Eukaryotes: Fungi, Algae, Protozoa 2

Algae (basic characteristics)

• Not strictly a taxonomic group

• Any unicellular photoautotroph that lives in an aquatic environment.

• Need water for growth/reproduction

• Lack roots, stems, and leaves

Algae (seaweed members)

• Phaeophyta (brown)

• Rhodophyta (red)

• Chlorophyta (green)

Photic zone

The top layer of water receives enough light for photosynthesis

• This is where algae live in aquatic habitats.

• Algal pigments often reflect the depths at which they live in the photic zone.

Common microscopic algae

• Chlamydomonas (often found ins freshwater, damp soil, ocean)

• Euglenoids (some have eyespot, flagellum, some are non-photosynthetic protists)

• Diatoms

• Dinoflagellates

Diatoms

• Silica in cell walls

• Features for form shells (frustules)

• Common: Chaetoceros, Fragiliariopsis and Minidiscus

Dinoflagellates

• Unicellular, not all photosynthetic

• Motile: have two flagella

• Some generate neurotoxin (saxitoxins) that can cause paralytic shellfish poisoning

• Common: Ceratium (widespread), Dinophysis (linked to HABs).

Roles of Algae in Nature

• Fix CO2 into organic molecules

• Algal blooms (high increase in planktonic algae)

  • Toxin release

  • massive oxygen consumption by heterotrophic microbes, leading to dead zones

  • Lead to an influx of nutrients

Protozoa (Bacic Characteristics)

• Unicellular eukaryotes

• Lack cell walls, have nuclei, and have ‘animal-like nutrition.’

• Heterotrophic

• Complex life cycles

• Some inhibit water/soil, part of normal microbiota, cause disease in humans and animals.

Protozoa (two life stages)

1) Trophozoite (feeding and growing stage)(motile, dividing stage)

2) Cyst (a dormant resting stage)(non-motile)(survival stage)

Protozoa (divided groups)

• Excavate

• Amoebozoa

• Apicomplexa

• Ciliates

Protozoa (excavata)

Move using flagella (flagellates) or by undulating their cell membrane.

Protozoa (Ameobozoa)

Move using pseudopods (‘flalse feet’)

Protozoa (Apicomplexa)

Are non-motile (also known as Sporozoa)

Protozoa (Ciliates)

Move using cilia

Protozoa (eating)

• Ciliates wave thair cillia toward a mouthlike cytosome

• Amebae phagocytize their food

In both cases, the food is digested in a vacuole

Common Protozoal pathogens

• Giardia Intestinalis (cuase giardiasis (type of diarrheal infection))

• Entamoeba (Can cause amebic dysentery (type of severe intestinal infection))

• Plasmodium (causes malaria (infects and destroys RBCs and liver cells))