Untitled Notes

Kingdom Protista

Definition: Domain Eukaryota encompasses all organisms whose cells contain a nucleus.
Organisms Included: The organisms within this domain include Protists, Fungi, Animals, and Plants.

Protists are primarily eukaryotic organisms that do not fall under the categories of plants, fungi, or animals.
Diversity: Protists are highly diverse, including both unicellular and multicellular organisms.
Most protists are unicellular and found primarily in aquatic environments.
Protists can be classified according to their nutritional modes:
- Heterotrophic: By ingesting other organisms (live or dead).
- Photosynthetic: Similar to plants but usually different in some biochemical pathways.
- Saprotrophic: Living off decomposing organic material, akin to fungi.
Evolutionary Importance: They represent the first eukaryotes and are the ancestors of more complex life forms such as animals, fungi, and plants.

Plant-like protists (e.g., phytoplankton and algae):
- Examples include Diatoms (single-celled algae with silica cell walls) and Spirogyra (filamentous algae with spiral chloroplasts).
- They can be multicellular as well, with notable examples being Red and Brown Algae (e.g., Kelp).
Animal-like protists:
- All are unicellular and utilize various forms of locomotion to obtain energy:
  - Amoebas: Move using pseudopodia (glob-like projections).
  - Flagellates: Move using one or a few whip-like tails.
  - Ciliates: Move through coordinated movements of numerous tiny hair-like structures.
Fungus-like protists:
- Includes slime molds, which can exist as single cells but can aggregate to form multicellular structures or giant cells.
- Unlike fungi, which absorb nutrients after extracellular digestion, slime molds ingest dead or rotting material through intracellular digestion.

Protists form the basis of many marine and aquatic food chains.
They play a significant role in carbon storage, helping keep carbon locked out of the atmosphere.
Certain protists serve as decomposers vital for nutrient cycling in ecosystems.

Diversity: The fungal kingdom is estimated to contain millions of species, with about 100,000 named.
Fungi can be classified as unicellular, like yeasts, or multicellular, typically composed of filamentous structures known as hyphae.

Fungi are primarily long networks of hyphae that extend throughout their food sources, such as soil or decaying material.
Hyphal Functions:
- Reproduction
- Sensory detection
- Nutrient absorption through secreting enzymes and then absorbing the digested materials (external digestion).
- Structures known as mycelium refer to a mass of hyphae.

Fungi are classified as heterotrophs, which means:
- They obtain energy by consuming organic material rather than producing it themselves.
- They carry out external digestion, yielding nutrients from consumed material.

Fungi reproduce through both sexual and asexual means:
- Asexual reproduction via conidia or spores.
- Sexual reproduction involves the formation of fruiting bodies followed by the union of mycelium from different individuals.

Fungi can serve multiple ecological roles:
- Decomposers: Breaking down dead organic matter, which recycles nutrients back into ecosystems.
- Parasites: Feeding on living hosts without immediate death (e.g., blights and human infections).
- Mutualists: Engaging in symbiosis with plants (e.g., mycorrhizal fungi support plant nutrient uptake while receiving photosynthetic sugars in return).

Food sources: Fungi are extensively used in the food industry, from baking to brewing.
Antibiotics: Derived from fungi, Penicillin is a notable medicine that revolutionized healthcare.
However, fungi can also cause diseases in humans, crops, and animals, leading to significant agricultural and public health impacts.
Examples include athlete’s foot, yeast infections, and crop diseases such as the potato blight.