Introduction to animals
Introduction to
Animals
Copyright cmassengale
Traits
Characteristics of Animals
• All multicellular (metazoans)
• Eukaryotes (cells with nucleus &
organelles)
• Ingestive heterotrophs (take in food and
internally digest it)
• Store food reserves as glycogen
Support Systems
• Have some type of skeletal support
• Endoskeleton inside and made of cartilage
&/or bone(Vertebrates)
• Exoskeletons found in arthropods
– Cover the outside of the body
– Limit size
– Must be molted making animal vulnerable
to predators
Cicada Molting Exoskeleton
Support Systems
• Worms and
echinoderms (starfish)
have fluid-filled
internal cavities giving
them support
• Called hydrostatic
skeletons
Movement
• Animals such as sponges may be
sessile (attached & non-moving)
• Animals that move very little are said
to be sedentary (clam)
• Animals that can move are motile
• Have muscular tissue to provide
energy for movement
SESSILE
Sponge
SEDENTARY
Chiton
MOTILE
Cheetah
Reproduction in Animals
• All animals are capable of sexual
reproduction
• Some animals like sponges and
earthworms are hermaphrodites
producing both eggs and sperm
• Hermaphrodites may exchange sperm
and NOT fertilize their own eggs
Reproduction in Animals
• Females of some animals produce
eggs, but the eggs develop without
being fertilized
• Called Parthenogenesis
• New offspring will be all female
Parthenogenesis occurs in some
fishes, several kinds of insects, and a
few species of frogs and lizards
Parthenogenesis in the Komodo Dragon
Levels of Organization
• Sponges are the ONLY animals that have
just the cellular level
• All other animals show these levels – cell,
tissue, organ, and system
• Cells may specialize (take own different
shapes and functions)
• Cells are held together by cell junctions to
form tissues
Atom
Molecule or
compound
Levels of Organization
Organ
Tissue
Organ
system
Organelle
CELL
Life begins
Organism
Invertebrate
groups
Characteristics of Invertebrates
• Simplest animals
• Contain the greatest number of different
species (2 million)
• Most are aquatic (found in water)
• Do NOT have a backbone
• Includes sponges, cnidarians, flatworms,
roundworms, annelids, mollusks, arthropods,
and echinoderms
Sponge - Porifera
Osculum of
Sponge
Sea Anemone - Cnidaria
Tentacles of Sea Anemone
More Cnidarians
Brain Coral
Red jellyfish
Flatworms - Platyhelminthes
Marine Flatworm
Planarian
Roundworms (Nematoda) and Segmented
Worms (Annelida)
Nematode
Leech (segmented worm)
Mollusca (With and Without Shells)
snail
nautilus
scallop
nudibranch
octopus
Arthropoda (insects, spiders, crustaceans,
horseshoe crab)
spider
crayfish
Horseshoe crab
Dung beetle
Echinoderms
Sea fan (crinoid)
starfish
Brittle star
Sand dollar
Sea cucumber
Vertebrate
Groups
Vertebrata
• More complex animals (58,000
species)
• Most have a backbone made up of
individual bones called vertebrae
• From simplest to most complex, the
phylum includes: fish, amphibians,
reptiles, birds, and mammals
Vertebrate Backbone
Vertebrata
• Vertebrates have endoskeletons
(internal)
• Some vertebrates have skeletons of
cartilage (sharks, rays, and skates)
• Other vertebrates have skeletons of
bone and cartilage (reptiles, birds, &
mammals)
Fish
lancelet
ray
damselfish
anglerfish
Amphibia
salamander
toad
frog
newt
Reptilia
Turtle
Snake
Lizard
Alligator
Birds - Aves
hummingbird
ostrich
lovebirds
Mammalia
Body
Areas
Surfaces
•
•
•
•
Dorsal – back or upper surface
Ventral – belly or lower surface
Anterior – head or front end
Posterior – tail or hind end opposite the
head
• Oral surface (echinoderms) – is where the
mouth is located (underside)
• Aboral surface (echinoderms) – is
opposite the mouth (top side)
Surfaces (Most Animals)
DORSAL
POSTERIOR
ANTERIOR
VENTRAL
Surfaces (Echinoderms)
ORAL
ABORAL
mouth
Symmetry
Body Symmetry
Body Symmetry
• Symmetry is the
arrangement of body
parts around a central
plane or axis
• Asymmetry occurs when
the body can’t be
divided into similar
sections (sponges)
Body Symmetry
• Radial symmetry occurs when body
parts are arranged around a central
point like spokes on a wheel
(echinoderms)
• Most animals with radial symmetry
are sessile (attached) or sedentary
(move very little)
Body Symmetry
• Bilateral symmetry occurs when
animals can be divided into equal
halves along a single plane
• Organisms will have right and left
sides that are mirror images of each
other
• More complex type of symmetry
Body Symmetry
• Animals with bilateral symmetry are
usually motile
• Animals have an anterior and
posterior ends
• Show cephalization (concentration of
sensory organs on the head or
anterior end)
Segmentation
Segmentation
• Occurs whenever animal bodies are
divided into repeating units or segments
• Found in more complex animals
• Earthworms show external segmentation
• Humans show internal segmentation
(backbone)
• Segments may fuse (cephalothorax)
Segmentation
cephalothorax
Tissues
Tissue Development
Stage One
Cleavage- Zygote (fertilized egg) undergoes
rapid cell divisions called cleavage
• Forms a hollow ball of cells called the
blastula
Blastula
•The blastocoel is the center cavity
of the blastula with 1 germ layer
(blastoderm)
Tissue Development
Stage 2-Gastrulation
• The blastula
INVAGINATES (folds
inward at one point)
forming a GASTRULA
• The opening is called the
blastopore
• The center is the
primitive gut or
Archenteron
Archenteron
blastopore
Tissue Development
• Blastopore may become the mouth
(Protostome) or anus (Deuterostome)
• Protostomes (mollusks, arthropods,
& annelids)
• Deuterostomes (echinoderms &
vertebrates)
• Some animals form a middle germ
layer called mesoderm
Embryonic Development
Germ Layers
• Form tissues, organs, & systems
• NOT present in sponges
• Ectoderm (outer) – forms the outer
layer of skin, nails, hair and the
nervous system including sense
organs.
• Endoderm (inner) – lining of the
urinary, reproductive and digestive
systems. Also forms the pancreas liver,
lungs and gills
• Mesoderm (middle) – forms skeleton,
muscles, circulatory system & other
systems
Body Layers (Germ Layers)
• Sponges have NO tissues or organs, only
specialized cells
• Cnidarians like jellyfish & coral have only
two body layers(Endo and Ecto). One
body opening (mouth/anus) called
gastrovascular cavity
• Cnidarians have outer epidermis & inner
gastrodermis with jelly-like mesoglea
between the layers
Body Layers (Germ Layers)
• All worms,
mollusks,
arthropods,
echinoderms, and
vertebrates have
three cell layers
– Ectoderm
– Endoderm
– mesoderm
Protostomes “First Mouth”
Types of development of embryos in animals with a
coelom
• the blastopore develops into a mouth, and a
second opening forms at the other end of the
archenteron, forming an anus.
• Undergo spiral cleavage
• process of coelom formation is called schizocoely
or “split body cavity.”
• mollusks, arthropods, & annelids
Deuterostomes
“Second Mouth”
Types of development of embryo in animals with a
coelom
• the blastopore develops into an anus, and a second
opening at the other end of the archenteron
becomes the mouth.
• Undergo radial cleavage
• This process of coelom formation is called
enterocoely which means “gut body cavity.”
• echinoderms & vertebrates
Embryonic Cleavage
Cleavage
• Cleavage – rapid mitosis (cell
division) of zygote
• Radial Cleavage – cells divide
parallel or perpendicular to
axis to each other
Cleavage
• Spiral Cleavage – cellular
divisions occur diagonally,
in a twisting pattern
Body Cavities
Coelom - Body Cavity
• Internal body cavity fully lined with mesoderm
• Body organs suspended in this cavity
• Mollusks, annelids, arthropods, chordates, and
echinoderms are coelomates
Coelom - Body Cavity
• Acoelomate animals have solid bodies
filled with cells and tissues
• Acoelomate animals include sponges,
cnidarians, & flatworms
Coelom - Body Cavity
• Pseudocoelomate animals
(roundworms) have a functional body
cavity NOT fully lined with mesoderm