Download Survey of the Phyla- Animalia, Invertebrates

Survey of the PhylaAnimalia,
Invertebrates
The Kingdom Animalia is in
the domain Eukarya and in
the supergroup Unikonta.
They are in the group
Opisthkonta with fungi.
Both groups have different
unicellular organisms that
they are their common
ancestor. That fact
indicates the groups
became multicellular
organisms independent of
one another.
Characteristics of the Animal Kingdom
1. Animals are multicellular, heterotrophic, ingestive and eukaryotic.
2. The cells lack cell walls and are held together by structural
proteins which are mostly collagen. They have intracellular
junctions such as tight junctions, desmosomes and gap junctions.
3. Animal cells have nervous and muscle tissues found only in this
kingdom.
4. Most animals have a diploid life cycle with a sperm fertilizing an
egg. The zygote undergoes cleavage forming a blastula (hollow ball
of cells). The blastula undergoes mass movement of cells to form a
gastrula giving rise to three layers of tissue, endoderm, mesoderm
and ectoderm. Often there is a larval stage to the animal which is
sexually immature. It often will undergo metamorphosis to become
an adult.
5. All animals contain both
homeotic genes (any of the genes
that control the overall body plan
of animal by controlling the
developmental fate of a group of
cells) and homeobox (a 180nucleotide sequence with a
homeotic gene) encoding the part
of the protein that binds to the
DNA of the genes regulated by the
protein. There is an increase in the
number of these genes with an
increase in the complexity of the
animal.
The protists most closely related to
animals are the choanoflagellates.
It is flagellated with a collar to
collect food. It will form colonies.
Diagramed are the steps thought to have given to evolution
of multicellular animals.
Other interesting points about animals
Embryonic development
-Deuterostomes versus protostomes. During development many
animals first form a hollow ball of cells or blastula. Afterward
that there is a mass movement of the cells called gastrulation.
This process results in three layers of tissue being established.
Ectoderm-becomes skin and nervous tissue
Mesoderm-notochord, lining of coelom, kidneys, muscles and
bone and circulatory system
Endoderm-interior lining of organs and liver, pancreas, lungs
and lining of digestive tract.
During this process of gastrulation, the first opening to the gut
or archenteron forms. In deuterostomes, this opening becomes
the anus but in protostomes it becomes the mouth.
Body plansAsymmetrical-These animals lack orientation like the sponges.
Radial symmetry-The body plan is around an axis and any
plane going through the axis will produce opposite halves.
-Bilaterial symmetry
The body forms a
body in a
longitudinal plan that
divides the body into
two equal but
opposite halves. It
allows the senses to
be concentrated up
in one area. Can
increase awareness,
mobility and
predation.
-Bilaterial symmetry
The body forms a body in a longitudinal plant that divides the
body into two equal but opposite halves.
Body cavities (coeloms)
-Acoelomate-These animals do not have a body cavity like a
flat worm or jelly fish
-True coelom-The body cavity is lined with tissue derived
from the mesoderm.
-Pseudocoelom-The body cavity is lined with mesoderm on
the outer part and with endoderm on the inside. Round
worms have pseudocoeloms.
Clade Parazoa or
sponges-Most closely
related to colonial
choano-flagellates. These
protists and animals have
a common ancestor.
Phylum Porifera
1. Sessile with no
specialized tissue i.e.
nerves or muscle.
2. Size 1 cm-2 m. Mostly
marine species with few
freshwater. The body of a
sponge has a cavity called
a spongocoel. The body is
perforated with pores.
Water flows into the pores and into the spongocoel and then out a
larger opening called the osculum. There are two layers of cells with
a gelatinous layer in between called the mesophyl. The outside of the
body is lined with epidermal cells.
3. The pores are lined with cells (porocytes). The inside layer is lined
with cells (choanocytes like choanoflagellates ). The flagella of
choanocytes beat creating a water current. The choanocyte cell has a
collar with a flagella. It also secretes mucus to filter and catch food.
There are also amoebocytes which take food from the choanocytes
and deliver it to the epidermal cells.
4. Sponges are hermaphrodites. Gametes come from amoebocytes
and choanocytes. Eggs reside in the mesohyl and sperm from
neighboring sponges fertilize them.
Clade Eumetozoa-Animals with true tissues. Two clades are found
in Clade Eumetazoa-Clade Radiata and Clade Bilateria
Clade Radiata-Animals with radial symmetry (top and
bottom with no head or rear end). Radiata has two tissue
layers ectoderm and endoderm and no mesoderm resulting in
dipolblastic embryos (no mesoderm).
Phylum Cnidaria-Jellyfish and hydra-The basic body plan is a sac
with a gastrovascular cavity (GVC). The single opening
functions as both the mouth and the anus. Two variations of
this body plan-the polyp and medusa. The polyp is a cylinder
form that is sessile and adheres to the bottom of the water.
The medusa is a "flattened-version of the polyp upsidedown". It moves in the water by drifting and contracting its
bell shaped body.
Some species exists as
polyps and others as
medusas and others
will have both forms
in their life cycles.
Both forms have two
layers of tissue with a
gelatinous layer of
material in between
called the mesoglea.
Surrounding the
mouth of these
animals are a ring of
tentacles.
These tentacles have stinging cells called cnidocyte cells. These cells
have poisonous, little dart like structures called nematocysts. No
muscles but cell will bundles of contractile fibers.
There is also nerve net that can detect stimuli causing the organism
to react. The gastrovascular cavity has specialized cells that release
digestive enzymes to aid in digestion.
Class Hydrozoa-(Portuguese man-of-war, hydras, some corals).
Mostly marine. Both medusa and polyp forms present. Polyp form
usually colonial.
Class Scypphozoa-(jellies, sea nettles). All marine. Polyp form
greatly reduced. Medusa form up to 2 m in diameter.
Class Cubozoa-(box jellies,and sea wasp) All marine. Polyp form
greatly reduced. Medusa forms a box like shape with complex eyes
and potent venom.
Class Anthozoa-(sea anemones, most corals, and sea fans). Medusa
stage completely absent sessile, many colonial.
Phylum Ctenophora-Superficially looks like cnidarian medusas.
These are the comb-jellies. Small and sperical or ovoid. 8 rows of
comblike plates fused cilia.
Clade Bilateria- These animals have bilateral symmetry. Gives
animals dorsal and ventral side as well as an anterior (head) and
posterior (tail) end. Cephalization is the movement of sensory organs
to the anterior end. The anterior end is first to encounter danger,
food and other important stimuli.
This clade divides up three smaller clades, Deuterostomia,
Lophotrochozoa, Ecdysozoa
The first clade are the deuterostomes. The deuterostomes are
characterizied by their embryonic development and formation of a
deuterostome.
The second clade are the lophotrochozoans either has a lophophore
(a crown of ciliated tentacles function in feeding) or the
development of a trochophore larva.
The third clade is Ecydysozoa. These are animals that form an
exoskeleton or thick cuticle. As the animals grow they molt or shed
their outer covering (ecdysis).
Clade Lophotrochozoa
Phylum Platyhelminthes: Flatworms
a. Have gastrovascular cavity with
pharynx as mouth on ventral side
b. Acoelomates
c. Nervous system is a pair of ventral
nerve cords. Can have eye spots on
anterior end that responds to light. In
the anterior region one can find a
ganglion.
d. Nitrogenous wastes removed by a
“flame cell” system
Four Classes found in this phylum
Class Tubellaria-Mosly free-living, most marine,
few terrestrial, predators, scavengers; body surface
ciliated.
Class Mongenea- Marine and freshwater parasites
on external surfaces of fish.
Class Trematoda- Flukes are parasites of
vertebrates. Complicated life history witn
intermediate host.
Class Cestodea-Tapeworms with scolex. No head or
digestive system. Complicated life history.
Phylum Rotifera-Rotifers have pseudocoelomates, jaws, crowns of
cilia and a complete digestive tract. Complete digestive tract allows
for individual organs and processing of food differently for
maximum extraction of nutrients. While many rotifers are smaller
than single-celled protista, they are much more complicated than
even flat worms. Some reproduction in some species is
parthenogenesis.
Phylum Ectoprocta- called moss animals because they resemble
moss. Most species are marine and are small and form colonies.
Most of the colony is enclosed in a hard skeleton with the
lophophores that extend through the pores when feeding.
Both phyla have
lophophores
Phylum Brachiopods-Look like clams but stand up vertically. Called
lampshells. Attach to bottom by a stalk. The shells are opened
slightly to allow water to flow through lophophores.
Phylum Nemertea-Ribbon worms seem to be acoelmate but contain
a fluid filled proboscis sac which is derived from a true coelom. A
proboscis is a long retractable hollow tube at the anterior end. Used
to probe enviroment, capture
Phylum Mollusca-Soft-bodied animals with shells.
This phylum includes snails, slugs oysters, clams octopuses and
squid. Most are marine with some fresh-water and terrestrial
species. They have three main parts:
-Muscular foot for locomotion
-Visceral mass that contains most of the internal organs.
-A mantle, which is a heavy fold of tissue that surrounds the visceral
mass and secretes
the shell. Many
will contain a
radula or rasping
tongue to scrap
food from
surfaces.
Some species are monoecious while others are dioecious. Gonads
are located in the viceral mass. It is possible that mollusks evolved
before annelids because they lack segmentation or from an annelid
like ancestor as they both have trochophore larva. Most have open
circulatory systems with a heart. Structures for gas exchange.
Ventral nerve chords with sensory organs.
Class Polyplacophora-This class includes chitons. They have an oval
shape with eight dorsal plate. The cling to rocks with foot a suction
cup. They have a radula to gather food.
Class Gastropoda-Snails and slugs. Largest class, mostly marine.
Torsion
occurs during development-Uneven growth in viceral mass causes
the mass to rotate 180 degrees putting the anus above the head.
Body protected by a conical shell. (absent in slugs and nudibrances).
Aquatic species have gills but terrestrial species use the mantel for
gas exchange.
Class Bivalvia-contains clams, oysters mussels and scallops. These
have a shell divided into two parts. Held together by two adductor
muscles. When open, the foot may be extended for motility or
anchorage. Siphons are used to move water over the gills. Most
are filter feeders. Head is absent and so is radula.
Class Cephalopods-Squids,
octopuses, and nautiluses.
Agile carnivores. Use a
beak to crush prey.
Mantel covers visceral
mass. The shell is either
reduced, internal/or
absent. Squid swim
backwards by drawing
water into the mantle and
firing the water in a
stream through the
excurrent siphon.
Directions can be changed
by pointing the siphon in
different directions. A
giant squid may reach 17
m longs and weigh 2 tons.
Phylum Annelida -Presence of a true coelom and segmentation are
two big advances in this phylum.
True coelom allows for
-development of complex organ systems
-protect internal structures
-permits internal organs to function separately from the body wall
muscles
-serve as a hydroskeleton
The body of annelids are divided up into many sections separated by
a septa. With the exception of certain parts most of the sections are
identical to one another. Digestion-complete digestive tract
phaynyx->esophagus->crop->gizzard->intestine
Closed circulatory
system with
hemoglobin is
present
-Main dorsal and
ventral vessels
connected by
longitudinal
vessels
-Five pair of
hearts
many vessels in the skin permit gas exchange. Marine annelids have
gills for each body section.
-Excretory system-For each section there is a pair of metanephrida
to remove waste from the coelomic fluid. They have an external
opening to the outside.
-Reproduction-Hermaphrodites with cross fertilization. Two
earthworms will exchange sperm and store it temporarily. The
clitellum secretes a smooth mucous cocoon which slides long the
worm picking up its eggs and stored sperm for fertilization. The
cocoon slips of the worm and the embryos develop inside the cocoon.
-Movement involves coordinating longitudinal and circular muscles
in each segment with the fluid filled coelom functioning as a
hydrostatic skeleton. Similar to peristalic waves.
Class Oligochaeta-Earthworms and some aquatic species. Important
for breaking down and fertilizing soil. Importantin farming.
Class Polychaeta-Mostly marine species. Some are plankton, some
crawl on ocean floor, others live in tubes. Each segment has a
parapodia which are highly vascularize for gas exchange and
motion.
Class Hirudinea-Majority are frewater with some terrestrial
Many are carnivorous
and others are
external parasites
feeding on blood. Blade like jaw splits
the skin or drills a
hole into the skin.
The third clade in the bilaterial clade is Clade Ecydysozoa, which
secretes and molts of an outer covering (ecdysis). Contains 8
phyla. Two most successful is Phylum Nematoda and Phylum
Arthropoda. Based on molecular DNA sequencing.
Phylum Nematoda-Round worms. These are nonsegmented
pseudocoelomates. A tough cuticle or exoskeleton covers the body
which the worm will periodically shed. Molecular genetics puts
its relationship closer to the arthropods than the annelids.
-Complete digestive tract.
-No circulatory system, fluid in the pseudocoelom is used to
deliver food. Many are parasites and pest of animals and many
attack the roots of plants. Pin worms and hook worms are
nematodes. Trichinella spiralis causes trichinosis in humans.
Caused by eating undercooked pork with juvenile worms
encysted in the muscle tissue. These develop into adults that
burrow into the human intestinal wall and invades other organs.
Phylum Arthropoda –Most
successful animal phyla.
Greatest variety of species and
more in terms of numbers than
any other animal phyla.
Arthropods are covered by a
cuticle or an exoskeleton
constructed of layers of protein
and chitin.
This can be thin and flexible for the joints and thick and hard for
other parts.
-Provide protection and points of attachment for muscles to move
appendages.
-Impermeable to water
-It must be shed to the animal to grow and a new one secreted.
Circulation-
-Open circulatory system with hemolymph present. Dorsal blood
vessel with one way valves and pores (ostia). The blood enters the
vessel and hearts pull the blood forward. The blood moves through
the hemocoel are sinuses which are different from the true coelom.
The true coelom is reduced in adult arthropods.
-Gas exchange -is varied because the arthropods are found in many
different environments. Include gills in aquatic species, tracheal
systems in insects and book lungs in spiders.
Digestive tract is complete with specialized organs. i.e. Grasshopper
-Specialized appendages for mouth
-Foregut and midgut has gastric ceca to secrete digestive enzymes
-Malpighian tubules between midgut and hindgut act like kidneys to
reclaim salts and water and to put nitogenous wastes into the
hindgut
Nervous system is extremely well developed with two ventral nerve
cords and extensive cephalization with many sensory structures
clustered at the anterior end. Sense organs include eyes, olfactory
receptors and tactile receptors.
Main LinesTrilobites-Extinct class but important. Extensive
segmented but little appendage specialization.
Evolutionary trend in arthropods is to fuse segments
and have fewer segments and specialization of
appendages to form antennae, wings, mouth parts and
so forth.
specialize appendages.
Subphylum Chelicerforms-have a feeding appendage called a
chelircerae. Has a cephalorthorax and posterior abdomen. Some
specialization with appendages.Ex. Horseshoe crab, arachnids like
spiders, scorpions, ticks and mites.
Subphylum Myriapoda-Worm-like arthropods are segments with
number of walking legs. Millipedes have two pair of legs/segment
and are nonpoisonous detritus eaters. Centipedes have one pair of
walking legs per segment and are poisonous carnivores.
Subphylum Hexapoda-Body with head, thorax and abdomen. 3
pairs of legs and modified mouth parts Ex insects and springtails
Subphylum Crustacea-Body with 2-3 parts. Antennae present and
chewing mouth parts. 3 or more pairs of legs. Ex crabs, lobsters and
shrimp.
Origins of segmentation-
Traditional classification suggests that arthropods evolved from
annelids based on the superficial similarities between annelids and
centipedes/millipedes but molecular evidence shows this not to be the
case. Segmentation is found in all three major clades of the
bilarterial cladeLophotrochozoa-annelids
Ecdysozoa-arthodpods
Deuterostomia-chordates
However, in each of these clades there are also phyla that are not
segmented.
Segmentation occurs during the development of the embryo.
During the course of development part of the embryo are sectioned
off or blocked-out into regions where certain body parts will
develop.
For example each bilateral animal has a particular linear
arrangement of anatomical features along its anterior (head) to
posterior axis. Eyes for example are located at the anterior end of
the animal.
Differential expression of various regulatory gene that code for
transcription factors play a key role in the blocking-out of anterior--->posterior anatomy in the developing embryo. The gene of the Hox
complex determine what organs will develop in each segment. For
example, differential expression of various Hox genes along the
embryo of lobster cause antennae to develop on certain segment and
walking legs to develop on other segments. But even in nonsegmented animals, such as flatworms, Hox genes determine where
certain organs, such as eyes, develop along the animal's length. In
fact, sponges have at least one Hox gene and cnidarian such as jellies
have several. In a cnidarian, for example, expression of a Hox gene
determines where tentacles will develop in the embryo.
It can be concluded that the original Hox gene originated prior to
bilateral symmetry. The mechanism for the development of
segmented bodies in certain animal phyla is a variation on a basic
regulatory scheme that dates back to the first animals. An increase
in the number of Hox genes through gene duplication and mutations,
along with adaptation of Hox gene function for development of
segmented bodies, made it possible for a great diversity.
Clade Deuterostomia-
Deuterostomes have1. Coelom from archenteron surrounded by mesodermal tissue.
2. Formation of the mouth at the opposite that of the anus which
developed from blastopore.
Clade Deuterostomia- contains Phylum Echinodermata and Phylum
Chordata
Phylum Echinodermata- Echinoderms with a water vascular system
and secondary radial anatomy.
Sessile or slow moving animals. The appendages are in multiples of
five that radiate out from a central disc and there is a thin skin over
hard calcareous plates.
-Water vascular system. This contains a networks of hydraulic
canals branching into extensive structures called tube feet that
function in locomotion, feeding and gas exchange.
There are about 7000 species of echinoderms. The six recognized
classes are:
1. Class Asteroidea -includes the sea stars which have five or more
arms extending from a central disc. They have tube feet on the
undersurface of the arms with suction cups at the end of each tube
foot. They are predators that attach tube feet to the prey and the
arms of the wrap around the prey
2. Class Ophiuroidea contains the brittle stars which differ from sea
stars with smaller central discs and longer more flexible arms that
have no suckers on their tube feet
3. Class Echinoidea contains sea urchins and sand dollars. Sea
urchins are spherical while sand dollars are flattened. These
echinoideans lack arms but have five rows of tube feet and muscles.
that pivot their spines for locomotion. They have a complex jaw like
structure used for feeding on seaweeds and other food
4. Class Crinoidea contains the sea lilies which are sessile, living
attached to substratum by stalks. A few are motile and use their
arms for a crawling form of locomotion. The arms circle the mouth
and are used in feeding.
5. Class Holothuroidea contains sea cucumbers which have little
resemblance to other echinoderms as they lack spines and the hard
endoskeleton is reduced. Their body is elongated. These species do
possess five rows of tube feet, a part of the unique water vascular
system and some tube feet around the mouth have developed into
feeding tentacles.
6. Class Concentricycloidea contains the sea dasies which are small
(less than 1 cm), disc shaped marine animals. They live in deep
water and do not possess arms. The tube feet are located around
disc margin with water vascular system consisting of two concetric
ring canals.