Biology, Quarter 2, Unit 2.1 Unicellular and Multicellular Life

Overview

Number of instructional days: 10 (1 day = 50 minutes)

Content to be learned Science processes to be integrated • Use data and observation to make connections • Use data and observations to ask questions. between, to explain, or to justify what a multicellular organism needs for survival. • Analyze and interpret data (quantitative and qualitative). • Use data and observation to make connections between, to explain, or to justify what a • Use evidence to draw conclusions. unicellular organism needs for survival. • Communicate understanding and ideas about • Explain that most multicellular organisms have interdependence and other aspects of the specialized cells to survive. natural world. • Explain that unicellular organisms perform all • Create and analyze models, diagrams, and/or survival functions and are not specialized. graphs. • Compare the roles of various subcellular • Use tools and techniques to investigate order structures in unicellular organisms to and organization. comparable structures in multicellular organisms.

Essential questions • What are the necessary functions of life for all • How do specialized cells in a multicellular living things? organism work together to carry out life’s functions? • How does a unicellular organism carry out all of life’s functions in only one cell? • How are various sub-cellular structures in a unicellular organism comparable to related structures in a multicellular organism?

Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-13 in collaboration with the Charles A. Dana Center at the University of Texas at Austin Biology, Quarter 2, Unit 2.1 Unicellular and Multicellular Life (10 days) 2011-2012

Written Curriculum

Grade-Span Expectations

LS1 - All living organisms have identifiable structures and characteristics that allow for survival (organisms, populations, & species).

LS1 (9-11) INQ+SAE+FAF -1 Use data and observation to make connections between, to explain, or to justify how specific cell organelles produce/regulate what the cell needs or what a unicellular or multi-cellular organism needs for survival (e.g., protein synthesis, DNA replication, nerve cells).

LS1 (9-11)-1 Students demonstrate understanding of structure and function-survival requirements by…

1b explaining that most multicellular organisms have specialized cells to survive, while unicellular organisms perform all survival functions. (e.g. nerve cells communicate with other cells, muscle cells contract, unicellular are not specialized).

LS1 (9-11)-1 Students demonstrate understanding of differentiation by…

1c comparing the role of various sub-cellular structures in unicellular organisms to comparable structures in multicellular organisms (e.g. oral groove, gullet, food vacuole in Paramecium compared to digestive systems in multicellular organisms).

Clarifying the Standards

Prior Learning

In grades K–4, students were expected to cite evidence distinguishing living from nonliving things. They identified the basic needs of plants and animals, such as water, air, food, and space. They also understood that living things need to reproduce. They learned how the physical structures of an organism allow it to survive in its habitat/environment.

In the grades 5–6, students recognized that different organisms have different features, such as gills or lungs; and behaviors, such as hibernation or migration, to meet their needs for survival. They should have been able to describe and compare how different organisms have mechanisms that work in a coordinated way to allow them to obtain energy, grow, move, respond, defend themselves, reproduce, and maintain internal balance. They described structures and/or behaviors that help organisms to survive in their habitat/environment.

Beginning in grade 7, students were introduced to the cell as the basic unit of life. They understood that a single cell has all of the same survival requirements as a “whole” organism. Students were expected to explain relationships between or amongst the structure and function of the cells, tissues, organs, and organ systems in an organism. They demonstrated an understanding of differentiation by identifying cells as the building blocks of organisms. They explained that specialized cells perform specialized functions. They should have been able to recognize and diagram the structural organization of an organism from the level of cell to tissue, tissues to organ, organs to organ system and organ systems to organism. They compared individual cells of tissues, and recognized similarities and the way that they work together to perform

C-14 Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, in collaboration with the Charles A. Dana Center at the University of Texas at Austin Unicellular and Multicellular Life (10 days) Biology, Quarter 2, Unit 2.1 2011-2012

specific functions. Students explained how each type of cell, tissue, etc. has a structure and function that serves the organism as a whole.

Current Learning

The instructional level for this unit is developmental in terms of understanding unicellular life forms, but reinforces the previous unit’s knowledge of subcellular structures. Students now compare and contrast unicellular and multicellular organisms, developing an understanding of how each is able to perform all of life’s functions.

Students use data and observation to make connections between, to explain, or to justify what a unicellular or multicellular organism needs for survival. This could involve a study of the various needs, such as nutrients, removal of wastes, reproduction, etc.

They then explain that most multicellular organisms have specialized cells to survive, while unicellular organisms perform all survival functions and are not specialized. One way to approach this would be to compare the roles of various subcellular structures in unicellular organisms to comparable structures in multicellular organisms. For example, students could compare the way that nutrients are obtained by a bacterium, protist, plant, fungus, and simple and complex animals.

Students use data and observations to question the role of various subcellular structures in unicellular organisms and comparable structures in multicellular organisms in relation to survival. They should analyze and interpret data in order to draw conclusions about the comparisons between unicellular and multicellular life. A way to accomplish this would be through viewing and analyzing various unicellular and multicellular life forms. This could be through the use of live specimen, prepared slides, or images. Students should be expected to evaluate differences and similarities amongst these organisms.

Student should communicate understanding and ideas by creating and/or analyzing models, using diagrams and/or graphs, or participating in discussion of these ideas. This unit lends itself very well to the use of tools and techniques of biologists (i.e., microscopy, slide preparation, etc.).

Students compare and contrast the structures and functions of various unicellular and multicellular organisms. They could use microscopes, models, diagrams, or images to accomplish this. Within multicellular organisms, the students consider different types of specialized cells and how this specialization provides for their function. Additionally, they recognize the interdependence of these different cell types, which work in a coordinated way that allows for survival.

In a classroom, students might be found researching and then presenting information about various ways in which unicellular and multicellular organisms accomplish the same function of life. For example, waste removal as carried out by a bacterium, protist, plant, fungus, simple and complex animal.

In this unit, students explore unicellular life for possibly the first time. In earlier grades, they had a clear understanding that living things have needs, however most of their experience was limited to plants and animals. Although they previously studied the structures and functions of the cell, they were not considering the cell as an independent living thing with all of the same needs as a multicellular organism. Students are now expected to make the connections between subcellular structures in a unicellular organism and related structures in a multicellular organism. Additionally, they now explore the interdependence of specialized cells in multicellular organisms, which will help bridge to the next unit: homeostasis.

Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-15 in collaboration with the Charles A. Dana Center at the University of Texas at Austin Biology, Quarter 2, Unit 2.1 Unicellular and Multicellular Life (10 days) 2011-2012

Future Learning

The next unit of study is homeostasis, which will require knowledge of the interdependence of specialized cells in a multicellular organism. It will also require an understanding that unicellular organisms have the same basic survival needs as a multicellular organism, including homeostasis.

This exploration of diversity (unicellular to multicellular) sets the stage for their later investigation of evolution and classification.

Additional Findings

Among 16-year-old students, there is some confusion about levels of organization. Responses suggest that pupils thought that molecules of protein are bigger than the size of a cell and that single-celled organisms contain intestines and lungs. The pupils in the study had been taught about cells in the previous year and superficially ‘knew’ a number of correct statements about them. However, over a third of responses revealed ‘inadequate’ alternative ideas about cells (Making Sense of Secondary Science , p. 25).

In a study of children aged 5–16, researchers found that almost all children recognized animal examples as living; 70–80 percent of 12- to 15-year-olds regarded a particular plant as living. Almost all the children attributed growth to plants, but apparently did consider this a prerequisite of life ( Making Sense , p. 19)

The familiar description and depiction of cells in blood sometimes lead students to the notion that organisms contain cells rather than that organisms are mostly made up of cells. Imagining the large number of cells is also a problem for young students. Large organisms are composed of about a trillion cells, but this number means little to middle school students. Students may have even more difficulty with the idea that cells are the basic unit in which life processes occur. Neither familiarity with functions of regular-sized organisms nor observations of single-celled organisms will reveal much about the chemical activities going on inside single cells (Benchmarks for Science Literacy , p. 110).

C-16 Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, in collaboration with the Charles A. Dana Center at the University of Texas at Austin