This is the Lab Final exam notes /summaries of all experiments conducted in-class. They are in details and all the questions came from these notes. If you study these notes, you will score at least 90% on the Lab Final exam.
Lab Exam Preparation (BISC 102)
Sex of C fern Gametophyte (Designing an experiment)
Testing for Natural Selection (Natural selection on leaf color in Brassica Rapa)
Assess fitness of Brassica Rapa plant based on leaves variation (normal vs variegated)
Independent variable: Leaf color variation in Brassica Rapa (normal green vs. variegated with
reduced chlorophyll).
Dependent variable: Fitness of Brassica Rapa plants (number of flowers, seed pots)
2 standardized variables: light intensity: Ensure that all plants receive the same amount of light,
as light availability can greatly influence plant growth and photosynthesis, which may affect fitness.
Soil composition: Maintain consistent soil composition and nutrient levels for all plants to ensure
that differences in growth and fitness are not due to variations in soil conditions.
Is flower number a suitable indicator of biological fitness? Explain
Yes, flower number can be a suitable indicator of biological fitness in Brassica Rapa.
Reproductive success: he primary function of flowers in plants is reproduction. More flowers
typically indicate a higher potential for successful reproduction, as each flower has the potential to
develop into a fruit containing seeds.
Seed production: More flowers often correlate with higher seed production, contributing to the
plant's ability to spread its genetic material and propagate future generations.
Genetic fitness: Plants that produce more flowers may have genetic traits that confer advantages
such as disease resistance, tolerance to environmental stressors, or better adaptation to local
conditions.
Is the difference between normal & variegated plants in number of flowers statistically
significant?
Null hypothesis: There is no significant difference in the number of flowers between normal and
variegated Brassica Rapa plants.
Alternative hypothesis: There is a significant difference in the number of flowers between normal
and variegated Brassica Rapa plants.
If the p-value is less than the predetermined significance level (commonly α = 0.05), you
reject the null hypothesis and conclude that there is a statistically significant difference in the
number of flowers between normal and variegated Brassica Rapa plants. Otherwise, if the p-value
is greater than α, you fail to reject the null hypothesis, indicating that there is insufficient
evidence to conclude a significant difference.
,List the 2 conditions that are necessary and sufficient for natural selection to act on a
population to bring about evolutionary change.
Variation: There must be heritable variation present within the population, meaning that
individuals within the population exhibit differences in traits that can be passed on to their
offspring genetically.
Differential reproductive success: Individuals with certain heritable traits must have differential
reproductive success, meaning that some traits provide a reproductive advantage over others in a
given environment. This advantage leads to individuals with advantageous traits producing more
offspring that survive to reproduce, thereby passing on those advantageous traits to future
generations.
Consider these 2 conditions with respect to variegation trait. Would natural selection select
for or against the variegation trait in this population?
If variegated plants experience reduced fitness compared to non-variegated plants (e.g., lower
growth rates, decreased seed production), then natural selection is likely to act against the
variegation trait. In this case, individuals with normal leaves would have a reproductive advantage,
leading to a decrease in the frequency of the variegation trait within the population over time.
Coot Chick color
Null hypothesis: Brightly colored coot chicks are fed as frequently, grow as rapidly, and
survive to fledging with the same frequency as dull chicks
Alternative hypothesis: Brightly colored coot chicks are fed more frequently, grow more
rapidly, and survive to fledging at a higher frequency than dull chicks.
Refer to lab manual page 47 for Q &A
Sexual selection in widowbirds
Research Q: Does the length of male widowbirds' tails influence female mating preferences, and
how does natural selection act to balance the costs and benefits associated with exaggerated tail
length?
Null hypothesis: There is no significant relationship between the length of male widowbirds' tails
and female mating preferences, and natural selection does not act to balance the costs and benefits
associated with exaggerated tail length.
Alternate hypothesis: There is a significant relationship between the length of male widowbirds'
tails and female mating preferences, and natural selection acts to balance the costs and benefits
associated with exaggerated tail length.
Experimental group 1(longer than average tail length):
- Females show a significant preference for males with longer tails
- Males with longer tails experience higher mating success compared to those with natural
tail lengths.
- Natural selection pressures may act to maintain or even further exaggerate the longer tail
lengths due to the mating advantage
,Experiment group 2 (shorter than average tail length)
- Females show reduced preference for males with shorter tails compared to males with
natural tail lengths.
- Males with shorter tails experience lower mating success compared to those with natural
tail lengths.
- Natural selection pressures may act to reduce the extent of tail length reduction, balancing
the costs and benefits associated with exaggerated tail length
Fossils
Explain how prokaryotes have changed Earth’s atmosphere and rocks
Prokaryotes, primarily through photosynthesis, have significantly altered Earth's atmosphere by
producing oxygen, transforming it from a reducing to an oxidizing environment. This process led to
the oxygenation of the atmosphere over billions of years. Additionally, prokaryotes have influenced
rock formation and composition through processes such as mineral weathering, which breaks
down rocks and releases minerals into the environment, shaping the Earth's surface over geological
time scales.
Interpret stromatolites and banded iron formations, and explain how each type of rock was
formed.
Stromatolites: Stromatolites are layered structures formed by the growth of microbial mats,
predominantly cyanobacteria, in shallow water environments. These microorganisms trap and bind
sediment particles, forming layers over time. As sediment accumulates and becomes lithified, it
preserves the layered structure of the microbial mats, resulting in the formation of stromatolite
rocks. Stromatolites are significant in the geological record as they provide evidence of early life on
Earth and offer insights into ancient environments.
Banded iron formations (BIFs): They are sedimentary rocks composed of alternating layers of
iron-rich minerals, such as hematite or magnetite, and silica-rich minerals. The formation of BIFs is
associated with the precipitation of iron and silica from ancient oceans. Initially, iron was dissolved
in seawater in its reduced form, but with the rise of atmospheric oxygen due to photosynthetic
activity of cyanobacteria, iron became oxidized and precipitated out of the seawater. This process
led to the deposition of alternating layers of iron oxides and silica, resulting in the distinctive
banded appearance of BIFs. BIFs are significant geological features as they provide evidence of the
Great Oxidation Event.
Describe what modern stromatolites and microbialites suggest about early life on Earth
Both modern stromatolites and microbialites are formed by the layering of microbial mats, similar
to those observed in ancient stromatolites. These microbial mats trap and bind sediment particles,
leading to the formation of layered structures. The presence of microbial mats in modern
stromatolites suggests that similar microbial communities may have been responsible for the
formation of ancient stromatolites.
, Despite harsh environmental conditions, modern stromatolites harbor diverse microbial
communities. Similarly, ancient stromatolites likely hosted a variety of microbial life forms,
indicating that early Earth supported diverse ecosystems even in extreme environments.
The existence of modern stromatolites in environments such as hypersaline lakes, hot springs, and
intertidal zones highlights the adaptability and resilience of microbial life. This suggests that
microbial communities in ancient stromatolites may have also adapted to various environmental
conditions, allowing them to thrive and persist through geological time scales.
Distinguish among different types of fossils (mineralized, imprint traces)
Mineralized: These fossils form when organic materials in an organism's body are replaced by
minerals, preserving the organism's shape and structure. This process typically occurs over millions
of years through the infiltration of groundwater rich in dissolved minerals. Mineralized fossils can
include bones, teeth, shells, and other hard parts of organisms. Examples include petrified wood,
fossilized bones, and ammonite shells.
Imprint: Imprint fossils are formed when an organism's remains leave an impression, or mold, in
sedimentary rock. Subsequent sediment fills the mold and hardens into rock, creating a cast of the
original organism. Imprint fossils often occur when an organism's soft tissues decay or are eroded
away before mineralization can occur. Examples include fossilized footprints, leaf impressions, and
imprints of shells or bones.
Trace fossils: Trace fossils are evidence of an organism's activity rather than the organism itself.
They include tracks, burrows, nests, and other signs of behavior preserved in sedimentary rock.
Trace fossils provide valuable information about ancient ecosystems, animal behavior, and
environmental conditions. Examples include dinosaur footprints, worm burrows, and fossilized
nests.
Describe two species from Burgess Shale and provide information about how they interacted
with their environment
Marrella splendens was a small arthropod with a spiny exoskeleton, likely inhabiting shallow
marine environments where it fed on suspended organic matter or scavenged on the sea floor. Its
spiny exoskeleton may have served as protection or camouflage. Marrella likely contributed to
nutrient cycling as a detritivore or scavenger, impacting marine ecosystems.
Anomalocaris canadensis was a large predatory arthropod, with grasping appendages near its
mouth and a segmented body. As an apex predator, it likely preyed on smaller marine organisms
such as trilobites and brachiopods, influencing the ecosystem dynamics. Its role as a top predator
would have impacted prey populations and shaped the Burgess Shale ecosystem, potentially leading
to adaptations among other organisms to avoid predation or compete for resources.
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