Focus’ 1 & 5 – PATTERNS IN NATURE

Outline the historical development of the cell theory, in particular the contributions of Robert Hooker and Robert Brown

Describe evidence to support the cell theory

The cell theory:

1. All living things made of cells2. Cells are the basic structural and functional unit of organisms3. All cells arise from pre-existing cells

** before introduction of simple/light microscopes - one accepted view = spontaneous generation**

Historical Development Evidence to supportROBERT HOOKE (1600S)

- Introduced the term “cell” - Used a simple compound microscope

to observe cork (dead plant cells) and saw the cells.

ROBERT BROWN (early 1800s)- First described the cell nucleus

- Observed plant cells in an orchid using a light microscope & later plant tissue – discover each cell had a nucleus

SCHLEIDEN & SCHWANN (early 1800s)- First time a common basic structure for

all living things had become evident- Statement that all plants & animals are

made of cells (cells are the basis for all living things)

- Formulated/proposed the cell theory

- Examined lots of plants & animals cells under light microscopes.

RUDOLPH VIRCHOW (1855)- Introduced idea that cells reproduce by

dividing cells can only arise from pre-existing cells.

- Studied the cells in living tissue dividing under a light microscope

DEVELOPMENT OF ELECTRON MICROSCOPE (1933-present)

- Higher magnification & resolution- 2 types (transmission, scanning)

n/a

Use evidence to assess the impact of technology, including the development of the microscope, on the development of the cell theory

Prior to proposal of cell theory – no technology to observe cells – theory of ‘spontaneous generation’

-- Cell theory wouldn’t have been developed without microscopes.- Light microscopes were developed – not limited by lense quality but limited by wavelength

of light (ability to resolve & magnify)- 2 main types:

o Light (compound) microscope o Electron microscope (scanning – 3D & transmission)– greater magnification &

resolution (greater detail)

LIGHT MICROSCOPE ELECTRON MICROSCOPEENERGY SOURCE Light ElectronsMAGNIFICATION Lower Higher RESOLUTION Lower HigherLIVE SPECIMENS Yes No DEAD SPECIMENS Yes YesADVANTAGES Smaller & lighter

(easier to move) Less expensive Images viewed

directly Can view live

specimens

Higher mag Higher resol.

Advancements: saw ultrastructure: many parts of the cell were seen for the first time after the invention of electron microscope – other parts seen with a light miscrope were now seen in far more detail providing increased knowledge about structure led to understanding of their function in cells. Additional statements to the cell theory

Identify cell organelles seen with light & electron microscopes and relate their structure to their function

ORGANELLE FUNCTION STRUCTURE CELL? MICROSCOPE (L OR E)?

Nucleus Control centre of the cell (regulates all cell activity)

Membrane bound structure containing DNA

Both Both

Nucleolus Produces ribosomes for protein synthesis

Prominent structure in nucleus containing DNA & RNA

Both Electron

Chloroplasts Responsible for process of photosynthesis (making food for

Membrane bound organelle containing pigment chlorophyll.

Plant Both

the cell) Stacks of inner membranes, increase SA = more chem. reactions occur

Smooth ER Transports substances around the cell

Folded membrane increase SA

Both Electron

Rough ER Transports substances (mainly proteins) around the cell

“ “ “ “Ribosomes attached

Both Electron

Golgi Body Involved in packaging, sorting & excretion of materials out of the cell.

Pinched off vesicles secrete materials out of cell

Both Electron

Cytoplasm Holds organelles within cell & where metabolic (chemical) processes occur

Fluid found throughout cell

Both Both

Cell membrane Controls movement of substances in and out of the cell

Membrane bound, Selectively permeable

Both Both

Cell wall Provides support to the cell

Rigid cellulose structure

Plant Both

Vacuole Provides support to the cell

Membrane bound organelle in which water and ions are stored

Plant Both

Lysosome Intracellular digestion

digestive enzymes break down worn out materials – recycled

Animal Electron

Ribosome Produces proteins for cell functioning and structure (protein synthesis)

Small size & rounded shape – increase SAContains chemicals RNA & protein

Both Electron

Mitochondrion Produces energy through chemical respiration

Inner folded membrane = increase SA for more chem. reactions

Both Electron

Perform a first-hand investigation to gather first-hand information using a light microscope to observe cells in plants and animals and identify nucleus, cytoplasm, cell wall, chloroplast and vacuoles.

- Prepare wet mount: Remove onion skin & lift thin – onion tissue from surface of layer Place onion & water (unstained) & iodine (stained) onto miscroscope slide Lower coverslip using dissecting needle – avoid air bubbles Paper towel – dry excess water or stain

Annoatate image from quiz etc.

Analyse electron micrographs of cells and identify mitochondria, chloroplast, Golgi bodies, lysosomes, endoplasmic reticulum, ribosomes, nucleus, nucleolus and cell membranes

INSERT IMAGES/SKETCHES OF EACH THING TO IDENTIFY IN MICROGRAPHS OF CELLS

Identify the sites of mitosis in plants, insects and mammals

PLANTS: meristems (plant growing areas) e.g. shoot tips, root tipsMAMMALS: gut lining, bone marrow, basal layer of skinINSECTS: dividing (mitosis) stage at puape/lava form

Identify mitosis as a process of nuclear division and explain its role - Mitosis is a process of nuclear division resulting in two identical daughter cells (genetic

stability)- ROLE: for Growth & repair and to keep cells small (not larger than original parent cell) –

larger SA for exchange of materials

Explain the need for cytokinesis in cell division CYTOKINESIS is the division of the cytoplasm at the end of mitosis and the production of new organelles in each daughter cell.Importance: for cell enlargement and to make cells identical

What organelles contain DNA in cells? - Nucleus- Mitochondria- chloroplasts

Prac to describe the sequence of changes in the nucleus of plant or animal cells undergoing mitosis

** used bio-viewers to observe animal & plant cells undergoing mitosis looking for each stage**

1. - Chromosomes are replicating but NOT visible- nuclear membrane visible

2. Chromosomes become thicker and shorter – exist as two strands of DNA (chromatids) joined together at the centromere

- Nuclear membrane begins to break down

3. – no nuclear membrane

- protein strands extend across centre forming the spindle

- chromosomes lined up along equator of cell with spindle fibres attach to their centromere

4. – spindle fibres pull apart the chromatids to each pole of the cell- no nuclear membrane

5. New nuclear membrane forms around the two groups of chromosones6. Cytokinesis cytoplasm divides to form two genetically identical cells.

Cell wall forms around plant cells

DIPLOID NO. – Original chromosome no. of parent cell (humans – 46 (23 pairs))>>>>>>>SKILLS>>>>>SIZE OF CELLS USING LIGHT MICROSCOPE!!!!!!!!!!!!

Focus 1 – LIFE ON EARTH

Identify the relationship between the conditions on early Earth and the origin of organic molecules

Earth formed about 4.6 billion years old

Conditions on early Earth- High volcanic activity (add many gases to atmosphere)- Violent storms – lightening - High amount of UV radiation- Atmosphere made up of water vapour, methane, ammonia, carbon dioxide, nitrogen,

hydrogen, NO free oxygenEVIDENCE conditions on other planets in solar system & chemicals that erupt from volcanoes today (probably always have)

1920s – two scientists suggested that conditions on primitive Earth:- First caused chemical reactions made complex organic molecules

- Chemicals came together to form a living organism- Life evolved into all species we know today

Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth

Describe two scientific theories relating to the evolution of the chemicals of life

Discuss the significance of the Urey and Miller experiments in the debate on the composition of the primitive atmosphere

Describe the experiments of Urey and Miller and use available evidence to analyse the: - Reason for their experiments - Result of their experiments- Importance of their experiments in illustrating the nature and practice of science- Contribution to hypotheses about the origin of life

Identify changes in technology that have assisted in the development of an increased understanding of the origin of life and evolution of living things