Download Introduction to Animals

Introduction to Animals
Characteristics
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All multicellular & eukaryotic
Cells lack cell walls
Heterotrophs
Have some type of skeletal support
Exoskeletons found in arthropods cover the outside of the body
Endoskeletons found in all vertebrates are found inside the body & are
made of cartilage &/or bone
Worms have fluid-filled internal cavities giving them skeletal support
Sponges have the simplest skeleton
May be sessile (attached & non-moving) or motile (able to move around)
Reproduce sexually
Show levels of organization including cell, tissue, organ, & system
Most show division of labor among cells
Cells are specialized for particular functions
Most vertebrates have a backbone or spine made of repeating bones
called vertebrae that protect the spinal cord
Some show cephalization (have a head with sensory organs concentrated
there)
Invertebrate Groups
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Simplest animals
Contains the greatest number of animal species
Most found in water
Do not have an backbone
Includes sponges, cnidarians, flatworms, roundworms, annelids
(segmented worms), mollusks, arthropods, & echinoderms
Vertebrate Groups
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More complex animals
Most have a backbone
Includes fish, amphibians, reptiles, birds, & mammals
Body Areas
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Dorsal is the back or upper surface
Ventral is the belly or lower surface
Anterior head or front end
Posterior is the tail or hind end opposite the head
DORSAL
ANTERIOR
POSTERIOR
VENTRAL
Body Symmetry
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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)
Radial symmetry occurs when similar body parts are arranged around a
central point like spokes on a wheel (echinoderms)
Bilateral symmetry occurs when animals can be divided into equal halves
along a single plane (right & left sides that are mirror images)
RADIAL SYMMETRY
BILATERAL SYMMETRY
Tissue Development
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All animals reproduce sexually, but some also reproduce asexually
(sponges bud & flatworms fragment)
Zygote is the fertilized egg all animals form from
Blastula folds inward at one point to form an opening & two cell or
germ layers; process called gastrulation
Inner germ layer called endoderm & outer germ layer called ectoderm
Opening may become the mouth or the anus
Protostomes (mollusks, arthropods, & annelids) develop mouth from
blastopore, while deuterostomes (echinoderms & vertebrates) develop
an anus from blastopore
Some animals form a third germ layer in the middle called mesoderm
Cells differentiation during development changing their shapes to fit
their function ( neurons or nerve cells become long to conduct
messages)
Germ Layers
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Form the tissues, organs, & systems of an animal
Ectoderm (outer) forms skin, nerves, & sense organs
Endoderm (inner) forms the digestive & respiratory organs & systems
Mesoderm (middle) forms muscles, circulatory system, reproductive &
excretory systems
Body Cavities
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Coelom is an internal body cavity lined with mesoderm
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Animals with a coelom are called coelomate animals (annelids, mollusks,
arthropods, & vertebrates)
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Acoelomate animals do not have a body cavity but have solid bodies
(sponges, flatworms, & cnidarians )
Pseudocoelomate animals have a body cavity only partially lined with
mesoderm (roundworms)