Key Terms: Excavates and SAR

Question 1

biological carbon pump

Answer 1

process by which inorganic carbon is fixed by photosynthetic species that then die and fall to the sea floor where they cannot be reached by saprobes and their carbon dioxide consumption cannot be returned to the atmosphere

Question 2

bioluminescence

Answer 2

generation and emission of light by an organism, as in dinoflagellates

Question 3

contractile vacuole

Answer 3

vesicle that fills with water (as it enters the cell by osmosis) and then contracts to squeeze water from the cell; an osmoregulatory vesicle

Question 4

cytoplasmic streaming

Answer 4

movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod

Question 5

endosymbiosis

Answer 5

engulfment of one cell within another such that the engulfed cell survives, and both cells benefit; the process responsible for the evolution of mitochondria and chloroplasts in eukaryotes

Question 6

mitosome

Answer 6

nonfunctional organelle carried in the cells of diplomonads (Excavata) that likely evolved from a mitochondrion

Question 7

mixotroph

Answer 7

organism that can obtain nutrition by autotrophic or heterotrophic means, usually facultatively

Question 8

plankton

Answer 8

diverse group of mostly microscopic organisms that drift in marine and freshwater systems and serve as a food source for larger aquatic organisms

Question 9

plastid

Answer 9

one of a group of related organelles in plant cells that are involved in the storage of starches, fats, proteins, and pigments

Question 10

test

Answer 10

porous shell of a foram that is built from various organic materials and typically hardened with calcium carbonate

Question 11

main traits that eukarya share

Answer 11

1. membrane-bound chromosomes
2. nuclei with nuclear envelope
3. linear chromosomes
4. sexual reproduction

Question 12

Lynn Margulis

Answer 12

suggested that the endosymbiotic theory described the origin of the mitochondria

Question 13

mitochondria

Answer 13

generate ATP, and clusters of iron and sulfur that are important for enzyme activity

Question 14

alpha-proteobacterium

Answer 14

evidence (such as the cristae within mitochondria) suggests that mitochondria started as this before becoming what they are today

Question 15

secondary endosymbiosis

Answer 15

• engulfment of one cell within another, and then engulfment of that cell within a new cell
• this creates four membranes
• the theory that explains the origin of eukaryotic chloroplasts (a protist engulfed a cyanobacterium)

Question 16

protist

Answer 16

• term used for Eukarya that are not land plants, fungi, or animals
• not particularly useful as a term because it does not reflect evolutionary history
• not a phylogenetic group

Question 17

alveolus

Answer 17

flattened, membrane-bound vesicles packed into a continuous layer supporting the cell plasma membrane, provide support for the cell

Question 18

amoeboid motion

Answer 18

• the extending of part of a cell, pushing down on something, and dragging the rest of the cell behind it
  (movement without cilia)
• seen in Rhizaria
• uses pseudopodia, which are long and hair-like

Question 19

ecosystem service

Answer 19

benefits that humans derive, directly or indirectly, from ecosystem functions