Evolution Lab 4 (2) graded A LATEST 2022-2023
This lab is adapted from Kit 747520 from Carolina Biological Supply Company and should
only be used in conjunction with the Kit purchased from carolina.com
BRINE SHRIMP AND NATURAL
SELECTION EVOLUTION LAB
Materials IV
Carolina Biological Kit 747520 spring water dissecting microscopes
50ml beakers (5) scissors sharpie marker
graduated cylinders weigh boats spatula
scale stirring rod Dixie cup (day 2 and 3)
Introduction
Environmental conditions on Earth are in a constant state of change. The conditions such as
temperature, moisture, amount of UV radiation, and salinity fluctuate. These changes may be
small-scale and short-term or large-scale and long-term, and any of them may influence the
survival of organisms. Scientific evidence points to our time as the period of the sixth mass
extinction that has occurred on Earth. A relatively large number of species has become
extinct since the last Ice Age and that extinction rate continues. The five other mass
extinctions that occurred were likely due to large-scale changes that took place more rapidly
than many populations' ability to adapt to them (e.g. periods of global warming or global
cooling). After each mass extinction, a period of speciation occurred. Numerous species
evolved from the populations of organisms that survived the extinction. The species derived
from populations that had inherited adaptations favored by the changed environmental
conditions. The availability of unoccupied new niches helped spur the radiation of new
species during each of these biological recoveries.
A population's ability to adapt to changing conditions begins with genetic variation among
individuals. Genetic variations arise from mutations of the genome. Mutations are often
harmful (such as those that lead to cancer or birth defects), and they are often benign;
however, they may also be beneficial. Some individuals in a population possess traits that allow
them to survive environmental conditions that others cannot tolerate. The genes that the
survivors pass on to their offspring include the genes for the beneficial trait (e.g. thicker fur).
Over time, these genes (and traits) become more prevalent.
There are many structural and physiological similarities among organisms. Shared characteristics
often indicate common descent. Phylogenetic trees and cladograms illustrate relationships
among groups of organisms and thus reflect evolutionary history.
A cladogram shows grouping on the basis of shared adaptations, referred to as “shared derived
characters,” which indicate probable relationships. For example, all organisms that belong to
the class of crustaceans known as branchiopods (meaning “gill foot”) have gills on their
appendages. Examine the cladogram of branchiopods (on the following page). The point at the
base represents the common ancestor of all the organisms included on the cladogram. The
organisms at the tips of the cladogram represent extant (living) species. The paths from the
common ancestor to the living organisms represent the possible evolutionary history. Each
horizontal line across the cladogram represents an adaptation shared by the group(s) above it
on the diagram. For example, the bivalve carapace is shared by two genera, Limnadia and
This study source was downloaded by 100000815611969 from CourseHero.com on 11-27-2022 00:47:28 GMT -06:00
https://www.coursehero.com/file/21882197/Evolution-Lab-4-2/
, Evolution Lab 4 (2) graded A LATEST 2022-2023
Lynceus. But only one genus, lynceus, has a hinged carapace. The more shared derived
characters two groups have in common, the more closely related they are considered to be.
Hutchinsoniella is not a branchiopod and does not share derived characters with other
organisms on the cladogram; it is presented as an “outgroup” on the cladogram, to help
viewers orient the branchiopods in the larger tree of life.
Figure 1. Cladogram showing physical adaptations and possible evolutionary relationships
of the branchiopods, the class of arthropods that includes brine shrimp
Brine Shrimp
Brine shrimp (Artemia sp.) are small crustaceans found in various saltwater lakes around the
world. Their development is easy to observe with a microscope. A unique adaptation makes
them an interesting model for studies of natural selection. Under ideal environmental
conditions, female brine shrimp produce eggs that hatch quickly into live young; however,
when conditions become less conducive, the shrimp instead produce cysts-encased embryos
that cease development (enter diapause) until conditions are again favorable. When the
temperature or the dissolved oxygen level becomes too low or the salinity too high, each egg
laid is covered in a hardened, brown chorion, which may keep the embryo viable for many
years (in a dry, oxygen-free environment). The brine shrimp used in this activity have been
stored in this dormant stage. Once the cysts are incubated in saltwater, the embryos quickly
resume their development and hatch.
After the cyst breaks open, the brine shrimp remains attached to the shell, surrounded by a
hatching membrane. This stage is known as the umbrella stage. The hatching membrane
remains attached to the cyst for a number of hours until the larval brine shrimp, known as a
This study source was downloaded by 100000815611969 from CourseHero.com on 11-27-2022 00:47:28 GMT -06:00
https://www.coursehero.com/file/21882197/Evolution-Lab-4-2/
This lab is adapted from Kit 747520 from Carolina Biological Supply Company and should
only be used in conjunction with the Kit purchased from carolina.com
BRINE SHRIMP AND NATURAL
SELECTION EVOLUTION LAB
Materials IV
Carolina Biological Kit 747520 spring water dissecting microscopes
50ml beakers (5) scissors sharpie marker
graduated cylinders weigh boats spatula
scale stirring rod Dixie cup (day 2 and 3)
Introduction
Environmental conditions on Earth are in a constant state of change. The conditions such as
temperature, moisture, amount of UV radiation, and salinity fluctuate. These changes may be
small-scale and short-term or large-scale and long-term, and any of them may influence the
survival of organisms. Scientific evidence points to our time as the period of the sixth mass
extinction that has occurred on Earth. A relatively large number of species has become
extinct since the last Ice Age and that extinction rate continues. The five other mass
extinctions that occurred were likely due to large-scale changes that took place more rapidly
than many populations' ability to adapt to them (e.g. periods of global warming or global
cooling). After each mass extinction, a period of speciation occurred. Numerous species
evolved from the populations of organisms that survived the extinction. The species derived
from populations that had inherited adaptations favored by the changed environmental
conditions. The availability of unoccupied new niches helped spur the radiation of new
species during each of these biological recoveries.
A population's ability to adapt to changing conditions begins with genetic variation among
individuals. Genetic variations arise from mutations of the genome. Mutations are often
harmful (such as those that lead to cancer or birth defects), and they are often benign;
however, they may also be beneficial. Some individuals in a population possess traits that allow
them to survive environmental conditions that others cannot tolerate. The genes that the
survivors pass on to their offspring include the genes for the beneficial trait (e.g. thicker fur).
Over time, these genes (and traits) become more prevalent.
There are many structural and physiological similarities among organisms. Shared characteristics
often indicate common descent. Phylogenetic trees and cladograms illustrate relationships
among groups of organisms and thus reflect evolutionary history.
A cladogram shows grouping on the basis of shared adaptations, referred to as “shared derived
characters,” which indicate probable relationships. For example, all organisms that belong to
the class of crustaceans known as branchiopods (meaning “gill foot”) have gills on their
appendages. Examine the cladogram of branchiopods (on the following page). The point at the
base represents the common ancestor of all the organisms included on the cladogram. The
organisms at the tips of the cladogram represent extant (living) species. The paths from the
common ancestor to the living organisms represent the possible evolutionary history. Each
horizontal line across the cladogram represents an adaptation shared by the group(s) above it
on the diagram. For example, the bivalve carapace is shared by two genera, Limnadia and
This study source was downloaded by 100000815611969 from CourseHero.com on 11-27-2022 00:47:28 GMT -06:00
https://www.coursehero.com/file/21882197/Evolution-Lab-4-2/
, Evolution Lab 4 (2) graded A LATEST 2022-2023
Lynceus. But only one genus, lynceus, has a hinged carapace. The more shared derived
characters two groups have in common, the more closely related they are considered to be.
Hutchinsoniella is not a branchiopod and does not share derived characters with other
organisms on the cladogram; it is presented as an “outgroup” on the cladogram, to help
viewers orient the branchiopods in the larger tree of life.
Figure 1. Cladogram showing physical adaptations and possible evolutionary relationships
of the branchiopods, the class of arthropods that includes brine shrimp
Brine Shrimp
Brine shrimp (Artemia sp.) are small crustaceans found in various saltwater lakes around the
world. Their development is easy to observe with a microscope. A unique adaptation makes
them an interesting model for studies of natural selection. Under ideal environmental
conditions, female brine shrimp produce eggs that hatch quickly into live young; however,
when conditions become less conducive, the shrimp instead produce cysts-encased embryos
that cease development (enter diapause) until conditions are again favorable. When the
temperature or the dissolved oxygen level becomes too low or the salinity too high, each egg
laid is covered in a hardened, brown chorion, which may keep the embryo viable for many
years (in a dry, oxygen-free environment). The brine shrimp used in this activity have been
stored in this dormant stage. Once the cysts are incubated in saltwater, the embryos quickly
resume their development and hatch.
After the cyst breaks open, the brine shrimp remains attached to the shell, surrounded by a
hatching membrane. This stage is known as the umbrella stage. The hatching membrane
remains attached to the cyst for a number of hours until the larval brine shrimp, known as a
This study source was downloaded by 100000815611969 from CourseHero.com on 11-27-2022 00:47:28 GMT -06:00
https://www.coursehero.com/file/21882197/Evolution-Lab-4-2/
