Transcript Structure and function

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
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Char. Of Life
Virus
Movement
No
Reproduction
Yes
Sensitivity
No
Growth
No
Respiration
No
Excretion
No
Nutrition
No
Viruses
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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
7
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
replication
A 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
BACK
14
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
Shape
Spherical (coccus)
Rod shaped
(bacillus)
Spiral (spirillum)
Example
Staphylococcus
E.coli
Vibrio cholerae
Bacteria structure
Structure functions
Cell wall: Maintains cell shape
Cell membrane: Controls entry and exit of
materials
Chromosome: Carries genetic information
Cytoplasm: fills cell and provides medium for
chemical reactions to occur
Flagellum: Assists the bacterium to move
Capsule: 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
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Light
Temperature
Chemicals
Acidity
Food supply
Bacterial Growth
Number of bacteria
Log or
Exponential
Optimal
conditions
Rapid
growth
Stationary
Toxin
production
causes
human
sickness
Lag
Time
Copy
Death
or
Decline
Competition
for food and
space means
bacteria die
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
Copy
Respiration
• Carry out aerobic and anaerobic respiration to create
energy from food
Micro-organisms are helpful
• Food production
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Bread
Alcohol
Cheese
Yoghurt
• Nutrient recycling
• Composting
• Medicine production
• Antibiotics
• Insulin
Sewage treatment by microbes
Microbes clean
our water
1. Reservoir
1. Stores rainwater
2. Metal grids keep out
weeds and debris
3. Coagulation
3. Chemicals make
particles stick together
4. Stands for 3hr to let
large particles sink
(digested by microbes)
5. Filtration
5. Gravel and sand
removes most
particles
6. Kills microbes
2. Screening
4. sedimentation
6. Chlorination