PSYC 388 Midterm exam with correct
answers
Proximate causality - CORRECT ANSWERS ✔✔- the 'how' questions
- biological mechanism
Ex: how do biological clocks work at the biological level
* most of the course
Ultimate causailty - CORRECT ANSWERS ✔✔the 'why' question
Ex: why do we have clocks, what 'caused' them to evolve and why have they
been conserved across phylogeny
- questions of function (what is the function or purpose of the circadian clock?)
* lecture 2 topic
Natural selection - CORRECT ANSWERS ✔✔differential reproductive fitness
that results from differential adaptation to features of the environment
Local features - CORRECT ANSWERS ✔✔more or less unique to that place
- temperature
- precipitation
- topography
drive speciation by favoring animals that have adaptations to these specific
features
,Global features - CORRECT ANSWERS ✔✔shared with other places; they are
- enduring
- stable
- nontrivial
- obvious: features associated with daily cycles of light (solar day)
When did circadian clocks evolve? - CORRECT ANSWERS ✔✔approximately
3.5 billion years ago
Multicellular organisms that exhibit circadian rhythms - CORRECT
ANSWERS ✔✔- fungi: Neurospora
- plants: Arabidopsis
- animals: nematodes, fruit flies, zebrafish, reptiles, birds, mice, humans
Unicellular eukaryotic oranisms (protisa) that exhibit circadian rhythms -
CORRECT ANSWERS ✔✔- green algae (chlamydomonas, acetabularia)
- gonyaulax, paramecium, euglena
- have true (bona fide) circadian rhythms
Prokaryotic organisms: How old are they and what are some characteristics
about them? - CORRECT ANSWERS ✔✔- about 3.5 billion years old
- no cell nuclei
- no membrane-bound organelles
,What prokaryotic organisms have circadian rhythms? (3) - CORRECT
ANSWERS ✔✔- cyanobacteria (blue-green algae)
- human gut bacteria
- some extremophile archaea (grow in high salinity or temp)
Prokaryotic organisms = the most ancient life forms on earth (evolved ~3.5
billion years ago) and have biorhythms = what can we conclude about
circadian rhythms based on this? (4) - CORRECT ANSWERS ✔✔- they are
ancient and widely conserved
- they likely appeared early in evolution
- likely evolved several times (bacteria, plants, and animals don't have the same
clock genes, which is expected if they evolved from the same organism)
- must continue to make important contributions towards survival and
reproductive fitness
What is hypothesis 1A: escape from light? - CORRECT ANSWERS ✔✔-
ionizing radiation (high energy ultraviolet light can damage molecules and
disrupt biochemical processes such as DNA repication and gene transcription
- earliest self-replicating organisms did not have barriers to block UV light
What was the solution to not having protection against UV light? (2) -
CORRECT ANSWERS ✔✔- restrict replication/transcription to the night
- mobilize light-avoidance behaviour in *anticipation* of sunrise
, What is the evidence for "escape from light"? - CORRECT ANSWERS ✔✔-
many genes exhibit a circadian rhythm of transcription
- most clock-controlled genes are transcribed only at night (Ex: drosophila)
- cells are more easily damaged by UV light in the early night, when cell
division and gene transcription occur (Ex: in chlamydamonas)
External coordination - CORRECT ANSWERS ✔✔- 1 biological challenge
faced by early life that led to evolution of circadian clocks
- challenge of coordinating biochemistry with daily cycles of solar radiation
and temperature (external)
Internal coordination - CORRECT ANSWERS ✔✔- 1 biological challenge
faced by early life that led to evolution of circadian clocks
- challenge of coordinating biochemical processes with each other so that they
occur in the the correct sequence and so that incompatible processes would
occur at different times of day
Hypothesis 1b: escape from oxygen (radicals) (5) - CORRECT ANSWERS ✔✔-
earliest circadian clocks appear back when atmospheric oxygen increased
rapidly, killing of other anaerobic forms
- bacteria would synthesize antioxidants prior to sunrise to remove toxic
metabolites (reactive O2 mlcs, H2O2 and free radicals) that are created as
byproducts of daytime photosynthesis and damage cells
- these metabolites must be removed for effective aerobic metabolism
- photosynthesis is dependent on light and restricted to the day, so clocks may
have been used to control production of antioxidants so organisms could use
O2 processes
answers
Proximate causality - CORRECT ANSWERS ✔✔- the 'how' questions
- biological mechanism
Ex: how do biological clocks work at the biological level
* most of the course
Ultimate causailty - CORRECT ANSWERS ✔✔the 'why' question
Ex: why do we have clocks, what 'caused' them to evolve and why have they
been conserved across phylogeny
- questions of function (what is the function or purpose of the circadian clock?)
* lecture 2 topic
Natural selection - CORRECT ANSWERS ✔✔differential reproductive fitness
that results from differential adaptation to features of the environment
Local features - CORRECT ANSWERS ✔✔more or less unique to that place
- temperature
- precipitation
- topography
drive speciation by favoring animals that have adaptations to these specific
features
,Global features - CORRECT ANSWERS ✔✔shared with other places; they are
- enduring
- stable
- nontrivial
- obvious: features associated with daily cycles of light (solar day)
When did circadian clocks evolve? - CORRECT ANSWERS ✔✔approximately
3.5 billion years ago
Multicellular organisms that exhibit circadian rhythms - CORRECT
ANSWERS ✔✔- fungi: Neurospora
- plants: Arabidopsis
- animals: nematodes, fruit flies, zebrafish, reptiles, birds, mice, humans
Unicellular eukaryotic oranisms (protisa) that exhibit circadian rhythms -
CORRECT ANSWERS ✔✔- green algae (chlamydomonas, acetabularia)
- gonyaulax, paramecium, euglena
- have true (bona fide) circadian rhythms
Prokaryotic organisms: How old are they and what are some characteristics
about them? - CORRECT ANSWERS ✔✔- about 3.5 billion years old
- no cell nuclei
- no membrane-bound organelles
,What prokaryotic organisms have circadian rhythms? (3) - CORRECT
ANSWERS ✔✔- cyanobacteria (blue-green algae)
- human gut bacteria
- some extremophile archaea (grow in high salinity or temp)
Prokaryotic organisms = the most ancient life forms on earth (evolved ~3.5
billion years ago) and have biorhythms = what can we conclude about
circadian rhythms based on this? (4) - CORRECT ANSWERS ✔✔- they are
ancient and widely conserved
- they likely appeared early in evolution
- likely evolved several times (bacteria, plants, and animals don't have the same
clock genes, which is expected if they evolved from the same organism)
- must continue to make important contributions towards survival and
reproductive fitness
What is hypothesis 1A: escape from light? - CORRECT ANSWERS ✔✔-
ionizing radiation (high energy ultraviolet light can damage molecules and
disrupt biochemical processes such as DNA repication and gene transcription
- earliest self-replicating organisms did not have barriers to block UV light
What was the solution to not having protection against UV light? (2) -
CORRECT ANSWERS ✔✔- restrict replication/transcription to the night
- mobilize light-avoidance behaviour in *anticipation* of sunrise
, What is the evidence for "escape from light"? - CORRECT ANSWERS ✔✔-
many genes exhibit a circadian rhythm of transcription
- most clock-controlled genes are transcribed only at night (Ex: drosophila)
- cells are more easily damaged by UV light in the early night, when cell
division and gene transcription occur (Ex: in chlamydamonas)
External coordination - CORRECT ANSWERS ✔✔- 1 biological challenge
faced by early life that led to evolution of circadian clocks
- challenge of coordinating biochemistry with daily cycles of solar radiation
and temperature (external)
Internal coordination - CORRECT ANSWERS ✔✔- 1 biological challenge
faced by early life that led to evolution of circadian clocks
- challenge of coordinating biochemical processes with each other so that they
occur in the the correct sequence and so that incompatible processes would
occur at different times of day
Hypothesis 1b: escape from oxygen (radicals) (5) - CORRECT ANSWERS ✔✔-
earliest circadian clocks appear back when atmospheric oxygen increased
rapidly, killing of other anaerobic forms
- bacteria would synthesize antioxidants prior to sunrise to remove toxic
metabolites (reactive O2 mlcs, H2O2 and free radicals) that are created as
byproducts of daytime photosynthesis and damage cells
- these metabolites must be removed for effective aerobic metabolism
- photosynthesis is dependent on light and restricted to the day, so clocks may
have been used to control production of antioxidants so organisms could use
O2 processes
