Wednesday 22/10
Homework for next tuesday: find out what can be done to
1/ slow down the growth of microbes
2/ kill microbes
Population and population growth:
A ……………………. is a group of one kind of animals or plants living in the
same…………………... Populations are able to grow very quickly in …………………………… .
However, some factors …………………… population growth:
- …………………………..
-……………………………
- ………………………….
- …………………………..
Experiment: Growth conditions needed by woodlice
Aim: to test which environmental conditions are preferred by woodlice
Input variable to be changed: …………………………………
Outcome variable to be measured: ………………………………………………. measured every minute
during 10 minutes
Variables to be kept the same:……………………………………………………………………..
Time (min)
0
1
2
3
4
5
6
7
8
9
10
Number of woodlice
Conclusion: Woodlice “prefer” ……………………and ……………………………….conditions (Class
results).
This is because in dark and damp areas, they are:
- less likely to …………………………
- less visible to ………………………………
Human population:
Human population is now growing very quickly as many factors that used to limit the
growth of our population are controlled in our modern life.
Limiting factor
Disease
Means of control
Overcrowding
Lack of food
Lack of water
Microbes
Microbes (also called micro-organisms) are organisms that are so tiny that they can
only be observed using a microscope  microscopic organisms
Microbes include bacteria, fungi and viruses.
Microbes can be found ………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………………………
Experiment: Which conditions are best for microbes to grow?
Aim: To test in which conditions microbes grow best
Outcome variable for all experiments:
Input variables studied:
Input variable
Value 1
Value 2
Value 3
Value 3
Temperature (°)
-10
6
21
35
-10
6
21
35
(Dry bred)
Temperature (°C)
(Wet bred)
Condition
Freezin
g and
dry
Freezin
g and
wet
Cold
(Fridge
) and
dry
Cold
(Fridge
)
and wet
Class result
Conclusion:
Microbes grow the best in wet and damp conditions
Lesson 3
Control of microbial population:
Researched based lesson
Encouraging population growth
Some microbes are really useful for humans:
Warm
and dry
Warm
and wet
Hot
and dry
Hot
and wet
Lesson 4
Recap of what was learnt last lesson in the form of a spider diagram
Some microbes are decomposers: they can make dead things rot.
Things that rot are called biodegradable, things that never rot are called nonbiodegradable.
Examples of biodegradable things:
- apples
- humans
- wood
- plants
Examples of non-biodegradable things:
- glass
- metal
- some plastics
- cans
In the lab, they are grown in nutrient broth.
Limiting the growth of microbes
Microbes cannot grow, or will grow very slowly in food which is:
- kept in the fridge or the freezer
- dry (packet of crisps, dried pasta)
- vacuum packed (no air)
- very salty (salted cod, crisps)
Killing microbes
In some places, all microbes have been killed in a process called…………………………………….
A place or an object without microbes is called ……………………….. (e.g. clean syringes).
Microbes can be killed by:
- heat (flame tools, boil water for more than 10 min)
- pressure (pressure cooker = autoclave)
- chemicals (bleach, alcohol)
- filtration (filters with microscopic holes)
- radiations (UV light)
Microbes are not killed by cold temperatures.
Competition between organisms
Competition : When organisms have a need for the same………………………………………………,
e.g……………………………………………………….., competition takes place.
For example, Robins compete for their territory.
Animals which compete for food with humans are called …………………………
Competition also happens between plants for ………………………………………………………………...
Competition : When organisms have a need for the same………………………………………………,
e.g……………………………………………………….., competition takes place.
For example, Robins compete for their territory.
Animals which compete for food with humans are called …………………………
Competition also happens between plants for ………………………………………………………………...
Exercise on keys
Lesson 6: Experiment: Which weed is the best competitor?
Weed
Dandelion
Plantain
Daisies
Conclusion:
Sample
1
Sample
2
Sample
3
Sample
4
Sample
5
Total
Lesson 7
Who eats whom in an environment?
Food is energy
A food chain shows the movement of energy between plants and animals. The arrow
shows the direction of the flow of energy.
For example:
Meadow:
grass
Sea Rock pool:
snail
seaweed
Tree: oak tree
hedgehog
limpet
seagull
caterpillar
black bird
cat
Food web:
A food web is made up of many interconnected food chains.
Fox
Owl
Weasel
Hedgehog
Vole
Rabbit
Worm
Snail
Oak
Grass
leaves
1/ Please write down all the food chains that you can find in this food web (6)
e.g. grass
grass
rabbit
rabbit
fox
weasel
Oak leaves
vole
weasel
Oak leaves
vole
owl
fox
fox
Oak leaves
worm
hedgehog
fox
Oak leaves
snail
hedgehog
fox
2/ What would happen if all the voles disappeared?
The weasel will not have as much food, they might start to die off. However, some will
survive as they can also eat rabbits.
3/ What would happen if the voles were present but the owl disappeared?
The owls would die as their only source of food as disappeared.
In a food chain, energy is lost at each level because plants and animals have to use
some of it to live.
Grass
Snail
Hedgehog
Energy
Lesson 8
Food pyramids show the number of organisms at each level of the food chain
Pyramids of numbers
Pyramids of numbers show they number of organisms at each level of the food chain.
Remember
- you need lots of salads to feed one rabbit, lots of rabbits to feed one fox, lots of
foxes to feed one eagle
- therefore, the number of organisms decreases (goes down) as you go up the food
chain
- there are always less predators than prey, otherwise predators would starve to
death!
For example:
grass
rabbit
Fox
fox