CLASSIFICATION OF LOWER ORGANISMS. Remember: There are 6 Kingdoms for all organisms Animalia,...
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Transcript of CLASSIFICATION OF LOWER ORGANISMS. Remember: There are 6 Kingdoms for all organisms Animalia,...
CLASSIFICATION OF LOWER ORGANISMS
Remember:
There are 6 Kingdoms for all organisms
Animalia, Plantae, Fungi, Protista, Eubacteria, Archaebacteria
“Lower organisms” are generally the Eubacteria, Archaebacteria, Protista and Fungi
Definitions
Phylum: the taxon containing closely related classes
Phylogeny: The evolutionary history of a group of organisms that share a common ancestor
Protists - Introduction
Single celled eukaryotes Appeared approximately 1.5 billion years ago 115 000 species, all very diverse in cell
structures, patterns of nutrition, reproduction and habitats
Their phylogeny is very complex and difficult to classify
To simplify in this class, protists have been broken down/classified based on their nutritional pattern: animal-like, fungus-like and plant-like
Animal-Like Protists
Also called Protozoans All are heterotrophs - they eat and ingest
material from their surroundings Are 4 phyla of protozoa, classified by
their type of locomotion Numerous in types of species and
population numbers, similar to bacteria
Animal –Like Protists:Zooflagellates Phylum Mastigophora Possess 1 or more flagella to help them move Feed on other protists or are internal
parasites on animals Reproduced asexually via longitudinal fission Example: Trypanosoma gambiensis causes
sleeping sickness that destroys RBCs, other tissues and one’s nervous system until the person loses consciousness
Animal-Like Protists:Amoebas Phylum Sarcodina Most are free-living forms No set body shape Psuedopods (projections of cytoplasm) enable
them to move and feed through endocytosis (engulfing organisms with their pseudopods)
Some are parasitic
Example: Entamoeba causes amoebic dysentery, found in the water in tropical regions
Animal –Like Protists:Ciliates Phylum Ciliophora Covered with hairlike projections called
cilia Rigid outer covering called pellicle
maintains their shape (amoebas don’t have this)
All ciliates are aquatic heterotrophs Paramecium is an example
Paramecium Digestion
Beating of its cilia sweeps food into oral groove
Membrane pinches off, surrounds food and a food vacuole is formed
Food vacuole joins up with a lysosome which breaks down the food with digestive enzymes
Usable products are absorbed in cytoplasm, undigested food is removed via anal pore
Paramecium & Structure
Have 2 types of nuclei – large macronucleus and smaller micronucleus
Reproduction by binary fission (asexual) Micronucleus (ei) divide by mitosis and
macronucelus simply pinches apart to produce two daughter macronucleus
Paramecium also use sexual reproduction via conjugation
Animal-Like Protists:Sporozoans Phylum Sporozoa Produce spores during asexual
reproduction Sporozoa are non-motile and parasitic;
get nutrients from bodies of hosts Best known sporozoan is genus
Plasmodium that causes malaria
Fungus-Like Protists
Also called....SLIME MOULDS!!!!
All are heterotrophic and most are decomposers that feed on dead plants and animals by endocytosis
Live in cool, damp habitats
Fungus-Like Protists:Acellular Slime Moulds Single celled Most of life is a wall-
less mass of cytoplasm with many nuclei
Cytoplasm moves using pseudopodia (network of strands)
Reproduce using spores; spores scatter and germinate
Fungus-Like Protists:Cellular Slime Mould Live in fresh water,
damp soil or decaying matter
Move like amoebalike cells
When food scarce, they form a large multicellular mass and eventually release spores
Fungus-Like Protists:Water Moulds
Most live in water; some on land
May have seen growing on dead fish as whitish cottony substance
Most land species decompose dead matter which is good, but few are parasitic to plants
Irish Potato famine in mid 1800s caused by Phytophthora infestans
Plant-Like Protists
Are 24 000 species of protists that contain chlorophyll and carry out photosynthesis, and so they resemble plants
We look at Euglenoids and Algae
Plant –Like Protists:Euglenoids Are unicellular
flagellates and many members of this group photosynthesize to produce food
Species called Euglena gets fed in 2 ways
In sunlight it is autotrophic (photosynthesis)
In dark feed as heterotroph on dead organic material in water
Plant –Like Protists:Algae Resemble plants because they have
chloroplasts that have chlorophyll
Some are single-celled, some live in colonies, some are multicellular
Are 6 main groups of algae; we discuss 3 here
Algae: Diatoms
Have golden colour due to yellow-brown pigments in their shells
Outer covering is made of two halves
Each species has a characteristic shape
Abundant in ocean; also classified as phytoplankton
Algae: Dinoflagellates
Are single-celled algae, have 2 flagella
Most are photosynthetic
Abundant in marine environments
Each species has a specific shape
Tend to be luminescent: when surrounding water is agitated, they give off light!!
Reproduce by mitosis
Interesting to Know....
Rapid population growth called an algal bloom
When dinoflagellate Gonyaulax polyhedron blooms it’s called a red tide
Algae: Green algae
Can be single celled or colonial Each cell has 2 flagella that move the
cell around Ancient green algae are thought to have
given rise to the first plants because they have cellulose in their cell walls and their chloroplasts are similar to those of plants
Multicellular algae known as seaweeds
Algae: Green algae
Colony of Algae (Volvex)Giant Kelp (multicellular Algae) can grow to 100 m and has the fastest growth rate of any organism.