Cells:The Basic Units of Life

Cells

Tissues

Organs

Organ Systems

Organisms

ORGANIZATION

OF

LIFE

Cells• Every living thing has at least one cell. – Some have only one and some have trillions.– Most cells are too tiny to be seen without a

microscope.– A chicken egg is one of the largest cells.– Not all cells look or act the same.– You have 200 different kinds of cells: blood cells,

bone cells, muscle cells …………

Tissues• A tissue is a group of cells working together to

perform a specific job in the body. The material around and between the cells is also part of the tissue. – Examples of tissue: red blood cells, fat, and muscle

Organs• When two or more tissues work together to

perform a specific job, the group of tissues is called an organ. – Examples of organs: stomach, heart, intestines,

liver, lung, and skin• Plants also have different kinds of tissues that

work together. A leaf is a plant organ that contains tissue that traps light energy to make food.

Examples of plant organs: stem and roots

The Skin

• The skin is the body’s largest organ. An average-sized person’s skin has a mass of about 4.5 kg (almost 10 pounds!).

Brain Food

• The part of the skin, hair, and nails that we can see is DEAD tissue. Isn’t it strange that we put so much effort into making sure our dead cells look nice?

Organ Systems

• Organs work together in groups to perform particular jobs. These groups are called organ systems.

• Each system has a specific job to do in the body.– Examples: • digestive system breaks down food to use by your body’s

cells• nervous system transmits information back in forth

between the brain and other parts of the body

There are 11 main organ systems.

• The organs in the organ system depend on each other. If any part of the system fails, the whole system is affected. And failure of one organ system can affect other organ systems.

• Main organ systems : integumentary system, skeletal system, muscular system, nervous system, endocrine system, cardiovascular system, lymphatic system, respiratory system, digestive system, urinary system, reproductive system

Organism: Independent Living

• Anything that can live on its own is called an organism.

• All organisms are made up of at least one cell.– organisms made up of one cell – unicellular– organisms made up of groups of cells –

multicellular

The Big Picture• Although unicellular and multicellular organisms can live

on their own, they usually do not live alone. Organisms interact with each other on many different ways.– Populations – groups of organisms that are of the same kind

and that live in the same area • Example – all the white tail deer in the forest

– Communities - two or more different populations living in the same area• All the populations combined in the forest (deer, rabbits, snakes, etc..)

– Ecosystems – all the communities and all the nonliving things that affect it, such as water, soil, rocks, temperature, and light• Ecosystems on land – terrestrial ecosystems• Ecosystems in water – aquatic ecosystems

Discovery of Cells

Seeing the first cells• 1665 - Robert Hooke – British scientist – used

cork (soft plant tissue found in the bark of a tree) – He saw tiny boxes and called them cells.

Early discoveries

• 1673 – Anton van Leeuwenhoek – Dutch merchant – used a handmade microscope to look at pond scum – He saw many small creatures. He also looked at blood from animals and teeth scrapings. First to see bacteria and discovered that yeast is a unicellular organism.

The Cell Theory Matthias Schleiden – 1838 – all plant parts are made of cellsTheodore Swann – 1839 - wrote the first part of the cell theory.

o All organisms are composed of one or more cells.o The cell is the basic unit of life in all living things.

1858 – Rudolf Virchow – wrote the third part of the cell theory

o All cells come from existing cells

• All cells have: – Cell membrane- surrounds all cells; acts as a barrier

between the inside of the cell and its environment; controls what comes in and what goes out

– Hereditary material – cells receive a copy of hereditary material (DNA) It controls all of the activities of the cell and contains the information needed for that cell to make new cells

– Organelles – structures within a cell that allow it to live, grow, and reproduce

– Cytoplasm – fluid that surrounds the organelles within a cell

– Small size – almost all cells are too small to see with the naked eye

Amoebas• An amoeba is a single celled (unicellular) organism. It

cannot get large enough to be seen. As a cell gets larger, it needs more food and produces more waste. Therefore more material must be able to move in and out through the cell membrane.

• To keep up with these demands, a growing cell needs a larger surface area through which to exchange materials. As the cell’s volume increases, its outer surface grows too.

• Go to page 12 to help explain!!! • Surface-to-Volume Ratio

Benefits of being Multicellular• A single cell as big as you would have an

incredibly small surface-to-volume ratio and would not survive because its outer surface would be too small to allow in the materials needed.

• Multicellular organisms grow by producing MORE cells, not LARGER cells. – An elephant has more cells than you, not larger

cells.

Many kinds of cells

• Having many different cells that are specialized for specific jobs allows multicellular organisms to perform more functions than unicellular organisms.

• Different kinds of cells can form tissues and organs with different functions.

• Some specialized cells: muscle cells, eye cells, brain cells….

• Be glad you are not UNICELLULAR! How boring!

Two types of cellsProkaryotic Cells• Also called bacteria• World’s smallest cells• No nucleus• Circular DNA (shaped like a

rubber band)• No membrane-covered

organelles

Eukaryotic Cells• More complex• All other cells• Have a nucleus• Have membrane-covered

organelles• Linear DNA stored in the

nucleus

Eukaryotic Cells

Animal Cells1. Nucleus2. Ribosomes3. Cell Membrane4. Endoplasmic Reticulum5. Lysosomes6. Mitochondria7. Golgi Complex

Plant Cells1. Nucleus2. Ribosomes3. Cell Membrane4. Endoplasmic Reticulum5. Lysosomes6. Mitochondria7. Golgi Complex8. Cell Wall9. Large Vacuole 10. Chloroplast

The Cell's Command Center -- The Nucleus

• Largest and most visible organelle in a eukaryotic cell

• Surrounded by a nuclear membrane for protection• Stores DNA that has information on how to make all

the cell’s proteins (almost all chemical reactions important to the cell’s life involve protein)

Read more: List of Organelles | eHow.com http://www.ehow.com/info_8642034_list-organelles.html#ixzz23M2NtNGk

The Energy Plant -- Mitochondria• ATP (molecule that supplies energy to fuel the

cell’s activities) made here from food molecules• Bean shaped – surrounded by two membranes • Must have oxygen• Highly active cells (such as heart and liver) have

thousand• Powerhouse of the cell

Protein Factory -- Ribosomes• Make protein chains out of amino acids• Smallest but MOST abundant organelle• Not covered with a membrane• ALL cells have ribosomes (prokaryotes included)

The Cell’s Delivery System – Endoplasmic Reticulum

• Membrane-covered compartment that makes lipids and other materials for use inside and outside the cell

• Breaks down drugs and other damaging chemicals

• Internal delivery system • Looks like flattened sacks stacked side by side

Shipping– Golgi Complex Packaging -Vesicles

• Looks like the ER but is located closer to the cell membrane

• Modifies lipids and proteins from the ER and delivers them to other parts of the cell or outside the cell

• Vesicles are pieces of the Golgi complex that pinches off and stores the final products

Trash Collector -- Lysosomes

• Specialized vesicles in animal cells• Contain enzymes• Destroy worn-out or damaged organelles• Get rid of waste materials and protect the

cell from foreign invaders• If the membrane of a lysosome opens, the

enzymes will spill out into the cell and kill the cell. (How a tadpole loses its tail)

Plant Cells -- Chloroplasts• Only found in plants and algae• Energy-converter• Has two membranes and structures like stacked

coins and contains chlorophyll – which makes the chloroplast green

• Chlorophyll traps the energy from sunlight and uses it to make sugar in the process photosynthesis.

• Mitochondria then use the sugar to make ATP.

Cell Wall• Found in plant cells • Outside the cell membrane• Made of cellulose (sugar)• Provides strength and support to cell

membrane

Water cooler- Vacuoles• Most plant cells have very large vacuoles.• Membrane-covered• Stores water and other liquids• When full, helps support the cell• When empty, the cell shrivels (causing the

plant to wilt)

Homeostasis• (1) The tendency of an organism or a cell to regulate its internal

conditions, so as to stabilize health and functioning, regardless of the outside changing conditions

• (2) The ability of the body or a cell to seek and maintain a condition of equilibrium or stability within its internal environment when dealing with external changes

• In humans, homeostasis happens when the body regulates body temperature in an effort to maintain an internal temperature around 98.6 degrees Fahrenheit. For example, we sweat to cool off during the hot summer days, and we shiver to produce heat during the cold winter season.

Connective Tissue• Joins, supports,

cushions and insulates

• Examples: blood, bone, cartilage, ligaments, tendons,

Epithelial Tissue• Epithelial tissues consist

of continuous sheets of cells that provide a protective covering over the whole body

• They also form the lining membranes of internal organs, cavities, and passageways and cover internal organs

Muscle Tissue• Contracts or

shortens to cause movement

Nerve Tissue• Carries message to

and from the brain• Allows us to see,

hear, feel…….• Makes up brain,

spinal cord and nerves