Intro to Animals

Intro to Zoology
What is an animal?
Typical Characteristics:
 1) Eukaryotic –each cell has a nucleus
 2) Multicellular-Made up of many cells
 Cells>Tissue>Organs>Organ Systems
 3) Heterotrophic- must eat food to get energy and
nutrients- through ingestion and digestion
 4) Do not have cell walls
 5) Can Move (some are sessile, which means that they
don’t move) EX: sponges and barnacles
 Origins of animals :
 Most likely evolved from colonial
 Believed to have developed in
the water
 Porifera
 Cnidaria
 Platyhelminthes
 Nematoda
 Annelida
 Mollusca
 Arthropoda
 Chordata
***There are
more than 9
phylums but
represent the
 Match the name of phylum with a picture of a member!
Reproduction and
 Most animals reproduce sexually.
 Some can reproduce asexually.
 Fertilization occurs when a sperm penetrates an egg to
form a single cell called a zygote.
 This may be external (outside male and female) EX:
Fish or internal ( inside the female) EX: Horse
Cell Division
 Zygote begins dividing by mitosis to form two new cells.
 Each new cell will continue to divide over and over
again until a hollow ball called a blastula is formed.
 One side of the blastula begins to fold inward, making
an inner pouch. At this point, the embryo is called a
Germ Layer Development
 The layers that form will eventually form the tissue and
organs of the animal. Most animals possess three
layers of tissue (sometimes called germ layers):
 1) Ectoderm: outermost layer of cells; eventually forms
the outer covering (skin) and nervous system.
 2) Mesoderm: middle layer of cells; eventually forms
the skeleton, muscles, and circulatory system
 3) Endoderm: Inner layer of cells; becomes the
digestive tract, internal organs, and respiratory tract
Body Cavities
 As the layers of tissue form organs and organ systems,
some organisms develop a fluid filled space that forms
between the digestive tract and the outer wall of the
body during development.
 Not found in simple animals
 May aid in movement
 Fluid may act as a reservoir for nutrients and wastes,
which diffuse into and out of the animal’s body
Types of Body Cavities
 Acoelomates: 3 layers of tissue, but no body cavity is
present ( Gut)
 Pseudocoelomates- 3 Layers of tissue and a modified
body cavity present ( not lined with mesoderm)
 Coelomates- a true body cavity present (lined with
Patterns of Symmetry
 Asymmetrical – an irregular shape. Some simple
animals do not display symmetry (EX: Sponges)
 Radial- Similar parts branch out in all directions from a
central line ( like spokes on a bicycle tire)
 Bilateral- two halves on either side of a central plane
are similar
 A. Usually exhibit cephalization –concentration of
sensory structures in the anterior (head) end of the
Bilateral Symmetry words
 Terms used to describe location of certain structures
and organs on an animal:
 Anterior: head end
 Posterior: Tail end
 Dorsal: Back
 Ventral: Front
 A body composed of repeating similar units
 In some phyla, segments may look different and have
different functions.
Support and Protection of
 Hydrostatic skeleton- body is supported by the
pressure of their fluid filled bodies (EX: jellyfish)
 Exoskeleton- A rigid outer covering that protects the
soft tissue of many animals ( includes many
invertebrates such as crabs and beetles)
 Endoskeleton- an internal skeleton that can support a
large, heavy body
Vertebrate VS. Invertebrate
 Most animals that exist today are classified as
invertebrates; animals that lack a backbone
 EX: insects, sponges, starfish, jellyfish, clams, worms,
 Humans are a type of chordate called a vertebrate, an
animal with a backbone.
 Chordata is the only phylum that contains vertebrates
(although not all chordates are vertebrates)
Digestive System
 In Sponges, digestion occurs within individual cells
 Gastrovascular Cavity- A digestive chamber with a
single opening (incomplete digestive system) Ex:
jellyfish and flatworms
 Digestive tract (or gut) runs from the mouth to the
posterior end or anus. EX: humans, earthworms, and
Respiratory System
 Gas Exchange: the process of exchanging carbon
dioxide (in the blood) with oxygen (in the environment)
 Gills: Organs that are specialized for gas exchange in
 Lungs: Organs for gas exchange, which are composed
of moist, membranous surfaces deep inside the
animal’s body
Circulatory System
 Moves blood or a similar fluid through the body to
transport oxygen and nutrients to the cells.
 Open circulatory system- blood like circulatory fluid is
pumped from vessels in the body into the body cavity (
it bathes the organs) then is returned to the vessels.
 Closed circulatory system- blood circulates through
the body in tubular vessels.

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