lecture 4: algae and terrestrialization

Question 1

monophyletic group

Answer 1

common ancestor and all its descendants
*algae = not a monophyletic group, just generally photosynthetic organisms that are not land plants
*lichen = not a monophyletic group

Question 2

ecological (functional) group

Answer 2

a set of taxa that share common ways of life, often in a community context
- may or may not overlap with phylogenetic relatednesss
- ex: decomposers, cushion plants
- lichens = an ecological group

Question 3

primary/secondary endosymbiosis

Answer 3

◆ primary endosymbiosis: eukaryote + nucleus engulfs cyanobacterium. branches to red alga or green alga.
◆ secondary symbiosis: more engulfing. leads to stramenopiles, alveolates, eglenids, etc with plastids

Question 4

diatoms

Answer 4

◆ unicellular algae
◆ a huge contributor to global NPP (25%)
◆ characteristics
- unique glass-like cell walls made of silica (silicon dioxide) embedded in an organic mix
- diatom deposits accumulate on the ocean floor
- uplifted fossil deposits are harvested as diatomaceous (soft, crumbly) earth –> key component of toothpaste, metal polishes, and water filtration systems

Question 5

dinoflagellates

Answer 5

◆ unicellular algae
◆ dinos = “whirling”
◆ characteristics:
- have two flagella, one of which is a spiral that can make them spin
- some are heterotrophs, some are mixotrophs (switch between modes)
◆ red tides (-)
- blooms produce toxins that leave massive fish kills and, when concentrated by mollusks, can poison humans
◆ symbiosis of corals with zooxanthellae (+)

Question 6

brown, red, green algae

Answer 6

• all types of algae that are unicellular or multicellular
• use alternation of generations if multicellular
• if unicellular, often multiply asexually

brown algae:
◆ marine algae including kelps
◆ kelps = keystone species of intertidal and deepwater
◆ can grow up to 200 ft long

red algae:
◆ often red because their pigments are tuned to abosrb blue light and reflect red light because only the former penetrates to lower depths
◆ can come in diverse colors and forms though

green algae:
◆ closest relatives to the plant kingdom
◆ very diverse forms and life cycles from unicellular to colonial to multicellular
◆ found in freshwater and seawater, and even in high elevation snow fields

Question 7

alternation of generations (haplodiplontic life cycle)

Answer 7

type of sexual life cycle with two multicellular stages of alternating ploidy

Question 8

phycocolloids

Answer 8

polysaccharide compiunds produce by cell walls to prevent drying (desiccation)

• regularly used in food, cosmetics, lab science, and medical applicaations

Question 9

lichen (photobiont/mycobiont)

Answer 9

◆ an ecological group
◆ COMBO of at least one heterotrophic fungus (the mycobiont) with one photographic alga or cyanobacterium (photobiont)
- neither are monophyletic
- both take on a form completely distinct from how they would grow individually
- photobiont provides sugars, mycobionts provide moisture, shelter, UV protections, minerals
◆ capacity to lichenize has evolved many times
◆ non-exclusive associations (fungi and algae or cyanobacteria usually can pair with multiple partners)
◆ maker of soil
◆ reproduce together or alone, and asexually
◆ defining characteristic: symbiosis

Question 10

soredia

Answer 10

bundle of fungi and algae