SPEAK OUR LANGUAGE

• CELL – Core Experience Learning Lab
• SDR – Scientist Data Record

ASK WHY

Great scientists question the world around them. We encourage our LabLearner students to do the same. In anticipation of this, we explain the importance of learning the concepts in the Ask Why section within the CELL. Our hope is that these explanations help students understand why science matters.

BRANCH OUT

Each Investigation introduces students to a different branch of science or STEM (Science, Technology, Engineering, Mathematics) career that utilizes the scientific concepts of the CELL. These real-world connections will help students see the relevance of what they are learning. STEM connections are also integrated into each Performance Assessment.

GET FOCUSED

The Focus Questions in each Investigation are designed to help teachers and students focus on the important concepts. By the end of the CELL, students should be able to answer the following questions:

Investigation 1:

• Why do individuals of a species have different traits?  The genotype of an individual determines the phenotype of the individual. Genetic variation ensures that there are many possible genotypes and phenotypes that an organism can possess. This genetic variation is a result of mutations, recombination of genes, and the random mating of individuals.

• What is the relationship between the survival of the individuals of a species and genetic variations? Genetic variation is the reason why there are many unique individuals of a species in a population. Genetic variation allows a population of species to survive different environmental pressures.

Investigation 2:

• How does genetic variation affect the type of traits or the adaptations in the individuals of a species? Genetic variation is responsible for all the different traits that an individual possesses.

• What is the relationship between genetic variation and natural selection? If members of a species did not have different traits no natural selection could exist because all the members of that species would be equally adapted to each environmental pressure. However, there is genetic variation in populations and some individuals are more adapted to their surroundings than others. The ones that survive are more likely to pass on their genes.

• How can an environmental change affect a population? Environmental pressures can affect the population because some members are more adapted to the new environment than others.

Investigation 3:

• How can an environmental change affect a population? When a new environmental pressure is introduced, some organisms in a population will not survive. The organisms with the genes that are most adapted to the environment will have the highest chance of surviving and passing their genes on to the next generation.

Note: These are succinct responses to the Focus Questions and are placed here for easy reference. Fully developed responses to the Focus Questions can be found on each PostLab page.

Note: Some questions may be revisited as the CELL progresses. As students acquire additional knowledge, their responses should reflect this.

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced within the CELL. These terms should be used, as appropriate, by teachers and students during everyday classroom discourse.

Note: Additional words may be bolded within the Backgrounds. These words are not Key Terms and are strictly emphasized for exposure at this time.

Investigation 1:

• Species: A group of organisms that possess similar genes and traits which no other group possesses
• Trait: One form of a visible characteristic or behavior determined by a particular allele
• Genetic Variation: Slight differences in an organism’s traits that are considered normal
• Adaptation: An increase in the proportion of the individuals of a species that possess a necessary trait, allowing the species to survive a change in an environmental factor
• Environment: An organism’s physical surroundings, such as food supply, soil, weather, water, trees, and mountains
• Allele: Different forms of the same gene that contain slightly different genetic information for slightly different traits
• Dominant: An allele that will produce a trait that masks another (recessive) trait for the same characteristic
• Recessive: An allele that produces a trait that is masked by a dominant trait
• Genotype: The genes that determine an organism’s phenotype
• Phenotype: The physical appearance, behavior or trait of an organism

Investigation 2:

• Environmental Pressure: A change in an organism’s environment that selects for organisms with slight differences in a trait that give that organism a survival or reproductive advantage
• Natural Selection: Sometimes called “Survival of the Fittest” Environmental pressures often give an organism with a favorable trait an advantage over other organisms without the trait. The organism with the trait is selected by the pressures and is able to survive and reproduce, but the organism without the trait cannot and is eventually forced into extinction.

Investigation 3:

• Fossil: The remains of an organism, often its bones that are left after it has died.
• Paleontologist: A scientist who uses fossils to study organisms that once existed but are now extinct.
• Extinct: When all individual organisms of a species have died

BE PREPARED

An overview of the materials for each lab is placed here for easy reference. Specific teacher preparation for the labs is placed at the beginning of each Lab page.

EXTEND YOUR THINKING

The following information is included so that teachers have additional background knowledge pertaining to the concepts introduced in the CELL. Teachers may choose to use this information enrich students during instruction, but this is optional and not necessary for the intended students’ learning outcomes.

Each species consists of individual organisms that appear more similar to one another than to the individuals of another, different species. The fact that each species consists of individual organisms that are slightly different from one another is a consequence of the normal genetic variation within a species. For example, the species Homo sapiens includes individuals who are very different in appearance from other human beings but appear more similar to each other than to individuals of any other primate species. A similar physical appearance or phenotype is due to the contribution of many different traits, all of which are similar but not identical for a species.

The genotype of a species is the combination of all the different genes that determine a species’ phenotype. The genotype of a species determines the phenotype of that species. In the simplest case, each trait is determined by one of two different alleles of a single gene, one dominant allele, and one recessive allele. In reality, most traits are so complex that each trait is determined by a combination of alleles of many different genes. Since the phenotypes within a species are slightly different, it is reasonable to assume that the genotypes within a species are also slightly different. These slight differences in both phenotype and genotype are a result of genetic variation.

The environment of a species includes factors such as weather, temperature, food supply, water supply, and other organisms. All of these factors have a direct effect on the well-being of a species. Changes in one factor of a species’ environment over either a short or long time interval affect whether a species will effectively survive and reproduce. Adaptation of the species occurs via an increase in the proportion of the individuals that possess a trait that permits survival. Adaptation to this environmental pressure is necessary if the species as a whole is to survive. If the species cannot survive an environmental change, all individuals will eventually perish and the species will become extinct.

As discussed, each individual within a species is slightly different because all of the traits of each individual are slightly different. When an environmental factor changes and environmental pressure is exerted, one of these slightly different traits may offer a survival advantage to the individuals that possess the trait. As these individuals reproduce, the trait is passed to the individuals’ offspring providing a survival advantage to new individuals. Those individuals without the advantageous trait do not survive, but those with the trait survive and reproduce until all individuals of the species possess the particular gene and exhibit the advantageous trait. What was once genetic variation is now a gene common to all individuals of the species. The environmental pressure on the individuals of a species results in adaptation of the species as a whole, a process that is termed Natural Selection.

As individuals of a species die, their fleshy remains decompose but the large bones of their skeletons remain. Through the replacement of the bone with long-lasting minerals, the bony remains of a species can be found millennia later in the form of fossils. Not all of the bones of a skeleton are typically found due to scavenging of the remains and erosion which separate the smaller from the larger bones. Usually only large, dense bones such as the femur, pelvis, and skull survive the process of fossilization. Occasionally the fossils of whole skeletons can be recovered if an organism is covered by sediment shortly after its death.

As time goes by, layers of soil and debris cover the fossilized remains of organisms from different time periods forming a vertical record of the extinction of many species. More recent remains are continuously deposited on top of the remains laid down earlier. By excavating vertically from top to bottom, a record of the extinction of many species can be constructed from recently extinct species to those species that became extinct long ago. The process of establishing the fossil record and constructing a timeline of extinction is studied by paleontologists.