Protists Flashcards

Differences Between Protists and Prokaryotes

• Protists are eukaryotes; prokaryotes include bacteria and archaea.
• Eukaryotes possess a nucleus and linear DNA; prokaryotes have no nucleus and contain circular DNA.

Species Diversity of Protists

• Protists represent 10% of species diversity within Eukarya.
• Diversity is low due to abundance in ecosystems, with plants, animals, and fungi excluded from the protist kingdom.

Paraphyletic Nature of Protists

• Protists form a group excluding one or more monophyletic groups of descendants.
• They lack shared derived characteristics that set them apart from other groups.

Red Tides

• Caused by toxin-producing dinoflagellates, a type of protist.
• Result in shellfish poisoning in humans.

Carbon Fixation by Protists

• Protists are responsible for fixing half of the world's carbon.
• Carbon fixation involves converting inorganic carbon into organic compounds.

Aquatic Food Chain

• Phytoplankton serves as the foundational base of the aquatic food chain.

Global Carbon Cycle

• Describes the movement of carbon atoms through various forms in the environment.

Phytoplankton as a Carbon Sink

• During photosynthesis, phytoplankton convert carbon dioxide into sugar molecules.

Role of Phytoplankton in Global Warming

• Function as a reservoir for carbon, mitigating global warming effects.

Earliest Eukaryotic Organisms

• Must have been unicellular, contained a nucleus, had mitochondria, and lacked a cell wall.

Life Cycle of Malaria

• Mosquitoes act as vectors; they transfer protists to human liver cells via bites.
• Protists reproduce within liver cells, then infect more human cells.
• Infected humans pass on the protist to mosquitoes, allowing reproduction during meiosis.

Origin of the Nuclear Envelope

• Hypothesis suggests the cell membrane folded inward, forming the endoplasmic reticulum (ER).
• Evidence includes infoldings in some bacteria and the nuclear envelope's continuity with the ER.
• Benefits include separation of transcription and translation processes.

Origin of Mitochondria

• Eukaryotic cells engulf bacteria, which become mitochondria.
• Mitochondria share size and genome similarities with bacteria and have double membranes.
• Mitochondria provide ATP; eukaryotes protect them in return.

Origin of Chloroplasts

• Photosynthesis originates in bacteria; protists engulf cyanobacteria through secondary endosymbiosis.
• Chloroplasts are characterized by four membranes.

Endosymbiosis Hypothesis

• Proposes that mitochondria became integrated into eukaryotic cells around 2 billion years ago.

Secondary Endosymbiosis

• Occurs when a eukaryotic cell engulfs another eukaryotic cell that has already undergone primary endosymbiosis.

Feeding Mechanisms in Protists

• Phagocytosis involves ingesting food packets, including bacteria and other protists.
• Absorptive feeding takes nutrients directly from the environment.

Absorptive Feeding in Protists

• Common among decomposer and parasitic protists.

Movement Types in Protists

• Movement methods include amoeboid motion via pseudopodia, swimming with flagella, and ciliary swimming.

Protists Within Eukarya

• Out of seven major lineages in Eukarya, six contain protists.

Unique Features of Protist Groups

• Amoebozoa, Rhizaria, Excavata, and others exhibit distinct morphologies, feeding strategies, and movement types.
• Specific examples include Euglenida in Excavata and Oomycota, along with diatoms and brown algae.