Key visualizations: Middle School Science

Variation in organisms and populations is a  key theme throughout secondary science.  Students begin looking at cells in sixth grade. They develop an understanding that organisms are composed of one or more cells, and that some cells have a nucleus (prokaryotes) while others do not (eukaryotes). Students also think about the variety of characteristics and behaviors in organisms and look at classification into Domains and Kingdoms. This understanding allows students to identify biotic and abiotic parts of ecosystems and define levels of organization within ecosystems. These concepts give students a foundation for examining how traits are passed from parent to offspring, and generation to generation in seventh grade. They also examine how changes in traits sometimes occur in populations over many generations and how change occurs by natural selection. In the eighth grade, students can use prior learning to investigate how organisms and populations in ecosystems depend on and compete for biotic and abiotic factors. They also explore how short-and long-term environmental changes affect organisms and traits in future populations. In high school students will develop a more complete understanding of the unity and diversity of life.

Connections to the TEKS []
This animation addresses the following Grade 7 TEKS for science:

This animation addresses the following Texas Essential Knowledge and Skills student expectations.
(11) Organisms and environments. The student knows that populations and species demonstrate variation and inherit many of their unique traits through gradual processes over many generations. The student is expected to:

(B) explain variation within a population or species by comparing external features, behaviors, or physiology of organisms that enhance their survival such as migration, hibernation, or storage of food in a bulb.
Students access this content through these process standards.

(2) Scientific investigation and reasoning. The student uses scientific inquiry methods during laboratory and field investigations. The student is expected to:

(E) analyze data to formulate reasonable explanations, communicate valid conclusions supported by the data, and predict trends.

(3) Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions and knows the contributions of relevant scientists. The student is expected to:

(B) use models to represent aspects of the natural world such as human body systems and plant and animal cells.


About this animation []

This animation helps students use qualitative data to develop an explanation for the importance of variation in organisms and populations. Students look at an example of what can happen when there is no variation. This visualization supports students as they consider how organisms are well suited to the environments in which they live and how this can favor survival.


The Irish are famous for their potatoes. The potato, however, is not native to Ireland. Potato plants originated in South America and were first imported to Ireland in about 1590.
During the 1700s, a variety of crops were still being grown in Ireland. Over time, farmers discovered that potatoes grew better in the poor soil than other crops and did not need as much fertilizer. In fact, certain potato varieties grew better than others. By the early 1800s, almost all potato crops in Ireland consisted of the Lumper variety of potato.
By this point, most farmers were completely dependent on the Lumper variety of potato. Other crops had died off and many people ate Lumper potatoes three times a day. What are some likely advantages and disadvantages of this lack of genetic variation among the potato crop?
In 1845, disaster struck. A fungus brought to Ireland from North America destroyed all of the Lumper potato crops. Had there been more potato varieties, some might have been resistant to the fungus and survived. Because of the lack of genetic variation, Ireland's main food source was wiped out.
This graph shows the population of Ireland before, during, and after the potato famine. What changes in Ireland's population resulted from the loss of the potato crop?