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Lesson Overview Homeostasis and Cells

Lesson Overview

7.4 Homeostasis and Cells


THINK ABOUT IT

The diversity of life is so great that you might have to

remind yourself that all living things

• Are composed of cells

• Use same basic chemistry

• Contain same kinds of organelles.

This does not mean that all living things are the same.

Differences arise from the ways in which

• cells are specialized

• cells associate with one another to form

multicellular organisms.


The Cell as an Organism

How do individual cells maintain homeostasis (including

unicellular organisms)?

To maintain homeostasis, unicellular organisms

• Grow

• Respond to the environment

• Transform energy

• Reproduce



A single-celled, or unicellular organism, does everything

you would expect a living thing to do.

Just like other living things, unicellular organisms must

achieve homeostasis, relatively constant internal

physical and chemical conditions.

Homeostasis Review from the BBC!

BBC - GCSE Bitesize Homeostasis activity (Low-360p).mp4



Based on numbers, unicellular organisms dominate life

on Earth.

Unicellular organisms include both prokaryotes and

eukaryotes.

Prokaryotes, especially bacteria, are remarkably

adaptable and live almost everywhere—in the soil, on

leaves, in the ocean, in the air, and even within the

human body.


Bacteria that cause infections:



Many eukaryotes also spend their lives

as single cells.

Some types of algae, which contain chloroplasts and

are found in oceans, lakes, and streams around the

world, are single celled.

Yeasts, or unicellular fungi, are also widespread.

Yeasts play an important role in breaking down

complex nutrients, which makes them available for

other organisms.

Algae on Pond



Whether a prokaryote or a eukaryote,

homeostasis is an issue for each

unicellular organism.

Every unicellular organism needs to

• Find sources of energy or food

• Keep water and mineral concentrations within certain

levels

• Respond quickly to changes in environment


Multicellular Life

How do the cells of multicellular organisms work

together to maintain homeostasis?

Cells of multicellular organisms become specialized. To

maintain homeostasis:

• Cells have specific tasks

• Cells communicate with one another


Multicellular Life

Cells of multicellular organisms are interdependent.

Example: Like members of a successful baseball team,

they work together.

In baseball, players take on a particular role, such as

pitcher, catcher, infielder, or outfielder. Messages and

signals are sent and understood by teammates and

coaches to play the game effectively.


Cell Specialization

Different cell types playing different roles.

Some cells are specialized to move, others to react to

the environment, and still others to produce

substances that the organism needs.

No matter what the role, each specialized cell

contributes to the overall homeostasis of the

organism.


Specialized Animal Cells Particles of dust, smoke, and bacteria are part of even

the cleanest air.

Specialized animal cells act like street sweepers to

keep the particles out of the lungs.

These cells are full of mitochondria, which provide a

steady supply of the ATP that powers the cilia on their

upper surfaces.

Cilia


Specialized Plant Cells

Pollen grains are highly specialized cells that are tiny

and light, with thick cell walls to protect the cell’s

contents.

Pine pollen grains have two tiny wings that enable the

slightest breeze to carry them great distances.


Levels of Organization

The specialized cells of multicellular organisms are

organized into tissues, then into organs, and finally

into organ systems.



A tissue is a group of similar cells that performs a

particular function.


Levels of Organization To perform complicated tasks, many groups of tissues

work together as an organ.

Each type of tissue performs an essential task to help

the organ function.

In most cases, an organ completes a series of

specialized tasks.


A group of organs that work together to perform a

specific function is called an organ system.

For example, the stomach, pancreas, and intestines

work together as the digestive system.




The organization of the body’s cells into tissues,

organs, and organ systems creates a division of

labor among those cells that allows the organism to

maintain homeostasis.


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Levels of organization

Cells are grouped together and work as a whole to perform special functions

copyright cmassengale


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Tissue

A group of similar cells to perform a particular function

Animals : epithelial tissue, muscular tissue

Plants : vascular tissue, mesophyll



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Organ

Different tissues group together to carry out specialized functions

Heart : consists of muscles, nervous tissue and blood vessels

Leaf : consists of epidermis, mesophyll and vascular tissue



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Stoma

Air Space

Spongy Mesophyll Cell

Chloroplast

The Structures of a Leaf (Plant Organ)

Palisade Mesophyll Cell



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The Structures of a Heart (Animal Organ)



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System

Several organs and tissues work together to carry out a particular set of functions in a co-ordinated way

Human : digestive, respiratory, excretory, circulatory and reproductive systems

Plant : root and shoot systems



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Human Body Systems

Examples of systems :

Digestive System

Respiratory System

Circulatory System

Nervous System

Reproductive System



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Examples of a Human Body System



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Examples of a Human Body System The Respiratory System



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Examples of a Human Body System Circulatory System



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Examples of a Human Body System

Nervous System



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Organisms—YOU!

What other levels of organization can we add from Ch. 2?


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ATOMS MOLECULES ORGANELLES (elements) (compounds like (Nucleus, ER, Golgi… carbohydrates & proteins)

Nonliving Levels Subatomic Particles (Protons, neutrons, electrons)


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CELLS – life starts here

TISSUES – Similar cells working together

Living Levels


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ORGANS ORGAN SYSTEMS

ORGANISM

Different tissues working together

Different organs working together

More Living Levels


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LEVELS OF ORGANIZATION

Living Levels continued:

• POPULATION (one species in an area)

• COMMUNITY (several populations in an area

• ECOSYSTEM (forest, prairie …)

• BIOME (Tundra, Tropical Rain forest…)

• BIOSPHERE (all living and nonliving things on Earth)


Cellular Communication Cells in a large organism communicate by means of

chemical signals that are passed from one cell to

another.

Cellular signals can speed

up or slow down the

activities of the cells that

receive them, and can

cause a cell to change

what it is doing.

Proteins in Cell Membrane


Cellular Communication

Some cells form connections, or cellular junctions, to

neighboring cells.

Some junctions hold cells

firmly together.


Proteins in Cell Membrane

Cellular Communication Junctions can allow small molecules carrying chemical

messages to pass directly from one cell to the next.

Cells must have a receptor to respond to the signal.

Chemical signals sent by

various types of cells can

cause important changes

in cellular activity.

For example, such junctions

enable the cells of the heart

muscle to contract in a

coordinated fashion.

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