Download CH 25: WHAT IS AN ANIMAL?

CH 24 WHAT IS AN
ANIMAL?
CHARACTERISTICS
OF ALL ANIMALS
Eukaryotic
Multicellular
Specialized cells (tissues & organs)
Ingestive heterotrophs
1.5 million species
STRUCTURES FOR SUPPORT
AND DEVELOPMENT
Exoskeletons –
- hard or tough outer coverings
- provide a framework for support
- protect soft body tissues
- prevent water loss
- protection against predators
Found on many invertebrates
Invertebrates – animals without backbones
- 95-99% of animal
species
- most have an
exoskeleton
- exoskeletons are
shed to make a
new one as the
animal grows
- Some invertebrates, sea urchins and sea stars;
have internal skeletons (endoskeletons)
Invertebrates Examples –
animals without backbones
- Sponges, Cnidarians – first animals to
evolve from a multicellular ancestor
- Worms: flatworms, roundworms,
segmented worms
- Mollusks: octopus, snails, squids, clams
- Arthropods: crustaceans, spiders, insects
- Echinoderms: sea stars, sea urchins,
sand dollars
- Invertebrate Chordates: lancelet, tunicates
Vertebrates –
animals with a backbone
Endoskeleton – internal
skeletons grow with the
animal
- calcium carbonate -sea urchins/sea
stars (invertebrates)
- cartilage – sharks
- bone – fishes, amphibians, reptiles,
birds, mammals
SEXUAL REPRODUCTION
(MOST)
Sperm
+ Egg = Zygote
Cleavage
-->
zygote divides
Embryo
-> an organism
in the early stages of
development
CELL LAYERS
(Most have three layers)
 Ectoderm
- outer layer (skin & nervous
tissue)
 Endoderm
- inner layer
(digestive organs)
–
middle layer (muscles, circulatory,
excretory and respiratory systems)
 Mesoderm
SYMMETRY
 Radial
- round, or sphere shaped
– right and
left halves form a
mirror image
 Bilateral
–
no definite shape
 Asymmetrical
BODY PLANES
Dorsal
- back surface
Ventral - belly surface
Anterior - top (head)
Posterior - tail end
BODY CAVITIES
Coelum - fluid-filled cavity mesoderm (earthworms)
Acoelomate no body cavity
(flatworms)