Download Kingdom Protista

Kingdom Protista
Unicellular or colonial eukaryotes, microscopic
About 64,000 species – over half identified from fossil remains (radiolarians and
“forams”)
Huge diversity of intracellular specialization – division of labor by variety of
organelles.
All imaginable kinds of symmetry present
No tissues/organs
Many free-living, symbiotic and parasitic forms
Locomotion by cilia, flagella, or pseudopodia
Protista Continued…
Some have an exoskeleton, most do not
Acquire nutrition from all possible sources – some autotrophs, heterotrophs,
saprozoic and combinations of these.
Reproduction most often is asexual, but many can also reproduce sexually
–Asexual: by binary fission cells duplicate by mitosis.
–Sexual: gametes are produced and mixed (as in Volvox) or micronuclei are
exchanged during conjugation (as in Paramecium)
The Importance of Protists
Plant-like protists, or “Algae,” form the basis of most freshwater and marine
ecosystems.
Over half of the photosynthesis on earth occurs in protists like Euglena and Volvox.
Marine Dinoflagellates are so numerous that blooms of certain toxic species causes
devastating ‘red tides’ in coastal areas around the world…
Origin of Protista
Derived from procaryotes about 600 mya
Complex energy-producing organelles like mitochondria and chloroplasts (now
inside other eukeryotes) were most likely derived from symbiotic bacteria…
The incorporation of these organelles paved the way for “higher organisms” like
plants and animals to be derived from protists.
First animals appear in fossil record soon after the first evidence of protists… (~50
my later)
Protistan Taxonomy
Kingdom Protista
Phylum Ciliophora (the “ciliates”)
Eg. Paramecium
Phylum Apicomplexa (all are parasites)
Class Sporozoa Eg. Plasmodium
Phylum Sarcomastigophora
Subphylum Mastigophora Eg. Euglena
Subphylum Sarcodina Eg. Amoeba
Phylum Ciliophora
Use cilia for locomotion
Have a pellicle surrounding the cell membrane, in which the cilia are connected
Have a cytostome- a hole through which they these ‘ciliates’ eat.
Like all protists, ciliates eat by phagocytosis- the cell membrane surrounds a food
item, which then becomes a food vacuole in cell.
Phylum Sarcomastigophora
Includes the protists which move using flagella (Mastigophora) and those that move
using pseudopodia (Sarcodina).
‘Flagellates’ include animal-like (Trypanosoma) and plant-like (Volvox) genera
Sardodina includes amoebas of many kinds, as well as “radiolarians” and
“foraminiferans.”
Kingdom Animalia
Phylum Porifera: the sponges
Phylum Porifera
characteristics
No true tissues (blender example), therefore no organs. Like protists, Cellular
level of organization
No reliable body symmetry (somewhat random)
Body covered in pores for water flow
Spicules, composed of calcium carbonate or silicon dioxide, and/or the protein
“spongin” provide skeletal support, also collagen (most common animal protein)
plays a structural role.
Specialized cells perform various functions
Most are Monoecious (have male and female gonads)
Sponge systems
Integumentary: thin layer of pinacocytes
Skeletal: spicules, spongin and collagen…
Muscular: none, individual cells move using pseudopodia and flagella
Nervous: none
Respiratory: none, cells get oxygen from water
Circulatory: none, amoebacytes share nutrients
Excretory: none, sponge is “isotonic” with the seawater
Endocrine: none
Digestive: intracellular, individual cells process food particles removed from water
Sponge Reproduction
Sponges monoecious but use asexual and sexual reproduction
Asexual- freshwater sponges produce “gemmules”, small packages of archaeocytes
that can grow into a new sponge. A second asexual method is by fragmentation
from damage/predation. Lastly, some sponges produce buds.
Sexual-
produce eggs and sperm in huge numbers which disperse and hopefully
join up with gametes from another sponge. Fertilization is external, hence lots and
lots of gametes produced…
Asexual
Poriferan Reproduction
Asexual
Budding
Fragmentation
Gemmule formation
Sponge Body Plans
ASCON (asconoid)- The simplest body plan, with a single osculum at the top, and
pore channels (ostia) channeling water into a “spongocoel” lined with choanocytes.
(see fig. 12-5, page 245) These sponges are small.
SYCON (syconoid)- still only one osculum, but pore channels (ostia) are complex
and lined with choanocytes. Single spongocoel has no collar cells. Internal openings
into spongocoel are called “apopyles”
More Body Plans
LEUCON (leuconoid)- most complex form, with many ostia and often many
oscula. External pores connected to “flagellated chambers” lined with choanocytes.
Chambers connect to excurrent canals and then out through oscula. These sponges
are often “lump shaped,” as in the bath sponges. (see fig 12-5, page 245).
Sponge cell types
Pinacocytes- together, form a “pinacoderm” an outer protective cover of flat cells.
Some of these can contract like tiny muscles (myocytes)
Archaeocytes- contained within a fluid “mesohyl” middle layer. Perform the
function of distributing nutrients from choanocytes to other cells. Also, these cells
can turn into any other type of sponge cell… Various types of these also produce
spicules, and secrete the proteins spongin and collagen.
Pinacocyte
Archeocytes
Cell types continued…
Choanocytes- also called collar cells, these have a circular baffle of microvilli
which acts as a seive to catch food particles in the water. A single flagellum beats,
and combined force of thousands of cells pumps water through the sponge, and out
the osculum (big hole on top).
Choanocytes
Feeding and Digestion
Poriferan Classes
DEMOSPONGIAE- Spongia, Spongilla
Most common class of sponges (most sponges belong to this group).
Mostly marine sponges with leucon body plan.
Skeleton primarily of spongin, spicules made of silicon (siliceous) if present.
Highly varied group contains “bath sponges” which lack spicules.
Contains the largest sponges, can be shaped like vases, fingers, or encrusting
(often
on coral)
More Poriferan Classes
CALCAREA- Grantia, Scypha, Leucosolenia
Tend to be small, with skeletons of calcium spicules
Body plans asconoid (Leucosolenia), syconoid (Scypha and Grantia), or leuconoid.
Less brightly colored than class Demospongiae
More Poriferan Classes
HEXACTINELLIDA- Euplectella
Unlike others, these sponges often have radial symmetry
Live in very deep waters, believed to be incredibly ancient and “primitive”
animals.
Spicules (often fused) are 6-rayed and siliceous- the ‘glass sponges’…
Body plan is syconoid or leuconoid
These sponges lack “pinacocytes” or the mesohyl layer- instead archaeocytes form
tiny chambers lined with choanocytes
PHYLUM CNIDARIA
“cnide” means nettle or stinger- most of the ~9000 species have cnidocysts or
stinging cells, which contains “nematocyst” -(stinging) organelle
This group includes the jellyfish, corals and sea anemones- found primarily in the
sea, except for a few freshwater jellyfish…
Radial symmetry is dominant, but a “planula” larvae, present in many, has
bilateral symmetry
Two true tissue layers: epidermis and gastrodermis, with “mesoglea” layer in
between (“diploblastic”)
Two body plans: polyp (sessile) and medusa (motile)
Many possess “alternation of generations”- both body plans present in single
species (see Obelia)
Cnidarian Systems
Integumentary: One cell thick, unlike higher forms…
Skeletal: small soft-bodied types have “hydrostatic skeleton,” in which the body is
strengthened with water pressure. Corals have calcium carbonate skeletons, and
many anemones have rigid protein endoskeleton.
Muscle: “epitheliomuscular” cells can contract in one direction. 2nd layer of cells
contract in another plane.
Digestive: incomplete (only one opening- no anus). Food is captured in a
“gastrovascular cavity” (often branched) lined with gastrodermis. Digestion is still
intracellular- there are no digestive organs.
Systems, continued…
Excretory: most isotonic, no organs
Respiratory: none, gases diffuse as in sponges
Circulatory: none, but substances shared among cells of epidermis and
gastrodermis via cell-to-cell junctions (gap junctions)
Nervous: a “nerve net” covers the body, composed of interconnected neurons, but
with no centralization (no ganglia, and no brain!) This means that all reactions are
reflexes, but can be shared with other regions.
Endocrine: neurons release hormones into cells to produce various responses.
Cnidarian Reproduction
Species can be monoecious or dioecious, but most reproduce asexually and
sexually.
Asexual- budding (cloning), seen in polyp body plan
Sexual- Primarily seen in medusa body plan (or phase), eggs and sperm are
released into seawater, and form zygote, which develops into tiny free-swimming
bilaterally symmetrical larva.
Obelia
Aurelia
Cnidarian body plans
Polyp- This is the sessile form, as seen in Hydra, all corals and anemones. Looks
like a stumpy rooted tree in which the branches are tentacles. A central mouth is
found at the central base of the tentacles.
Medusa- This form is seen in jellyfish, and looks like a pulsating open umbrella.
As in polyp form, tentacles are found around a central mouth (remember, there’s no
anus…) This time, the mouth is facing down instead of up.
Most species retain one body plan, but some have both! See figure 13-2, page 256
for body plans
Two Cnidarian Body Plans
Cnidocyte- a cell containing
a nematocyst. (fig 13-3)
Cnidarian Classes: Hydrozoa
CLASS HYDROZOA: contains mostly marine colonial polyps (live in large
numbers together covering an underwater surface).
Also, most display alternation of generations (see Obelia in figure 13-9)- meaning
that they are both polyps and medusas within the same animal.
Members of the genus Hydra are polyps only, but display the typical small size and
variety of reproductive styles common in this class.
Some members are obligate medusae. Most freshwater jellyfish are in this class.
An interesting hybrid, the Portuguese man-o-war is a floating colony of hydroids.
Cnidarian Classes: Scyphozoa
The “cup animals”, this group contains the larger medusae, or jellyfish.
Most have no alternation of generations- they are always sexually reproductive
jellyfish.
Most are free-living motile forms, made up largely of water (95%)
They have a thick mesoglea layer, and the medusae of this class have features not
seen in “hydromedusae” ie: rhopalium- containing statocysts and ocelli
More Scyphozoa…
This class has the most complex arrangement of the GVC, extending into gastric
filaments, radial canals and a ring canal
Indivuduals are dioecious, and fertilization is internal. A free-swimming planula
larva results, after being protected during development on the oral arms of the
female.
The planula then forms a strobila (sessile stack of medusae), or the planula
develops directly into an adult (see fig. 13-18)
Cnidarian Classes: Cubozoa
Recently considered an order within scyphozoa, these “box jellies” have many
unique features…
Most have only four tentacles, attached to a cube-shaped body
They are fast swimmers, and seem to have “good” vision
They have a “pedalium” at the base of each tentacle- used in prey capture (fig. 1320)
Very predatory, eating worms, fish, other jellyfish species…
After planula larva forms, polyp develops directly into adult (no strobila is formed)
(see 13-18)
Cnidarian Classes: Anthozoa
The “flower animals”- the most plant-like in shape and color
Also, diverse and beautiful (see our great fish tank!)
No medusa stage, most have skeleton of calcium (corals) or protein (anemones)
All are marine only
Most forms of large hard corals and typical anemones fall into order Zoantharia,
comprised of individuals with six-fold biradial symmetry
More Anthozoa
Other corals (sea fans and sea pens) have eight tentacles per polyp, instead of six.
These colonial animals belong to the order Alcyonaria.
All Anthozoans have a GVC divided into Septae, which may be large and paired in
the case of anemones (see fig. 13-23)
In corals, the polyps form one huge colonial animal, with hundreds of tiny
interconnected polyps. Most of these are filter-feeding polyps, with one continuous
GVC! (see fig. 13-27)
Coral Reefs
Formed over thousands of years from successive layers of coral skeleton deposits
(calcium carbonate forms underwater mountains of coral animal skeletons)
The underwater equivalent of the amazon jungle- very high species diversity and
biomass (count the phyla!)
Reefs contain sponges, colonial hydrozoans, anemones, many varieties of coral,
fish, many types of worms we’ve not discussed, not to mention bryozoans,
ctenophores, protists, bacteria, etc etc..