Definitions• Parasites feed on living hosts• Saprophytes feed on dead matter• Decomposers breakdown dead matter and

recycle the nutrients• Pathogens are disease causing organisms

(most parasites are also pathogens)• Extra cellular digestion is the process by

which bacteria and fungi feed• Binary fission is the process by which

bacteria reproduce

Viruses

Viruses

Char. Of Life Virus

Movement No

Reproduction Yes

Sensitivity No

Growth No

Respiration No

Excretion No

Nutrition No

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Viruses

• Viruses are simple but effective pathogens

• Viruses can infect all living things

• Range from 20 to 20millionth of a millimetre.

• Can only be seen with an electron microscope.

Viral structure

• Viruses come in a variety of shapes

• Consists of a core of genetic material surrounded by a protein coat=capsid

• Some viruses also have a membrane. This membrane can have proteins embedded in it

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Viral reproduction• Essentially all a virus is is a set of instructions for making

new viruses.

• MRS GREN is not followed by viruses and the only ‘living’ characteristic that they have is reproduction

• They lie on the border between the living and no living worlds

Viral reproduction• Essentially all a virus is is a set of instructions for making

new viruses.

• MRS GREN is not followed by viruses and the only ‘living’ characteristic that they have is reproduction

• They lie on the border between the living and no living worlds

Viral replicationA virus cannot reproduce itself independently, it needs another cells parts to replicate itself.

When a virus lands on the surface of a cell it inserts its genes into the host cell.

The viral genes take over the cells processes to produce new viruses.

These build up in the cell until it eventually bursts releasing the new viruses into the host where they can infect new cells.

Smallpox, Mumps, Measles - Virus

POXVIRUSES

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BACK

Bacteria

Bacteria

• Bacteria are unicellular organisms with no nucleus

• Sphere, rod, or spiral shaped• Usually 0.01mm in length and only visible

under the higher powers of the microscope• Over 3000 known kinds• They are found almost everywhere including

in living things • Colonies growing on agar look like shiny

spots of various colours

Spherical (coccus) Staphylococcus

Rod shaped E.coli(bacillus)

Spiral (spirillum) Vibrio cholerae

Shape Example

Bacteria structure

Structure functions

Cell wall: Maintains cell shapeCell membrane: Controls entry and exit of materialsChromosome: Carries genetic informationCytoplasm: fills cell and provides medium for

chemical reactions to occurFlagellum: Assists the bacterium to moveCapsule: Provides protection from external environment

MRS GREN

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

Movement

• Many bacteria move by

hair-like threads called flagella.

• These are made up of long stands of protein

• Non-flagellum bacteria float in water or on the wind.

• Or are carried/spread by

their hosts

Respiration

• Not breathing!

• The process of releasing energy from food molecules

• Bacteria carry out:

- Aerobic respiration (requires oxygen)

- Anaerobic respiration (without the presence of oxygen)

http://www.youtube.com/watch?v=d0UfS1bqscM

Sensitivity

Bacteria display sensitivity to their environment.

They can move along concentration gradients until they reach their optimum environment.

i.e. Temperature/ acidity/ Oxygen/ Magnetic

Growth

In optimum conditions bacteria do grow, but their goal is reproduction so they grow up to a certain point where they have enough resources to reproduce.

Reproduction

• Reproduce asexually by a process called Binary fission

• The bacterium’s chromosome is duplicated and the cell then pinches in half and two identical

daughter cells are

produced

Excretion

Bacteria excrete by allowing waste to diffuse out of the cell membrane into the environment

i.e. CO2 from aerobic respiration

Nutrition

• Bacteria ‘feed’ by secreting enzymes which break down their food source into smaller molecules that can be absorbed by the bacteria.

• This is called

extra-cellular

digestion.

• Parasites – Live on or in larger organisms and feed off them. If they cause disease they are called pathogens.

• Saprophytes – Consume dead matter. These bacteria are scavengers and decomposers.

• Autotrophs – Self-feeders. They can make food from non-living materials i.e. chemicals/ sunlight.

- Green and purple sulfur bacteria.

Factors that inhibit bacteria growth• Light

• Temperature

• Chemicals

• Acidity

• Food supply

Bacterial Growth

Competition for food and space means bacteria die

Death or Decline

StationaryLog or Exponential

Lag

Optimal conditionsRapid growth

Toxin production causes human sickness

Time

Num

ber

of b

acte

ria

Fungi

Fungi

• A group of immobile organisms that feed on dead or living organisms and exposed food

• 70,000 known kinds• 50 fungi among NZ’s most threatened

species• Can be unicellular and

multi-cellular• Most common cause of

plant disease

Structure

• Hyphae: Fine feeding threads

• Sporagium: Spore capsule that produces spores

• Spores: reproductive cell, germinates and spreads out hyphae

Mass of Hyphae

MRS GREN

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

Movement

• Immobile

• But can spread by producing networks of hyphae.

Reproduction

• Asexual and sexual production of spores

• Spores germinate when they land on tissue and put out hyphae.

Yeasts

Sensitivity

• Show active responses to their surroundings

Growth• Grow by spread of hyphae

Respiration

• Carry out aerobic and anaerobic respiration to create energy from food

Excretion

• Allow waste to diffuse out of cells and into the surrounding envrionment

Nutrition• Secrete enzymes that break down food, the absorb digested

food

• Extra-cellular digestion in fungi

Respiration

• Carry out aerobic and anaerobic respiration to create energy from food

Micro-organisms are helpful

• Food production• Bread• Alcohol• Cheese• Yoghurt

• Nutrient recycling• Composting

• Medicine production• Antibiotics• Insulin

Sewage treatment by microbes

Microbes clean our water

1. Stores rainwater2. Metal grids keep out

weeds and debris3. Chemicals make

particles stick together4. Stands for 3hr to let

large particles sink (digested by microbes)

5. Gravel and sand removes most particles

6. Kills microbes

1. Reservoir

4. sedimentation3. Coagulation

6. Chlorination5. Filtration

2. Screening