Bio Lab Activity 7

Question 1

organelles

Answer 1

(subcellular structures that perform specialized functions) that are present in almost all eukaryotic cells: the nucleus (containing DNA for protein synthesis), the endomembrane system (for packaging and moving proteins and enzymes), the mitochondria (generating energy), and the cell membrane.

Some of these core organelles are visible using light microscopy, although they are at the limits of our resolution.

Existence of these membrane bound organelles is the defining adaptation that sets the eukaryotes apart from the other two domains, the Bacteria and the Archaea. (again, often referred to collectively as prokaryotes, but this is not a phylogenetic grouping)

In the protists, may be able to identify the nucleus, the mitochondria, the cell membrane, and some of the endomembrane system (golgi apparatus, food vacuoles, and if present, the contractile vacuole

Question 2

contractile vacuole

Answer 2

contractile vacuole works to maintain the water balance within the cell in environments where there are fewer non-penetrating solutes outside the cell membrane, resulting in water constantly moving across the membrane with net movement into the cell (a hypotonic environment similar to freshwater)

If the protist or eukaryotic organism has a cell wall outside the cell membrane then it will likely not have a contractile vacuole as the cell wall prevents the membrane from bursting in freshwater, and both cell walls and contractile vacuoles come with energetic costs.

contractile vacuole may also be absent in saltwater protists, as the environment inside and outside the cell generally have a similar concentration of non-penetrating solutes (an isotonic environment).

can probably make an argument for the number of organisms that can survive in environments where there is a higher concentration of non-penetrating solutes outside of the cell (a hypertonic environment)

Question 3

LECA

Answer 3

Last eukaryotic common ancestor.

There is some debate had a flagellum. flagella are present in multiple Supergroups so if it was not present in the common ancestor it arose independently multiple times

Question 4

flagellum

Question 5

hypotonic environment

Question 6

Hypertonic environment

Question 7

Isotonic environment

Question 8

Cell wall

Question 9

Chloroplast

Answer 9

Chloroplasts harvest light energy from the sun to fix inorganic carbon (carbon dioxide) into sugars that can be utilized by the plant to fuel the mitochondria.

The primary pigment that absorbs the light energy in the chloroplast is chlorophyll ɑ (giving a blue-green color), and in certain groups the chloroplast may also have an accessory pigment chlorophyll b (giving an olive-green color).

There may be additional pigments present depending on the chloroplast lineage that can change the color of the chloroplast to red, brown, or golden.

Question 10

endosymbiotic events

Answer 10

origin of eukaryotic cell organelles is believed to involve endosymbiotic events, the first events occurring between an archaean and a bacterium.

mitochondrion is believed to be derived from a bacterium in the α-proteobacteria group.
-Support for this theory is seen in the high level of similarity between DNA contained within the mitochondria, the DNA of α-proteobacteria, and all eukaryotes examined show evidence of a mitochondria (even if very reduced)

Chloroplasts are also thought to have evolved through a separate endosymbiotic event; the DNA sequences found within chloroplasts are very similar to those found in cyanobacteria.
-extra membranes surrounding the chloroplasts of some protists suggests that the resulting primary photosynthetic organism was in turn ingested by other eukaryotes, or secondary endosymbiotic events, that resulted in many diverse lineages with chloroplasts (these secondary chloroplasts have additional membranes compared to the primary chloroplasts)

Question 11

Endosymbiosis

Answer 11

Where a cell of one species is engulfed by the cell of a second species (the host), and the engulfed cell survives and over many generations becomes an organelle within the host

Question 12

Supergroups

Question 13

History of unicellular protists

Question 14

Protists are commonly divided into three categories:

Answer 14

1. algae,
2. fungus-like protists
3. protozoans.

The division is based on their mode of nutrition.

autotrophs

heterotrophs

mixotrophs