Download WHAT IS AN ANIMAL?

WHAT IS AN ANIMAL?
Chapter 18
ALL ANIMALS ARE...
Multicellular
Eukaryotic
Heterotrophic
Obtain nutrients by
ingestion
Lack cell walls
So, how are they different from plants? Fungi?
ALL ANIMALS ARE...
PLANTS
Multicellular
Eukaryotic
Autotrophic
Obtain nutrients by
absorption
Have cell walls (cellulose)
ALL ANIMALS ARE...
FUNGI
Multicellular
Eukaryotic
Autotrophic
Obtain nutrients by
decomposition
Have cell walls (chitin)
ANIMAL LIFE CYCLE
Adults are diploid and make haploid gametes via
meiosis
Egg (female) and sperm (male) fuse to make a zygote
Zygote divides by mitosis producing a blastula (hollow
ball of cells)
Hollow blastula then folds inward (for most animals),
forming gastrula. Internal sac becomes digestive tract
After gastrulation,most animals develop into adults, some go
through larva/metamorphosis
Notice that later gastrulation produces internal layers
EVOLUTIONARY HISTORY
Animals most likely evolved from a “colonial” protist during the precambrian
period over 575 million years ago
Protists are eukaryotic, but normally single-celled organisms. However they can
form loose associations with other cells...colonies. However, colonies of lack
cellular specialization as would be found in true multicellular organisms (tissues).
ALMOST ALL ANIMALS
ARE INVERTEBRATES
Some have radial symmetry
(tend to be sedentary),
others are bilateral (tend to
be mobile...sense organ
clustered to front)
ANIMAL BODY PLANS
Most animals (except sponges)
have true tissues
Most have three tissue layers
that develop during
gastrulation: endoderm
(becomes digestive tract) ,
mesoderm (internal organs),
ectoderm (outer covering)
COMMON PHYLA:
PORIFERA
“Sponges”
Lack true tissues, sedentary
Suspension feeders
Most are marine
simplest of all animals
COMMON PHYLA:
CNIDARIAN
“Jelly fish and sea
anemones”...named for
“stinging cells”
radially symmetric
carnivorous
simple bodies with some
tissues, one opening
digestive tract
marine
COMMON PHYLA:
NEMATODA
“Round worms”
Digestive tract with 2
openings
tough outer covering
some parasitic,
decomposers, or free living
most species look very
similar
COMMON PHYLA:
ANNELIDA
“Segmented worms”
segmentation aids in
movement
closed circulatory system
earthworms, leeches
COMMON PHYLA:
PLATYHELMINTHES
“Flat worms”...like
planarian (at left)
simplest of bilaterally
symmetrical animals
most parasitic, some free
living
one-opening in
gastrovascular cavity
COMMON PHYLA:
MOLLUSCA
Name means “soft-bodied”
Most protected by hard
shell
very varied body forms
(octopus , squid, clams,
oysters, snails)
open circulatory system
COMMON PHYLA:
ARTHROPODA
Name means “jointed feet”
most successful of all
animals in terms of sheer
numbers of species
have exoskeleton and open
circulatory system
includes: insects, crabs,
lobsters, spiders, scorpions
COMMON PHYLA:
ECHINODERMATA
Name means “spiny skin”
have endoskeleton
radially symmetric
includes: starfish, urchins
COMMON PHYLA:
CHORDATA
Have dorsal nerve chord
notochord (supportive
structure near nerve chord)
pharyngeal slits and postanal tail
includes: some
invertebrates and all
“familiar” animals (birds,
reptiles amphibians,
mammals, fish)
Human embryo
~35-40 days
pharyngeal slits
post-anal tail
ANIMAL FORM AND FUNCTION
Chapter 20
BEING AN ANIMAL
HAS ITS CHALLENGES
Unlike unicellular, aquatic
organisms, animals must:
Obtain nutrients and
oxygen from environment
and distribute throughout
body
excrete wastes
sense and respond to
environment
move and reproduce
THE BIG IDEA...
The relationship between form and function has repeated
itself throughout the year...
At many levels of biological hierarchy...from molecules, to
cellular structures, to tissues, to organs and systems,
to body shapes... the forms taken by structures have been
shaped by natural selection for their function
Animals solve their challenges, and reflect form/function
relationships with specialization
EPITHELIAL TISSUE
Covers and lines surfaces,
cavities and organs
Varies in terms of
layering (simple vs
stratified)
Varies in terms of cell
shape (squamous vs
columnar vs cuboidal)
CONNECTIVE TISSUE
sparse cells distributed in a matrix...primary function: support
High degree of variation in forms
Examples: bone, blood, adipose (fat), cartilage, fibrous, loose.
MUSCLE TISSUE
consists of long cells
called fibers which aid in
movement
most abundant tissue
(mass) in most animals
Examples: cardiac,
skeletal, smooth.
NERVOUS TISSUE
cells are called neurons
senses stimuli and
transmits information
ORGANS ARE MADE OF
TISSUES
multiple tissues perform
different roles which allow
the organ to function
For example the small
intestine consists of
epithelial, smooth muscle,
and connective tissues
ANIMALS MUST EXCHANGE
MATTER WITH ENVIRONMENT
Structural adaptations increase the efficiency of exchange
• Wherever exchange is required (gills, lungs, digestive tract,
urinary system, etc) linings tend to be thin with few layers of
cells
• Shapes (folds, sacs, elongated tubes) can maximize SA:Vol
ratio...remember why cells themselves are small
HOMEOSTASIS
Maintenance of stable
internal conditions
A dynamic relationship
between outside forces that
tend to want to change the
internal environment vs.
internal controls that resist
such change
Mostly based on negative
feedback