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Learning Target: Human Body OrganizationI 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

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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?

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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

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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.

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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 mRNAStem 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.

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

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

process

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Ectoderm• Skin• Nervous system• Face & NeckMesoderm• Muscle• Blood & Vessels• Bone &

Connective tissue

Endoderm• Digestive &• Respiratory tracts

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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

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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

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• Pluripotent – Can naturally become any other type of cell except totipotent

• Multipotent – Can naturally become closely related types of cells

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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

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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

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Some cells are even predetermined to die

Apoptosis – programmed cell death WHY?• During development of embryo/fetus, some

cells need to die

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Bio-organization

1st unit of matter

Molecules

Organelles

Cells1st unit of

Life

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Cells1st 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

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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

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Level 2 Human Body – Five levels of Bio-organization

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Human Body – Five levels of Bio-organization Level 3

Organs – groups of tissues working together to perform a specialized function

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Human Body – Five levels of Bio-organization Level 4

System – two or more organs working together to perform a specialized function

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Human Body – Five levels of Bio-organization Level 5

Organism – complex combination of cells, tissues, organs and systems working together

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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 √:

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Learning Target: Human Body OrganizationI 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

HomeworkRead Ch. 28.1 & 28.2

(pp. 852-861) & Complete

SG WS