T12

Question 1

CHLOROPLAST

Answer 1

photosynthetic cyanobacteria which was engulfed by a phagocyotic eukaryote

• where photosynthesis occurs in eukaryotes, contains chlorophyll to absorb light

Question 2

evolutionary benefit of chloroplasts and photosynthesis

Answer 2

with chloroplasts - delayed digestion as there is a slow input of energy, continues to increase

without = immediate digestion which gives an initial rush of energy and then no more

natural selection drives delayed digestion as the allele for cyanobacteria in an organism lasts longer and benefits the organism, so keeps selection for the cyanobacteria to last longer and longer in eukaryote until becomes apart of the organism

Question 3

How do you think photosynthesis became scattered across the Eukaryote tree of life?

Answer 3

By organisms from various lineages swallowing a photosynthetic Eukaryote, and turning it into a plastid.

Question 4

algae diversity

Answer 4

red algae and green algae
- chlorophyll A - red spectra
- chlorophyll B - blue spectra

together the blue and red light are absorbed leaving green light not absorbed and reflected back, appearing green

Question 5

red algae

Answer 5

found in the deep ocean where blue and green light penetrate further than red so need to absorb green light rather than red light
- use red accessory pigments called phycoerythrin: these absorb light at different wavelengths to the chlorophyll and then transfers these energy to the chlorophyll for photosynthesis

Question 6

brown algae

Answer 6

still got chlorophyll A and B but different accessory pigments

Question 7

secondary endosymbiosis

Answer 7

photosynthetic eukaryote was engulfed and kept alive as used as a plastid, over time selection will gradually reduce the plastid

Question 8

colonial lifestyle (algae)

Answer 8

all cells are equal

each cell is metabolically independent

cooperation helps occupy the best habitat

usually not attached to the substrate

all cells are capable of sex

cells remain attached after mitosis - evolutionary advantage

Question 9

multicellular lifestyle in comparison

Answer 9

all cells are not equal - specialised roles - allows for complexity and forming different tissues/organs

some/all cells are not metabolically independent - allows for complexity and cell communication

usually attached to a substrate

allows for simultaneous occupation of more than one microenvironment - soil+air, air+water

all cells cannot have sex

Question 10

kleptoplasts

Answer 10

ciliates that steal chloroplasts as they engulf bacteria that contain them
- new host takes over the plastid maintenance and benefits from it as it keeps the cell alive

Question 11

mixotroph

Answer 11

euglena
- has permanent plastids (chloroplast) but also feeds by predation