AP Biology
Lecture #49
Non-Vertebrate Animals
Characteristics of Animals
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Animals are:
Multicellular
Heterotrophs
Eukaryotic
Have tissues and differentiated cells
Eat
Reproduce and Develop
1.3 millions species have been identified,
estimates of 10 to 200 million exist
Early Embryonic Development
• Sperm and egg meet
through fertilization
to form a zygote
• The zygote undergoes
mitosis, called
cleavage
• A blastula, or multicelled hollow ball
forms
• These cells form
Eras of Animal Life
• Neoproterozoic Era (1 B  542 mya): First
fossilized animals are from this time period.
• Paleozoic Era (542 251 mya): the Cambrian
explosion occurs, huge diversity of animal
species, including vertebrates, evolve
• Mesozoic Era (251  65.5 mya): animal life
spreads across the planet
• Cenozoic Era (65.5 mya present): dinosaurs,
birds, and mammals all evolve
Body Plans
• Animals can have radial symmetry, in which
the parts of an animal radiate out from the
center (starfish)
• Or they can have bilateral symmetry, with
equal left and right sides (lobsters, humans)
• Animals with a distinct forward facing head at
the top of the body have gone through
cephalization.
Tissue Layers
• The tissue layers of an animal
embryo are called germ layers,
and form organs.
• The ectoderm is the outermost
layer and forms the skin and
nervous system.
• The endoderm is the inner layer
of the embryo and turns into the
digestive system.
• Some animals have a third layer,
called the mesoderm, which
forms the other body organs.
Body Cavities
• Some animals have body cavities, a fluid-filled
space that separates the digestive tract from
the outer body wall, this is called a coelom.
• Pseudocoelomates have a body cavity that is
formed from a different type of tissue.
• Acoelomates do not have body cavities.
Protostomes and Deuterostomes
• Protostomes, like
worms and bugs,
develop a mouth first
during fetal
development.
• Deuterostomes, like
people and starfish,
develop an anus before
they develop mouths.
Invertebrates
• Invertebrates are animals without a backbone.
• The main phyla we will talk about are:
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Porifera
Cnidaria
Platyhelminthes
Nemotodes
Mollusks
Annelids
Arthropods
Echinodermata
Some chordates
Parazoa
• Invertebrates: animals
without backbones
• Closest lineage to
protists
• Loose federation of
cells (unspecialized); no
tissues
• Phylum.: (only one)
Porifera (sponges)
The Sponges – Phylum Porifera
• Phylum Porifera are the sponges.
• They may have radial symmetry, or no
symmetry.
• They are non-motile filter feeders.
• Individual cells are specialized, but they have
no true organs.
General Information
Size range –
1 cm to
2 meters in diameter
Giant Barrel sponges
Eumetazoa: Animals with true body tissue
The Radiata, I
• Diploblastic
• Radial symmetry
• Phylum: Cnidaria (hydra, jellies, sea
anemones, corals)
– tissues, but no organs
– two cell layers
– predators
• tentacles surround
gut opening
• extracellular
digestion
– release enzymes
into gut cavity
– absorption by cells
lining gut
Stinging cells of Cnidarians
mouth
tentacles
sensory
cell
stinging
cell
hydra
trigger
stinging cell
with nematocyst
discharged
nematocyst
undischarged
nematocyst
The Radiata, II
• Phylum: Ctenophora
(comb jellies)
• 8 rows of comblike plates
of fused cilia (largest
animals that use cilia for
locomotion)
• Tentacles with colloblasts
(adhesive structures that
capture prey)
Eumetazoa: The Acoelomates
• Phy: Platyhelminthes
(flatworms, flukes, tapeworms)
• Bilateral; no body cavity
• Predators, scavengers,
parasites
• Some cephalization~
development of brain
concentration of sense organs in
head
ectoderm
mesoderm
acoelomate
endoderm
Eumetazoa: Pseudocoelomates, I
• Body cavity partially
derived from
mesodermally derived
tissue
• Phylum: Rotifera
• 1st with a complete
digestive tract
• Hydrostatic skeleton
• Parthenogenesis: type of
reproduction in which
females produce offspring
from unfertilized eggs
Eumetazoa: Pseudocoelomates, II
C. elegans
• Phylum: Nematoda
(roundworms)
• Very widespread group of
animals (900,000 sp. ?)
• Cuticle (tough exoskeleton)
• Decomposition and nutrient
cycling
• Complete digestive track; no
circulatory system
many are parasitic
• hookworm
• Trichinella spiralis
The Coelomates: Protostomes, I
• Phylogenetics debated….
• Phy: Nemertea (proboscis and
ribbon worms)
• Complete digestion and closed
circulatory system (blood)
• Phy: the lophophorates (sea
mats, tube worms, lamp shells)
• Lophophore: Circular shaped
body fold with ciliated
tentacles around the mouth
The Coelomates: Protostomes, II
• Phylum: Mollusca (snails,
slugs, squid, octopus, clams,
oysters, chiton)
• Soft body most protected by a
hard shell of calcium carbonate
• Foot (movement), visceral
mass (internal organs); mantle
(secretes shell); radula (rasplike scraping organ)
true coelem
• increases complexity &
specialization of internal
organs
• There are 3 types of mollusks:
• Gastropods: sea slugs, snails and slugs
• Bivalves: clams, oysters, mussels, and scallops
(2 hinged shells)
• Cephalopods: built for speed and motility,
include squid and octopi; have sophisticated
sense organs.
Class Cephalopoda
squids, octopus, cuttlefish, nautilus
The Coelomates: Protostomes, III
• Phylum: Annelida
(earthworms, leeches,
marine worms)
• True body segmentation
(specialization of body
regions)
• Closed circulatory system
• Metanephridia: excretory
tubes
• “Brainlike” cerebral
ganglia
• Hermaphrodites, but
cross- fertilize
fan worm
leech
The Coelomates: Protostomes, IV
• Phy: Arthropoda trilobites
(extinct); crustaceans (crabs,
lobsters, shrimps); spiders,
scorpions, ticks (arachnids);
insects (entomology)
• 2 out of every 3 organisms
(most successful of all phyla)
• Segmentation, hard
exoskeleton (cuticle)~ molting,
jointed appendages; open
circulatory system
(hemolymph); extensive
cephalization
Arthropod groups
arachnids
8 legs, 2 body parts
spiders, ticks, scorpions
crustaceans
gills, 2 pairs antennae
crab, lobster, barnacles,
shrmp
insects
6 legs, 3 body parts
The Coelomates: Deuterostomes, I
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Phylum: Echinodermata (sea
stars, sea urchins, sand
dollars, sea lilies, sea
cucumbers, sea daisies)
Spiny skin; sessile or slow
moving
Often pentaradial
Water vascular system
They are radially symmetrical
as adults, and bilateral as
larvae.
Water Vascular System
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Madreporite
stone canal
ring canal
radial canal
lateral canals
Ampulae
tube feet