Transcript Animal cells lack cell walls

Characteristic Of
Animals
Most are Motile at
some point in life
cycle
No Cell Walls
Multicellular
Dominant
Generation is
Diploid
Heterotrophic
Eukaryotic
Heterogametic
~34 animal
phyla
Cell Structure and Specialization
•
Animal cells lack cell walls that provide
structural supports for plants and fungi.
–
–
The multicellular bodies of animals are held
together with the extracellular proteins,
especially collagen.
Other structural proteins create several types
of intercellular junctions
•
tight junctions, desmosomes, gap junctions.
Animals have 2 unique types of tissues:
1. nervous tissue - impulse conduction
2. muscle tissue- movement
Embryonic development
Consist of 3 basic stages:
1. Cleavage-After fertilization the
zygote undergoes
cleavage, a succession
mitotic cell divisions,
leading to the
formation of a
multicellular, hollow ball
of cells called the
blastula
2. Gastrulation
3. Organogenesis
Development:
– Blastula
• Each cell is
called a
blastomere.
• Center;
blastocoel
Fig 32-2
–During
gastrulation,
part of the
embryo folds
inward,
forming the
blind pouch
–This produces two tissue layers: the endoderm
characteristic as the inner layer and the ectoderm as the
of the
outer layer
gastrula.
Stages of Development
– Some animals
develop directly
through transient
stages into
adults, but
others have
distinct larval
stages.
• Metamorphosis
Sexually immature stage that is morphologically distinct
from the adult, usually eats different foods, and may live in a
different habitat from the adult.
Gastrovascular Cavity- Gut
twoway
Oneway
Cephalization
An evolutionary
trend toward
the
concentration
of sensory
equipment on
the anterior
end.
Classification Criteria
Traditionally classified based on anatomical
features and embryonic development
1-Body Symmetry
1.Asymmetry
2.Radial
3.Bilateral
1-Body Symmetry
•The symmetry of
an animal generally
fits its lifestyle.
•Radial animals are
sessile or planktonic
and need to meet the
environment equally
well from all sides.
•Animals that move
actively are bilateral,
such that the head
end is usually first to
encounter food,
danger, and other
stimuli.
2- Germ Layers
(Viscera)
WEBSITE
ECTODERM
• Epidermis of skin and its
derivatives (including sweat
glands, hair follicles)
• Epithelial lining of mouth
and rectum
• Sense receptors in
epidermis
• Cornea and lens of eye
• Nervous system
• Adrenal medulla
• Tooth enamel
• Epithelium or pineal and
pituitary glands
Figure 47.16
MESODERM
•
•
•
•
Notochord
Skeletal system
Muscular system
Muscular layer of
stomach, intestine, etc.
• Excretory system
• Circulatory and lymphatic
systems
• Reproductive system
(except germ cells)
• Dermis of skin
• Lining of body cavity
• Adrenal cortex
ENDODERM
• Epithelial lining of
digestive tract
• Epithelial lining of
respiratory system
• Lining of urethra, urinary
bladder, and reproductive
system
• Liver
• Pancreas
• Thymus
• Thyroid and parathyroid
glands
2- Germ Layers
• Diploblastic
– 2 germ layers
– Porifera & Cnidarian
• Triploblastic
– 3 germ layers
– All other phyla
3- Body Cavities
1. Acoelomates lack a body cavity or coelom;
•
a coelom is a body cavity lined by mesoderm.
2.Pseudocoelomates possess a
pseudocoelom; body cavity is
incompletely lined by mesoderm.
3.Coelomates possess a coelom completely lined with
mesoderm.
Body cavity between the digestive tract and body wall; it is lined by mesoderm
allows digestive system to move independent of body wall
coelomic fluid assists respiration and circulation by diffusing nutrients, and
excretion by accumulating wastes
cavity may serve as a storage area for eggs and sperm
fluid protects internal organs and also serves as a hydrostatic skeleton
A body cavity has many
functions.
1.
Fluid cushions the internal
organs
2. Fluid of the body cavity
can function as a
hydrostatic skeleton
against which muscles can
work.
3. The present of the cavity enables the internal organs to
grow and move independently of the outer body wall.
Coelomates are either
Protostomes or Deuterostomes
• During early development of the zygote, cell
division (cleavage) is very orderly.
• Two specific patterns of cleavage.
– Spiral: Protostomes
• Slight angle to the vertical axis of the embryo
• First infolding (blastopore) becomes the mouth
• Cell’s future decided by 4-cell stage
– Radial: Deuterostomes
• Parallel to the vertical axis of the embryo
• Blastopore becomes the anus
• Each cells retain ability to develop into an embryo.
• This
phylogenetic
tree is
bases
on
nucleotide
sequences
from the
small subunit
ribosomal
RNA.