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Animal Body
Arthropods
Biochem
Cell Cycle
Cell Interactions
Cell Structure
Circulation
Respiration
Communities
Digestion
DNA
Ecosystems
Energy
Evolution Evidence
Future of
Biosphere
Genetic Engineering
Gene Function
Genetics
Hormones
Human Evolution
Immunity
Species
Interaction
Kidneys
Locomotion
Membranes
Mollusks
Mutation
Nervous
Non-Coelmic
Photosynthesis
Plant Physiology
Population Genetics
Population
Dynamics
Cellular Respiration
Sensory
Speciation
Taxonomy
Vertebrates
Vertebrate
Org
Vocabulary:
1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,
16,17,18,19,20,
21,22,23,24,25,
26,27,28,29,30,
31,32,33,34,35,
36,37,38,39,40,
41,42,43,44,45,
46,47,48,49,50,
51,52,53,54
The Animal Body
I. The Great Diversity Of Animals Results From A Long Evolutionary History
A. Key Evolutionary Innovations Have Occurred in the
Animals
1. Progressive nature of animal evolution
2. Key elements of body architecture
B. Body Plan Results from Gene Programmed Development
II. Some General Features Of Animals
A. All Animals Are Heterotrophs
1. Depend on photosynthetic organisms
directly or indirectly
2. Most are able to move from place
to place in search of food
3. Ingestion of food is followed by
digestion within an internal cavity
B. All Animals Are Multicellular
1. Unicellular heterotrophs, "Protozoa,"
are Protists
2. At least ten million species are
currently alive
a) Most animals
are invertebrates
b) Only 1% of all
species are vertebrates
3. Animals are diverse in form and
include 35 phyla
a) Size ranges from
microscopic forms to enormous whales
b) Most are marine,
some are freshwater, few are terrestrial
c) Arthropods, mollusks
and chordates dominate the land
C. Animals Constructed in a Common Manner
1. Lack cell walls and are relatively
flexible
2. Cells are generally organized into
tissues, except for sponges
3. Are capable of movement
a) Directly related
to flexibility of cells
b) Flying is the
most specialized form of locomotion
4. Most reproduce sexually
a) Nonmotile eggs
are much larger than motile sperm
b) Cells formed
by meiosis function directly as gametes
c) There is no animal
counterpart to plant gametophyte or sporophyte
d) Adults and young
are generally diploid
e) Gametes are the
only haploid cells
5. Zygote becomes an adult through
process of embryonic development
a) Zygote divides
mitotically forming a hollow ball of cells, a blastula
b) This ball folds
inward to form a hollow sac, a gastrula
c) Opening of sac
called the blastopore
d) Cells subsequently
grow and move in relation to one another
e) Details differ
from one phylum to another, but provide clues regarding their evolutionary
relationships
III. Animals Without Tissue: Sponges
A. Sponges Are the Simplest of Animals
1. Lack definite symmetry
2. Cells not organized into tissues
a) Body is little
more than a mass of specialized cells
b) Cells exhibit
cell recognition
(1)
Key property of animal cells
(2)
Sponge passed through mesh will reaggregate
B. General Biology of Sponges
1. Adults are anchored to sea floor
2. Functions as water-filtering machine
3. Body is vase shaped, perforated
by tiny holes
a) Choanocytes:
specialized flagellated cells that line internal cavity
b) Water forced
through passageways by beating flagella
c) Food particles
in water trapped and ingested
4. Choanocytes structurally resembles
choanoflagellates
a) Protist with
a single flagellum
b) Likely ancestor
of sponges
IV. Advent Of Tissue Leads To Greater Specialization: Cnidarians
A. Animals Other than Sponges are Eumetazoans
1. Possess definite symmetry
2. Form three distinct cell layers
a) Outer ectoderm,
inner endoderm, intermediate mesoderm
b) Layers give rise
to tissues of adult body
(1)
Ectoderm forms coverings of body and nervous system
(2)
Mesoderm forms skeleton and muscles
(3)
Endoderm forms digestive organs and intestines
B. Most Primitive Eumetazoans Are Radially Symmetrical
1. Body parts arranged around a central
axis
2. Exemplified by two phyla
a) Cnidaria: hydroids,
jellyfish, sea anemones and corals
b) Ctenophora:
comb jellies
3. All other eumetazoans are fundamentally
bilaterally symmetrical
4. Echinoderm adults radially symmetrical,
larvae bilaterally symmetrical
C. General Biology of Cnidarians
1. Carnivores, capture food with tentacles
that surround mouth
2. Possess cnidocytes: specialized
structures located on tentacles
3. Exhibit two body forms
a) Polyp: cylindrical,
generally attached to a substrate
b) Medusa: umbrella-shaped,
free floating, gelatinous
4. Evolutionary innovation: extracellular
digestion of food
a) Sponge choanocyte
or amoeboid cell takes food particle directly into itself
b) Cnidarians digest
food outside of cells in a gut cavity
c) Same strategy
pursued by fungi, but process occurs outside of body
d) Innovation retained
by all other advanced groups of animals
e) Animals then
able to digest something larger than its own cells
V. Bilateral Symmetry: Solid Worms
A. Comparison of Bilateral Symmetry to Radial Symmetry
1. Bilateral symmetry found in all
higher forms
2. Bilateral organisms exhibit right
and left halves, mirror images to each other
3. Allows for differential adaptation
of various parts of body
a) Evolution of
cephalization
b) Move through
environment headfirst
c) Evolved various
sensory organs generally grouped at head end
4. More efficient in seeking food
and avoiding predators
B. Simplest Bilaterally Symmetrical Animals Are the
Solid Worms
1. Largest phylum is Platyhelminthes,
includes flatworms
2. Simplest phylum in which organs
occur
a) Organ: collection
of different tissues that function as one unit
b) Example: reproductive
organs, testes and uterus
3. General biology
a) Dorsoventrally
flattened bodies
b) Bodies are solid,
gut is the only internal cavity
c) Body construction
is acoelomate, without a body cavity
d) Bodies must be
thin to allow diffusion of gases and nutrients
e) Digestive system
is branched with a single opening
f) Most species
are parasitic
VI. The Advent Of A Body Cavity: Roundworms
A. All Other Bilaterally Symmetrical Animals Possess
a Body Cavity
1. Importance of the evolution of
a body cavity
a) Circulation:
Fluids moving within cavity function as a circulatory system
b) Movement: fluid
in cavity makes body rigid
c) Organ function:
organs can function without being deformed
(1)
Food movement not controlled by locomotion of animal
(2)
Digestion and waste removal more efficient
B. Pseudocoelomate Animals
1. Include seven phyla
2. Body cavity, pseudocoel, located
between endoderm and mesoderm
3. Have complete, one-way digestive
tracts
4. Nematoda contains the most members,
most are microscopic
VII. Building A Better Body Cavity: Mollusks
A. Coelomates Constitute the Bulk of the Animal Kingdom
1. Coelom body cavity develops entirely
within mesoderm
2. Supports various evolutionary relationships
a) Acoelomates could
give rise to coelomates or be derived from them
b) Pseudocoelomate
phyla could all have different origins
B. Success of Coelomate Body Cavity Stems from Embryonic
Development
1. During primary induction primary
tissues interact with each other
2. Coelomate body plan allows necessary
contact between mesoderm and endoderm
a) Permits development
of localized portions of digestive tract, i.e. stomach
b) Mesoderm and
endoderm separated by body cavity in psuedocoelomates
c) Limits developmental
interactions
3. Coelom allows digestive tract to
be longer than animal's body length
a) Allows for storage
of undigested food or food remnants: limits exposure to predators
b) Longer exposure
of food to enzymes improves digestion
c) Tube-within-a-tube
design allows for more flexibility and greater mobility
4. Architecture of the coelomate animal
a) Gut and internal
organs suspended in coelom
b) Coelom surrounded
by epithelium layer, derived from mesoderm
(1)
Parietal peritoneum lines outer wall
(2)
Visceral peritoneum lines internal organs within cavity
5. Internal body cavity provides space
for expansion of gonads
a) Allows for accumulation
of eggs and sperm
b) Advanced phyla
able to evolve diverse reproductive strategies
c) Large numbers
of gametes stored and released under favorable conditions
6. Requires development of sophisticated
circulatory system
a) Network of vessels
carries fluid, blood, to all parts of body
b) Blood carries
nutrients and oxygen to tissues
c) Removes wastes
and carbon dioxide from tissues
d) Circulation effected
by contraction of muscular hearts
C. Mollusks Are the Least Advanced Coelomates
1. Only major coelomates without segmented
bodies
2. Second largest phylum of animals
3. Second most successful land animals,
next to insects
4. More terrestrial mollusks than
terrestrial vertebrates
5. Mollusk bodies composed of three
segments: head, central visceral mass, foot
6. Three classes: Gastropods, Bivalves,
Cephalopods
VIII. The Rise Of Segmentation: Annelids
A. Early Innovation in Coelomates Was Segmentation
1. Body built from series of similar
segments
a) Like prefabricated
building
b) Segmentation
obvious in mesoderm early on
c) Later reflected
in endoderm and ectoderm
2. Advantages to early embryonic segmentation
a) Repetition of
organ systems less lethal if one segment damaged
b) Locomotion more
effective when segments can move independently
3. Offers evolutionary flexibility
a) Small change
in a segment can produce segment with new function
b) Segments can
be modified for various activities
B. Segmentation First Evolved in Annelid Worms
1. Two-thirds are marine, rest are
terrestrial
2. Characterized by three principle
features
a) Repeated segments
(1)
Visible as ring-like structures along body length
(2)
Separated internally by partitions
(3)
Each segment contains digestive, excretory and locomotor organs
(4)
Fluid in segments creates hydrostatic skeleton that gives the segment
rigidity
(5)
Each segment can expand or contract independently
b) Specialized segments
(1)
Anterior segments modified with sensory organs
(2)
Well-developed brain contained within one anterior segment
c) Connections
(1)
Provide ways for materials to pass between segments
(2)
Circulatory system carries blood between segments
(3)
Nerve cords connect ganglia in each segment
C. Segmentation in Other Coelomates
1. Present in arthropods and chordates,
may not be obvious
2. Many arthropod segments are fused
3. Segments not apparent in human
adults, visible in embryo
a) Vertebrate muscles
develop from repeated blocks called somites
b) Vertebral column
segmentation is more apparent
IX. Invention Of Jointed Appendages: Arthropods
A. Jointed Appendages Characteristic of the Most Successful
Animal Phylum
1. Arthropod most certainly evolved
from annelids
2. Arthropod segmentation not as evident
as annelid segmentation
3. Importance of jointed appendages
verified in human skeletal joints
B. Exoskeleton is a Limitation of the Arthropods
1. Skeleton is rigid, made of chitin
a) Muscles attach
to the interior of the hard shell
b) Provides protection,
limits water loss
2. Chitin cannot support great weight
a) Exoskeleton must
be thick to bear pull of muscles in large arthropods
b) Extremely large
arthropods are non-existent
c) Strong flexible
endoskeleton required to overcome limitation
X. Redesigning The Embryo: Echinoderms
A. Coelomates Characterized into Two Groups by Embryology
1. Protostomes
a) Include mollusks,
annelids, arthropods
b) Mouth (stom a)
develops from or near blastopore
c) Anus develops
in another region of embryo
d) Original state
was characteristic of common ancestor of all eumetazoans
2. Deuterostomes
a) Includes echinoderms,
chordates, few other related phyla
b) Anus forms at
or near blastopore
c) Mouth develops
from another region of blastula
d) Derived from
protostome pattern of development
B. Other Fundamental Differences Between Deuterostomes
and Protostomes
1. Present two different cleavage
patterns
a) Protostomes exhibit
spiral cleavage
(1)
New cell buds off at oblique angle
(2)
Produces closely packed array of cells
b) Deuterostomes
exhibit radial cleavage
(1)
Cells divide parallel to and at right angles to polar axis
(2)
Produces loosely packed array of cells
2. Differences in developmental fate
of cells
a) Protostome cell
fate is fixed when that cell first appears
(1)
Individual cells will not develop into complete animal if separated
(2)
Chemicals controlling developmental signals are localized early
b) Deuterostome
cell fate is fixed later in development
(1)
Daughter cells from early divisions are totally identical
(2)
Cells from early stages can become complete individuals
3. Differences in development of celom
from mesoderm
a) Occurs simply
and directly in protostomes
(1)
Cells move away from one another
(2)
Coelomic cavity expands within mesoderm
b) Complex development
in deuterostomes
(1)
Groups of cells move around forming new tissue associations
(2)
Coelom produced from invagination of archenteron
4. Deuterostomes clearly derived from
protostomes early in their evolution
C. Echinoderms Were the First Deuterostomes
1. Name "spiny skin" refers
to hard endoskeleton just beneath delicate skin
a) Endoskeleton
composed of ossicles, calcium-rich plates
(1)
Are totally encase in living skin when first formed
(2)
Fuse forming hard shell in adults
2. Include sea stars, sea urchins,
sand dollars, sea cucumbers
3. Echinoderms exhibit secondary radial
symmetry
a) Are bilaterally
symmetrical as larva
b) Become radially
symmetrical as adults
4. Adults possess five-part body plan
5. Lack a centralized brain or central
nervous system
6. Possess a unique water vascular
system
a) Hydraulic system
to aid movement
b) Central ring
with five radial canals
c) Ultimately controls
contraction or extension of hollow tube feet
XI. Improving The Skeleton: Chordates
A. Chordates Employ a Truly Internal Endoskeleton
1. Characterized by flexible rod along
back of embryo
2. Muscles attach to rod providing
flexible locomotion
3. Leads to possibility of truly large
animals
4. Three features characterize chordates
a) Single dorsal
hollow nerve cord
b) Long, stiff rod-like
notochord, beneath nerve cord
c) Pharyngeal slits
located behind mouth
5. Features may not be apparent at
all times
a) Human possess
three characteristics as embryos
b) Adult humans
retain nerve cord, one pair of slits becomes Eustachian tubes
B. Chordate Body Plan
1. Are deuterostomes, nearest relatives
are echinoderms
2. Are more or less segmented
3. Many have jointed appendages
C. Vertebrates Are Specialized Group of Chordates
1. Tunicates and lancets are non-vertebrate
chordates
2. Special characteristics of vertebrates
a) Possess backbone
(1)
Notochord surrounded and replaced by bony vertebral column
(2)
Hollow tube of bones protecting dorsal nerve cord
b) Exhibits distinct
head, also called craniate chordates
3. Vertebrate endoskeleton is made
of bone
a) Special tissue
containing collagen protein coated with calcium phosphate salt
b) Bone is strong
without being brittle, like chitin