The Origin and Diversification of Eukaryotes (ch 19)

From which domain of life did eukaryotes evolve?

Archaea. (Specifically, a group like Lokiarchaeota is the closest known relative).

What are the TWO key organelles in eukaryotic cells that arose through endosymbiosis?

Mitochondria and Chloroplasts.

From what type of bacterium did mitochondria evolve?

An alphaproteobacterium.

From what type of bacterium did chloroplasts evolve?

A cyanobacterium.

What is the MAIN advantage the first eukaryotic cell gained by acquiring a mitochondrion?

Efficient ATP generation through aerobic respiration, especially as oxygen levels rose.

What key feature did the ancestral archaeon develop that allowed it to become larger and engulf other cells?

A flexible cell surface (due to loss of a rigid cell wall) and a cytoskeleton.

What is the difference between PRIMARY and SECONDARY endosymbiosis?

1. Primary: A prokaryote is engulfed by a eukaryote.

2. Secondary: A eukaryotic alga is engulfed by another eukaryote.

How can you tell a chloroplast originated from secondary endosymbiosis?

It is surrounded by FOUR membranes instead of two.

What is a "protist"?

An informal term for a diverse group of mostly single-celled, microscopic eukaryotes. It is NOT a formal taxonomic group.

What unique structure do all Alveolates share?

A system of sacs called alveoli under their cell membrane.

What are the three main types of Alveolates?

Dinoflagellates, Apicomplexans, and Ciliates.

What vital role do Dinoflagellates play in coral reefs?

They live as symbionts inside coral polyps, providing them with nutrients via photosynthesis.

What is "coral bleaching"?

When corals expel their symbiotic dinoflagellates due to stress, causing them to turn white and potentially die.

What group of Alveolates includes serious parasites like Plasmodium (malaria)?

Apicomplexans.

What is the defining feature of Stramenopiles?

They have two flagella, one of which is "hairy" (covered in bristles).

What are Diatoms, and why are they ecologically crucial?

Stramenopiles with glass-like (silica) cell walls. They are a major component of phytoplankton and produce about 20% of the world's oxygen.

What is the name of the Stramenopile group that includes plant pathogens like the cause of the Irish Potato Famine?

Oomycetes (water molds).

What characteristic feature do Rhizarians like Foraminiferans and Radiolarians have?

Long, thin pseudopods for movement and feeding.

What important geological rock is formed from the accumulated shells of Foraminiferans?

Limestone.

Which Excavate group causes diseases like African Sleeping Sickness and Giardiasis?

Kinetoplastids (e.g., Trypanosoma) and Diplomonads (e.g., Giardia).

What is a major characteristic of many Excavates like Giardia?

They lack mitochondria or have highly reduced ones.

What supergroup includes animals, fungi, and their close protist relatives like choanoflagellates?

Opisthokonta.

Has multicellularity evolved once or multiple times in eukaryotes?

Multiple times independently in different lineages (e.g., animals, plants, brown algae, slime molds).

What three things are needed for a unicellular organism to evolve into a multicellular one?

1. Variation in clusters, 2. Heritability of that variation, 3. Differential Fitness (the variation must affect survival/reproduction).