3.2 Marine Algae - Terms

Monophyletic

A group that

evolved from a common ancestor

includes all descendants of that common ancestor; sister groups are always monophyletic.

Sister taxa / sister groups

Two groups that split from a common node; sister taxa are pairs of terminal taxa that are each other's closest relatives.

Protist

Any eukaryote that is not a land plant, fungus, or animal; a throwback term from an older view of eukaryote classification, and protists are not monophyletic.

Plantae

A group that includes red algae, green algae, and land plants, whose members all have chloroplasts with double membranes; roughly equivalent to Archaeplastids.

Archaeplastids

A group of photosynthetic eukaryotes (roughly equal to 'Plantae') including red algae, green algae, and land plants; all species have chloroplasts with double membranes.

Opisthokonts

A monophyletic group of eukaryotes that includes fungi, choanoflagellates, and animals.

Chloroplasts

The structures all photosynthetic eukaryotes use for photosynthesis; thought to have originated when a single-celled eukaryote engulfed a cyanobacterium, and they have their own circular DNA, replicate by fission, and have at least a double membrane.

Endosymbiosis

A relationship in which one organism lives inside another; chloroplasts originated when a single-celled eukaryote engulfed a cyanobacterium (primary endosymbiosis), which occurred in the common ancestor of Plantae.

Secondary endosymbiosis

The process by which other eukaryote groups acquired chloroplasts when a predatory protist engulfed a photosynthetic protist (with a red algal or green algal chloroplast), leading to a chloroplast with 3 or 4 membranes.

Thallus

The individual body of a brown alga, which has no complex vascular system.

Trophic cascade

An ecological effect in which a change at one level of a food web ripples down to other levels, such as sea otters preventing sea urchins from destroying kelp forests; kelp forests are an example of keystone species and trophic cascades.

Alternation of generations

The predominant life cycle in algae and land plants, which alternates between two multicellular life stages: a haploid (n) gametophyte and a diploid (2n) sporophyte.

Sporophyte

The multicellular diploid (2n) form in alternation of generations, which produces spores by meiosis.

Gametophyte

The multicellular haploid (n) form in alternation of generations, which produces gametes (n) by mitosis

marine photosynthetsizers

phytoplankton

diatom

brown algae

red algae

phytoplankton

• single-celled

• 50% of global photosynthesis

• every ocean animal relies on it for food

• made of: photosynthetic bacteria & diatoms (photosynthetic eukaryote)

brown algae

• multicellular

• chloroplasts with 4 membranes

• no complex vascular system

• colour: carotenoid pigment used in photosynthesis

red algae

• unicellular & multicellular

• live in deep depths

• most diverse marine seaweeds

• colour: carotenoid pigment (phycoerythrin) used in photosynthesis

phycoerythrin: absorbs blue light (therefore not blue)

• blue light penetrates deep, so lives at deep