Topic 8

Question 1

What is the oxygen revolution?

Answer 1

oxygen began accumulating ~2.7 BYA

photosynthetic cyanobacteria: use sun’s energy to split water into hydrogen and oxygen

O2 was toxic to most early life

other prokaryotes adapted to oxygen-rich atmosphere and began respiring aerobically

Question 2

What is the domain of eukarya?

Answer 2

DNA in linear chromosomes in membrane bound nucleus

membrane-bound organelles such as mitochondria and chloroplasts

often much larger than prokaryotes

diverse morphology

Question 3

What is the theory of endosymbiosis?

Answer 3

1. Infoldings of cell membrane (endoplasmic reticulum, nuclear envelope)
2. Ancestral host cell took on an endosymbiotic aerobic heterotrophic prokaryote (uses oxygen and organic matter for energy, eventually become mitochondrion)
3. Other lineages engulfed photosynthetic prokaryotes (most likely cyanobacteria, use light and CO2 to make organic compounds)

Question 4

What is the evidence for endosymbiosis found in the mitochondria and chloroplasts?

Answer 4

self-replicating (binary fission)

resemble bacteria in size and nature

DNA: circular (as in prokaryotes)

2 cell membrane layers: inner one homologous to plasma membrane of prokaryotes

Question 5

What is primary endosymbiosis?

Answer 5

2 membranes

Question 6

What is secondary endosymbiosis?

Answer 6

3 membranes

Question 7

What is a protist?

Answer 7

the informal name of group of mostly unicellular eukaryotes, but there are some colonial and multicellular species

Question 8

What is the kingdom Protista?

Answer 8

animals, fungi, plants each closely related to a different protist group

group is paraphyletic

Question 9

What is the support for supergroup?

Answer 9

all eukaryotes seem to possess mitochondria or related organelles from alpha-proteobacteria

Chromalveolata, excavata, and plantae have plastids from cyanobacteria

Question 10

What are the advantages of multicellularity?

Answer 10

strength in numbers

specialization

protection

size

structural diversity

mobility

different types of cells

survival

Question 11

What are the disadvantages of multicellularity?

Answer 11

slow reproduction = evolve slowly

high metabolic cost

easier to see

cancer

Question 12

What are the two hypotheses of multicellualrity?

Answer 12

1. Large Size is Advantageous (diffusion is effective only over short distances)
2. “Left Wall of Minimum Complexity” (no other option)

Question 13

How did multicellularity evolve?

Answer 13

1. Symbiosis (two cells of different DNA)
2. Internal Division of Multinucleate Organisms (cells have different DNA)
3. Coloniality (best of the three)

Question 14

What are autotrophic protists (algae)?

Answer 14

photoautotroph: make own food with chloroplast

aquatic

single cells or multicellular

asexual and sexual reproduction

alternation of generations

function in global ecosystem (production of energy, uptake of CO2 and release of O2)

cause environmental problems

Question 15

How are red and green algae closely related to land plants?

Answer 15

over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont

photosynthetic descendants of this ancient protist evolved into red algae and green algae

land plants are descended from algae

Question 16

What is plantae?

Answer 16

the supergroup that includes red algae, green algae, and land plants

chloroplasts have two membranes

Question 17

What is red algae?

Answer 17

reddish in color due to accessory pigment called phycoerythrin, which masks the green of chlorophyll

usually multicellular, largest are seaweeds

Question 18

What are single-celled algae?

Answer 18

major component of marine and freshwater plankton

Question 19

What are chlorophytes (green algae)?

Answer 19

green pigments in chloroplasts

live in fresh water

range in size from single cells to mutlicellular

Question 20

What are charophytes (green algae)?

Answer 20

multicellular + morphologically complex

closely-related to land plants

charophytes and land plants share a common ancestor

sister taxon to land plants

Question 21

What is the supergroup Unikonta?

Answer 21

this group is somewhat controversial and has recently been divided into two supergroups Amoebozoans and Opisthokonts

Question 22

What are the five supergroups?

Answer 22

Excavata

Chromalveolata

Rhizaria

Archaeplastida

Unikonta

Question 23

How do protists asexually reproduce?

Answer 23

is based on mitosis and cell division in eukaryotic organisms as well as fission in bacteria and archaea

results in daughter cells genetically identical to the parent

Question 24

How do protists sexually reproduce?

Answer 24

is based on meiosis and fusion of gametes

results in cells that are genetically different from their parents and from each other

most undergo asexual reproduction routinely but sexual reproduction intermittently

Question 25

What’s the benefit of sex?

Answer 25

meiosis is adaptive because genetically variable offspring may be able to thrive if the environment changes

the genotypes of many protists and pathogens evolve very quickly