Science 8 Unit B Section Science 8 Unit B Section 2.02.0

Cells play a vital role in living Cells play a vital role in living things.things.

Section OutcomesSection Outcomes

Students will be able to identify the parts Students will be able to identify the parts of a microscopeof a microscope

Students will be able to use a microscope Students will be able to use a microscope and prepare slidesand prepare slides

Students will be able to explain the role of Students will be able to explain the role of cells as a basic unit of lifecells as a basic unit of life

Students will be able to identify plant and Students will be able to identify plant and animal cellsanimal cells

Section OutcomesSection Outcomes

Students will be able to identify the Students will be able to identify the differences between one-celled and differences between one-celled and multicelled organismsmulticelled organisms

Students will be able to explain osmosis Students will be able to explain osmosis and diffusionand diffusion

Students will recognize the roles of cells, Students will recognize the roles of cells, tissues, and organstissues, and organs

2.1 – The Microscope2.1 – The Microscope

The human eye is limited in how well it can The human eye is limited in how well it can see small objectssee small objects

The limit to human vision is objects that The limit to human vision is objects that have a diameter of about 0.1 mmhave a diameter of about 0.1 mm

Humans cannot see individual objects that Humans cannot see individual objects that are less than this sizeare less than this size

Therefore, to observe smaller objects, we Therefore, to observe smaller objects, we need a microscopeneed a microscope

The Compound Light MicroscopeThe Compound Light Microscope

Compound light microscopes all use light Compound light microscopes all use light passing through a specimen and then a passing through a specimen and then a number of lenses to magnify objectsnumber of lenses to magnify objects

We’ll look at the microscope and identify We’ll look at the microscope and identify its parts:its parts:

Parts of the MicroscopeParts of the Microscope

Ocular Lens (Eyepiece)Ocular Lens (Eyepiece)

Coarse Adjustment KnobCoarse Adjustment Knob

Parts of the MicroscopeParts of the Microscope

Fine Adjustment KnobFine Adjustment Knob

Revolving NosepieceRevolving Nosepiece

Parts of the MicroscopeParts of the Microscope

Objective LensesObjective Lenses

StageStage

Parts of the MicroscopeParts of the Microscope

Stage ClipsStage Clips

Condenser LensCondenser Lens

Parts of the MicroscopeParts of the Microscope

DiaphragmDiaphragm

Lamp (Light Source)Lamp (Light Source)

Parts of the MicroscopeParts of the Microscope

ArmArm

BaseBase

Using MicroscopesUsing Microscopes

Microscopes are precision instruments Microscopes are precision instruments and are therefore fragileand are therefore fragile

Keep the following pointers in mind when Keep the following pointers in mind when using them:using them:

2.2 – The Cell is the Basic Unit of 2.2 – The Cell is the Basic Unit of LifeLife

Cells are the smallest functioning unit of Cells are the smallest functioning unit of lifelife

Cells are visible using microscopesCells are visible using microscopes

The internal structures in the cell may be The internal structures in the cell may be visible depending on:visible depending on:

1.1. The type of microscope usedThe type of microscope used

2.2. The power of the lensesThe power of the lenses

3.3. The quality of the prepared slidesThe quality of the prepared slides

Preparing SlidesPreparing Slides

Not all specimens that you will study come Not all specimens that you will study come on prepared slideson prepared slides

Often scientists have to produce their own Often scientists have to produce their own slidesslides

This is a delicate process – improper This is a delicate process – improper preparation of a specimen will produce a preparation of a specimen will produce a slide that is difficult to studyslide that is difficult to study

Preparing a Wet MountPreparing a Wet Mount

1.1. A clean slide, cover slip, eyedropper, A clean slide, cover slip, eyedropper, tweezers, water and a specimen must be tweezers, water and a specimen must be collectedcollected

2.2. Handle the slide only by the edgesHandle the slide only by the edges

3.3. Place a drop of water in the centre of the slidePlace a drop of water in the centre of the slide

4.4. Lay the specimen on the drop of waterLay the specimen on the drop of water

5.5. Carefully place the cover slip over the Carefully place the cover slip over the specimen, trying not to trap air bubbles specimen, trying not to trap air bubbles underneathunderneath

Plant CellsPlant Cells

Animal CellsAnimal Cells

Structures in CellsStructures in Cells

NucleusNucleus

MitochondriaMitochondria

Cell MembraneCell Membrane

Structures in CellsStructures in Cells

VacuolesVacuoles

CytoplasmCytoplasm

Cell WallCell Wall

Structures in CellsStructures in Cells

ChloroplastsChloroplasts

Identifying Plant and Animal CellsIdentifying Plant and Animal Cells

Plant cells can be identified by two Plant cells can be identified by two structures that are not present in animal structures that are not present in animal cells:cells:

1.1. Cell wallCell wall

2.2. ChloroplastsChloroplasts

2.3 – Organisms Can be Single-2.3 – Organisms Can be Single-Celled or MulticelledCelled or Multicelled

The smallest kind of organisms known are The smallest kind of organisms known are called mycoplasmacalled mycoplasma

These are so small that they need to be These are so small that they need to be viewed under an electron microscopeviewed under an electron microscope

They are single-celled (unicellular) They are single-celled (unicellular) organismsorganisms

Unicellular OrganismsUnicellular Organisms

There are a number of different There are a number of different unicellular organisms:unicellular organisms:

1.1. DiatomsDiatoms

2.2. BacteriaBacteria

3.3. ProtistsProtists

The Disadvantage of Unicellular The Disadvantage of Unicellular OrganismsOrganisms

Unicellular organisms have to carry out all Unicellular organisms have to carry out all of their processes within a single cellof their processes within a single cell

This means that they also must absorb all This means that they also must absorb all of their nutrients through their cell of their nutrients through their cell membranemembrane

Therefore, the cells must remain small Therefore, the cells must remain small otherwise they cannot absorb enough otherwise they cannot absorb enough materials to stay alivematerials to stay alive

Multicellular OrganismsMulticellular Organisms

Multicellular organisms have tissuesMulticellular organisms have tissues

These collections of cells allow a “division These collections of cells allow a “division of labour”of labour”

With the presence of tissues, organisms With the presence of tissues, organisms can become larger – cells can be can become larger – cells can be specialized to a single taskspecialized to a single task

These specialized cells often are These specialized cells often are dependent on each otherdependent on each other

2.4 – How Substances Move Into 2.4 – How Substances Move Into and Out of Cellsand Out of Cells

Recall from the particle model of matter Recall from the particle model of matter that all particles are always movingthat all particles are always moving

This also means that various particles This also means that various particles move across cell membranesmove across cell membranes

The movement of materials across a The movement of materials across a membrane can come in one of three membrane can come in one of three forms:forms:

DiffusionDiffusion

Diffusion:Diffusion:

Diffusion occurs naturally as long as the Diffusion occurs naturally as long as the particles are small enough to cross a particles are small enough to cross a membranemembrane

Therefore, it requires the cell to use no Therefore, it requires the cell to use no energyenergy

OsmosisOsmosis

Osmosis:Osmosis:

Cell membranes are selectively permeable Cell membranes are selectively permeable – they only allow certain materials to pass – they only allow certain materials to pass thoughthough

Therefore, osmosis can occur across cell Therefore, osmosis can occur across cell membranesmembranes

The Effects of Osmosis on CellsThe Effects of Osmosis on Cells

Isotonic environment (identical solute Isotonic environment (identical solute concentrations)concentrations)

Hypotonic environment (lower solute level Hypotonic environment (lower solute level outside the cell than inside)outside the cell than inside)

Hypertonic environment (higher solute level Hypertonic environment (higher solute level outside the cell than inside)outside the cell than inside)

Active TransportActive Transport

Active TransportActive Transport

This process requires energyThis process requires energy

Often this process is used to collect Often this process is used to collect nutrients from the environment around a nutrients from the environment around a cellcell

2.5 – Cells Combine to Form 2.5 – Cells Combine to Form Tissues and OrgansTissues and Organs

Unicellular organisms are limited in sizeUnicellular organisms are limited in size

Therefore, when they reach a certain size, Therefore, when they reach a certain size, they divide as shown below:they divide as shown below:

Multicellular Organisms & Multicellular Organisms & Specialized CellsSpecialized Cells

Although our body cells are specialized, Although our body cells are specialized, they do reproduce in the same manner as they do reproduce in the same manner as unicellular organismsunicellular organisms

Our specialized cells gather together to Our specialized cells gather together to form tissuesform tissues

There are three main types of tissues in There are three main types of tissues in animals:animals:

Animal Tissue TypesAnimal Tissue Types

1.1. Connective TissueConnective Tissue

2.2. Epithelial TissueEpithelial Tissue

Animal Tissue TypesAnimal Tissue Types

3.3. Nervous TissueNervous Tissue

4.4. Muscle TissueMuscle Tissue

Plant TissuesPlant Tissues

1.1. Photosynthetic TissuesPhotosynthetic Tissues

2.2. Protective TissuesProtective Tissues

3.3. Transport TissuesTransport Tissues