (order)

salamanders and newts, adults retain tails (class amphibia) (phylum chordata)

anurans (order)

frogs and toads, adults typically lack tails (class amphibia) (phylum chordata)