2 2
Protista
Classifying ProtistsGeneral Biology of Protists
The Kingdom Protista is divided into four major groups, not technical divisions but instead grouped by lifestyle:
A- The protozoans.
B- The slime molds.
C- The unicellular algae.
D- The multicellular algae.
3 3
Protista
Protists are the most diverse of the four kingdoms in the domain Eukarya.Fossil history 2.5 billion years old artificial group of convenience
single-celled eukaryotic organisms Not plant not animal not fungi
little consensus about classification
4 4
They are first eukaryotes, having a well organized nucleus and complex membranous organelles.They are unicellular or colonial forms without distinct division of labor.
5 5
They are autotrophic or heterotrophic showing varieties of metabolic systemsLocomotion is by pseudopodia, flagella or cilia.They show mitosis, meiosis and simplest type of sexual reproduction for the first time. Common examples are Ameba, Paramecium, Euglena, diatoms and dinoflagellates.
6 6
Ameba
A single-celled (protozoan) organism that constantly changes shape. The word "ameba" is from the Greek "amoibe" meaning "change."
7 7
Structure of an amoeba: unicellular animal with pseudopods that lives in fresh or saltwater.Pseudopodium: part of the amoeba used for locomotion.Ectoplasm: vitreous superficial layer of an amoeba.Endoplasm: central part of an amoeba.Cell membrane: membrane covering an amoeba.Contractile vacuole: cavity of the amoeba that is able to contract.Food vacuole: cavity of the amoeba responsible for digestion.Nucleus: central organelle for an amoeba.Digestive vacuole: cavity of the amoeba responsible for digestion.
8 8
Classification
Protozoans include all protists that ingest their food, they live primarily in aquatic habitats, such as ponds, drops of water in soil, or the digestive tracts of animals.
A small group of protozoans function as parasites.
The second group, the slime molds, are unique in having both unicellular and multicellular stages.
10 10
Evidence for the endosymbiont theory is that mitochondria and chloroplasts:
- Are appropriate size to be descendants of eubacteria. - Have inner membranes similar to those on
prokaryotic plasma membranes. - Replicate by splitting, as in prokaryotes. - DNA is circular and different from the DNA of the
cell's nucleus. - Contain their own components for DNA transcription
and translation into proteins . - Have ribosomes similar to prokaryotic ribosomes. - Molecular systematics lend evidence to support this
theory. - Many extant organisms are involved in
endosymbiotic relationships.
12 12
General Biology of the Protists
Cell surface possess varied array of cell surfaces
Plasma membrane only, extracellular material – cells walls (diatoms –silica)
Locomotor organelles chiefly flagellar rotation or pseudopodial
movement Pseudopodia – false foot – extension of body
Cyst formation dormant form of a cell with resistant outer
covering in which metabolism is essentially shut down (harsh environments – gastric secretions)
13 13
General Biology of the Protists Nutrition
employ all forms but chemoautotrophic phototrophs heterotrophs
phagotrophs - visible food particles osmotrophs - food in soluble form
14 14
General Biology of the Protists Reproduction
typically reproduce asexually binary fission - equal halves budding - progeny cell smaller schizogony - multiple fission - multiple individuals simultaneously
sexual reproduction in times of stress gametic meiosis - before gametes
Diploid - haploid zygotic meiosis - after fertilization
Individuals are Haploid until diploid zygote is produces intermediary meiosis – alternating (alternation of generation) haploid
and diploid undergo mitosis
17 17
Protists
Six identified lineages: Euglenozoa Alveolata Stramenopila Rhodophyta Chlorophyta Choanoflagellida
18 18
Euglenozoa
Euglenoids most are freshwater about one-third are autotrophic, rest
heterotrophic pellicle (interlocking proteinaceous strips in
helical pattern (flexibility) lies within plasma membrane stigma - light sensitive organ that aids in orienting
toward light Euglena
two flagella attached to reservoir contain numerous chloroplasts
20 20
EuglenozoaKinetoplastids - 2nd group within Euglenozoa unique, single mitochondrion in each trypanosome
(2 types of DNA) mini-circles and maxi-circles Trypanosomes are kinetoplastids that cause many serious
human diseases. Usually tropical African sleeping sickness Chagas
21 21
AlveolataDinoflagellates Most are photosynthetic Fresh and Saltwater Encased in cellulose/silica plates distinctive
flagella -single spins as it moves, protective coats (cellulose/silica plates), and
biochemistry –chlorophyll a and c and carotenoids
reproduce primarily by asexual cell division responsible for “red tides” – poisonous toxins
inhibit diaphragm and cause respiratory failure in many vertebrates
22 22
AlveolataApicomplexes spore-forming animal parasites
unique arrangement of fibrils, microtubules, vacuoles, and other cell organelles
Most famous - malarial parasite - Plasmodium malaria eradication
eliminating mosquito vectors poison parasites inside human body - Quiinine develop vaccines
24 24
AlveolataCiliates most feature large numbers of cilia
usually arranged in longitudinal rows or spirals around the body
form vacuoles to ingest food and regulate water balance
waste emptied through cytoproct
Paramecium
26 26
Stramenopila and RhodophytaStramenopila includes brown algae,
diatoms, and oomycetes brown algae - conspicuous
seaweeds alternation of generations
diatoms (phylum Chrysophyta) - photosynthetic, unicellular organisms with double shells of opaline silica
28 28
Stramenopila and RhodophytaStramenopila oomycetes (water molds) - parasites or
saprobes. comprise water molds, white rusts, and downy
mildews motile zoospores bear two unequal flagella life cycles characterized by gametic meiosis and
a diploid phase
29 29
Stramenopila and RhodophytaRhodophyta Red algae range in size from
microscopic to very large. origin a source of controversy
tentatively treated as a sister clade of green algae (Chlorophyta)
30 30
Chlorophyta
Green algae are the ancestors of the plant kingdom. extensive fossil record dating back
900 million years mostly aquatic Chlamydomonas well-known genus
probably represents primitive state Chlorophyta did not give rise to land
plants.
32 32
Choanoflagellida
Choanoflagellates are most like the common ancestor of the sponges and all animals. contain a single emergent flagellum
surrounded by a funnel-shaped, contractile collar
33 33
Amoebas
contain pseudopods that can form at any point on the cell body and can move in any direction Phylum Actinopoda (radiolarians)
secrete glassy exoskeletons of silica.
34 34
Foraminifera
heterotrophic marine protists with pore-studded shells complex life cycle with alternation
between haploid and diploid generations
35 35
Slime MoldsSlime molds originated at least three distinct times. plasmodial slime molds
stream along as a non-walled, multinucleate mass of cytoplasm, plasmodium
produces sporangium during times of resource shortage
forms spores that quickly undergo meiosis
36 36
Slime MoldsCellular slime molds individual organisms behave as separate
amoebas, moving through soil or other substrate and ingesting bacteria individual organisms aggregate and form
moving mass “slug” when food becomes scarce
38 38
SummaryEndosymbiosisClassifying ProtistsGeneral Biology of ProtistsSix Lineages Euglenozoa Alveolata Stramenopila Rhodophyta Chlorophyta Choanoflagellida