1. KEY CONCEPT Cells work together to carry out complex functions.

2. Objectives
Describe the specialization in multicellular organisms.
Identify different types of stem cells.

3. Vocabulary
Tissue
Group of cells that work together to perform a similar function.
Organ
Group of different types of tissues that work together to perform a specific function or related functions.
Organ System
Two or more organs that work in a coordinated way to carry out similar functions.

4. Vocabulary
Cell Differentiation
Processes by which unspecialized cells develop into their mature form and function.
Stem Cell
Cell that can divide for long periods of time while remaining undifferentiated.

5. Tissues are groups of cells that perform a similar function.
Multicellular organisms depend on interactions among different cell types.
vascular
tissue
leaf
stem
lateral
roots
primary
root
SYSTEMS
root system
shoot system
Tissues are groups of cells that perform a similar function.
Organs are groups of tissues that perform a specific or related function.
Organ systems are groups of organs that carry out similar functions.
CELL
TISSUE
ORGAN

6. Specialized cells perform specific functions.
Cells develop into their mature forms through the process of cell differentiation.
Cells differ because different combinations of genes are expressed.
A cell’s location in an embryo helps determine how it will differentiate.
Outer: skin cells
Middle: bone cells
Inner: intestines

7. Stem cells are unique body cells.
Stem cells have the ability to
divide and renew themselves
remain undifferentiated in form
develop into a variety of specialized cell types

8. Stem cells are classified into three types.
totipotent, or growing into any other cell type
pluripotent, or growing into any cell type but a totipotent cell
multipotent, or growing into cells of a closely related cell family

9. Stem cells come from adults and embryos.
Adult stem cells can be hard to isolate and grow.
The use of adult stem cells may prevent transplant rejection.
The use of embryonic stem cells raises ethical issues
Embryonic stem cells are pluripotent and can be grown indefinitely in culture.
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

10. The use of stem cells offers many currently realized and potential benefits.
Stem cells are used to treat leukemia and lymphoma.
Stem cells may cure disease or replace damaged organs.
Stem cells may revolutionize the drug development process.

11. Question/Answer
Suppose your family goes out of town and forgets to ask your neighbor to water the plants. Do you think the plants’ stomata will be open or closed? Explain.
Because the plants are not receiving any water, they will need to conserve the water that they have. The stomata will most likely be closed.
Why is regulation of the differentiation process during the early stages of development so critical?
The early stages of differentiation lead to the development of progressively more specialized tissues and organs. Distribution of cell differentiation in the early stages could cause severe abnormalities in an organism’s body structure.

12. Question/Answer
List treatment benefits and risks of both types of stem cells.
Adult stem cells taken from a patient’s body are less likely to be rejected. However, they can be difficult to isolate and grow, and have limited potential as far as what tissue can develop. Embryonic stem cells can develop into almost any cell type. However, they may be rejected by a patient’s body.