WHAT IS AN ANIMAL?
CH. 26
WHAT ARE ANIMALS?
• Animals are multicellular
Eukaryotes, heterotrophic
organisms with cells that lack cell
walls.
INVERTEBRATES VS. VERTEBRATES
• Invertebrate: no vertebrate; without
a backbone
• Vertebrate: having a
backbone/spinal column
ANIMAL BODY SYSTEMS
SUPPORT
• An animal’s skeleton supports the animal’s
body and helps with movement.
• Hydrostatic (water - standing)- body cavity
that is filled with water & helps with support
• Exoskeleton (outside – skeleton): hard,
external supporting structure.
• Endoskeleton (inside – skeleton): internal
skeleton made of bone & cartilage
WHAT SKELETON DO I HAVE?
BODY SYSTEMS
• Digestive & Excretory Systems:
• Digestive system – extracts
(takes) energy and nutrients from
the food
• Excretory system – removes
waste products from the body
• Gastrovascular (Stomach –
vascular) cavity: cavity for
digestive & circulatory purpose in
cnidarians
NERVOUS SYSTEMS
• Nervous system – carries information about
the environment through the body &
coordinates responses & behaviors.
• Nerve net – simplest arrangement of nerves
• Ganglia – cluster of nerve cells that
coordinate responses
• ADVANCED: true brain with sensory
structures
BODY CAVITIES
• Bilateral symmetry – 3 basic kinds of
internal body plans
• Coelom – fluid-filled space found
between the body wall and the gut
• Acoelomate (no body cavity)
• Pseudocoelom (false coelom)
• Coelomate (True coelom) – lined with
mesoderm and wraps around the gut
CIRCULATORY SYSTEM
• Transports gases, nutrients, and other
substances within the body.
• Open circulatory system: fluid leaves the
blood vessels; washes the tissues
• Closed circulatory system: blood remains
inside the blood vessels; small vessels in
body tissues
REPRODUCTION
• Asexual reproduction: (no-sex)
• Sexual reproduction: male gametes
(sperm) & female gametes (eggs)
BODY SYMMETRY
• How can an animal’s body be divided into
similar pieces?
• Asymmetrical (a=no; symmetry=regularity of
form)
• Radial symmetry – body parts arranged
around a central axis
• Bilateral symmetry: mirror-image halves
• Cephalization – concentration of nerve tissue
& sensory organs at the anterior end of an
organism
SO WHAT IS AN ANIMAL?