Can be unicellular, filamentous, or multicellular.
*Biologists have hypothesized that Green Algae are most closely related to plants.
Phylum Chlorophyta: Green Algae
*Chlamydomonas, a Unicellular Green Alga**
Photoautotrophs
has a definite cell wall
contains a pyrenoid, which is a dense body where starch is synthesized
2 long, whiplike flagellas
chloroplast contains a red-pigmented eyespot (stigma) which is sensitive to light and helps bring the organism into the light, where photosynthesis can occur
often reproduces asexually as many as 16 daughter cells within the parent wall
-can also reproduce sexually when growth condition become unfavorable.
-gametes of two different mating types come into contact and join to form a zygote
-A heavy wall forms around the zygote, and it becomes a resist zygospore that undergoes a period of dormancy.
-When a zygote germinates, it produces four zoospores by meiosis
-A spore is a reproductive cell that develops into a new organism without the need to fuse with another reproductive cell.
-Zoospores, which are flagellated spores, are typical of aquatic species.
SUMMARY:
MOTILE GREEN ALGAE
DURING ASEXUAL-STRUCTURES ARE HAPLOID
DURING SEXUAL-MEIOSIS FOLLOWS ZYGOTE STAGE - WHICH IS THE ONLY DIPLOID PART OF CYCLE
Phylum Chlorophyta: Green Algae
**Spirogyra, a Filamentous Green Algae**
Photoautotrophs
Unbranched, filamentous green algae
Found in green masses on the surfaces of ponds and streams
sexual reproduction where it undergoes conjugation
Conjugation - temporary union during which the cells exchange genetic material, forming diploid zygotes.
- These zygotes survive the winter, and in the spring they undergo meiosis to produce new haploid filaments.
Phylum Chlorophyta: Green Algae
**Ulva**
Multicellular green algae
Commonly called sea lettuce
Phylum Chlorophyta: Green Algae
*Stoneworts*
live in freshwater lakes and ponds
called stonewarts because they have heavily calcified cell walls.
Example: Chara -forms a cell plate during cell division and has multicellular sex organs
-zygote is retained for a time in the female sex organ
*DNA analysis suggest that among green algae, stoneworts are the most closely related to plants.
Phylum Chlorophyta: Green Algae
**Volvox, a Colonial Green Alga**
Colony-loose association of independent cells in which some cells maybe specialized for reproduction.
Flagella beat in a coordinated fashion
Phylum Rhodophyta: Red Algae
multicellular or can have filamentous branches
gametes do not contain flagella
mainly live in warmer seawater, shallow or deep waters
Main species have commercial importance:
Agar - gelatin-like product primarily from the algae Gelidium and Gracilaria.
-
agar used in making capsules for vitamins/drugs, material for dental impression, base for cosmetics
-In the lab, agar is used for gel electrophoresis.
Example: Chondrus crispus -emulsifying agent for the production of chocolate and cosmetics.
Phylum Phaeophyta: Brown Algae
multicellular
flagellated sperm cells
contain chlorophyll a & c
contains carotenoid pigment called fucoxanthin that gives them that color
reserve food is a carbohydrate called laminarin
found along the rocky coasts
They dry out slowly because their cell walls contain a mucilaginous water-retaining material.
*Most brown algae have the alternation of generations life cycle, but some species of Fucus are unique in that meiosis produces gametes and the adult is always diploid, as in animals.
Some brown algae are giant seaweeds, or kelps - grows along the shoreline
Other examples: Macrocystis, Laminaria, Fucus, kelp
Phylum Bacillariophyta: Diatoms
most numerous unicellular algae in the oceans
plentiful in freshwater
have tests (shells) that fit together like a box with a lid. The tests consist of silica (SiO2) --a common ingredient in glass
reproduce asexually and sexually
significant producers of food and oxygen in aquatic ecosystems because of their sheer abundance.
Phylum Pyrrophyta: Dinoflagellates
unicellular
cells usually bounded by protective cellulose plates impregnanted with silicates
typically have 2 flagella(one lies longitudinal, other transverse)
Chloroplasts vary in color because in addition to chlorophyll a & c, dinoflagellates also contain carotenoids.
part of the phytoplankton
usually reproduce asexually
Like diatoms, one of the most important producers in marine environments.
Gonyaulax, an example, contains a red pigment that is responsible for "red tides"
Phylum Euglenophyta: Euglenoids
unicellular
live in freshwater
some have chloroplasts, other do not
-those that lack chloroplasts ingest or absorb their food.
have two flagella---one called a tinsel flagellum because it has hairs on it
near base of flagella---is an eyespot that permits phototaxis (ability to move in response to light)
Instead of a cellulose wall, they have thin, protein strips called pellicles that wrap over their cell membranes.
reproduce by longitudinal cell division
sexual reproduction is not known to occur.
Phylum Zoomastigophora: Zooflagellates
colorless
lack plastids
heterotropic
has one flagella
most are symbiotic
many are parasitic
**well known for causing various diseases in humans
*Trypanosoma brucei a cause of African sleeping sickness
*Trypanosomes, trasmitted by the bite of a tsetse fly
* WBC accumulate around the blood vessels leading to the brain and cut of circulation, causes an inadequate supply of oxygen
*Giardia lamblia, whose cysts are transmitted by way of contaminated water attaches to the human intestinal wall and causes severe diarrhea
*Trichomonas vaginalis, sexually trasmitted, infects vagina, urethra of women, and prostate/seminal vesicles, and urethra of men.
Protozoans
-unicellular eukaryote
*are considered "animal-like"
includes both photosynthetic and heterotrophic organisms. (mainly heterotrophic)
some heterotrophic organisms ingest their food by endocytosis
usually has some form of locomotion--> flagella, pseudopods, cilia.
consume living cells (predatory, or parasitic), or dead organic matter
What is a pseudopod?
Pseudopods are processes that form when cystoplasm streams forwards in a particular direction.
Protists that have pseudopods usually live in aquatic environments
-oceans, freshwater, lakes, ponds
Protists with Pseudopods:
Protozoa: Phylum Rhizopoda: amoeboids
move and ingest their food by pseudopods
absorb food by phagocytosis
Digestion occurs within a food vacuole.
Examples:
Amoeba proteus: have contractile vacuoles where excess water from the cytoplasm collects before the vacuole appears to "contract" releasing water through a temporary opening in the plasma membrane
Entamoeba histolytica: parasitic amoeboid: lives in the human intestine and causes amoebic dysentery.
