1. Learning Target: Human Body Organization I Can…Explain how the levels of human body organization are created and organized to construct a precise functioning complex organism I Will… Describe how the processes of determination and differentiation allow for different cell types to develop from a single zygote cell List each level of bio-organization and identify an example of each level 1

2. KEY CONCEPT: The human body has five levels of organization To understand this concept we must first ask: How do we get from a single-cell diploid zygote (union of haploid egg and haploid sperm) to an ≈ 75 trillion-cell organism with over 200 different types of cells that all work together? 2

3. The zygote divides by mitosis into a ball of identical cells called a blastocyst. The blastocyst contains stem cells that have the potential to become any kind of human body cell or support cells 3

4. Key Concept: In multicellular life forms, cells must work together to carryout complex functions which rely on the interactions of many different cell types. Cells need to communicate and work together. Each type of cell performs highly specialized functions. 4

5. Determination – cell genetically commits to developing into one specific type of cell Loses its ability to express some genes Genes are still present, but “Turned off” – not used Made inaccessible – cannot be accessed by enzymes to make mRNA Stem cell- DNA wrapped loosely around histone proteins Differentiated cell- DNA segments not required for specialized function are shut down and wrapped tightly around histone proteins. 5

6. Differentiation – process by which committed cells acquire the structures (anatomy) and function (physiology) of the determined specialized cell type 6

7. Cell’s location within embryo helps determine how it will differentiate. Cells migrate to specific areas Chemical signals start differentiation process 7

8. Ectoderm Skin Nervous system Face & Neck Mesoderm Muscle Blood & Vessels Bone & Connective tissue Endoderm Digestive & Respiratory tracts 8

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10. Stem Cells have unique ability to: Divide and remain viable for long periods of time Remain in undifferentiated form Develop into a variety of specialized cell types or 10

11. Potential/Potency - The number of different kinds of mature cells a given stem cell can become, or differentiate into. Totipotent – Can become all types of cells Only the zygote and first few cellular divisions All body cells All necessary developmental support tissue i.e. placenta, amnion, umbilical cord 11

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13. Pluripotent – Can naturally become any other type of cell except totipotent Multipotent – Can naturally become closely related types of cells 13

14. Stem Cells are classified by origin: Embryonic - Most donated blastocysts from IVF clinics Pluripotent Indefinite culture line Adult Somatic – Remain partially undifferentiated Multipotent or Unipotent 14

15. Induced Pluripotent Stem (IPS) Cells Created artificially Reprograms mature specialized cell Can become any cell type (except Totipotent) Less expensive than ES cells Genetic modification uncertain 15

16. Some cells are even predetermined to die Apoptosis – programmed cell death WHY? During development of embryo/fetus, some cells need to die 16

17. Bio-organization 1 st unit of matter Molecules Organelles Cells 1 st unit of Life 17

18. Cells 1 st unit of Life Human Body – Five levels of Bio-organization Human body has: Over 200 different types of cells Between 50 – 75 trillion total cells Level 1 18

19. Human Body – Five levels of Bio-organization Tissues – groups of cells working together to perform a specialized function Four general types Epithelial – protective e.g. skin, mucus linings Connective – join and support e.g. tendons, ligaments, bones, blood Muscular – contract to produce movement Three types Smooth – internal organ Cardiac – heart Skeletal – attached to bone Nervous Communication Level 2 19

20. Level 2 Human Body – Five levels of Bio-organization 20

21. Human Body – Five levels of Bio-organization Level 3 Organs – groups of tissues working together to perform a specialized function 21

22. Human Body – Five levels of Bio-organization Level 4 System – two or more organs working together to perform a specialized function 22

23. Human Body – Five levels of Bio-organization Level 5 Organism – complex combination of cells, tissues, organs and systems working together 23

24. Let’s Pause and THINK… Why is regulation of the differentiation process during early developmental stages so critical? Answer: Early stages of development lead to development of more, progressively, specialized tissues and organs which make up and affect the organism. Learning Check √: 24

25. Learning Target: Human Body Organization I Can…Explain how the levels of human body organization are created and organized to construct a precise functioning complex organism I Will… Describe how the processes of determination and differentiation allow for different cell types to develop from a single zygote cell List each level of bio-organization and identify an example of each level 25 Homework Read Ch. 28.1 & 28.2 (pp. 852-861) & Complete SG WS